Mitosis in developing rabbit retina: an immunohistochemical study

The proliferation of cells in the embryonic and postnatal rabbit retina was studied with the MIB-1 antibody which demonstrates the Ki-67 antigen. Already at embryonic day 15 there were postmitotic cells (i.e. cells that do not stain with the MIB-1 antibody) in the basal part of the neuroblastic cell mass which are presumably the differentiating ganglion cells. After the formation of an inner plexiform layer at around embryonic day 25, postmitotic cells were seen in the proximal part of neuroblastic cell mass (presumably amacrine cells) as well as in the ganglion cell layer. Proliferating cells accumulated distal to the layer of postmitotic cells and their number gradually decreased towards the pigmented epithelium. At birth, proliferation ceased in the central parts of the retina but in the peripheral parts it continued for 7 days although rare cells could be seen for up to 15 days. After the formation of the outer plexiform layer, the proliferating cells in the outer nuclear layer accumulated close to the outer plexiform layer whereas the postmitotic cells (the differentiating photoreceptors) did so at the distal part of outer nuclear layer. Some cells in the middle of the inner nuclear layer (presumably the Müller cells) and some cells in the ganglion cell layer or nerve fiber layer (presumably the astrocytes) proliferated for the longest period of time.