This work was supported in part by a grant from NIH grant R01 GM087609 (to H.P.L.), a Gift from Ingrid Lai and Bill Shu in honor of Anthony Shu (to H.P.L.), NIH grant U01 HL099776 (to M.T.L.), the Hagey Laboratory for Pediatric Regenerative Medicine and The Oak Foundation (to M.T.L. and H.P.L.). G.G.W. was supported by the Stanford School of Medicine, the Stanford Medical Scientist Training Program, and NIGMS training grant GM07365. M.S.H. was supported by CIRM Clinical Fellow Training Grant TG2-01159. W.X.H. was supported by funding from the Sarnoff Cardiovascular Foundation.

NOTE: All procedures described in this paper are performed according to guidelines established by the Stanford Administrative Panel on Laboratory Animal Care (APLAC).
1. Timed Pregnancies &#8211; Superovulation Technique (Figure 1)
NOTE: Precisely timing the gestational age of mouse embryos for fetal surgery at E16.5 and E18.5 is of critical importance. In this section we detail our protocol for timing mouse pregnancies using pregnant mares serum (PMS) and human chorionic gonadotropin (HCG) injections to induce superovulation.
<ol>
	<li>Inject female mice (&#60;5 per cage) intraperitoneally (IP) with 3.0-5.0 international units (IU) of PMS in a volume of 100 &#956;l PBS between 1:00 and 3:00 PM for day 1.</li>
	<li>Between 12:00 and 2:00 PM of day 3 (forty-five to 47 hr after PMS injection), inject female mice IP with 3.0-5.0 IU of HCG in a volume of 100 &#956;l PBS. 
	NOTE: The HCG injection induces ovulation approximately 12 hr post-injection.</li>
	<li>Immediately following HCG injections, mate females with males aged 8-16 weeks. 
	NOTE: We typically place two females into a cage of individual males.</li>
	<li>Separate females from males on the morning of day 4 (6:00 &#8211; 10:00 AM) and record as fetal age E0.5. 
	NOTE: Vaginal plugs can be checked at this time; however, the observation of a vaginal plug does not guarantee pregnancy and females can become pregnant when no plug is observed. Given that pregnancy is typically observable by visual inspection and/or palpation at gestational ages E16.5 and E18.5, checking for vaginal plugs on the morning of day 4 is not strictly necessary. In our experience, and depending on the strain, approximately 30-50% of super-ovulated females become pregnant using the technique described here.</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/52297/52297fig1highres.jpg" /> 
Figure 1. Schematic for Superovulation Technique.&#160;Schematic showing procedure for superovulation timed pregnancies in mice. <a href="https://www.jove.com/files/ftp_upload/52297/52297fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Murine Fetal Surgery (Dorsal Wounding) on E16.5 and E18.5 Embryos (Figure 2)
<ol>
	<li>Before the procedure, clean all surfaces of the operating room and equipment with 70% isopropyl alcohol. In addition, sterilize all surgical supplies and instruments that will be used in the procedure by autoclaving them. Some institutions may allow subsequent use of hot bead sterilization.&#160;Per operation, use sterile packs that include gauze and surgical instruments.</li>
	<li>Induce anesthesia in pregnant mothers (fetal age E16.5 or E18.5) under 2.5% isoflurane/oxygen mixture at 2 L per min followed by maintenance anesthesia at 1 L per min.</li>
	<li>To confirm proper anesthetization, ensure the deep pedal reflexes of the mouse are suppressed and place the mouse in the prone position.</li>
	<li>Apply a vet ophthalmic ointment such as Puralube to prevent eye irritation or dryness during the procedure.</li>
	<li>Prepare abdomen by administering a light application of depilatory cream for no longer than 30 sec (Figure 2A).</li>
	<li>Prepare abdomen for aseptic surgery with povidone-iodine and alcohol (Figure 2B and 2C).</li>
	<li>Perform midline laparotomy under microscope using microsurgical scissors (Figure 2D and 2E).</li>
	<li>Gently expose uterus and fetus selected for surgery (Figure 2F).</li>
	<li>Irrigate surgical field with warm (38 &#176;C) phosphate-buffered saline (PBS) using a blunt-tip needle 
	NOTE: One can be made by carefully bending the tip of a large-bore needle. (Figure 2G and 2H).</li>
	<li>Position the fetus in a manner that allows full access to dorsum.</li>
	<li>Pass a purse string stitch using 7-0 nylon suture through the uterus overlying the site of intended dorsal wounding (Figure 2I). Position purse string over a region of dorsum to the left or right of spinal cord, and in a region of uterine wall devoid of large blood vessels.</li>
	<li>Make a 3 mm incision through uterine wall and amniotic sac in the center of the purse string (Figure 2J).</li>
	<li>Irrigate incision site with warm (38 &#176;C) PBS.</li>
	<li>Using microsurgical scissors, cut a single full-thickness excisional wound, approximately 1 mm in length, in the dorsum of the fetus.</li>
	<li>Gently blot incision site dry with cotton-tip applicator.</li>
	<li>Inject 3 &#956;l volume India ink subcutaneously into the wound site to mark location of wound (Figure 2K).</li>
	<li>Irrigate with warm (38 &#176;C) PBS to ensure ink has been retained within wound site.</li>
	<li>Have surgical assistant inject warm (38 &#176;C) PBS through blunt-tip 10 G&#160;syringe into the amniotic sac as the purse string is closed ( Figure 2L). Retract syringe as purse string closure nears completion (Figure 2M).</li>
	<li>Gently return uterus into the abdominal cavity (Figure 2N).</li>
	<li>Evert skin and peritoneum.</li>
	<li>Have surgical assistant irrigate abdominal cavity with warm (38 &#176;C) PBS.</li>
	<li>Close abdomen quickly by stapling skin and peritoneum closed (Figure 2O).&#160;The standard closure is performed in two layers; peritoneum and abdominal muscle in one layer, subcutaneous tissue and skin in the second layer. For immediate sacrifice and harvesting of the fetus, our demonstration shows closure in one layer.</li>
	<li>Place the animal under observation in a warm incubator set at 37 &#176;C for 30 min&#160;or until the animal regains sufficient consciousness to maintain sternal recumbency.</li>
	<li>Do not return the animal to the company of other animals until it has fully recovered from the procedure.</li>
	<li>Upon awaking from anesthesia and during the subsequent 48 hr, administer subcutaneous injection of buprenorphine (0.05 mg/kg) every 12 hr for analgesia as needed based on pain assessment. Administer carprofen (5 mg/kg) via subcutaneous injection for additional post-operative pain relief as needed.</li>
