Pecam1, also known as platelet endothelial cell adhesion molecule-1 or CD31, is a member of the immunoglobulin superfamily. It is expressed in various immune cells like monocytes, neutrophils, macrophages, as well as endothelial cells. Pecam1 is crucial for the development and maturation of B lymphocytes and plays important roles in angiogenesis, vascular permeability, and immune response [2,3].

Pecam1 may be a potential biomarker for the diagnosis and treatment of bone metastases. Its expression decreases in bone metastatic tumor tissues, and knocking down its expression in bone marrow-derived lymphocytes promotes osteoclast differentiation and the proliferation and migration of tumor cells [1]. In lymphedema patients, rare variants in Pecam1 were found, suggesting its importance in lymphatic vasculature formation [2]. In pulpitis, PECAM1 combines with CXCR4 to trigger inflammatory cell infiltration and pulpitis progression through activating the NF-κB signaling pathway [4]. Also, in women with recurrent implantation failure, the expression of PECAM1 and TGF-β1 (mediated by PECAM1) is significantly decreased in the mid-secretory endometrium, indicating their role in modulating endometrial receptivity [5].

In conclusion, Pecam1 is essential for multiple biological processes, including immune cell development, angiogenesis, and tissue-specific functions. Studies, especially those involving functional changes like knockdown experiments, have revealed its significance in diseases such as bone metastases, lymphedema, pulpitis, and recurrent implantation failure. Understanding Pecam1's functions can potentially lead to new diagnostic and therapeutic strategies for these conditions.