Regeneration of mouse digital corpuscles

Changes in morphology and nonspecific cholinesterase (ChE) activity during the reinnervation of digital corpuscles of mouse toe pads after transection of the sciatic nerve were examined by light and electron microscopy. Reinnervation occurred about 30 days after nerve section. A small-diameter axon was present near the shrunken atrophic lamellae of the previously denervated corpuscle. From 40 to 60 days after nerve transection, the ingrowing axons branched; and the enlarged tip of each branch contained numerous mitochondria. Lamellar cells and cytoplasmic lamellae at this stage were still smaller than normal. Lamellar cells had normal structure by 4 months after nerve section. Following reinnervation, evidence of ChE activity in the interlamellar spaces at first remained unchanged in intensity and distribution from that of the denervated corpuscle. About 10 days after reinnervation, enzyme activity increased in the perineural spaces and was evident, as in the normal corpuscle, in the cisternae of the rough endoplasmic reticulum and nuclear envelope of the lamellar cell body. By 4 months after nerve division, the intensity and distribution of the ChE activity were almost the same as in the normal corpuscle. From the above findings the following conclusions could be drawn: (1) The shrunken atrophic lamellar cells remaining after denervation are utilized are utilized by the ingrowing axons to regenerate normal digital corpuscles. (2) The lamellar cell is dependent on the well-developed axon terminals to maintain its normal morphology and to synthesize ChE.