We would like to thank Philippa Warren for her kind help.

1. Boundary Assay:
<ol>
<li>Basic preparation: Chamber slides are coated with Poly-D-Lysine overnight and sterile glass slides are prepared before starting the experiment. Medium is prepared using Dulbecco's Modified Eagle's Medium (DMEM), supplemented with 10% fetal calf serum (FCS), and 1% Penicillin-Streptomycin-Fungizon(PSF). Also a bottle of Calcium/Magnesium free Hanks balanced salt solution (HBSS) is prepared.</li>
<li>Primary rat Schwann cells cultured in flask are trypsinized for 3 minutes using 0.1% Trypsin. Primary rat astrocyte culture is trypsinized for 5 minutes using 0.1% trypsin. 
Trypsin is inactived by adding DMEM supplemented with 10% FCS and 1% PSF.</li>
<li>Trypsinized Schwann cells and astrocytes are transferred to separate 15 mL falcon tubes and centrifuged at 300G for 5 minutes.</li>
<li>Schwann cells and astrocytes are re-suspended at the density of 2 x 106 (see representative results section for variations in cell density).</li>
<li>50 &mu;L drop of Schwann cell suspension is placed at one end of PDL coated chamber slide wells. A glass strip was used to smear the drop towards the centre of the chamber to generate a straight edge. (Using a glass cutter, a rectangular glass coverslips are cut longitudinally so that it would fit the width of chamber slides used for boundary assays)</li>
<li>A second drop of 50 &mu;L of astrocyte suspension was placed at the opposite end of the same well and smeared towards the centre to create a straight edge parallel to the first drop smear with a small 0.2mm gap between them.</li>
<li>The chamber slides containing the drops are placed in the incubator at 37&deg;C for 2 hours.</li>
<li>After 2 hours, cultures were washed with DMEM to remove non-attached cellular debris and fresh medium containing DMEM/ 10%FCS/ 1% PSF added. 
Note: DMEM/ 10%FCS/ 1% PSF can be supplemented with forskolin (2&mu;M) and Bovine pituitary extract (BPE) (10&mu;g/ mL) stimulate Schwann cell proliferation. BPE will supply the growth factors necessary to allow long term Schwann cell culture and forskolin raises the cyclic adenosine monophosphate levels within the Schwann cells to induce proliferation</li>
<li>Cells are cultured for approximately 8-10 days at 37&deg;C , 7% CO2 incubator. The medium requires to be changed every 3 days. The two cell fronts will eventually reach each other and a sharp boundary will form between the two cell types. At this stage experiments can be carried out analyzing factors involved in boundary formation.</li>
<li>Co-culture can be fixed using 4% formaldehyde and Schwann cells can be immunostained with anti-P75 antibody and astrocytes with anti-GFAP antibodies to identify the cells in co-culture. P75 antibody recognizes low affinity NGF receptor on Schwann cells which astrocytes lack. Anti-GFAP antibody recognizes glial firbrillary acidic protein which localizes to astrocyte cytoplasm. (Please see Figure 1A for representative boundary)</li>
</ol>
2. Migration Assay:
<ol>
<li>4 well plates (15mm wells) are PDL coated overnight and prepared for creating astrocyte monolayers.</li>
<li>Primary astrocyte culture is trypsinized for 5 minutes using 0.1% trypsin.
Trypsin is inactivated by adding DMEM supplemented with 10% FCS and 1% PSF and cell centrifuged at 300G for 5 minutes. (See Figure 2)</li>
<li>Astrocytes are re-suspended at 1x105 cells/ mL. 1 mL of this solution is added to each PDL coated well in 4 well plates. Astrocytes are cultured for 24-48 hours until the monolayer is completely confluent.</li>
<li>To assess Schwann cell migration on astrocyte monolayers, parallel to creating astrocyte monolayers, circular PDL-coated glass coverslips are placed in a 50 mL tube and crushed using a plastic pipette to create small fragments of glass.</li>
<li>Glass fragments are transferred into a well in 6 well plate dish and using forceps suitable sized fragments are chosen and placed in other wells. 5 glass fragments are placed in each well in 6 well plates.</li>
<li>Primary Schwann cells cultured in flask are trypsinized for 3 minutes using 0.1% trypsin. Trypsinized Schwann cells are transferred to separate 15 mL falcon tube and centrifuged at 300 G for 5 minutes. Schwann cells are re-suspended at 2x 106 cells/ mL in DMEM/10%FCS/1%PSF.</li>
