This protocol is supported by a grant NRF-2015R1A2A1A01003410 from the Ministry of Science, ICT and Future Planning, Republic of Korea.

All experiments involving animals were approved by the institutional Animal Care and Use Committee of Ajou University School of Medicine.
1. Culture Preparation of Dissociated Adult DRG Neuron
<ol>
	<li>Before setting up the culture, pre-coat a 6-well plate with poly-D-lysine and laminin. Incubate a 6-well plate with 0.01% poly-D-lysine at 37&#176;C for 2 h or at 4&#176;C overnight. Then, wash the plate twice with distilled water.</li>
	<li>Incubate the plate with laminin solution at a conce...

<ol>
	<li>Donnelly, D. J., Popovich, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+and+its+role+in+neuroprotection,+axonal+regeneration+and+functional+recovery+after+spinal+cord+injury.">Inflammation and its role in neuroprotection, axonal regeneration and functional recovery after spinal cord injury.</a> Exp Neurol. 209 (2), 378-388 (2008).</li><li>Festoff, B. W., 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=Minocycline+neuroprotects,+reduces+microgliosis,+and+inhibits+caspase+protease+expression+early+after+spinal+cord+injury.">Minocycline neuroprotects, reduces microgliosis, and inhibits caspase protease expression early after spinal cord injury.</a> J Neurochem. 97 (5), 1314-1326 (2006).</li><li>Bowers, C. A., Kundu, B., Hawryluk, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methylprednisolone+for+acute+spinal+cord+injury:+an+increasingly+philosophical+debate.">Methylprednisolone for acute spinal cord injury: an increasingly philosophical debate.</a> Neural Regen Res. 11 (6), 882-885 (2016).</li><li>Gensel, J. C., Kigerl, K. A., Mandrekar-Colucci, S. S., Gaudet, A. D., Popovich, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Achieving+CNS+axon+regeneration+by+manipulating+convergent+neuro-immune+signaling.">Achieving CNS axon regeneration by manipulating convergent neuro-immune signaling.</a> Cell Tissue Res. 349 (1), 201-213 (2012).</li><li>DiSabato, D. J., Quan, N., Godbout, 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=Neuroinflammation:+the+devil+is+in+the+details.">Neuroinflammation: the devil is in the details.</a> J Neurochem. 139 Suppl 2, 136-153 (2016).</li><li>Jin, X., Yamashita, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+in+central+nervous+system+repair+after+injury.">Microglia in central nervous system repair after injury.</a> J Biochem. 159 (5), 491-496 (2016).</li><li>Yin, Y., 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=Macrophage-derived+factors+stimulate+optic+nerve+regeneration.">Macrophage-derived factors stimulate optic nerve regeneration.</a> J Neurosci. 23 (6), 2284-2293 (2003).</li><li>Yin, Y., 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=Oncomodulin+is+a+macrophage-derived+signal+for+axon+regeneration+in+retinal+ganglion+cells.">Oncomodulin is a macrophage-derived signal for axon regeneration in retinal ganglion cells.</a> Nat Neurosci. 9 (6), 843-852 (2006).</li><li>Gensel, J. 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=Macrophages+promote+axon+regeneration+with+concurrent+neurotoxicity.">Macrophages promote axon regeneration with concurrent neurotoxicity.</a> J Neurosci. 29 (12), 3956-3968 (2009).</li><li>Barrette, 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=Requirement+of+myeloid+cells+for+axon+regeneration.">Requirement of myeloid cells for axon regeneration.</a> J Neurosci. 28 (38), 9363-9376 (2008).</li><li>Kwon, M. J., 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=Contribution+of+macrophages+to+enhanced+regenerative+capacity+of+dorsal+root+ganglia+sensory+neurons+by+conditioning+injury.">Contribution of macrophages to enhanced regenerative capacity of dorsal root ganglia sensory neurons by conditioning injury.</a> J Neurosci. 33 (38), 15095-15108 (2013).</li><li>Niemi, J. P., 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+critical+role+for+macrophages+near+axotomized+neuronal+cell+bodies+in+stimulating+nerve+regeneration.">A critical role for macrophages near axotomized neuronal cell bodies in stimulating nerve regeneration.</a> J Neurosci. 33 (41), 16236-16248 (2013).</li><li>Hannila, S. S., Filbin, 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=The+role+of+cyclic+AMP+signaling+in+promoting+axonal+regeneration+after+spinal+cord+injury.">The role of cyclic AMP signaling in promoting axonal regeneration after spinal cord injury.</a> Exp Neurol. 209 (2), 321-332 (2008).</li><li>Kwon, M. J., 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=CCL2+Mediates+Neuron-Macrophage+Interactions+to+Drive+Proregenerative+Macrophage+Activation+Following+Preconditioning+Injury.">CCL2 Mediates Neuron-Macrophage Interactions to Drive Proregenerative Macrophage Activation Following Preconditioning Injury.</a> J Neurosci. 35 (48), 15934-15947 (2015).</li><li>Niemi, J. P., DeFrancesco-Lisowitz, A., Cregg, J. M., Howarth, M., Zigmond, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Overexpression+of+the+monocyte+chemokine+CCL2+in+dorsal+root+ganglion+neurons+causes+a+conditioning-like+increase+in+neurite+outgrowth+and+does+so+via+a+STAT3+dependent+mechanism.">Overexpression of the monocyte chemokine CCL2 in dorsal root ganglion neurons causes a conditioning-like increase in neurite outgrowth and does so via a STAT3 dependent mechanism.</a> Exp Neurol. 275 Pt 1, 25-37 (2016).</li><li>Cafferty, W. 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=Conditioning+injury-induced+spinal+axon+regeneration+fails+in+interleukin-6+knock-out+mice.">Conditioning injury-induced spinal axon regeneration fails in interleukin-6 knock-out mice.</a> J Neurosci. 24 (18), 4432-4443 (2004).</li><li>Cai, D., 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=Neuronal+cyclic+AMP+controls+the+developmental+loss+in+ability+of+axons+to+regenerate.">Neuronal cyclic AMP controls the developmental loss in ability of axons to regenerate.</a> J Neurosci. 21 (13), 4731-4739 (2001).</li><li>Neumann, S., Woolf, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regeneration+of+dorsal+column+fibers+into+and+beyond+the+lesion+site+following+adult+spinal+cord+injury.">Regeneration of dorsal column fibers into and beyond the lesion site following adult spinal cord injury.</a> Neuron. 23 (1), 83-91 (1999).</li></ol>

