This protocol was tested and optimized in the laboratory of Dr. David Scadden. Funding is provided by the Dana Farber Cancer Institute/Massachusetts General Hospital Clinical Hematology and Oncology Fellowship Program.

<ol>
<li> We begin the homing experiment by extracting cells to be used in the experiment. For this current experiment we are interested in finding out if the homing of whole bone marrow to the niches in the long bones of recipient animals is different for bone marrow cells extracted from WT animals such as C57BL/6J (WT) and those that are transgenic knockouts for Lysophosphatidic Receptor 1 (LPAR1) (KO).</li>
<li>Before we start the experiment, we will collect the materials we need for this experiment. In our lab all mouse dissections are carried out in a laminar flow tissue culture hood especially if the cells are going to be transplanted into a recipient animal instead of being used for ex-vivo analysis. We start by placing a blue sheet inside the hood. Other objects needed include a pair of forceps and a sharp pair of scissors which have been autoclaved , a sterile disposable scalpel and alcohol swabs. We will need modified PBS and a sterile 6 well plate, a mortar, pestle, 50cc blue topped conical tube and a 70uM disposable filter.</li>
<li>We start by taking one WT and one KO mouse.</li>
<li>These mice are euthanized by CO2 inhalation and then dipped in 70% isopropranolol for 5 seconds. This step prevents contamination of the cells of interest with mouse fur and in our hands has not led to any compromise in yield of cells or experimental results.</li>
<li>The mice are then dissected in turn using a pair of forceps and sharp scissors. We usually start with the WT mouse as a matter of routine. A small snip is made in the ventral skin of the mouse overlying the abdomen and the skin is then stretched using the hands. The skin comes off the hind limbs easily. The femur and tibia are then extracted taking care not to dislodge the head of the femur as this contains a large amount of bone marrow. The upper limbs are detached from the animal&rsquo;s torso by simply applying traction to them while keeping the torso immobile. This removes the upper limbs as one piece. The humeri are then extracted from the upper limbs.</li>
<li>The removed bones are placed in modified PBS which has been added to 6 well plates. Modified PBS is made by adding 2 ml of heat inactivated Fetal Bovine Serum and 2 cc of EDTA 0.5 M pH8. This solution is then filtered through a Nalgene 0.45 uM filter and can be stored at 4 degrees Celcius for at least a month.</li>
<li>It is essential to label the wells in the plate in order to be able to identify WT and KO bones correctly.</li>
<li>The mouse carcasses are removed and disposed off.</li>
<li>A new sheet is placed in the hood and the bones are cleaned using a disposable scalpel.</li>
<li>The cleaned bones are placed one mouse at a time in the mortar. Two ml of modified PBS is added to the mortar and the bones are crushed using a pestle. It is important to first fragment the bones with 10 to and fro movements of the pestle and then pulverize them with circular rotatory movements. I usually do 50 clockwise, then 50 counterclockwise movements and so on until the material left in the mortar is white in color and the modified PBS added to the material remains white or transparent.</li>
<li>After every set of 50 circular crushing movements, we transfer the fluid from the mortar to a 70 uM filter placed on top of a 50 ml conical tube. Do not forget to add 2 ml of PBS to the mortar after every transfer to the filter. You do not want to try and pulverize dry bones or leave them dry for any length of time as this will lead to apoptosis of cells.</li>
<li>Once the material in the mortar becomes white, the material in the filter is transferred to the mortar and the crushing is again performed. This ensures that the cells in the filter are not wasted. Usually it takes one or two sets of circular rotatory movements to again make the material in the mortar white in color at which time the extraction of cells is complete.</li>
<li>The solution in the conical tube is now centrifuged (please remember to keep the cells from the WT and KO mouse separate. Hence you will have two different tubes (one with WT cells, the other with KO cells). Centrifuge at 1200 rpm for 10 minutes.</li>
<li>Aspirate off the supernatant using separate aspirator pipettes for each tube. Add 2 cc of ACK lysis buffer to each pellet. This lysis buffer should be sterile. Incubate on ice for 5 minutes.</li>
<li>Add 8 cc of modified PBS to each tube. Take 10 ul from each tube and pipette into two separate wells in a 96 well plate. Place the tubes in the centrifuge and spin them at 1200 rpm for 10 minutes.</li>
<li>While the tubes are spinning, add 30 ul of tryphan blue dye and 60 ul of modified PBS to each well of the 96 well plate that carries the cells of interest.</li>
<li>Add 10 ul of this mixture (please mix well by pipetting up and down) to a hemocytometer and count the cells in the four outer squares.</li>
<li>The cell count in each sample per ml is the number of cells thus counted divided by 4 and multiplied by 100 000.</li>
<li>Once the centrifugation is complete, remove the tubes from the centrifuge and resuspend the cells in PBS without calcium, magnesium or L glutamine at a concentration of 20 million cells per ml. You will likely have about 5 ml of volume for the WT and 5 ml of volume for the KO animal. From this step onward we will be using PBS, not modified PBS for the protocol.</li>
<li>To each tube add DiI, a cell staining dye, to achieve a final concentration of 5uM. Vortex immediately for 10 seconds. Incubate at 37 degrees for 10 minutes and avoid exposure to light.</li>
<li>Fill the tubes with PBS and spin for 10 minutes at 1200 rpm.</li>
<li>After centrifugation, aspirate the supernatant and resuspend the cells in PBS at 40 million cells per ml.</li>
<li>Load 500 ul into 1 cc syringes with a 27G needle (5 syringes for the WT mouse and 5 syringes for the KO mice). It may be prudent to prepare 6 syringes for each cohort. Having one extra can help as tail vein injections which we are going to do next can be tricky.</li>
<li>Cover the syringes with foil in order to keep the DiI from disintegrating.</li>
<li>Inject 500 ul of the cell mixture into each recipient animal; (5 for each cohort).</li>
<li>These animals need to be irradiated with 9 Gy of irradiation 4-24 hours prior to injection.</li>
<li>48 hours after injection, harvest bone marrow from the hind limbs of each recipient animal.</li>
<li>Process as described above for the donors. Resuspend the cells from each animal in 1 cc of PBS. Obtain a cell count using a hemacytometer.</li>
<li>Read on the LSR II flow cytometer from BD or an equivalent instrument. The result can be expressed as the percentage or absolute number of cells in the analyzed bone marrow which are DiI positive.</li>
</ol>

