After the central nervous system injuries, three myelin major inhibitors, including NogoA, myelin-associated glycoprotein (MAG) and oligodendrocyte myelin glyco- protein, play an important role in limiting axonal regeneration by interacting with Nogo receptor NgR (now also termed NgR1) [1]. It was reported that NgR appear to be expressed in neuron and certain non-neuronal cells,including oligodentrocytes and mcrophage [2,3]. Recently, some groups also found that it could be detected in neural stem cells(NSCs) as well as exert an effect on NSCs differention in vitro [4,5]. A recent study in vitro also has indicated NgR agonist prevent NGF-stimulated p75NTR -dependent death of cultured embryonic motor neurons and confer protection on spinal cord motor neurons after neonatal sciatic nerve axotomy [6]. Therefore, I propose additional roles for NgR in NSCs could exist.

There is evidence that NgR has been shown to be involed in migration and adhesion for olfactory ensheathing cells (OECs). When NgR was released from the OECs surface with phosphatidylinositolspecific phospholipase- C or neutralized by NgR antibody, the effect of Nogo-66 on OEC adhesion and migration was markedly attenuated in vitro [7]. More over, they demonstrate that treatment with anti-NgR antibody promoted migration of implanted OECs in a spinal cord injury model. These reflect an attractive effect for NgR expressed in OECs with myelin.

However, another group showed that NgR expressed in macrophage reduced binding to myline and MAG in vitro ,which is revised by NgR siRNA knockdown and by inhibiting Rho-associated kinase [3]. NgR1 is also expressed by glioma cells and inhibit adhesion and migration of these cells in response to MAG [8]. This inhibitory effect may reflect a repulsive interaction between NgR expressed in macrophages and glioma cells as well as myelin.

Thus, I endorse a hypothesis that expresstion of NgR in NSCs may contribute to the change of migration or adhesion between NSCs and three myelin inhibitors in vivo or vitro, especially in the injuried spinal cord.

This hypothesis may remind us that after spinal cord or brain injury, when implanted NSCs for treatment these disorders, perhaps we should take into account the effect of NgR on NSCs migration and adhesion. Because it may further influence the survival, differention and secreting---neurotrophic factor of NSCs.Thus, the importance of NgR for NSCs treatment of central nervous system injuries may be considered as one potential strategy.

This study was supported by the Scientific Research initiation founding of Wenzhou medical college (No.QTJL0009).