DEVELOPMENTAL EXPRESSION OF INTERSTITIAL COLLAGEN GENES IN FETAL BLADDERS

Bovine bladders at 3 stages during fetal development were examined for expression of collagens by immunohistochemistry as well as by measure ment of steady state mRNA levels. Expression of type I and type III co llagens during the fetal period was compared with that of adult cows a s well as a young animal (heifer). Each bladder was separated into a d etrusor and a urothelial-lamina propria sample which were then analyze d separately. Distribution and fiber arrangement of types I and III co llagens were different depending upon the region of the bladder wall e xamined. Type III collagen, in particular, has a ''coiled'' appearance which is especially prominent within the lamina propria. Collagen gen e expression showed a distinctive pattern which was different for both type I and type III collagen. While type I collagen gene expression p eaked during the late second to early third trimester, type III collag en expression progressively decreased throughout the fetal period. In addition, expression of both collagens was greater in the urothelial-l amina propria fractions. These data demonstrate that the pattern of co llagen gene expression in the developing bladder is developmentally re gulated and is unique to each of the two major structural layers.