<ol>
	<li>Adams, G. B., 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=Stem+cell+engraftment+at+the+endosteal+niche+is+specified+by+the+calcium-sensing+receptor.">Stem cell engraftment at the endosteal niche is specified by the calcium-sensing receptor.</a> Nature. 439 (7076), 599-603 (2006).</li><li>Broxmeyer, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemokines+in+hematopoiesis.">Chemokines in hematopoiesis.</a> Curr Opin Hematol. 15 (1), 49-58 (2008).</li></ol>

Homing is the process whereby bone marrow cells including stem cells, progenitor cells and differentiated cells, their way into the bone marrow after being injected into the blood stream or bone marrow cavity of mice. As is obvious from the definition, a scientist may chose to study the homing of hematopoietic stem cells, progenitor cells or differentiated cells identified by immunophenotyping and isolated by cell sorting. Typically scientists inject bone marrow cells depleted for lineage markers and hence enriched for...

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		<th>Material Name</th>
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		<th>Comment</th>
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<td>DPBS (Dulbecco&#x2019;s Phosphate Buffered Saline</td>
<td>&nbsp;</td>
<td>Mediatech, Inc</td>
<td>21-031-CV</td>
<td>&nbsp;</td>
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<td>Sterile Fetal Bovine Serum</td>
<td>&nbsp;</td>
<td>Valley Biomedical, Inc</td>
<td>BS3033</td>
<td>&nbsp;</td>
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<td>0.5M EDTA (pH 8.0)</td>
<td>&nbsp;</td>
<td>Boston BioProducts</td>
<td>BM-150</td>
<td>&nbsp;</td>
<tr>
<td>Tryphan Blue solution</td>
<td>&nbsp;</td>
<td>Mediatech, Inc</td>
<td>25-900-CI</td>
<td>&nbsp;</td>
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<td>ACK Lysing Buffer</td>
<td>&nbsp;</td>
<td>Lonza</td>
<td>10-548E</td>
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<td>Isopropranolol U.S.P.</td>
<td>&nbsp;</td>
<td>Denison Pharmaceuticals, Inc</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
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<td>Vybrant DiD cell-labelling solution</td>
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<td>Invitrogen</td>
<td>V22887</td>
<td>&nbsp;</td>
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<td>Vybrant DiI cell-labelling solution</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
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homing of hematopoietic cells to the bone marrow

