LOCATION OF TYPE-XV COLLAGEN IN HUMAN TISSUES AND ITS ACCUMULATION INTHE INTERSTITIAL MATRIX OF THE FIBROTIC KIDNEY

An antipeptide antibody was produced against the carboxyl-terminal non collagenous domain of human type XV collagen and used to localize this recently described collagen in a number of human tissues. The most co nspicuous findings were powerful staining of most of the capillaries a nd staining of the basement membrane (BM) zones of muscle cells. Not a ll of the BM zones were positives, however, as shown by the lack of st aining in the developing fetal alveoli and some of the tubules in deve loping kidney. Nor was type XV collagen staining restricted to the BM zones, as some could be observed in the fibrillar collagen matrix of t he papillary dermis and placental villi, for example. Interestingly, d ifferences in the expression of type XV collagen could be observed dur ing kidney development, and staining of fetal lung tissue suggested th at changes in its expression may also occur during the formation of va scular structures. Another intriguing finding was pronounced renal int erstitial type XV collagen staining in patients with kidney fibrosis d ue to different pathological processes. This suggests that the accumul ation of type XV collagen may accompany fibrotic processes. Full-lengt h human type XV collagen chains with an apparent molecular mass of app roximately 200 kd were produced in insect cells using a baculovirus ex pression system. The fact that these had a markedly higher molecular m ass than the 100- to 110-kd type XV collagen chains found in homogenat es of heart and kidney tissue suggest either proteolytic processing du ring the synthesis of type XV collagen or an inability to solubilize c omplete molecules from tissues.