<li>20 &mu;L droplets of Schwann cells suspension is added over each 5 coverslip fragments placed in 6 well plates and cells are incubated at 37&deg;C , 7% CO2 for 2 hours.</li>
<li>After 2 hours, the Schwann cells are attached to the coverslip fragments and DMEM/10% FCS/1% PSF (Supplemented with 2&mu;M of forskolin and 10&mu;g/ mL of BPE is added to each well so that the fragments are completely covered with medium).</li>
<li>The 6 well plates containing the fragments are then placed in the incubator for 24-48 hours until the glass fragments are fully confluent with Schwann cells.</li>
<li>Once fragments are confluent with Schwann cells, each fragment is picked up carefully using sharp forceps and dipped in HBSS to remove unattached cells and then inverted face down on to astrocyte monolayer.</li>
<li>Each well is then covered with 1 mL of DMEM/10%FCS/1%PSF and Schwann cells are allowed to migrate for 24 to 48 period. During this period experimental reagents such as growth factors can be added to assess their effect on the number and distance of migration of Schwann cells.</li>
<li>Following the migration period, the glass fragments are fixed to the bottom of each well by adding 4% paraformaldehyde (PFA) for 30 minutes. Following fixation, immunostain the Schwann cells for p75 (recognizing low affinity NGF receptor) then stain them using ABC strepavidin kit-diaminobenzidine(DAB), to allow visualization of the Schwann cells under light microscope.</li>
</ol>
3. Representative Results:
Following 8-10 days Schwann-astrocyte co-cultures show a sharp boundary between the two cell types. This boundary is more pronounced if forskolin and BPE is used in the culture as Schwann cell proliferation is enhanced.
If no boundary is observed during the 10 day period, the time of culture can be increased further until the boundaries are established. Changing the ratio of cell density is an alternative way to increase the boundary formation. A ratio of 3:1 Schwann: astrocyte cell density can be used when preparing cell suspensions 8,18.
Following immunostaining to identify the Schwann cells and astrocytes, to assess cell intermingling a line can be drawn where the boundary is established and the number of Schwann cells migrating into the astrocyte territory can be counted under fluorescence microscope.
Below are two examples of images obtained boundaries, one with well-formed segregation of Schwann cells and astrocytes (Figure 1A) and one where the cells have not segregated well into different territories due to poor technique (Figure 1B).
<img src="/files/ftp_upload/2214/2214fig2.jpg" alt="Figure 1" /> 
Figure 1. Boundary assay: Schwann-astrocyte interaction. A) A 10 day co-culture assay in the presence of forskolin and BPE to stimulate Schwann cell proliferation demonstrates a sharp boundary between the two cell types(red=P75, green=GFAP). B) A 10 day co-culture assay where the boundary is not formed and the two cell fronts mixed. This was due to mixing of the two droplets while placing astrocyte and Schwann cell droplets next to each other during the preparation of the boundary (red=P75, green=GFAP).
<img src="/files/ftp_upload/2214/2214fig1.jpg" alt="Figure 2" /> 
Figure 2. Representative image of confluent astrocyte monolayer
Migration assays assess movement of one cell type over the surface of another cell type and therefore assess a different phenomenon from that of boundary formation.
Practice is needed to ensure inverting the coverslips onto monolayers does not lead to damage to the Schwann cell-covered glass fragments and astrocyte monolayers by the sharp forceps. To assess the migration of Schwann cells, the maximum distance of migration and the number of migrating cells from the edge of coverslip can be measured under light microscope.
Below is the image of Schwann cells stained with P75 antibody using DAB staining on the surface of astrocyte monolayer (Figure 3). 
<img src="/files/ftp_upload/2214/2214fig3.jpg" alt="Figure 3" /> 
Figure 3. Migration assay using inverted coverslip assay.
A) Schwann cells (brown, immunostained with p75 antibody) migrating away from the edge of coverslip. Arrow points to the direction of the cell migration away from the coverslip.