	<li>Return animals to the cage and provide them with food and water ad libitum.</li>
	<li>Monitor closely for manifestations of pain.</li>
	<li>48 hr post-surgery, sacrifice pregnant mother with an overdose of isoflurane and harvest wounded fetus. In order to do this, adjust isoflurane concentration to 5% or higher and maintain exposure for 1 min after cessation of breathing. Confirm euthanasia with cervical dislocation. Harvest an unwounded embryo for age-matched control.&#160;Late embryos should have a separate method of euthanasia consistent with IACUC recommendations, such as decapitation, cervical dislocation, or chemical injection.</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/52297/52297fig2highres.jpg" /> 
Figure 2. Schematic for Murine Fetal Surgery.&#160;General steps for dorsal wounding in E16.5 and E18.5 mouse embryos. (A) Depilation of mouse abdomen. (B and C) Preparation of mouse abdomen. (D) Microscope used for surgical procedure. (E) Midline laparotomy. (F) Exposure of uterus. (G) Creation of blunt-tip needle. (H) Irrigation of uterus with warm saline. (I) Creation of purse string suture. (J) Incision through uterine wall and 1 mm full thickness excisional wound generation. (K) Subcutaneous injection of India ink. (L and M) Closure of purse string suture. (N and O) Closure of abdomen. <a href="https://www.jove.com/files/ftp_upload/52297/52297fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<ol>
	<li>Larson, B. J., Longaker, M. T., Lorenz, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scarless+fetal+wound+healing:+a+basic+science+review.">Scarless fetal wound healing: a basic science review.</a> Plastic and reconstructive surgery. 126, 1172-1180 (2010).</li><li>Wilgus, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regenerative+healing+in+fetal+skin:+a+review+of+the+literature.">Regenerative healing in fetal skin: a review of the literature.</a> Ostomy/wound management. 53, 16-31 (2007).</li><li>Wulff, B. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mast+cells+contribute+to+scar+formation+during+fetal+wound+healing.">Mast cells contribute to scar formation during fetal wound healing.</a> The Journal of investigative dermatology. 132, 458-465 (2012).</li><li>Lorenz, H. P., Adzick, N. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scarless+skin+wound+repair+in+the+fetus.">Scarless skin wound repair in the fetus.</a> The Western journal of medicine. 159, 350-355 (1993).</li><li>Longaker, M. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wound+healing+in+the+fetus.+Possible+role+for+inflammatory+macrophages+and+transforming+growth+factor-beta+isoforms.">Wound healing in the fetus. Possible role for inflammatory macrophages and transforming growth factor-beta isoforms.</a> Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society. 2, 104-112 (1994).</li><li>Longaker, M. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+in+fetal+wound+healing.+IV.+Hyaluronic+acid-stimulating+activity+distinguishes+fetal+wound+fluid+from+adult+wound+fluid.">Studies in fetal wound healing. IV. Hyaluronic acid-stimulating activity distinguishes fetal wound fluid from adult wound fluid.</a> Annals of surgery. 210, 667-672 (1989).</li><li>Colombo, J. A., Napp, M., Depaoli, J. R., Puissant, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trophic+influences+of+human+and+rat+amniotic+fluid+on+neural+tube-derived+rat+fetal+cells.">Trophic influences of human and rat amniotic fluid on neural tube-derived rat fetal cells.</a> International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience. 11, 347-355 (1993).</li><li>Colwell, A. S., Longaker, M. T., Peter Lorenz, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+differentially+regulated+genes+in+fetal+wounds+during+regenerative+repair.">Identification of differentially regulated genes in fetal wounds during regenerative repair.</a> Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society. 16, 450-459 (2008).</li><li>Hu, M. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+expression+in+fetal+murine+keratinocytes+and+fibroblasts.">Gene expression in fetal murine keratinocytes and fibroblasts.</a> The Journal of surgical research. , (2014).</li><li>Colwell, A. S., Krummel, T. M., Longaker, M. T., Lorenz, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+in+vivo+mouse+excisional+wound+model+of+scarless+healing.">An in vivo mouse excisional wound model of scarless healing.</a> Plastic and reconstructive surgery. 117, 2292-2296 (2006).</li><li>Wilgus, T. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+of+cyclooxygenase-2+mediated+inflammation+on+scarless+fetal+wound+healing.">The impact of cyclooxygenase-2 mediated inflammation on scarless fetal wound healing.</a> The American journal of pathology. 165, 753-761 (2004).</li><li>Iocono, J. A., Ehrlich, H. P., Keefer, K. A., Krummel, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyaluronan+induces+scarless+repair+in+mouse+limb+organ+culture.">Hyaluronan induces scarless repair in mouse limb organ culture.</a> Journal of pediatric surgery. 33, 564-567 (1998).</li><li>Chopra, V., Blewett, C. J., Krummel, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transition+from+fetal+to+adult+repair+occurring+in+mouse+forelimbs+maintained+in+organ+culture.">Transition from fetal to adult repair occurring in mouse forelimbs maintained in organ culture.</a> Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society. 5, 47-51 (1997).</li><li>Adzick, N. S., Longaker, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+for+the+study+of+fetal+tissue+repair.">Animal models for the study of fetal tissue repair.</a> The Journal of surgical research. 5, 47-51 (1991).</li><li>Block, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wound+healing+in+the+new-born+opossum+(Didelphis+virginianam).">Wound healing in the new-born opossum (Didelphis virginianam).</a> Nature. 187, 340-341 (1960).</li><li>Longaker, M. T., Dodson, T. B., Kaban, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rabbit+model+for+fetal+cleft+lip+repair.">A rabbit model for fetal cleft lip repair.</a> Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 48, 714-719 (1990).</li><li>Longaker, M. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+model+for+fetal+cleft+lip+repair+in+lambs.">A model for fetal cleft lip repair in lambs.</a> Plastic and reconstructive surgery. 90, 750-756 (1992).</li></ol>

