AIM:To determine the function of peritoneal mesothelial cells on the inflammatory microenvironment by administration of endometrial cells,and further define the pathogenesis of endometriosis.METHODS:Homogenous mouse endometrial epithelial and stromal cells were injected into the peritoneal cavities of Swiss Webster mice.After 4,24,and 72 h,a number of endpoints evaluated:protein concentrations of cytokine MCP-1,IL-1 ?,IL-6 in peritoneal lavage and gene expressions of MCP-1,IL-1 ?,IL-6 in peritoneal mesothelial cells and macrophages.RESULTS:The intraperitoneal administration of endometrial cells increased the protein expressions of cytokines in the peritoneal lavage of the recipient mice,which increased at 4-hour points and subsequently decreased with time.Gene expressions of cytokines in peritoneal mesothelial cells paralleled with the protein quantities in peritoneal lavage.The peak time of gene expression of cytokines in peritoneal macrophages was at the 24-hour point.The endometrial epithelial cells stimulated stronger inflammatory responses in the peritoneal cavity than the endometrial stromal cells.CONCLUSION:The recipient mice have a non-specific inflammatory response to the presence of endometrial cells in the peritoneal cavity.Mesothelial cells may be the targets of early inflammatory stress initiated in the presence of endometrial cells.