<ol>
	<li>Assouline, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+astrocytes+and+Schwann+cells+in+culture+synthesize+nerve+growth+factor-like+neurite-promoting+factors.">Rat astrocytes and Schwann cells in culture synthesize nerve growth factor-like neurite-promoting factors.</a> Brain Res. 428, 103-118 (1987).</li><li>Taylor, J. S., Bampton, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+secreted+by+Schwann+cells+stimulate+the+regeneration+of+neonatal+retinal+ganglion+cells.">Factors secreted by Schwann cells stimulate the regeneration of neonatal retinal ganglion cells.</a> J Anat. 204, 25-31 (2004).</li><li>Reichardt, L. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrins+and+cell+adhesion+molecules:+neuronal+receptors+that+regulate+axon+growth+on+extracellular+matrices+and+cell+surfaces.">Integrins and cell adhesion molecules: neuronal receptors that regulate axon growth on extracellular matrices and cell surfaces.</a> Dev Neurosci. 11, 332-347 (1989).</li><li>Chiu, A. Y., Monteros, ., Espinosa de los, A., Cole, R. A., Loera, S., de Vellis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laminin+and+s-laminin+are+produced+and+released+by+astrocytes,+Schwann+cells,+and+schwannomas+in+culture.">Laminin and s-laminin are produced and released by astrocytes, Schwann cells, and schwannomas in culture.</a> Glia. 4, 11-24 (1991).</li><li>Blakemore, W. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Remyelination+of+CNS+axons+by+Schwann+cells+transplanted+from+the+sciatic+nerve.">Remyelination of CNS axons by Schwann cells transplanted from the sciatic nerve.</a> Nature. 266, 68-69 (1977).</li><li>Andrews, M. R., Stelzner, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+olfactory+ensheathing+and+schwann+cells+after+implantation+into+a+dorsal+injury+of+adult+rat+spinal+cord.">Evaluation of olfactory ensheathing and schwann cells after implantation into a dorsal injury of adult rat spinal cord.</a> J Neurotrauma. 24, 1773-1792 (2007).</li><li>Iwashita, Y., Fawcett, J. W., Crang, A. J., Franklin, R. J., Blakemore, W. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schwann+cells+transplanted+into+normal+and+X-irradiated+adult+white+matter+do+not+migrate+extensively+and+show+poor+long-term+survival.">Schwann cells transplanted into normal and X-irradiated adult white matter do not migrate extensively and show poor long-term survival.</a> Exp Neurol. 164, 292-302 (2000).</li><li>Lakatos, A., Franklin, R. J., Barnett, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Olfactory+ensheathing+cells+and+Schwann+cells+differ+in+their+in+vitro+interactions+with+astrocytes.">Olfactory ensheathing cells and Schwann cells differ in their in vitro interactions with astrocytes.</a> Glia. 32, 214-225 (2000).</li><li>Lakatos, A., Barnett, S. C., Franklin, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Olfactory+ensheathing+cells+induce+less+host+astrocyte+response+and+chondroitin+sulphate+proteoglycan+expression+than+Schwann+cells+following+transplantation+into+adult+CNS+white+matter.">Olfactory ensheathing cells induce less host astrocyte response and chondroitin sulphate proteoglycan expression than Schwann cells following transplantation into adult CNS white matter.</a> Exp Neurol. 184, 237-246 (2003).</li><li>Ghirnikar, R. S., Eng, L. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Astrocyte-Schwann+cell+interactions+in+culture.">Astrocyte-Schwann cell interactions in culture.</a> Glia. 11, 367-377 (1994).</li><li>Ghirnikar, R. S., Eng, L. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chondroitin+sulfate+proteoglycan+staining+in+astrocyte-Schwann+cell+co-cultures.">Chondroitin sulfate proteoglycan staining in astrocyte-Schwann cell co-cultures.</a> Glia. 14, 145-152 (1995).</li><li>Plant, G. W., Bates, M. L., Bunge, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibitory+proteoglycan+immunoreactivity+is+higher+at+the+caudal+than+the+rostral+Schwann+cell+graft-transected+spinal+cord+interface.">Inhibitory proteoglycan immunoreactivity is higher at the caudal than the rostral Schwann cell graft-transected spinal cord interface.</a> Mol Cell Neurosci. 17, 471-487 (2001).</li><li>Fishman, P. S., Nilaver, G., Kelly, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Astrogliosis+limits+the+integration+of+peripheral+nerve+grafts+into+the+spinal+cord.">Astrogliosis limits the integration of peripheral nerve grafts into the spinal cord.</a> Brain Res. 277, 175-180 (1983).</li><li>Fok-Seang, J., Mathews, G. A., ffrench-Constant, C., Trotter, J., Fawcett, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Migration+of+oligodendrocyte+precursors+on+astrocytes+and+meningeal+cells.">Migration of oligodendrocyte precursors on astrocytes and meningeal cells.</a> Dev Biol. 171, 1-15 (1995).</li><li>Wilby, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N-Cadherin+inhibits+Schwann+cell+migration+on+astrocytes.">N-Cadherin inhibits Schwann cell migration on astrocytes.</a> Mol Cell Neurosci. 14, 66-84 (1999).</li><li>Grimpe, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+proteoglycans+in+Schwann+cell/astrocyte+interactions+and+in+regeneration+failure+at+PNS/CNS+interfaces.">The role of proteoglycans in Schwann cell/astrocyte interactions and in regeneration failure at PNS/CNS interfaces.</a> Mol Cell Neurosci. 28, 18-29 (2005).</li><li>Afshari, F. T., Kwok, J. C., White, L., Fawcett, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schwann+cell+migration+is+integrin-dependent+and+inhibited+by+astrocyte-produced.">Schwann cell migration is integrin-dependent and inhibited by astrocyte-produced.</a> Glia. , (2010).</li><li>Santos-Silva, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FGF/heparin+differentially+regulates+Schwann+cell+and+olfactory+ensheathing+cell+interactions+with+astrocytes:+a+role+in+astrocytosis.">FGF/heparin differentially regulates Schwann cell and olfactory ensheathing cell interactions with astrocytes: a role in astrocytosis.</a> J Neurosci. 27, 7154-7167 (2007).</li><li>Afshari, F. T., Kwok, J. C., Fawcett, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Astrocyte-produced+ephrins+inhibit+schwann+cell+migration+via+VAV2+signaling.">Astrocyte-produced ephrins inhibit schwann cell migration via VAV2 signaling.</a> J Neurosci. 30, 4246-4255 (2007).</li></ol>

