Fibroblast growth factor treatment produces differential effects on survival and neurite outgrowth from identified bulbospinal neurons in vitro.
The in vivo application of appropriate trophic factors may enhance regeneration of bulbospinal projections after spinal cord injury. Currently, little is known about the sensitivities of specific bulbospinal neuron populations to the many identified trophic factors. We devised novel in vitro assays to study trophic effects on the survival and neurite outgrowth of identified bulbospinal neurons. Carbocyanine dye crystals implanted into the cervical spinal cord of embryonic day (E)5 chick embryos retrogradely labeled developing bulbospinal neurons. On E8, dissociated cultures containing labeled bulbospinal neurons were prepared. Fibroblast growth factor (FGF)-2 (but not FGF-1) promoted the survival of bulbospinal neurons. FGF receptor expression was widespread in the E8 brainstem, but not detected in young bulbospinal neurons, suggesting that nonneuronal cells mediated the FGF-stimulated survival response. Astrocytes synthesize a variety of trophic factors, and astrocyte-conditioned medium (ACM) also promoted the survival of bulbospinal neurons. As might be expected, FGF-2 function blocking antibodies did not suppress ACM-promoted survival, nor did an ELISA detect FGF-2 in ACM. This suggests that nonneuronal cells synthesize other factors in response to exogenous FGF-2 which promote the survival of bulbospinal neurons. Focusing on vestibulospinal neurons, dissociated (survival assay) or explant (neurite outgrowth assay) cultures were prepared. FGF-2 promoted both survival and neurite outgrowth of identified vestibulospinal neurons. Interestingly, FGF-1 promoted neurite outgrowth but not survival; the converse was true of FGF-9. Thus, differential effects of specific growth factors on survival or neurite outgrowth of bulbospinal neurons were distinguished.
Pataky
D M
DM
CORD, Collaboration On Repair Discoveries, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, V6T 1Z4, Canada.
Borisoff
J F
JF
Fernandes
K J
KJ
Tetzlaff
W
W
Steeves
J D
JD
D000818:Animals; D001933:Brain Stem / Q000187:drug effects* / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D017077:Culture Media, Conditioned; D016220:Fibroblast Growth Factor 1; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology* / Q000502:physiology / Q000627:therapeutic use; D051525:Fibroblast Growth Factor 9; D005346:Fibroblast Growth Factors; D006133:Growth Substances / Q000494:pharmacology / Q000502:physiology / Q000627:therapeutic use; D016501:Neurites / Q000187:drug effects* / Q000502:physiology; D013119:Spinal Cord Injuries / Q000188:drug therapy / Q000503:physiopathology; D013127:Spinal Nerves / Q000187:drug effects* / Q000502:physiology; D014981:Xenopus
D017077:Culture Media, Conditioned; D051525:Fibroblast Growth Factor 9; D006133:Growth Substances; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; D005346:Fibroblast Growth Factors