Homing is the phenomenon whereby transplanted hematopoietic cells are able to travel to and engraft or establish residence in the bone marrow. Various chemomkines and receptors are involved in the homing of hematopoietic stem cells. [1, 2]
This paper outlines the classic homing protocol used in hematopoietic stem cell studies. In general this involves isolating the cell population whose homing needs to be investigated, staining this population with a dye of interest and injecting these cells into the blood stream of a recipient animal. The recipient animal is then sacrificed at a pre-determined time after injection and the bone marrow evaluated for the percentage or absolute number of cells which are positive for the dye of interest. In one of the most common experimental schemes, the homing efficiency of hematopoietic cells from two genetically distinct animals (a wild type animal and the corresponding knock-out) is compared. This article describes the hematopoietic cell homing protocol in the framework of such as experiment.

Watch this Scientific Journal Video about Homing of Hematopoietic Cells to the Bone Marrow at JoVE.com

Homing of Hematopoietic Cells to the Bone Marrow

This article describes a protocol used to study the homing of hematopoietic cells to their niches in the bone marrow.

Homing is the phenomenon whereby transplanted hematopoietic cells are able to travel to and engraft or establish residence in the bone marrow.  Various ...

homing-of-hematopoietic-cells-to-the-bone-marrow

Research

JoVE Journal

Biology

29.4K Views.  MGH - Massachusetts General Hospital. מאמר זה מתאר פרוטוקול המשמש ללימוד ביות של תאים hematopoietic אל נישות שלהם במח העצם.

Video: Homing of Hematopoietic Cells to the Bone Marrow

Isolation and Analysis of Hematopoietic Stem Cells from the Placenta

Hematopoietic stem cells (HSCs) have the ability to self-renew and generate all cell types of the blood lineages throughout the lifetime of an individual. All HSCs emerge during embryonic development, after which their pool size is maintained by self-renewing cell divisions. Identifying the anatomical origin of HSCs and the critical developmental events regulating the process of HSC development has been complicated as many anatomical sites participate during fetal hematopoiesis. Recently, we identified the placenta as a major hematopoietic organ where HSCs are generated and expanded in unique microenvironmental niches (Gekas, et al 2005, Rhodes, et al 2008). Consequently, the placenta is an important source of HSCs during their emergence and initial expansion.
In this article, we show dissection techniques for the isolation of murine placenta from E10.5 and E12.5 embryos, corresponding to the developmental stages of initiation of HSCs and the peak in the size of the HSC pool in the placenta, respectively. In addition, we present an optimized protocol for enzymatic and mechanical dissociation of placental tissue into single-cell suspension for use in flow cytometry or functional assays. We have found that use of collagenase for single-cell suspension of placenta gives sufficient yields of HSCs. An important factor affecting HSC yield from the placenta is the degree of mechanical dissociation prior to, and duration of, enzymatic treatment.
We also provide a protocol for the preparation of fixed-frozen placental tissue sections for the visualization of developing HSCs by immunohistochemistry in their precise cellular niches. As hematopoietic specific antigens are not preserved during preparation of paraffin embedded sections, we routinely use fixed frozen sections for localizing placental HSCs and progenitors.

We have identified the placenta as a major hematopoietic organ during development. We found that hematopoietic stem cells (HSCs) are both generated and expanded in the placenta in unique microenvironmental niches. Here, we describe experimental techniques required for isolation and visualization of HSCs in the mouse placenta.