There are several critical steps for the generation of this co-culture system. It is important to ensure that the mouse DRG neurons and peritoneal macrophages are prepared fresh and healthy. We have experienced diminished neurite outgrowth activity of the CM when the dissection of all the DRGs took more than 30 min. In addition, the contamination of blood components in peritoneal macrophages also led to a decrease of neurite outgrowth activity in the CM. In order to elicit robust neuron-macrophage interaction by db-cAMP,...

A variety of studies have sought to enhance CNS axon regeneration after the injuries of the spinal cord or brain. Inflammatory reactions, inevitably accompanying the injuries in the nervous system, are traditionally thought to participate in secondary pathological processes leading to the deleterious outcomes1,2. Indeed, methylprednisolone that can suppress inflammatory reactions is the only approved therapy for acute spinal cord injury3. However, more recent studies have provided evidence that macrophages, a representative inflammatory cell type, can participate in the regeneration or repair of injured nervous system4,5,6. For example, infiltrating macrophages following a lens injury produce pro-regenerative molecules to promote the regeneration of the retinal ganglion neurons7,8. In addition, transplanted DRG neurons increased axon growth up the region where macrophages were activated by zymosan9. Moreover, the macrophages at the lesion site can create a growth-permissive milieu for injured peripheral nerves10.
Our work also provided strong evidence that macrophages can contribute to the capacity of axon regeneration in adjacent neurons. We have shown that the activation of macrophages in the dorsal root ganglia (DRG) were essential in the enhanced regenerative capacity of DRG sensory neurons following a preconditioning peripheral nerve injury11. Similar research was independently reported from another laboratory12. We also showed that intraganglionic injection of dibutyryl cyclic AMP (db-cAMP), which is a well-known molecule to enhance the capacity of axon regeneration13, induced the activation of macrophages. The deactivation of macrophages abolished the effects of db-cAMP on neurite outgrowth activity. Subsequent works identified injury-induced expression of CCL2 in neurons as a signal to stimulate macrophages with a pro-regenerative phenotype14,15.
Based on the above experimental results, we have established an in vitro model resembling molecular events that occur in the DRGs following a preconditioning injury model11,14. In this model, db-cAMP is applied to the neuron-macrophage co-cultures eliciting intercellular signaling that leads to the activation of macrophages with a pro-regenerative phenotype. Here, we describe detailed protocols by which we can generate macrophages that secrete molecular factors promoting neurite outgrowth (Figure 1). This experimental model illustrates a concept that macrophages can be stimulated or induced to support axon regeneration following the injuries to nervous system. Our model will also be useful in studying mechanisms in intercellular signaling that leads to the activation of pro-regenerative macrophages.

