Cystatin A and B in the Development of human squamous epithelia

Abstract

The expression of cystatin A (Acid cysteine proteinase inhibitor) and B (Neutral cysteine proteinase inhibitor) during human embryogenesis was studied immunohistochemically by using the PAP-complex method. Both inhibitors were visible first in the developing mucosal tissue at the age of about 9 weeks. In the fetal epidermis (periderm), cystatin B was demonstrated at the age of 11 weeks and cystatin A at 12 weeks. In these young fetuses, the staining was visible in the basal cells, whereas in fetuses older than 17 weeks the staining of both inhibitors diminished in the basal cells. In the skin of 17 to 25 weeks old fetuses, the epidermal staining of cystatin B become weaker than that of cystatin A, and at the age of about 26 weeks, cystatin B disappeared totally. At this stage, cystatin A was localized in the cytoplasm of the middle to upper cell layers of the epidermis. In the squamous epithelia of the mucosal tissues, the staining of the both inhibitors reached their maximal intensity when the fetuses were about 16 weeks old. At the mature fetuses, infants as well as adults, both cystatin A and B seemed to be present in wet squamous epithelia while in the epidermis only cystatin A was expressed.