Hyperosmolality suppresses but TGFβ1 increases MMP9 in human peritoneal mesothelial cells

Hyperosmolality suppresses but TGFβ1 increases MMP9 in human peritoneal mesothelial cells. Peritoneal mesothelial cells are directly exposed to hyperosmolar dialysates which may enhance extracellular matrix accumulation and hence compromise ultrafiltration. Because these cells are laid on a type IV collagen containing basement membrane, we examined the pattern of type IV collagenases produced by cultured human mesothelial cells and their regulation by hyperosmolality and TGFβ1. A cell line (HMrSV5) exhibiting major features of normal peritoneal mesothelial cells was derived from a primary culture retrovirally transduced with SV40 large-T antigen. Zymography and Western blot analysis showed that: (i) human peritoneal mesothelial cells produced and excreted MMP2 and MMP9 and their inhibitors TIMPl and TIMP2; (ii) hyperosmolality drastically reduced the expression of MMP9 irrespective of the osmolyte used in a time- and concentration-dependent manner; (iii) TGFβ1 unexpectedly increased MMP9 activity and protein in exponentially growing cells and could restore MMP9 activity suppressed by hyperosmolality in confluent cultures. To exclude a specific effect of SV40 large-T antigen on matrix metalloproteinases production and regulation, these results were confirmed in primary cultures derived from visceral peritoneal samples from different donors. Therefore, the hyperosmolality of dialysates may favor an accumulation of type IV collagen and thickening of peritoneal basement membrane, while TGFβ1 released during infections may induce the degradation of type IV collagen and its replacement by interstitial collagens.