The authors have nothing to disclose.

The surgical protocol presented here describes an excisional model of fetal murine scarless healing first published in 2006 by our laboratory10. In addition to other established models of excisional wounding11, incisional models of fetal murine scarless healing exist as well12,13. Investigations of fetal scarless wound healing in the monkey, lamb, rabbit, opossum, and rat have been reported14-17. However, mice represent an ideal model for exploring fetal scarless wound healing ...

Fetal skin wounds heal rapidly and scarlessly until late in gestation1. Fetal scarless wound repair is characterized by regeneration of normal tissue architecture and function. The transition from a scarless to scarring phenotype occurs in the third trimester of pregnancy in humans and around embryonic day 18 (E18) in mice2,3. In comparison to adult, fetal wound repair is characterized by rapid epithelialization, connective tissue deposition, and fibroblast migration.
Many studies have offered possible explanations for the phenomenon of scarless wound healing during early fetal development. Inflammation is a fundamental component of adult wound repair; however, fetal wounds are characterized by a lack of acute inflammation4. Whether this is a consequence of the functional immaturity of the immune system during fetal stages remains unclear. A recent study suggested that differences in the abundance, maturity, and function of mast cells in E15 vs. E18 fetal skin may be responsible for the transition from a scarless phenotype, at least in the mouse3. Other studies posit that differences in the properties and abundance of fetal and adult wound macrophages are responsible for the reformation of normal extracellular matrix (ECM) during fetal wound repair5.
Differences in environmental factors during fetal and adult development may also affect wound repair. Longaker and colleagues showed that wound fluid from the fetus possesses high levels of hyaluronic acid-stimulating activity compared to none in adult wound fluid6. Consequently, higher levels of hyaluronic acid, a glycosaminoglycan that promotes a microenvironment conducive to cell motility and proliferation, in the fetal wound environment may be responsible for the scarless phenotype seen during early fetal development. Other lines of evidence point to the fact that the fetal wound environment is relatively hypoxemic and submerged in sterile amniotic fluid rich in growth factors7. However, no definitive answer has been provided for a critical event or factor during embryogenesis that triggers the transition from scarless regeneration to fibrotic repair.
Understanding the mechanisms responsible for scarless healing in the fetus necessitates a precise and reproducible model. Here we detail a reproducible model of fetal scarless wound healing in the dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos. Additionally, minor variations of this model can be utilized to perform a number of further studies, such as gene expression analysis of fetal wounds and skin8,9. Given that precisely timed pregnancies are critical for successful recapitulation of this fetal scarless wound healing model, we also detail our protocol for superovulation timed pregnancies.