<table>
	<tbody>
		<tr>
			<td>Cell culture insert transparent PET membrane 0.4&#956;m pore size</td>
			<td>Corning,Falcon</td>
			<td>353090</td>
			<td>Transparent PET membrane with 0.4-&#956;m pore size, for 6-well plate</td>
		</tr>
		<tr>
			<td>70-&#956;m nylon cell strainer</td>
			<td>Corning, Falcon</td>
			<td>352350</td>
			<td></td>
		</tr>
		<tr>
			<td>8-well culture slide</td>
			<td>Biocoat</td>
			<td>354632</td>
			<td>with a uniform application of Poly-D-Lysine</td>
		</tr>
		<tr>
			<td>Red blood cell lysis buffer</td>
			<td>Qiagen</td>
			<td>158904</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase from Clostridium histolyticum</td>
			<td>Sigma-Aldrich</td>
			<td>C9407-100MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurobasal medium</td>
			<td>Thermo Fisher Scientific, Gibco</td>
			<td>21103-049</td>
			<td>Containing 1% glutamax and 1% penicilin-streptomycin</td>
		</tr>
		<tr>
			<td>B-27 supplement, serum free</td>
			<td>Thermo Fisher Scientific, Gibco</td>
			<td>17504-044</td>
			<td>extracellular solution</td>
		</tr>
		<tr>
			<td>Glutamax</td>
			<td>Thermo Fisher Scientific, Gibco</td>
			<td>35050-061</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-streptomycin</td>
			<td>Thermo Fisher Scientific, Gibco</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-D-lysine Hydrobromide</td>
			<td>Sigma-Aldrich</td>
			<td>P6407-5MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminin</td>
			<td>Thermo Fisher Scientific, Invitrogen</td>
			<td>23017-015</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenosine 3&#39;, 5&#39;-cyclic monophosphate, N6,O2&#39;-dibutyryl-, sodium salt</td>
			<td>Merck Millipore Corporation, Calbiochem</td>
			<td>28745</td>
			<td></td>
		</tr>
		<tr>
			<td>10% Normal Goat Serum</td>
			<td>Thermo Fisher Scientific</td>
			<td>16210072</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton-X-100</td>
			<td>Daejung Chemical and Metal Co</td>
			<td>8566-4405</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti &#946; III tubulin (Tuj-1)</td>
			<td>Promega Corporation</td>
			<td>G7121</td>
			<td>Mouse monoclonal antibody</td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG (H+L) secondary antibody</td>
			<td>Thermo Fisher Scientific, Invitrogen</td>
			<td>A11005</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemacytometer</td>
			<td>Marienfeld-Superior</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture CO2 incubator</td>
			<td>Panasonic</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting stereomicroscope</td>
			<td>Carl Zeiss</td>
			<td>Stemi DV4</td>
			<td></td>
		</tr>
		<tr>
			<td>Twist shaker</td>
			<td>FINEPCR</td>
			<td>Tw3t</td>
			<td></td>
		</tr>
		<tr>
			<td>Tabletop centrifuge</td>
			<td>Sorvall</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Olympus America Inc</td>
			<td>IX71</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS (Fetal Bovine Serum)</td>
			<td>VWR International, Hyclone</td>
			<td>SH30919.03</td>
			<td></td>
		</tr>
		<tr>
			<td>Friedman Pearson Rongeurs</td>
			<td>FST (Fine Science Tools)</td>
			<td>16021-14</td>
			<td>Stainless steel, 14cm, curved, single joint action</td>
		</tr>
		<tr>
			<td>Fine Scissors - Tungsten Carbide &#38; ToughCut</td>
			<td>FST (Fine Science Tools)</td>
			<td>14558-11</td>
			<td>sharp, serrated</td>
		</tr>
		<tr>
			<td>Dumont #7 Forceps</td>
			<td>FST (Fine Science Tools)</td>
			<td>11272-30</td>
			<td>Dumoxel, 0.07 x 0.04mm, curved</td>
		</tr>
		<tr>
			<td>Vannas Spring Scissors</td>
			<td>FST (Fine Science Tools)</td>
			<td>15000-00</td>
			<td>straight, 3mm cutting-edge, sharp</td>
		</tr>
		<tr>
			<td>Qualitron DW-41 Micro-Centrifuge</td>
			<td>Artisan Technology Group</td>
			<td>DW-41</td>
			<td>Input Voltage: 115VAC</td>
		</tr>
	</tbody>
</table>

neuron-macrophage co-cultures to activate macrophages secreting molecular factors with neurite outgrowth activity