Hematopoietic stem cells (HSCs) have the ability to self-renew and generate all cell types of the blood lineages throughout the lifetime of an individual. ...

Culture of myeloid dendritic cells from bone marrow precursors

Myeloid dendritic cells (DCs) are frequently used to study the interactions between innate and adaptive immune mechanisms and the early response to infection. Because these are the most potent antigen presenting cells, DCs are being increasingly used as a vaccine vector to study the induction of antigen-specific immune responses. In this video, we demonstrate the procedure for harvesting tibias and femurs from a donor mouse, processing the bone marrow and differentiating DCs in vitro. The properties of DCs change following stimulation: immature dendritic cells are potent phagocytes, whereas mature DCs are capable of antigen presentation and interaction with CD4+ and CD8+ T cells. This change in functional activity corresponds with the upregulation of cell surface markers and cytokine production. Many agents can be used to mature DCs, including cytokines and toll-like receptor ligands. In this video, we demonstrate flow cytometric comparisons of expression of two co-stimulatory molecules, CD86 and CD40, and the cytokine, IL-12, following overnight stimulation with CpG or mock treatment. After differentiation, DCs can be further manipulated for use as a vaccine vector or to generate antigen-specific immune responses by in vitro pulsing using peptides or proteins, or transduced using recombinant viral vectors. 

This video demonstrates the procedure for differentiating myeloid dendritic cells from mouse bone marrow. Isolation of mouse tibia and femur, and processing of bone marrow are demonstrated. Pictures demonstrating cell morphology before and after differentiation, and figures depicting cell phenotype and IL-12 production following maturation using CpG are shown.

Myeloid dendritic cells (DCs) are frequently used to study the interactions between innate and adaptive immune mechanisms and the early response to ...

Generation of Bone Marrow Derived Murine Dendritic Cells for Use in 2-photon Imaging

Several methods for the preparation of murine dendritic cells can be found in the literature. Here, we present a method that produces greater than 85% CD11c high dendritic cells in culture that home to the draining lymph node after subcutaneous injection and present antigen to antigen specific T cells (see video). Additionally, we use Essen Instruments Incucyte to track dendritic cell maturation, where, at day 10, the morphology of the cultured cells is typical of a mature dendritic cell and &lt;85% of cells are CD11chigh. The study of antigen presentation in peripheral lymph nodes by 2-photon imaging revealed that there are three distinct phases of dendritic cell and T cell interaction1, 2. Phase I consists of brief serial contacts between highly motile antigen specific T cells and antigen carrying dendritic cells1, 2. Phase two is marked by prolonged contacts between antigen-specific T cell and antigen bearing dendritic cells1, 2. Finally, phase III is characterized by T cells detaching from dendritic cells, regaining motility and beginning to divide1, 2. This is one example of the type of antigen-specific interactions that can be analyzed by two-photon imaging of antigen-loaded cell tracker dye-labeled dendritic cells.

Antigen presentation in secondary lymphoid organs by dendritic cells is crucial for the initiation of the T cell mediated adaptive immune response. Here we demonstrate the culture of bone marrow derived murine dendritic cells, activation, and labeling for 2-photon imaging.

Several methods for the preparation of murine dendritic cells can be found in the literature. Here, we present a method that produces greater than 85% ...

The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell  electroporation system and Gene Pulser  electroporation buffer were specifically developed to transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells.This video demonstrates how to establish primary hematopoietic cell cultures from murine bone marrow, and then prepare them for electroporation in the MXcell system. We begin by isolating femur and tibia. Bone marrow from both femur and tibia are then harvested and cultures are established. Cultured bone marrow cells are then transfected and analyzed.

This procedure describes how to establish primary hematopoietic cell cultures from murine bone marrow and is followed by transfection using the Gene Pulser MXCell electroporation system.

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser ...

