Immunohistochemical study of 28-kD heat shock protein in the lens of young human embryos.

The localization of 28-kD heat shock protein (HSP28) in the lenses of human embryos (Carnegie stages 13-21) was studied immunohistochemically using antibodies for HSP28. At stage 13, HSP28 was observed in the lens placode. At stage 15, when the lens vesicle is formed by the invagination of the lens placode, HSP28 was observed in the posterior portion of the lens vesicle. From stages 16 to 18, when the posterior portion of the lens epithelium elongates toward the anterior lens epithelium and forms the primary lens fiber, HSP28 was observed in the apical and basal sides of the primary lens fiber. At stage 19, when the primary lens fiber attaches to the anterior lens epithelium, immunoreactivity to HSP28 appeared in the anterior lens epithelium. At stage 21, the anterior lens epithelium and the equator portion of the lens, where the secondary lens fiber is formed, were intensely immunoreactive to HSP28. Although alpha B-crystallin is thought to be one of the small HSPs, the distribution of HSP28 in the lenses of human embryos was different from that of alpha B-crystallin which we previously reported.