<table border="0" cellpadding="0" cellspacing="0" width="665">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:219px;">Name of Material/Equipment</td>
			<td style="width:184px;">Company</td>
			<td style="width:108px;">Catalog Number</td>
			<td style="width:155px;">Comments/Description</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">7-O MONOSOF Suture</td>
			<td>eSuture</td>
			<td>SN-1647G</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Surgical Forceps</td>
			<td>Kent Scientific</td>
			<td>INS650916</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Micro-scissors</td>
			<td>Kent Scientific</td>
			<td>INS600127</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Autoclip 9mm</td>
			<td>Texas Scientific Instruments</td>
			<td>205060</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Insulin Syringe</td>
			<td>Thermo Fisher Scientific</td>
			<td>22-272-382</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Black Pigment</td>
			<td>AIMS</td>
			<td>242</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">BD Safety-Lok 3ml Syringe</td>
			<td>BD Biosciences</td>
			<td>309596</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Phosphate Buffered Saline</td>
			<td>Life Technologies</td>
			<td>10010-049</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">OPMI-MD Surgical Microscope</td>
			<td>Carl Zeiss Surgical Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Pregnant Mares Serum (PMS)</td>
			<td>Millipore</td>
			<td>367222</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Human Chorionic Gonadotropin (HCG)</td>
			<td>Sigma-Aldrich</td>
			<td>CG10</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Povidone Iodine Prep Solution</td>
			<td>Dynarex</td>
			<td>1415</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Nair (depilatory cream)</td>
			<td>Church and Dwight Co.</td>
			<td>22600267058</td>
			<td></td>
		</tr>
	</tbody>
</table>

a mouse fetal skin model of scarless wound repair

Early in utero, but not in postnatal life, cutaneous wounds undergo regeneration and heal without formation of a scar. Scarless fetal wound healing occurs across species but is age dependent. The transition from a scarless to scarring phenotype occurs in the third trimester of pregnancy in humans and around embryonic day 18 (E18) in mice. However, this varies with the size of the wound with larger defects generating a scar at an earlier gestational age. The emergence of lineage tracing and other genetic tools in the mouse has opened promising new avenues for investigation of fetal scarless wound healing. However, given the inherently high rates of morbidity and premature uterine contraction associated with fetal surgery, investigations of fetal scarless wound healing in vivo require a precise and reproducible surgical model. Here we detail a reliable model of fetal scarless wound healing in the dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos.

For histologic analysis, cutaneous wounds in the dorsal skin of E16.5 and E18.5 mouse embryos should be harvested 48 hr post-wounding, fixed in 4% PFA, and paraffin-embedded. In fluorescent transgenic models, cryopreservation with OCT may be appropriate. There are several stains that may be used to visualize cellular and connective tissue architecture. Hematoxylin and eosin is a two-color stain that stains nuclei blue and eosinophilic structures (i.e., cytoplasm and extracellular collagen) various shades of red,...

Watch this Scientific Journal Video about A Mouse Fetal Skin Model of Scarless Wound Repair at JoVE.com

A Mouse Fetal Skin Model of Scarless Wound Repair

During mammalian development, early gestational skin wounds heal without a scar. Here we detail a reliable and reproducible model of fetal scarless wound healing in the cutaneous dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos.

Early in utero, but not in postnatal life, cutaneous wounds undergo regeneration and heal without formation of a scar. Scarless fetal wound healing occurs ...

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12.2K visualizações.  Stanford University School of Medicine. During mammalian development, early gestational skin wounds heal without a scar. Here we detail a reliable and reproducible model of fetal scarless wound healing in the cutaneous dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos.

