Proteases, their inhibitors and the extracellular matrix: factors in nerve-muscle development and maintenance.

Abstract

Over the last decade, the basement membrane or basal lamina of the adult skeletal muscle fiber has been emphasized as playing an important, if not critical, role in muscle regeneration after injury[1-9]. A concept of considerable stability and persistence of this structure or several components of it, has developed from studies principally in the frog that suggest it has major roles in the reinnervation of denervated adult muscle over and above any potential contributions by the principal cellular elements: nerve axon, Schwann cell or muscle fiber itself, in this process[10, 11]. In the last few years other studies suggest that one or more macro- molecules within the synaptic region of the basement membrane influence or cause the accumulation of acetylcholine receptors (AChRs) in the absence of the nerve[12,13]. Using much the same experimental paradigm, these same authors conclude that the same or different molecules, ‘stably’ attached to the synaptic basal lamina, regulate or ‘direct’ the accumulation of acetylcholinesterase (AChE), again at original synaptic sites[14].