Induction of hyaluronan metabolism after mechanical injury of human peritoneal mesothelial cells in vitro

Background. Hyaluronan(HA) is an important extracellular matrix component t hat is involved in cell movement and tissue repair. In vertebrates, HA synt hase genes (HAS 1, HAS 2, and HAS 3) that control the synthesis of HA have been identified. In this article, we investigated HA synthesis in the respo nse of human peritoneal mesothelial cells (HPMCs) to injury. Methods. The expression of HAS 1, HAS 2, and HAS 3 mRNA and the synthesis o f [H-3]-labeled HA were examined in an in vitro model of peritoneal mesothe lial cell damage. The staining for uridine diphosphoglucose dehydrogenase, a key enzyme in the synthesis of HA, and biotinylated HA-binding protein wa s used to determine the cellular location of HA synthesis and its site of d eposition. Results. Growth-arrested human HPMCs expressed low levels of mRNA for HAS 2 and HAS 3 but not HAS 1. Following injury to the monolayer, HAS 2 was up-r egulated by 6 hours, reaching maximal expression between 12 and 24 hours. I n contrast, the expression of HAS 3 was down-regulated. During the same tim e period, synthesis of HA was increased in the injured monolayer. This synt hetic activity appeared to be restricted to cells at the edge of the wound and to cells entering the wound. In a separate series of experiments, the a ddition of HA to the injured monolayer at a concentration range found in pe ritoneal fluid (50 to 3300 ng/mL) increased the migration of cells into the wound in a dose-dependent manner. Conclusions. These studies provide evidence that HA is an important compone nt of peritoneal mesothelial cell migration. The results also suggest that in this process, there is differential regulation of HAS gene expression an d that the synthesis of HA is limited to cells located at the leading edge of the wound.