Embryo-fetal development of iris: Immunohistochemestry of morphogen Shh Desarrollo embriofetal del iris: Inmunotinción del morfógeno Shh

Abstract

In order for the iris to develop, a specification of the peripheral layer of the optic cup to a non-neuronal target is required, as well as the migration of periocular mesenchymal cells. Our aim was to recognize the histological changes of peripheral derivatives of the optic cup and periocular mesenchyme, as well as recognize the presence of the morphogen Sonic hedgehog (Shh) in the layers constituting the outline of the iris. 15 female mice (Mus musculus) pregnant young adults were used. Euthanasia was performed with sodium thiopental. Embryos and fetuses of 12, 14.5 and 17 days post-coital (dpc) were processed with histological and immunohistochemical technique with anti-Shh antibody (scbt, H-160, rabbit) with dilution 1:100 in PBS. At 12 dpc, an optic cup showing internal and external retinal layers is observed, and the iris is not observed. Between the lens and the superficial ectoderm, 4 layers of mesenchymal cells are identified. At 14.5 dpc, the iris contains two epithelial layers (internal and external) that are continued with the neural and pigmentary layers of the retina. 8 layers of mesenchymal cells are observed. At 17 dpc, the inner epithelial layer of the iris presents a more elongated segment with positive immunostaining to Shh and another part that constitutes an epithelium of simple cylindrical cells negative to this antibody. The outer epithelial layer presents the same immunonegative epithelium. The layers of the retina are also positive, as well as the periphery of the lens. The iris is not formed nor is the ciliary body.The immunopositivity in the lens, in the first segment of the inner layer of the iris outline and in the retinal ganglion layer at 17 dpc, is related to the late differentiation of the iris and the closed eyes of the offspring at birth.