Apoptosis in mammalian eye development: lens morphogenesis, vascular regression and immune privilege

Abstract

Formation of the mammalian eye requires a complex series of tissue interactions that result in an organ of exquisite sensory capability. The early steps in eye development involve extensive cell death associated with morphogenesis. Later, suppression of programmed cell death is essential for tissue differentiation and in the adult, the immune privileged status of the eye is maintained in part through factors that induce inflammatory cell apoptosis. Experimental evidence suggests that suppression of apoptosis in cells of the lens lineage by fibroblast growth factors is one component of their action during lens morphogenesis. Fibroblast growth factors are also required for normal lens fiber-cell differentiation. This includes a degenerative step for organelles that is presumably an adaptation for the clearance of light scattering elements from the optic axis. The process of organelle degeneration may be related to apoptosis in a few of its features. Activelyinduced apoptosis becomes important for eye development as the temporary ocular vasculatures regress. This too, is presumably an adaptation for the disposal of cells that would disturb the passage of light to the retina. Ocular macrophages appear to be essential for the induction of apoptosis in the endothelial cells comprising the ocular vasculatures. In the adult, inflammatory cells entering the eye are exposed to the pro-apoptotic agents transforming growth factor-b2 and Fas ligand. The expression of these molecules in the eye, and their action in killing inflammatory cells, has evolved as a means of preventing inflammation and subsequent loss of vision. Thus, the eye offers a unique and versatile system for studying the role of programmed cell death in lens development, vascular regression and immune privilege.

Identification of an HLA-A*0201-restricted cytotoxic T lymphocyte epitope from the lung carcinoma antigen, Lengsin

“…Lengsin protein is overexpressed irrespective of the histological type of lung carcinoma, but not in normal tissues other than the lens. Because the eye lens is an immune-privileged site (17,18), similar to the case of the testis, Lengsin can be an attractive target for tumor antigen-specific immunotherapy, as with cancer-testis antigens.…”

Estudio de los mecanismos de apoptosis y mitosis en el globo ocular: Modelo experimental del síndrome tóxico gestacional

“…Un poco mas tarde, la supresión de la muerte celular programada es fundamental para la diferenciación del tejido en el adulto. Hay estudios que describen que la supresión de la apoptosis en célu-las del cristalino por factores de crecimiento (FGF) es uno de los principales componentes de sus acciones durante el desarrollo del cristalino (26). La apoptosis inducida es esencial en determinados momentos del desarrollo, por ejemplo durante la reabsorción de la vascularización primitiva.…”

Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature

“…The critical maturation period of the rat lens is related to the atrophy of a supporting vascular bed tissue (tunica vasculosa lentis) (Fris and Midelfart Garde et al (2018) NAMMCO Scientific Publications, Volume 10 2007). By the fourth week after birth the tunica vasculosa lentis has completely regressed and delivery of several compounds to the avascular lens tissue significantly reduced (Lang 1997: Fig. 3 for illustration of the regressing tunica vasculosa lentis).…”