MP17-03 HYALURONAN AND ITS HYALURONAN RECEPTORS IN RAT BLADDER REGENERATION AND THEIR ROLE IN ANGIOGENESIS

Abstract

INTRODUCTION AND OBJECTIVES: Hyaluronic acid (HA), a non-sulfated glycosaminoglycan and an essential component of the extracellular matrix (ECM), plays critical roles in phases of wound healing and tissue regeneration. This study was designed to characterize temporal and anatomical HA deposition and its major receptors (CD44, LYVE-1, RHAMM, and HARE) expression in a rat bladder regeneration model and to understand the effectiveness of HA in promoting angiogenesis. METHODS: Fifteen Sprague-Dawley rats were subjected to partial cystectomy with interposition of distal sections of porcine small intestinal submucosa (SIS). SIS-augmented bladders were harvested on post-operative days 2, 7, 14, 28, and 56 for histological studies. Effectiveness of HA in stimulating endothelial cell proliferation, tube formation, and angiogenic activity were determined in vitro cell and ex ovo chick chorioallantoic membrane (CAM) models. RESULTS: Bladder regeneration proceeded without complications; and all regenerated bladders had complete urothelial lining and smooth muscle bundle formation by day 56 post-augmentation. As determined by immunohistochemistry, strong positive HA staining was observed on days 28 and 56 post-operation in the ECM of the stroma. CD44 immunoreactivity was detected on days 28 and 56 in the cytoplasm of urothelial cells and LYVE-1 immunoreactivity was detected exclusively in lymphatic vessels at days 28 and 56. RHAMM mRNA increased within 2 days post-operation, whereas HARE mRNA level did not change during the course of bladder regeneration. Exogenous HA significantly stimulated growth and tube formation of cultured endothelial cells, and enhanced angiogenesis in CAM assay. CONCLUSIONS: During bladder regeneration HA is synthesized throughout the course of regeneration processes. HA deposition coincides with urothelial differentiation. Temporal regulation and spatial distribution of two major HARs (CD44 and LYVE-1) follow the same temporal pattern as HA deposition. Therapeutic modalities through local delivery of exogenous HA can be viable to significantly improve angiogenesis and enhance the outcome and completeness of bladder regeneration.