Stimulation of axon growth from the spinal cord by a regenerating limb blastema in newts.
The effects of limb blastemas of Pleurodeles waltl on axon growth from fragments of spinal cord were studied in vitro. Cultured in a defined medium, spinal cord fragments regenerated sparse, short axons. The culture of spinal fragments in the presence of blastemas greatly enhanced the length, number and survival of axons. Testing separately each of the two components of the blastema showed that only the mesenchyme exerts a neurotropic effect on the spinal fragments. Other tissues such as muscle or skin had a limited neurotrophic effect. Additionally, the neurotrophic activity of blastemas seems to be dependent of its proliferation status. Compared with blastemas of regenerating limbs from young animals, irradiated blastemas (devoid of mitotic activity) and blastemas of regenerating limbs from old animals or differentiated blastemas (both characterized by a low mitotic activity), exhibited a weaker neurotrophic influence. The blastema neurotrophic factor is not an attachment molecule but a soluble one and cannot be nerve growth factor (NGF) or fibroblast growth factor (FGF). It has a relatively low molecular weight (less than 15 kDa) and its protein nature was ascertained by its sensitivity to heating and proteases. As the production of this mesenchyme-derived neurotrophic factor depends upon mesenchymal cell proliferation of the blastema, we suggest that there is loop of positive regulation between spinal nerves and blastema. Blastema tissues may stimulate nerve regeneration allowing the stimulation of proliferation of blastema cells by regenerating nerve fibers. Alternatively, blastema cells may produce a neurotrophic factor whose secretion might be dependent on cell proliferation.
Bauduin
B
B
Equipe Facteurs de Croissance, Laboratoire de Biologie du Développement (UPRES 1033), Bât SN3, Université de Lille I, 59655 Villeneuve d'Ascq Cedex, France.
Lassalle
B
B
Boilly
B
B
D000672:Amputation Stumps / Q000294:innervation*; D000818:Animals; D001369:Axons / Q000502:physiology*; D002452:Cell Count / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology; D046508:Culture Techniques; D005552:Forelimb / Q000294:innervation; D018878:Limb Buds / Q000166:cytology / Q000254:growth & development / Q000294:innervation* / Q000528:radiation effects; D008648:Mesoderm / Q000166:cytology; D008970:Molecular Weight; D009414:Nerve Growth Factors / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D010999:Pleurodeles / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology* / Q000187:drug effects / Q000502:physiology
D017077:Culture Media, Conditioned; D009414:Nerve Growth Factors