There is strong evidence that macrophages can participate in the regeneration or repair of injured nervous system. Here, we describe a protocol in which macrophages are induced to produce conditioned medium (CM) that promotes neurite outgrowth. Adult dorsal root ganglion (DRG) neurons are acutely dissociated and plated. After the neurons are stably attached, peritoneal macrophages are co-cultured on a cell culture insert overlaid on the same well. Dibutyryl cyclic AMP (db-cAMP) is applied to the co-cultures for 24 h, after which the cell culture insert containing the macrophages is moved to another well to collect CM for 72 h. The CM from the co-cultures treated with db-cAMP, when applied to a separate adult DRG neuron culture, exhibits robust neurite outgrowth activity. The CM obtained from the db-cAMP-treated cultures consisting of single cell type alone, either DRG neuron or peritoneal macrophage, did not exhibit neurite outgrowth activity. This indicates that the interaction between neurons and macrophages is indispensable for the activation of macrophages secreting molecular factors with neurite outgrowth activity into CM. Thus, our co-culture paradigm will also be useful to study intercellular signaling in the neuron-macrophage interaction to stimulate the macrophages to be endowed with a pro-regenerative phenotype.

We describe a protocol that can generate macrophages capable of secreting molecular factors with neurite outgrowth activity. The macrophage CM obtained from the co-cultures treated with db-cAMP resulted in robust neurite outgrowth when applied to a separate DRG neuron culture (Figure 2A). In comparison, CM obtained from the PBS-treated co-cultures did not induce neurite outgrowth in our 15-h culture duration (Figure 2B). When db-...

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Neuron-Macrophage Co-cultures to Activate Macrophages Secreting Molecular Factors with Neurite Outgrowth Activity

The current protocol presents experimental procedures to stimulate cultured macrophages to be endowed with capacity to release molecular factors that promote neurite outgrowth. Treatment of cAMP to the neuron-macrophage co-cultures induces the macrophages to produce conditioned medium that possesses strong neurite outgrowth activity.

There is strong evidence that macrophages can participate in the regeneration or repair of injured nervous system. Here, we describe a protocol in which ...

