Mesenchymal stem cell administration induces changes in neuronal nitric oxide synthase expression in dorsal root ganglia from rats subjected to sciatic nerve constriction

M.F. CORONEL; P.L. MUSOLINO; M.J. VILLAR

Atlanta, USA

Congreso; Society for Neuroscience; 2006

Society for Neuroscience

Sciatic nerve lesions upregulate the expression of neuronal nitric oxide synthase (nNOS) in dorsal root ganglia (DRGs) (Coronel et al, SFN, 2004). Nitric oxide (NO) has been demonstrated to exert antinociceptive actions in several experimental models of neuropathic pain. In rats subjected to a sciatic nerve constriction, mesenchymal stem cells (MSCs) preferentially migrate into the ganglia affected by the lesion (Coronel et al, SFN, 2005) and reduce thermal and mechanical allodynia (Musolino et al, SFN, 2005). We now demonstrate that the intraganglionic (L4) administration of MSCs to rats with a sciatic nerve single ligature nerve constriction (SLNC) results in an upregulation of nNOS in primary afferent neurons. Whole marrow was aspirated from the tibiae and femurs of adult Sprague-Dawley rats, the mononuclear cells were isolated using a density gradient and plated at a concentration of 5 x 106 cells/ml in DMEM, 10% FBS in 25 cm2 cell culture flasks. MSCs were isolated by their adherence to plastic, cultured until confluence and harvested. A suspension of cells (2 x 105 in saline) was injected into the right L4-DRG of Sprague-Dawley rats. Immediately after, their right sciatic nerve was exposed and constricted to a 40-80% of its original diameter, using a thin strip of polyethylene. Control animals were either only constricted or constricted following an intraganglionic PBS injection. After 7 days of survival, they were perfused through the heart and the ipsi and contralateral L4-5 DRGs were dissected out and processed for standard ABC immunohistochemistry, using a nNOS specific antibody. As expected, SLNC induced a marked upregulation in the expression of the enzyme, mostly in small and medium sized DRG neurons. The intraganglionic injection of PBS did not modify the number of nNOS-expressing cells. On the contrary, MSCs induced a further upregulation of the enzyme, with almost a 40% increase in the number of nNOS-positive neurons. The subsequent release of NO may explain, at least in part, the analgesic effects exerted by MSCs after peripheral nerve injury. Further studies should be carried out in order to evaluate the mechanisms involved in MSCs induction of nNOS upregulation.