Primary peritoneal fibroblasts are resident mesenchymal cells located in the submesothelial layer of the peritoneum. They constitute a functionally heterogeneous population characterized by the expression of markers such as CD34 and Thy-1, with distinct subsets exhibiting divergent profibrotic properties. Under physiological conditions, these fibroblasts maintain extracellular matrix homeostasis. However, in pathological states including peritoneal dialysis-associated fibrosis, endometriosis, and peritoneal carcinomatosis, they undergo activation toward a myofibroblastic phenotype, characterized by increased expression of α-smooth muscle actin, collagen I, and transforming growth factor-β1. This transition contributes to excessive extracellular matrix deposition, submesothelial thickening, and compromised peritoneal membrane function. Furthermore, peritoneal fibroblasts actively participate in inflammatory responses, secreting chemokines and cytokines that modulate immune cell recruitment within the peritoneal cavity. In the context of peritoneal metastasis, they also promote tumor cell attachment and invasion, underscoring their multifaceted roles beyond structural support.