Vídeo: A Mouse Fetal Skin Model of Scarless Wound Repair

A Contusive Model of Unilateral Cervical Spinal Cord Injury Using the Infinite Horizon Impactor

While the majority of human spinal cord injuries occur in the cervical spinal cord, the vast majority of laboratory research employs animal models of spinal cord injury (SCI) in which the thoracic spinal cord is injured. Additionally, because most human cord injuries occur as the result of blunt, non-penetrating trauma (e.g. motor vehicle accident, sporting injury) where the spinal cord is violently struck by displaced bone or soft tissues, the majority of SCI researchers are of the opinion that the most clinically relevant injury models are those in which the spinal cord is rapidly contused.1 Therefore, an important step in the preclinical evaluation of novel treatments on their way to human translation is an assessment of their efficacy in a model of contusion SCI within the cervical spinal cord. Here, we describe the technical aspects and resultant anatomical and behavioral outcomes of an unilateral contusive model of cervical SCI that employs the Infinite Horizon spinal cord injury impactor.
Sprague Dawley rats underwent a left-sided unilateral laminectomy at C5. To optimize the reproducibility of the biomechanical, functional, and histological outcomes of the injury model, we contused the spinal cords using an impact force of 150 kdyn, an impact trajectory of 22.5&deg; (animals rotated at 22.5&deg;), and an impact location off of midline of 1.4 mm. Functional recovery was assessed using the cylinder rearing test, horizontal ladder test, grooming test and modified Montoya's staircase test for up to 6 weeks, after which the spinal cords were evaluated histologically for white and grey matter sparing.
The injury model presented here imparts consistent and reproducible biomechanical forces to the spinal cord, an important feature of any experimental SCI model. This results in discrete histological damage to the lateral half of the spinal cord which is largely contained to the ipsilateral side of injury. The injury is well tolerated by the animals, but does result in functional deficits of the forelimb that are significant and sustained in the weeks following injury. The cervical unilateral injury model presented here may be a resource to researchers who wish to evaluate potentially promising therapies prior to human translation.

A reliable and repeatable way to produce a cervical unilateral spinal cord injury using the Infinite Horizon impactor is described. The method takes advantage of a custom designed frame and clamp to stabilize the spine. The standardized procedure and biomechanical injury parameters result in sufficient and sustained injuries.

While the majority of human spinal cord injuries occur in the cervical spinal cord, the vast majority of laboratory research employs animal models of ...

A Simplified Technique for Producing an Ischemic Wound Model

One major obstacle in current diabetic wound research is a lack of an ischemic wound model that can be safely used in diabetic animals. Drugs that work well in non-ischemic wounds may not work in human diabetic wounds because vasculopathy is one major factor that hinders healing of these wounds. We published an article in 2007 describing a rabbit ear ischemic wound model created by a minimally invasive surgical technique. Since then, we have further simplified the procedure for easier operation. On one ear, three small skin incisions were made on the vascular pedicles, 1-2 cm from the ear base. The central artery was ligated and cut along with the nerve. The whole cranial bundle was cut and ligated, leaving only the caudal branch intact. A circumferential subcutaneous tunnel was made through the incisions, to cut subcutaneous tissues, muscles, nerves, and small vessels. The other ear was used as a non-ischemic control. Four wounds were made on the ventral side of each ear. This technique produces 4 ischemic wounds and 4 non-ischemic wounds in one animal for paired comparisons. After surgery, the ischemic ear was cool and cyanotic, and showed reduced movement and a lack of pulse in the ear artery. Skin temperature of the ischemic ear was 1-10 &deg;C lower than that on the normal ear and this difference was maintained for more than one month. Ear tissue high-energy phosphate contents were lower in the ischemic ear than the control ear. Wound healing times were longer in the ischemic ear than in the non-ischemic ear when the same treatment was used. The technique has now been used on more than 80 rabbits in which 23 were diabetic (diabetes time ranging from 2 weeks to 2 years). No single rabbit has developed any surgical complications such as bleeding, infection, or rupture in the skin incisions. The model has many advantages, such as little skin disruption, longer ischemic time, and higher success rate, when compared to many other models. It can be safely used in animals with reduced resistance, and can also be modified to meet different testing requirements.

We have developed a minimally invasive technique to create a rabbit ischemic ear wound model by dividing the central artery and nerve and the cranial neurovascular bundle. A subcutaneous tunnel then cuts all subcutaneous tissues. This procedure causes minimal skin disruption and can be safely used in diabetic animals.

One major obstacle in current diabetic wound research is a lack of an ischemic wound model that can be safely used in diabetic animals. Drugs that work ...

