Peripheral nerve fiber outgrowth from developing spinal cord is proposed to be under the influence of the limb bud target which, at the time of nerve fiber invasion, is in an essentially premuscular, mesenchymal condition. Thus, the true target for elongating spinal nerve fibers in early development is mesenchyme rather than differentiated skeletal muscle. Spinal cord explants derived from stage V larval Rana pipiens were cultured in a defined medium in the presence or absence of mesenchymal limb tissue or limb-conditioned medium (LCM). Analysis of quantified neuritic outgrowth under these conditions demonstrated a dependency on the target tissue for enhanced nerve fiber density and oriented growth. The characteristics of neuritic growth in the presence of limb mesenchyme or LCM changed from the relatively sparse and straight outgrowth of control cords to dense, wavy arborizations. Areas of the cord explants nearest the limb tissue exhibited the greatest increases in nerve fiber density and morphologic complexity. Additionally, an inverse relationship existed between growth enhancement and the cord-to-target distance. Regulation of directed nerve growth in vitro is suggested to result from a diffusible, target-originated growth factor that binds to the attachment substratum as a concentration gradient guidance pathway with implications for mechanisms of in vivo nerve growth.
Dorsal root ganglia of larval frog extended elaborate neuritic arrays in vitro under minimal culture conditions in the absence of medium-supplemented stimulatory factors. The highly adhesive attachment substratum polylysine provided the necessary condition for exuberant outgrowth, the extent of which was dependent on the developmental stage of the animal from which the neural tissue was derived, as was the capability for long-term survival. It appears that an appropriate substratum can substitute for added growth factors in eliciting robust and long-lived sensory neurites in vitro.
Nerve fibers readily extend from larval frog spinal cord explants when cultured on a commercially available reconstituted basement-membrane-like matrix derived from the EHS mouse sarcoma. This superior, naturally derived substratum enables the in vitro development of complex neuritic arrays with long survival times in a defined medium, thus permitting the detailed analysis of spontaneous and target-mediated neuritogenesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.