The overall goal of this procedure is to generate macrophages that can secrete molecular factors promoting neurite growth. This method can help answer key questions on how neurons and macrophages interact with each other to activate the pro-regenerative macrophagicphenotype to promote excellent regeneration. The main advantage of this technique is that we use Cyclic AMP, an adenosine serum molecule, which is much more physiologic enzymesone used in previous studies to stimulate macrophages with the pro-regenerative phenotype.We first had the idea for this method when we found that macrophage activation is essential in the enhancement of axion growth capacity and those can produce excellent neurons following precaution in permanent lobe injury. Before setting up the culture, precode a six well plate with poly-D Lycine and laminin. Next, incubate the six well plate with 0.01 poly-D Lycine at 37 degrees Celsius for two hours or at four degrees Celsius overnight.After that, wash the plate twice with distilled water. Then incubate the plate with laminin solution at a concentration of three micrograms per milliliter for two hours at room temperature. Following this, wash the plate twice with distilled water and dry the plate at room temperature for at least one hour.Now, incise the skin overlying the vertebral column of a euthanized mouse with a surgical blade and dissect the pair of vertebral muscles bilaterally to expose the vertebral bones. Remove the vertebral bones meticulously using a narrow-tipped surgical rongeur until the DRG are fully exposed. Under a dissecting microscope, remove the DRG bilaterally from S1 all the way up to the C1 level using iridectomy scissors and fine tipped forceps.Transfer the DRG to a 1.5 milliliter eppendorf tube using a blue pipette tip with a cut off end. Then remove DMEM after a quick spin for several seconds using a minicentrifuge. Add one milliliter of DMEM containing 125 units per milliliter type 11 collagenous and incubate the tube for 90 minutes with a gentle rotation using a twister shaker at 37 degrees Celsius.Afterward, discard collagenase containing DMEM and add one milliliter of fresh DMEM. Transfer the DRG to a 15 milliliter conical tube using a blue pipette tip with a cut off end. Then pipette up and down gently at least 15 times to make a homogenous cell suspension.Centrifuge the tube at 239 G for three minutes and carefully discard the supernatant with floating debris. Add one milliliter of neurobasil medium supplemented with B27 and re-suspend the cell pellet by gently pipetting up and down five to ten times. Next pass the cell suspension through a 70 micrometer cell strainer overlayed on top of a 50 milliliter conical tube.Then plate all the collected DRG neurons onto two wells of the six well plate. To prepare primary peritoneal macrophages from an adult mouse, incise the abdominal skin delicately to expose the peritoneum and avoid cutting the peritoneum to prevent a leakage of lavage fluid. Next puncture the peritoneum using a syringe with a 22 gauge needle and inject 10 milliliters of ice cold PBS into the peritoneal cavity.Gently massage the peritoneum for one to two minutes. Then pull out the needle and squeeze out the PBS through the needle puncture site and collect the lavage fluid in a 50 milliliter conical tube. Afterward centrifuge the lavage fluid at 239 g for 10 minutes at four degrees Celsius to pellet the cellular components.Subsequently re-suspend the pellet with three milliliters of the red blood cell lysis buffer for three minutes at room temperature. Then centrifuge the cell suspension again at 239 g for 10 minutes at four degrees Celsius. Re-suspend the pelletted cells in one milliliter of neurobasil B27 medium.Plate half of all collected macrophages on a cell culture insert with the effective area of 4.2 centimeters squared, which is placed on top of the well of dissociated DRG. Four hours after the neuron macrophage have been co-cultured add two microliters of 100 micromolar DB cyclic amp solution to the neuron macrophage co-cultures. After 24 hours, fill an empty well with one milliliter of macrophage culture medium in the same six well plate.Transfer the cell culture insert in the neuron macrophage co-culture to the empty well with macrophage culture medium. After 72 hours, centrifuge the macrophage conditioned medium at 239 times g for five minutes to remove the cellular components. Pass the supernatant through a 0.2 micrometer filter to remove any remaining cellular debris.In this procedure, precoat an eight well chamber slide with poly-D lycine and laminin. Then obtain the dissociated adult DRG neurons and neurobasil medium, supplemented with B27 using the same methods as described previously. Plate five times 10 to the four cells per well onto a precoated eight well chamber slide.Next place the chamber slide in a 37 degree Celsius incubator for two hours allowing the cells to attach to the bottom. Then replace the culture medium with the thawed, conditioned medium that is preheated at 37 degrees Celsius. 15 hours after the initial plating, remove the medium and wash the cells with PBS once, then add 200 microliters of ice cold, 4%paraformaldehyde solution to the wells and incubate the cells with the paraformaldehyde solution for 20 minutes at four degrees Celsius.Subsequently, incubate the fixed cells with primary antibody solution diluted with 10%normal goat serum for four hours at room temperature or overnight at four degrees Celsius. Afterward, take images using a fluorescence microscope to visualize neurite outgrowth. The macrophage conditioned medium obtained from the co-cultures treated with DB cyclic AMP resulted in robust neurite outgrowth when applied to a separate DRG neuron culture.In comparison, conditioned medium obtained from the PBS treated co-cultures did not induce neurite outgrowth. When DB cyclic AMP is treated to the culture with macrophage alone, conditioned medium was not effective in supporting neurite outgrowth. This suggests that neuron macrophage interaction is indispensable to stimulate macrophages to be endowed with a pro-regenerative capacity.We also tested the conditioned medium obtained from DB cyclic AMP treated neuron only culture and found no neurite outgrowth. It is important to remember that neurons and microplates should be prepared fresh and healthy. We experienced diminished neurite outgrowth activity of the constant medium when dissection lasted too long or peritoneum macrophages were contaminated with blood components.In this protocol, the dissociated DRG neurons were fiscally separated from the macrophages on the cell culture insert. Therefore our co-culture system will allow the identification of cellular factors responsible for intercellular signaling that mediate the activation of fully regenerative macrophages.

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8.6K Views.  Ajou University School of Medicine. The overall goal of this procedure is to generate macrophages that can secrete molecular factors promoting neurite growth. This method can help answer key questions on how neurons and macrophages interact with each other to activate the pro-regenerative macrophagicphenotype to promote excellent regeneration. The main advantage of this technique is that we use Cyclic AMP, an adenosine serum molecule, which is much more physiologic enzymesone used in previous studies to stimulate macrophages wi...