Assessing Teratogenic Changes in a Zebrafish Model of Fetal Alcohol Exposure

Fetal alcohol syndrome (FAS) is a severe manifestation of embryonic exposure to ethanol. It presents with characteristic defects to the face and organs, including mental retardation due to disordered and damaged brain development. Fetal alcohol spectrum disorder (FASD) is a term used to cover a continuum of birth defects that occur due to maternal alcohol consumption, and occurs in approximately 4% of children born in the United States. With 50% of child-bearing age women reporting consumption of alcohol, and half of all pregnancies being unplanned, unintentional exposure is a continuing issue2. In order to best understand the damage produced by ethanol, plus produce a model with which to test potential interventions, we developed a model of developmental ethanol exposure using the zebrafish embryo. Zebrafish are ideal for this kind of teratogen study3-8. Each pair lays hundreds of eggs, which can then be collected without harming the adult fish. The zebrafish embryo is transparent and can be readily imaged with any number of stains. Analysis of these embryos after exposure to ethanol at different doses and times of duration and application shows that the gross developmental defects produced by ethanol are consistent with the human birth defect. Described here are the basic techniques used to study and manipulate the zebrafish FAS model.

In order to understand the molecular mechanisms of the ethanol-induced developmental damage, we have developed a zebrafish model of ethanol exposure and are exploring the physical, cellular, and genetic alterations that occur after ethanol exposure1. We then seek to find potential interventions and rapidly test them in this animal model.

Fetal alcohol syndrome (FAS) is a severe manifestation of embryonic exposure to ethanol. It presents with characteristic defects to the face and organs, ...

A Novel Surgical Approach for Intratracheal Administration of Bioactive Agents in a Fetal Mouse Model

Prenatal pulmonary delivery of cells, genes or pharmacologic agents could provide the basis for new therapeutic strategies for a variety of genetic and acquired diseases. Apart from congenital or inherited abnormalities with the requirement for long-term expression of the delivered gene, several non-inherited perinatal conditions, where short-term gene expression or pharmacological intervention is sufficient to achieve therapeutic effects, are considered as potential future indications for this kind of approach. Candidate diseases for the application of short-term prenatal therapy could be the transient neonatal deficiency of surfactant protein B causing neonatal respiratory distress syndrome1,2 or hyperoxic injuries of the neonatal lung3. Candidate diseases for permanent therapeutic correction are Cystic Fibrosis (CF)4, genetic variants of surfactant deficiencies5 and &alpha;1-antitrypsin deficiency6.
Generally, an important advantage of prenatal gene therapy is the ability to start therapeutic intervention early in development, at or even prior to clinical manifestations in the patient, thus preventing irreparable damage to the individual. In addition, fetal organs have an increased cell proliferation rate as compared to adult organs, which could allow a more efficient gene or stem cell transfer into the fetus. Furthermore, in utero gene delivery is performed when the individual's immune system is not completely mature. Therefore, transplantation of heterologous cells or supplementation of a non-functional or absent protein with a correct version should not cause immune sensitization to the cell, vector or transgene product, which has recently been proven to be the case with both cellular and genetic therapies7.
In the present study, we investigated the potential to directly target the fetal trachea in a mouse model. This procedure is in use in larger animal models such as rabbits and sheep8, and even in a clinical setting9, but has to date not been performed before in a mouse model. When studying the potential of fetal gene therapy for genetic diseases such as CF, the mouse model is very useful as a first proof-of-concept because of the wide availability of different transgenic mouse strains, the well documented embryogenesis and fetal development, less stringent ethical regulations, short gestation and the large litter size.
Different access routes have been described to target the fetal rodent lung, including intra-amniotic injection10-12, (ultrasound-guided) intrapulmonary injection13,14 and intravenous administration into the yolk sac vessels15,16 or umbilical vein17. Our novel surgical procedure enables researchers to inject the agent of choice directly into the fetal mouse trachea which allows for a more efficient delivery to the airways than existing techniques18.

We developed a novel surgical approach for intratracheal administration of bioactive agents into the mouse fetus. The delivery route is more efficient in targeting the fetal mouse lungs than the commonly used intra-amniotic injection. This procedure has to date not been described in a mouse model.

Prenatal pulmonary delivery of cells, genes or pharmacologic agents could provide the basis for new therapeutic strategies for a variety of genetic and ...