No conflicts of interest declared.

The assays described above have been used in various studies demonstrating the role of multiple factors involved in boundary formation between the Schwann-astrocytes and limited Schwann cell migration in astrocytic environment.
Understanding the mechanisms underlying these events is essential as it would allow development of strategies to optimise and enhance the integration of Schwann cell grafts following transplantation and in doing so facilitate the exit of the regenerating axons from the...

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>DMEM</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>41966-029</td>
<td>&nbsp;</td>
<tr>
<td>HBSS</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>14170-088</td>
<td>&nbsp;</td>
<tr>
<td>FCS</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>10091-148</td>
<td>&nbsp;</td>
<tr>
<td>PSF</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>15240-062</td>
<td>&nbsp;</td>
<tr>
<td>BPE</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>13028-014</td>
<td>&nbsp;</td>
<tr>
<td>Forskolin</td>
<td>&nbsp;</td>
<td>Calbiochem</td>
<td>344273</td>
<td>&nbsp;</td>
<tr>
<td>Coverlips</td>
<td>&nbsp;</td>
<td>VWR-International</td>
<td>631-0149</td>
<td>&nbsp;</td>
<tr>
<td>Coverlips(rectangle)</td>
<td>&nbsp;</td>
<td>MENZEL-GLASER (Supplied by Thermo Scientifics)</td>
<td>BB022050A1</td>
<td>&nbsp;</td>
<tr>
<td>Chamber slides</td>
<td>&nbsp;</td>
<td>Nunc-LabTek </td>
<td>177380</td>
<td>&nbsp;</td>
<tr>
<td>4 well plates, 6 well plates</td>
<td>&nbsp;</td>
<td>Nunc</td>
<td>&nbsp;</td>
<td>4 well plates 
6 well plates</td>
</tr>
<tr>
<td>rat p75 antibody</td>
<td>&nbsp;</td>
<td>Millipore, Temecula,California</td>
<td>MAB365</td>
<td>&nbsp;</td>
<tr>
<td>GFAP antibody</td>
<td>&nbsp;</td>
<td>Dako</td>
<td>Z0334</td>
<td>&nbsp;</td>
<tr>
<td>Secondary antibodies (Alexa-conjugated)</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>A-11004 A-11034</td>
<td>Goat anti mouse 568 
Goat anti Rabbit 488</td>
</tr>
<tr>
<td>Secondary biotinylated </td>
<td>&nbsp;</td>
<td>Vector</td>
<td>&nbsp;</td>
<td>Goat anti mouse</td>
</tr>
<tr>
<td>DAB tablets </td>
<td>&nbsp;</td>
<td>Sigma-aldrich</td>
<td>D4418</td>
<td>&nbsp;</td>
<tr>
<td>ABC elite kit</td>
<td>&nbsp;</td>
<td>Vector</td>
<td>PK-6100</td>
<td>&nbsp;</td>
<tr>
<td>Fine Forceps </td>
<td>&nbsp;</td>
<td>FST</td>
<td>11295-10</td>
<td>&nbsp;</td>
<tr>
<td>Paraformaldehyde</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>P6168</td>
<td>&nbsp;</td>
<tr>
<td>Fluorosave</td>
<td>&nbsp;</td>
<td>Calbiochem</td>
<td>345789</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

analysis of schwann-astrocyte interactions using in vitro assays

Schwann cells are one of the commonly used cells in repair strategies following spinal cord injuries. Schwann cells are capable of supporting axonal regeneration and sprouting by secreting growth factors 1,2 and providing growth promoting adhesion molecules 3 and extracellular matrix molecules 4. In addition they myelinate the demyelinated axons at the site of injury 5.
However following transplantation, Schwann cells do not migrate from the site of implant and do not intermingle with the host astrocytes 6,7. This results in formation of a sharp boundary between the Schwann cells and astrocytes, creating an obstacle for growing axons trying to exit the graft back into the host tissue proximally and distally. Astrocytes in contact with Schwann cells also undergo hypertrophy and up-regulate the inhibitory molecules 8-13.
In vitro assays have been used to model Schwann cell-astrocyte interactions and have been important in understanding the mechanism underlying the cellular behaviour.
These in vitro assays include boundary assay, where a co-culture is made using two different cells with each cell type occupying different territories with only a small gap separating the two cell fronts. As the cells divide and migrate, the two cellular fronts get closer to each other and finally collide. This allows the behaviour of the two cellular populations to be analyzed at the boundary. Another variation of the same technique is to mix the two cellular populations in culture and over time the two cell types segregate with Schwann cells clumped together as islands in between astrocytes together creating multiple Schwann-astrocyte boundaries.
The second assay used in studying the interaction of two cell types is the migration assay where cellular movement can be tracked on the surface of the other cell type monolayer 14,15. This assay is commonly known as inverted coverslip assay. Schwann cells are cultured on small glass fragments and they are inverted face down onto the surface of astrocyte monolayers and migration is assessed from the edge of coverslip.
Both assays have been instrumental in studying the underlying mechanisms involved in the cellular exclusion and boundary formation. Some of the molecules identified using these techniques include N-Cadherins 15, Chondroitin Sulphate proteoglycans(CSPGs) 16,17, FGF/Heparin 18, Eph/Ephrins19.
This article intends to describe boundary assay and migration assay in stepwise fashion and elucidate the possible technical problems that might occur.

