SPATIAL DISTRIBUTION OF FIBROBLAST GROWTH FACTOR RECEPTOR 2 IN NORMAL AND LESIONED CENTRAL NERVOUS SYSTEM OF <I>PLEURODELES WALTLII</I>

Abstract

Fibroblast Growth Factors (FGFs) have been implicated in numerous cellular processes including proliferation, migration, differentiation and neuronal survival. One of these growth factors, Fibroblast Growth Factor 2 (FGF2), is apparently implicated in the ability of the adult salamander (Pleurodeles waltlii) to recover locomotion following complete transection of the spinal cord. In a previous study, we reported up regulation of FGF2 during regeneration of damaged axons and recovery of hind limb locomotion. In this study reported here, we investigated the spatial distribution of FGFR2-one of the receptors that mediate the effects of FGF2-using a variety of techniques, namely, western blot, immunohistochemistry and in situ hybridization. We find that in intact animals FGFR2 is mainly expressed in the most posterior part of body Spinal Cord (SC3) specifically in neurons. However, lesioning the spinal cord produces increased expression in Brainstem (BS) neurons and decreased expression in posterior parts of the spinal cord not only in neurons but also in the neuroglial ependymal cells lining the central canal. This suggests that FGF2 simultaneously activates FGFR1 and 2, perhaps at different points in the regeneration process and thus FGFR2 might play at least an indirect role in the spontaneous regeneration observed in this species and might be relevant to the treatment of spinal cord lesions in humans. Verification of this possibility will require studies of additional time points.

Neurogenesis and growth factors expression after complete spinal cord transection in Pleurodeles waltlii

“…In previous studies (Moftah et al, 2008 , 2012 ), we correlated the recovery of locomotor activity with FGF-2 and FGFR2 mRNAs expression. To investigate the relation between the transcriptional activity of this growth factor and its receptor with neurogenesis, we studied the distribution of FGF-2 and FGFR2 mRNA in the same regions we used for nestin immunohistochemistry, by using in situ hybridization (Figure 5 ).…”

“…It has been recently shown that quiescent ependymoglial cells can be activated to proliferate and regenerate the lost cells after a CNS lesion (Berg et al, 2010 ). As ependymal remodeling occurs, there are interactions between ependymal cells and neurons and, possibly, between ependymal cells and fibrous astrocytes and oligodendrocytes (Chernoff, 1996 ; Moftah et al, 2008 , 2012 ; Fahmy and Moftah, 2010 ).…”

“…The presence of FGF2 protein was determined by western blot analysis. All animal groups were anesthetized and treated as previously described (Moftah et al, 2012 ). In summary, spinal cords were exposed by laminectomy then divided into two segments (anterior and posterior) corresponding respectively to the pre- and post-lesional parts of the cord (in spinalized animals).…”

“…Previously removed and frozen spinal cord portions ( n = 5) were treated as previously described (Moftah et al, 2012 ). In short, specimens were separately homogenized in ice cold buffer.…”

“…Anesthetized animals ( n = 5/experiment) were perfusion-fixed via the ascending aorta. Spinal cord was dissected out and treated as described earlier (Moftah et al, 2012 ). In summary, blocked sections were incubated (1:1000 in 2,4,6-trinitrotoluene, TNT/bovine serum albumin, BSA) with rabbit anti-nestin (Abcam, Paris, France) and mouse anti-pan neural NF (Sternberger Monoclonals Incorp., Lutherville, MD, USA) primary antibodies.…”