Lentiviral-mediated Knockdown During Ex Vivo Erythropoiesis of Human Hematopoietic Stem Cells

Erythropoiesis is a commonly used model system to study cell differentiation. During erythropoiesis, pluripotent adult human hematopoietic stem cells (HSCs) differentiate into oligopotent progenitors, committed precursors and mature red blood cells 1. This process is regulated for a large part at the level of gene expression, whereby specific transcription factors activate lineage-specific genes while concomitantly repressing genes that are specific to other cell types 2. Studies on transcription factors regulating erythropoiesis are often performed using human and murine cell lines that represent, to some extent, erythroid cells at given stages of differentiation 3-5. However transformed cell lines can only partially mimic erythroid cells and most importantly they do not allow one to comprehensibly study the dynamic changes that occur as cells progress through many stages towards their final erythroid fate. Therefore, a current challenge remains the development of a protocol to obtain relatively homogenous populations of primary HSCs and erythroid cells at various stages of differentiation in quantities that are sufficient to perform genomics and proteomics experiments.
Here we describe an ex vivo cell culture protocol to induce erythroid differentiation from human hematopoietic stem/progenitor cells that have been isolated from either cord blood, bone marrow, or adult peripheral blood mobilized with G-CSF (leukapheresis). This culture system, initially developed by the Douay laboratory 6, uses cytokines and co-culture on mesenchymal cells to mimic the bone marrow microenvironment. Using this ex vivo differentiation protocol, we observe a strong amplification of erythroid progenitors, an induction of differentiation exclusively towards the erythroid lineage and a complete maturation to the stage of enucleated red blood cells. Thus, this system provides an opportunity to study the molecular mechanism of transcriptional regulation as hematopoietic stem cells progress along the erythroid lineage. 
Studying erythropoiesis at the transcriptional level also requires the ability to over-express or knockdown specific factors in primary erythroid cells. For this purpose, we use a lentivirus-mediated gene delivery system that allows for the efficient infection of both dividing and non-dividing cells 7. Here we show that we are able to efficiently knockdown the transcription factor TAL1 in primary human erythroid cells. In addition, GFP expression demonstrates an efficiency of lentiviral infection close to 90%. Thus, our protocol provides a highly useful system for characterization of the regulatory network of transcription factors that control erythropoiesis.

Lentiviral-mediated Knockdown During Ex Vivo Erythropoiesis of Human Hematopoietic Stem Cells

An ex vivo protocol to generate mature human red blood cells from hematopoietic stem/progenitors is described. Additionally we describe an efficient lentiviral-delivery method to knockdown the transcription factor TAL1 in primary erythroid cells. The efficiency of lentivirus mediated gene delivery is demonstrated using GFP expressing viruses.

Erythropoiesis is a commonly used model system to study cell differentiation. During erythropoiesis, pluripotent adult human hematopoietic stem cells ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Osteoclast Derivation from Mouse Bone Marrow

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease.
As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation.
An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. 
Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.

Osteoclasts are the principal bone-resorbing cell in the body. An ability to isolate osteoclasts in large numbers has resulted in significant advances in the understanding of osteoclast biology. In this protocol, we describe a method for isolation, cultivating and quantifying osteoclast activity in vitro.

Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the ...

Expression of Fluorescent Fusion Proteins in Murine Bone Marrow-derived Dendritic Cells and Macrophages

Dendritic cells and macrophages are crucial cells that form the first line of defense against pathogens. They also play important roles in the initiation of an adaptive immune response. Experimental work with these cells is rather challenging. Their abundance in organs and tissues is relatively low. As a result, they cannot be isolated in large numbers. They are also difficult to transfect with cDNA constructs. In the murine model, these problems can be partially overcome by in vitro differentiation from bone marrow progenitors in the presence of M-CSF for macrophages or GM-CSF for dendritic cells. In this way, it is possible to obtain large amounts of these cells from very few animals. Moreover, bone marrow progenitors can be transduced with retroviral vectors carrying cDNA constructs during early stages of cultivation prior to their differentiation into bone marrow derived dendritic cells and macrophages. Thus, retroviral transduction followed by differentiation in vitro can be used to express various cDNA constructs in these cells. The ability to express ectopic proteins substantially extends the range of experiments that can be performed on these cells, including live cell imaging of fluorescent proteins, tandem purifications for interactome analyses, structure-function analyses, monitoring of cellular functions with biosensors and many others. In this article, we describe a detailed protocol for retroviral transduction of murine bone marrow derived dendritic cells and macrophages with vectors coding for fluorescently-tagged proteins. On the example of two adaptor proteins, OPAL1 and PSTPIP2, we demonstrate its practical application in flow cytometry and microscopy. We also discuss the advantages and limitations of this approach.