Watch this Scientific Journal Video about Analysis of Schwann-astrocyte Interactions Using In Vitro Assays at JoVE.com

Analysis of Schwann-astrocyte Interactions Using In Vitro Assays

This article intends to describe in stepwise fashion the commonly used in vitro assays used in studying Schwann cell-asrtocyte interactions.

Analysis of Schwann-astrocyte Interactions Using In Vitro Assays

Schwann cells are one of the commonly used cells in repair strategies following spinal cord injuries. Schwann cells are capable of supporting axonal ...

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12.2K Views.  University of Cambridge. This article intends to describe in stepwise fashion the commonly used in vitro assays used in studying Schwann cell-asrtocyte interactions.

Video: Analysis of Schwann-astrocyte Interactions Using In Vitro Assays

Rapid Homogeneous Detection of Biological Assays Using Magnetic Modulation Biosensing System

A magnetic modulation biosensing system (MMB) [1,2] rapidly and homogeneously detected biological targets at low concentrations without any washing or separation step. When the IL-8 target was present, a 'sandwich'-based assay attached magnetic beads with IL-8 capture antibody to streptavidin coupled fluorescent protein via the IL-8 target and a biotinylated IL-8 antibody. The magnetic beads are maneuvered into oscillatory motion by applying an alternating magnetic field gradient through two electromagnetic poles. The fluorescent proteins, which are attached to the magnetic beads are condensed into the detection area and their movement in and out of an orthogonal laser beam produces a periodic fluorescent signal that is demodulated using synchronous detection. The magnetic modulation biosensing system was previously used to detect the coding sequences of the non-structural Ibaraki virus protein 3 (NS3) complementary DNA (cDNA) [2]. The techniques that are demonstrated in this work for external manipulation and condensation of particles may be used for other applications, e.g. delivery of magnetically-coupled drugs in-vivo or enhancing the contrast for in-vivo imaging applications.

Magnetic modulation biosensing system is utilized to rapidly, sensitively and simply detect biological assays, such as DNA molecules and proteins.

A magnetic modulation biosensing system (MMB) [1,2] rapidly and homogeneously detected biological targets at low concentrations without any washing or ...

In Vitro Analysis of PDZ-dependent CFTR Macromolecular Signaling Complexes

Cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel located primarily at the apical membranes of epithelial cells, plays a crucial role in transepithelial fluid homeostasis1-3. CFTR has been implicated in two major diseases: cystic fibrosis (CF)4 and secretory diarrhea5. In CF, the synthesis or functional activity of the CFTR Cl- channel is reduced. This disorder affects approximately 1 in 2,500 Caucasians in the United States6. Excessive CFTR activity has also been implicated in cases of toxin-induced secretory diarrhea (e.g., by cholera toxin and heat stable E. coli enterotoxin) that stimulates cAMP or cGMP production in the gut7.
Accumulating evidence suggest the existence of physical and functional interactions between CFTR and a growing number of other proteins, including transporters, ion channels, receptors, kinases, phosphatases, signaling molecules, and cytoskeletal elements, and these interactions between CFTR and its binding proteins have been shown to be critically involved in regulating CFTR-mediated transepithelial ion transport in vitro and also in vivo8-19. In this protocol, we focus only on the methods that aid in the study of the interactions between CFTR carboxyl terminal tail, which possesses a protein-binding motif [referred to as PSD95/Dlg1/ZO-1 (PDZ) motif], and a group of scaffold proteins, which contain a specific binding module referred to as PDZ domains. So far, several different PDZ scaffold proteins have been reported to bind to the carboxyl terminal tail of CFTR with various affinities, such as NHERF1, NHERF2, PDZK1, PDZK2, CAL (CFTR-associated ligand), Shank2, and GRASP20-27. The PDZ motif within CFTR that is recognized by PDZ scaffold proteins is the last four amino acids at the C terminus (i.e., 1477-DTRL-1480 in human CFTR)20. Interestingly, CFTR can bind more than one PDZ domain of both NHERFs and PDZK1, albeit with varying affinities22. This multivalency with respect to CFTR binding has been shown to be of functional significance, suggesting that PDZ scaffold proteins may facilitate formation of CFTR macromolecular signaling complexes for specific/selective and efficient signaling in cells16-18.
Multiple biochemical assays have been developed to study CFTR-involving protein interactions, such as co-immunoprecipitation, pull-down assay, pair-wise binding assay, colorimetric pair-wise binding assay, and macromolecular complex assembly assay16-19,28,29. Here we focus on the detailed procedures of assembling a PDZ motif-dependent CFTR-containing macromolecular complex in vitro, which is used extensively by our laboratory to study protein-protein or domain-domain interactions involving CFTR16-19,28,29.