Murine Model of Wound Healing

Wound healing and repair are the most complex biological processes that occur in human life. After injury, multiple biological pathways become activated. Impaired wound healing, which occurs in diabetic patients for example, can lead to severe unfavorable outcomes such as amputation. There is, therefore, an increasing impetus to develop novel agents that promote wound repair. The testing of these has been limited to large animal models such as swine, which are often impractical. Mice represent the ideal preclinical model, as they are economical and amenable to genetic manipulation, which allows for mechanistic investigation. However, wound healing in a mouse is fundamentally different to that of humans as it primarily occurs via contraction. Our murine model overcomes this by incorporating a splint around the wound. By splinting the wound, the repair process is then dependent on epithelialization, cellular proliferation and angiogenesis, which closely mirror the biological processes of human wound healing. Whilst requiring consistency and care, this murine model does not involve complicated surgical techniques and allows for the robust testing of promising agents that may, for example, promote angiogenesis or inhibit inflammation. Furthermore, each mouse acts as its own control as two wounds are prepared, enabling the application of both the test compound and the vehicle control on the same animal. In conclusion, we demonstrate a practical, easy-to-learn, and robust model of wound healing, which is comparable to that of humans.

A murine model of cutaneous wound healing that can be used to assess therapeutic compounds in physiological and pathophysiological settings.

Wound healing and repair are the most complex biological processes that occur in human life. After injury, multiple biological pathways become activated. ...

Fetal Echocardiography and Pulsed-wave Doppler Ultrasound in a Rabbit Model of Intrauterine Growth Restriction

Fetal intrauterine growth restriction (IUGR) results in abnormal cardiac function that is apparent antenatally due to advances in fetoplacental Doppler ultrasound and fetal echocardiography. Increasingly, these imaging modalities are being employed clinically to examine cardiac function and assess wellbeing in utero, thereby guiding timing of birth decisions. Here, we used a rabbit model of IUGR that allows analysis of cardiac function in a clinically relevant way. Using isoflurane induced anesthesia, IUGR is surgically created at gestational age day 25 by performing a laparotomy, exposing the bicornuate uterus and then ligating 40-50% of uteroplacental vessels supplying each gestational sac in a single uterine horn. The other horn in the rabbit bicornuate uterus serves as internal control fetuses. Then, after recovery at gestational age day 30 (full term), the same rabbit undergoes examination of fetal cardiac function. Anesthesia is induced with ketamine and xylazine intramuscularly, then maintained by a continuous intravenous infusion of ketamine and xylazine to minimize iatrogenic effects on fetal cardiac function. A repeat laparotomy is performed to expose each gestational sac and a microultrasound examination (VisualSonics VEVO 2100) of fetal cardiac function is performed. Placental insufficiency is evident by a raised pulsatility index or an absent or reversed end diastolic flow of the umbilical artery Doppler waveform. The ductus venosus and middle cerebral artery Doppler is then examined. Fetal echocardiography is performed by recording B mode, M mode and flow velocity waveforms in lateral and apical views. Offline calculations determine standard M-mode cardiac variables, tricuspid and mitral annular plane systolic excursion, speckle tracking and strain analysis, modified myocardial performance index and vascular flow velocity waveforms of interest. This small animal model of IUGR therefore affords examination of in utero cardiac function that is consistent with current clinical practice and is therefore useful in a translational research setting.

We describe examination of fetal cardiac function with contemporary functional fetal echocardiography and fetoplacental Doppler ultrasound using the VisualSonics VEVO 2100 microultrasound in a surgically induced model of intrauterine fetal growth restriction in a rabbit.

Fetal intrauterine growth restriction (IUGR) results in abnormal cardiac function that is apparent antenatally due to advances in fetoplacental Doppler ...

A New Murine Model of Endovascular Aortic Aneurysm Repair

Endovascular aneurysm exclusion is a validated technique to prevent aneurysm rupture. Long-term results highlight technique limitations and new aspects of Abdominal aortic aneurysm (AAA) pathophysiology. There is no abdominal aortic aneurysm endograft exclusion model cheap and reproducible, which would allow deep investigations of AAA before and after treatment. We hereby describe how to induce, and then to exclude with a covered coronary stentgraft an abdominal aortic aneurysm in a rat. The well known elastase induced AAA model was first reported in 19901 in a rat, then described in mice2. Elastin degradation leads to dilation of the aorta with inflammatory infiltration of the abdominal wall and intra luminal thrombus, matching with human AAA. Endovascular exclusion with small covered stentgraft is then performed, excluding any interactions between circulating blood and the aneurysm thrombus. Appropriate exclusion and stentgraft patency is confirmed before euthanasia by an angiography thought the left carotid artery. Partial control of elastase diffusion makes aneurysm shape different for each animal. It is difficult to create an aneurysm, which will allow an appropriate length of aorta below the aneurysm for an easy stentgraft introduction, and with adequate proximal and distal neck to prevent endoleaks. Lots of failure can result to stentgraft introduction which sometimes lead to aorta tear with pain and troubles to stitch it, and endothelial damage with post op aorta thrombosis. Giving aspirin to rats before stentgraft implantation decreases failure rate without major hemorrhage. Clamping time activates neutrophils, endothelium and platelets, and may interfere with biological analysis.