In this article, we provide a detailed protocol for the expression of fluorescent fusion proteins in murine bone marrow derived dendritic cells and macrophages. The method is based on the transduction of bone marrow progenitors with retroviral constructs followed by differentiation into macrophages and dendritic cells in vitro.

Dendritic cells and macrophages are crucial cells that form the first line of defense against pathogens. They also play important roles in the initiation ...

Isolation, Purification, and Differentiation of Osteoclast Precursors from Rat Bone Marrow

Osteoclasts are large, multinucleated, and bone-resorbing cells of the monocyte-macrophage lineage that are formed by the fusion of monocytes or macrophage precursors. Excessive bone resorption is one the most significant cellular mechanisms leading to osteolytic diseases, including osteoporosis, periodontitis, and periprosthetic osteolysis. The main physiological function of osteoclasts is to absorb both the hydroxyapatite mineral component and the organic matrix of bone, generating the characteristic resorption appearance on the surface of bones. There are relatively few osteoclasts compared to other cells in the body, especially in adult bones. Recent studies have focused on how to obtain more mature osteoclasts in less time, which has always been a problem. Several improvements in the isolation and culture techniques have developed in laboratories in order to obtain more mature osteoclasts. Here, we introduce a method that isolates bone marrow in less time and with less effort compared to the traditional procedure, using a special and simple device. With the use of density gradient centrifugation, we obtain large amounts of fully differentiated osteoclasts from rat bone marrow, which are identified by classical methods.

Osteoclasts are tissue-specific macrophage polykaryons derived from the monocyte-macrophage lineage of hematopoietic stem cells. This protocol describes how to isolate bone marrow cells so that large quantities of osteoclasts are obtained while reducing the risk of accidents found in traditional methods.

Osteoclasts are large, multinucleated, and bone-resorbing cells of the monocyte-macrophage lineage that are formed by the fusion of monocytes or ...

Proplatelet Formation Dynamics of Mouse Fresh Bone Marrow Explants

The last stage of megakaryopoiesis leads to cytoplasmic extensions from mature megakaryocytes, the so-called proplatelets. Much has been learned about the proplatelet formation using in vitro-differentiated megakaryocytes; however, there is an increasing evidence that conventional culture systems do not faithfully recapitulate the differentiation/maturation process that takes places inside the bone marrow. In this manuscript, we present an explant method initially described in 1956 by Thi&#233;ry and Bessis to visualize megakaryocytes which have matured in their native environment, thus circumventing potential artifacts and misinterpretations. Fresh bone marrows are collected by flushing the femurs of mice, sliced into 0.5 mm cross sections, and placed in an incubation chamber at 37 &#176;C containing a physiological buffer. Megakaryocytes become gradually visible at the explant periphery and are observed up to 6 hours under an inverted microscope coupled to a video camera. Over time, megakaryocytes change their shape, with some cells having a spherical form and others developing thick extensions or extending many thin proplatelets with extensive branching. Both qualitative and quantitative investigations are carried out. This method has the advantage of being simple, reproducible, and fast as numerous megakaryocytes are present, and classically half of them form proplatelets in 6 hours compared to 4 days for cultured mouse megakaryocytes. In addition to the study of mutant mice, an interesting application of this method is the straightforward evaluation of the pharmacological agents on the proplatelet extension process, without interfering with the differentiation process that may occur in cultures.

Here, we detail the bone marrow explant method, from sample preparation to microscopic slide analysis, to evaluate the ability of megakaryocytes which have differentiated in their physiological environment to form proplatelets.

The last stage of megakaryopoiesis leads to cytoplasmic extensions from mature megakaryocytes, the so-called proplatelets. Much has been learned about the ...