In Vitro Analysis of PDZ-dependent CFTR Macromolecular Signaling Complexes

Cystic fibrosis transmembrane conductance regulator (CFTR), an epithelial chloride channel, has been reported to interact with various proteins and regulate important cellular processes; among them the CFTR PDZ motif-mediated interactions have been well documented. This protocol describes methods we developed to assemble a PDZ-dependent CFTR macromolecular signaling complex in vitro.

Cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel located primarily at the apical membranes of epithelial cells, plays a ...

In vitro Cell Migration and Invasion Assays

Migration is a key property of live cells and critical for normal development, immune response, and disease processes such as cancer metastasis and inflammation. Methods to examine cell migration are very useful and important for a wide range of biomedical research such as cancer biology, immunology, vascular biology, cell biology and developmental biology. Here we use tumor cell migration and invasion as an example and describe two related assays to illustrate the commonly used, easily accessible methods to measure these processes. The first method is the cell culture wound closure assay in which a scratch is generated on a confluent cell monolayer. The speed of wound closure and cell migration can be quantified by taking snapshot pictures with a regular inverted microscope at several time intervals. More detailed cell migratory behavior can be documented using the time-lapse microscopy system. The second method described in this paper is the transwell cell migration and invasion assay that measures the capacity of cell motility and invasiveness toward a chemo-attractant gradient. It is our goal to describe these methods in a highly accessible manner so that the procedures can be successfully performed in research laboratories even just with basic cell biology setup.

In vitro Cell Migration and Invasion Assays

Commonly used, highly accessible methods for examining cell migration and invasion in vitro are described. The first method is the cell wound closure assay that measures cell motility. The second method is the transwell migration and invasion assay that assesses the chemotactic and invasive capacity of cells.

Migration is a key property of live cells and critical for normal development, immune response, and disease processes such as cancer metastasis and ...

Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

The 3&#8217; end of mammalian mRNAs is not formed by abrupt termination of transcription by RNA polymerase II (RNPII). Instead, RNPII synthesizes precursor mRNA beyond the end of mature RNAs, and an active process of endonuclease activity is required at a specific site. Cleavage of the precursor RNA normally occurs 10-30 nt downstream from the consensus polyA site (AAUAAA) after the CA dinucleotides. Proteins from the cleavage complex, a multifactorial protein complex of approximately 800 kDa, accomplish this specific nuclease activity. Specific RNA sequences upstream and downstream of the polyA site control the recruitment of the cleavage complex. Immediately after cleavage, pre-mRNAs are polyadenylated by the polyA polymerase (PAP) to produce mature stable RNA messages.
Processing of the 3&#8217; end of an RNA transcript may be studied using cellular nuclear extracts with specific radiolabeled RNA substrates. In sum, a long 32P-labeled uncleaved precursor RNA is incubated with nuclear extracts in vitro, and cleavage is assessed by gel electrophoresis and autoradiography. When proper cleavage occurs, a shorter 5&#8217; cleaved product is detected and quantified. Here, we describe the cleavage assay in detail using, as an example, the 3&#8217; end processing of HIV-1 mRNAs.

Analysis of RNA Processing Reactions Using Cell Free Systems: 3&#039; End Cleavage of Pre-mRNA Substrates in vitro

RNA polymerase II synthesizes a precursor RNA that extends beyond the 3' end of the mature mRNA. The end of the mature RNA is generated cotranscriptionally, at a site dictated by RNA sequences, via the endonuclease activity of the cleavage complex. Here, we detail the method to study cleavage reactions in vitro.

The 3&#8217; end of mammalian mRNAs is not formed by abrupt termination of transcription by RNA polymerase II (RNPII). Instead, RNPII synthesizes ...

In Vitro Aggregation Assays Using Hyperphosphorylated Tau Protein

Alzheimer's disease is one of a large group of neurodegenerative disorders known as tauopathies that are manifested by the neuronal deposits of hyperphosphorylated tau protein in the form of neurofibrillary tangles (NFTs). The density of NFT correlates well with cognitive impairment and other neurodegenerative symptoms, thus prompting the endeavor of developing tau aggregation-based therapeutics. Thus far, however, tau aggregation assays use recombinant or synthetic tau that is devoid of the pathology-related phosphorylation marks. Here we describe two assays using recombinant, hyperphosphorylated tau as the subject. These assays can be scaled up for high-throughput screens for compounds that can modulate the kinetics or stability of hyperphosphorylated tau aggregates. Novel therapeutics for Alzheimer's disease and other tauopathies can potentially be discovered using hyperphosphorylated tau isoforms.

