Histochemical study of lamellar cell development of Meissner corpuscles.

The development of the lamellar cells of mouse digital corpuscles (Meissner corpuscle) was studied by light and electron microscopic histochemistry for cholinesterase (ChE) The materials used were the hind limbs taken from fetuses at 14, 17 and 20 days of gestation, and from young mice at 1, 5, 7, 15 and 20 days after birth. Embryonal Schwann cells had non-specific ChE activity in the cisternae of the rough endoplasmic reticulum and the nuclear envelope, suggesting that they had the ability of synthesizing the enzyme. After birth, such ability gradually decreased and by five days of age non-specific ChE activity was no longer demonstrable in Schwann cells at the time when myelin sheath formation began. However, Schwann cells which were associated with the axonal tips penetrating into the epidermis still had an intense non-specific ChE activity. Such Schwann cells surrounded the axons in gradually increasing numbers of cytoplasmic processes, which later became the lamellae around the axon terminals; thus by 20 days after birth they had differentiated into mature lamellar cells of Meissner corpuscles. These lamellar cells had, as in the embryonal Schwann cells, an intense ChE activity in the cytoplasm. These findings indicate that the lamellar cell is a specialized form of Schwann cell which still retains the embryonal characteristics for synthesizing non-specific ChE.