Role of cathepsins and cystatins in patients with recurrent miscarriage

In the implantation, trophoblasts penetrate maternal decidua by secreting proteases. It has been reported that cathepsins are highly expressed in the mouse villi, and play an important role in normal embryonal growth and decidualization. In this study, we evaluated cathepsins and their endogenous inhibitors, cystatins, in tissue and serum of patients with recurrent miscarriage. Decidua and villi were surgically collected from 22 patients and 12 healthy women. Immunohistochemistry was performed with antibodies against cathepsins, stefin A (cystatin A), stefin B (cystatin B) and cystatin C. The concentrations of cathepsins, stefins and cystatin C were measured by Enzyme-linked immunosorbent assay. In addition, we measured the serum level of cystatin C in 85 Japanese women with recurrent miscarriage. Staining of cathepsin B, D, H, L, stefin B and cystatin C was observed in the cytoplasm of epithelial cells in decidua. Stefin A was expressed on the surface of the trophoblast. The concentration of cathepsin B and H in patients' decidua was significantly higher than in control individuals. The serum level of cystatin C was significantly lower in patients than in control individuals. Our findings suggest that the regulation of the cathepsin-cystatin system may play an important role in patients with recurrent miscarriage.