In Vitro Aggregation Assays Using Hyperphosphorylated Tau Protein

Unmodified and hyperphosphorylated tau proteins were used in two in vitro aggregation assays to reveal the hyperphosphorylation-dependent fast aggregation kinetics. These assays pave the way for future screens for compounds that can modulate the propensity of hyperphosphorylated tau to form fibrils that underlie the progression of Alzheimer&#8217;s disease.

Alzheimer's disease is one of a large group of neurodegenerative disorders known as tauopathies that are manifested by the neuronal deposits of ...

Comparative Analysis of Human Growth Hormone in Serum Using SPRi, Nano-SPRi and ELISA Assays

Sensitive and selective methods for the detection of human growth hormone (hGH) over a wide range of concentrations (high levels of 50-100 ng ml&#8722;1 and minimum levels of 0.03 ng ml&#8722;1) in circulating blood are essential as variable levels may indicate altered physiology. For example, growth disorders occurring in childhood can be diagnosed by measuring levels of hGH in blood. Also, the misuse of recombinant hGH in sports not only poses an ethical issue it also presents serious health threats to the abuser. One popular strategy for measuring hGH misuse, relies on the detection of the ratio of 22 kDa hGH to total hGH, as non-22 kDa endogenous levels drop after exogenous recombinant hGH (rhGH) administration. Surface plasmon resonance imaging (SPRi) is an analytical tool that allows direct (label-free) monitoring and visualization of biomolecular interactions by recording changes of the refractive index adjacent to the sensor surface in real time. In contrast, the most frequently used colorimetric method, enzyme-linked immunosorbent assay (ELISA) uses enzyme labeled detection antibodies to indirectly measure analyte concentration after the addition of a substrate that induces a color change. To increase detection sensitivity, amplified SPRi uses a sandwich assay format and near infrared quantum dots (QDs) to increase signal strength. After direct SPRi detection of recombinant rhGH in spiked human serum, the SPRi signal is amplified by the sequential injection of detection antibody coated with near-infrared QDs (Nano-SPRi). In this study, the diagnostic potential of direct and amplified SPRi was assessed for measuring rhGH spiked in human serum and compared directly with the capabilities of a commercially available ELISA kit.

The proposed work assesses the diagnostic potential of direct and amplified surface plasmon resonance imaging (SPRi) assays, particularly for the detection of recombinant human growth hormone in spiked human serum, by comparing SPRi results directly with commercially available enzyme-linked immunosorbent assay (ELISA) kit.

Sensitive and selective methods for the detection of human growth hormone (hGH) over a wide range of concentrations (high levels of 50-100 ng ml&#8722;1 ...

Effect of Fluorescent Proteins on Fusion Partners Using Polyglutamine Toxicity Assays in Yeast

For the investigation of protein localization and trafficking using live cell imaging, researchers often rely on fusing their protein of interest to a fluorescent reporter. The constantly evolving list of genetically encoded fluorescent proteins (FPs) presents users with several alternatives when it comes to fluorescent fusion design. Each FP has specific optical and biophysical properties that can affect the biochemical, cellular, and functional properties of the resulting fluorescent fusions. For instance, several FPs tend to form nonspecific oligomers that are susceptible to impede on the function of the fusion partner. Unfortunately, only a few methods exist to test the impact of FPs on the behavior of the fluorescent reporter. Here, we describe a simple method that enables the rapid assessment of the impact of FPs using polyglutamine (polyQ) toxicity assays in the budding yeast Saccharomyces cerevisiae. PolyQ-expanded huntingtin proteins are associated with the onset of Huntington&#39;s disease (HD), where the expanded huntingtin aggregates into toxic oligomers and inclusion bodies. The aggregation and toxicity of polyQ expansions in yeast are highly dependent on the sequences flanking the polyQ region, including the presence of fluorescent tags, thus providing an ideal experimental platform to study the impact of FPs on the behavior of their fusion partner.

This article describes protocols to assess the effect of fluorescent proteins on the aggregation and toxicity of misfolded polyglutamine expansion for the rapid evaluation of a newly uncharacterized fluorescent protein in the context of fluorescent reporters.

For the investigation of protein localization and trafficking using live cell imaging, researchers often rely on fusing their protein of interest to a ...

Microbiota Analysis Using Two-step PCR and Next-generation 16S rRNA Gene Sequencing