Histological and biochemical modifications after aneurysm endograft exclusion are still unclear. We describe a new model of endograft implantation on a murine aneurysm. Through thrombus analysis with and without persistant circulating blood stream interface, and new endovascular biomaterials evaluation, this model will help to better understand endovascular aneurysm exclusion pathobiology.

Endovascular aneurysm exclusion is a validated technique to prevent aneurysm rupture. Long-term results highlight technique limitations and new aspects of ...

Ischemic Tissue Injury in the Dorsal Skinfold Chamber of the Mouse: A Skin Flap Model to Investigate Acute Persistent Ischemia

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are still occurring, particularly in reconstructive flap surgery. Multiple experimental flap models have been developed to analyze underlying causes and mechanisms and to investigate treatment strategies to prevent ischemic complications. The limiting factor of most models is the lacking possibility to directly and repetitively visualize microvascular architecture and hemodynamics. The goal of the protocol was to present a well-established mouse model affiliating these before mentioned lacking elements. Harder et al. have developed a model of a musculocutaneous flap with a random perfusion pattern that undergoes acute persistent ischemia and results in ~50% necrosis after 10 days if kept untreated. With the aid of intravital epi-fluorescence microscopy, this chamber model allows repetitive visualization of morphology and hemodynamics in different regions of interest over time. Associated processes such as apoptosis, inflammation, microvascular leakage and angiogenesis can be investigated and correlated to immunohistochemical and molecular protein assays. To date, the model has proven feasibility and reproducibility in several published experimental studies investigating the effect of pre-, peri- and postconditioning of ischemically challenged tissue.

The window of the murine dorsal skinfold chamber presented visualizes a zone of acute persistent ischemia of a musculocutaneous flap. Intravital epi-fluorescence microscopy permits for direct and repetitive assessment of the microvasculature and quantification of hemodynamics. Morphologic and hemodynamic results can further be correlated with histological and molecular analyses.

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are ...

A Surgical Procedure for Resecting the Mouse Rib: A Model for Large-Scale Long Bone Repair

This protocol introduces researchers to a new model for large-scale bone repair utilizing the mouse rib. The procedure details the following: preparation of the animal for surgery, opening the thoracic body wall, exposing the desired rib from the surrounding intercostal muscles, excising the desired section of rib without inducing a pneumothorax, and closing the incisions. Compared to the bones of the appendicular skeleton, the ribs are highly accessible. In addition, no internal or external fixator is necessary since the adjacent ribs provide a natural fixation. The surgery uses commercially available supplies, is straightforward to learn, and well-tolerated by the animal. The procedure can be carried out with or without removing the surrounding periosteum, and therefore the contribution of the periosteum to repair can be assessed. Results indicate that if the periosteum is retained, robust repair occurs in 1 - 2 months. We expect that use of this protocol will stimulate research into rib repair and that the findings will facilitate the development of new ways to stimulate bone repair in other locations around the body.

The overall goal of this procedure is to successfully resect a portion of bone from the rib of a mouse. The procedure was developed as a model to study large-scale long bone repair.

This protocol introduces researchers to a new model for large-scale bone repair utilizing the mouse rib. The procedure details the following: preparation ...

Demonstration of the Rat Ischemic Skin Wound Model

The propensity for chronic wounds in humans increases with ageing, disease conditions such as diabetes and impaired cardiovascular function, and unrelieved pressure due to immobility. Animal models have been developed that attempt to mimic these conditions for the purpose of furthering our understanding of the complexity of chronic wounds. The model described herein is a rat ischemic skin flap model that permits a prolonged reduction of blood flow resulting in wounds that become ischemic and resemble a chronic wound phenotype (reduced vascularization, increased inflammation and delayed wound closure). It consists of a bipedicled dorsal flap with 2 ischemic wounds placed centrally and 2 non-ischemic wounds lateral to the flap as controls. A novel addition to this ischemic skin flap model is the placement of a silicone sheet beneath the flap that functions as a barrier and a splint to prevent revascularization and reduce contraction as the wounds heal. Despite the debate of using rats for wound healing studies due to their quite distinct anatomic and physiologic differences compared to humans (i.e., the presence of a panniculus carnosus muscle, short life-span, increased number of hair follicles, and their ability to heal infected wounds) the modifications employed in this model make it a valuable alternative to previously developed ischemic skin flap models.

The rat, due to its size, availability, and rather docile behavior, has been utilized as a research model for many years. The goal of this protocol is to utilize the rat as an ischemic skin wound healing model to provide valuable insight into the pathophysiology of chronic wounds.

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Subtitles

A Mouse Fetal Skin Model of Scarless Wound Repair