The human gut is colonized by trillions of bacteria that support physiologic functions such as food metabolism, energy harvesting, and regulation of the immune system. Perturbation of the healthy gut microbiome has been suggested to play a role in the development of inflammatory diseases, including multiple sclerosis (MS). Environmental and genetic factors can influence the composition of the microbiome; therefore, identification of microbial communities linked with a disease phenotype has become the first step towards defining the microbiome&#8217;s role in health and disease. Use of 16S rRNA metagenomic sequencing for profiling bacterial community has helped in advancing microbiome research. Despite its wide use, there is no uniform protocol for 16S rRNA-based taxonomic profiling analysis. Another limitation is the low resolution of taxonomic assignment due to technical difficulties such as smaller sequencing reads, as well as use of only forward (R1) reads in the final analysis due to low quality of reverse (R2) reads. There is need for a simplified method with high resolution to characterize bacterial diversity in a given biospecimen. Advancements in sequencing technology with the ability to sequence longer reads at high resolution have helped to overcome some of these challenges. Present sequencing technology combined with a publicly available metagenomic analysis pipeline such as R-based Divisive Amplicon Denoising Algorithm-2 (DADA2) has helped advance microbial profiling at high resolution, as DADA2 can assign sequence at the genus and species levels. Described here is a guide for performing bacterial profiling using two-step amplification of the V3-V4 region of the 16S rRNA gene, followed by analysis using freely available analysis tools (i.e., DADA2, Phyloseq, and METAGENassist). It is believed that this simple and complete workflow will serve as an excellent tool for researchers interested in performing microbiome profiling studies.

Described here is a simplified standard operating procedure for microbiome profiling using 16S rRNA metagenomic sequencing and analysis using freely available tools. This protocol will help researchers who are new to the microbiome field as well as those requiring updates on methods to achieve bacterial profiling at a higher resolution.

The human gut is colonized by trillions of bacteria that support physiologic functions such as food metabolism, energy harvesting, and regulation of the ...

In Vitro Analysis of E3 Ubiquitin Ligase Function

The covalent attachment of ubiquitin (Ub) to internal lysine residue(s) of a substrate protein, a process termed ubiquitylation, represents one of the most important post-translational modifications in eukaryotic organisms. Ubiquitylation is mediated by a sequential cascade of three enzyme classes including ubiquitin-activating enzymes (E1 enzymes), ubiquitin-conjugating enzymes (E2 enzymes), and ubiquitin ligases (E3 enzymes), and sometimes, ubiquitin-chain elongation factors (E4 enzymes). Here, in vitro protocols for ubiquitylation assays are provided, which allow the assessment of E3 ubiquitin ligase activity, the cooperation between E2-E3 pairs, and substrate selection. Cooperating E2-E3 pairs can be screened by monitoring the generation of free poly-ubiquitin chains and/or auto-ubiquitylation of the E3 ligase. Substrate ubiquitylation is defined by selective binding of the E3 ligase and can be detected by western blotting of the in vitro reaction. Furthermore, an E2~Ub discharge assay is described, which is a useful tool for the direct assessment of functional E2-E3 cooperation. Here, the E3-dependent transfer of ubiquitin is followed from the corresponding E2 enzyme onto free lysine amino acids (mimicking substrate ubiquitylation) or internal lysines of the E3 ligase itself (auto-ubiquitylation). In conclusion, three different in vitro protocols are provided that are fast and easy to perform to address E3 ligase catalytic functionality.

In Vitro Analysis of E3 Ubiquitin Ligase Function

The present study provides detailed in vitro ubiquitylation assay protocols for the analysis of E3 ubiquitin ligase catalytic activity. Recombinant proteins were expressed using prokaryotic systems such as Escherichia coli culture.

The covalent attachment of ubiquitin (Ub) to internal lysine residue(s) of a substrate protein, a process termed ubiquitylation, represents one of the ...

In Silico Identification and Characterization of circRNAs During Host-Pathogen Interactions

Circular RNAs (circRNAs) are a class of non-coding RNAs that are formed via back-splicing. These circRNAs are predominantly studied for their roles as regulators of various biological processes. Notably, emerging evidence demonstrates that host circRNAs can be differentially expressed (DE) upon infection with&#160;pathogens (e.g., influenza and coronaviruses), suggesting a role for circRNAs in regulating host innate immune responses. However, investigations on the role of circRNAs during pathogenic infections are limited by the knowledge and skills required to carry out the necessary bioinformatic analysis to identify DE circRNAs from RNA sequencing (RNA-seq) data. Bioinformatics prediction and identification of circRNAs is crucial before any verification, and functional studies using costly and time-consuming wet-lab techniques. To solve this issue, a step-by-step protocol of in silico prediction and characterization of circRNAs using RNA-seq data is provided in this manuscript. The protocol can be divided into four steps: 1) Prediction and quantification of DE circRNAs via the CIRIquant pipeline; 2) Annotation via circBase and characterization of DE circRNAs; 3) CircRNA-miRNA interaction prediction through Circr pipeline; 4) functional enrichment analysis of circRNA parental genes using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). This pipeline will be useful in driving future in vitro and in vivo research to further unravel the role of circRNAs in host-pathogen interactions.

In Silico Identification and Characterization of circRNAs During Host-Pathogen Interactions

The protocol submitted here explains the complete in silico pipeline needed to predict and functionally characterize circRNAs from RNA-sequencing transcriptome data studying host-pathogen interactions.

Circular RNAs (circRNAs) are a class of non-coding RNAs that are formed via back-splicing. These circRNAs are predominantly studied for their roles as ...