Functional Expression of TRP Ion Channels in Endometrial Stromal Cells of Endometriosis Patients

Endometriosis is a common gynecological disease that is characterized by the presence of functional endometrial-like lesions in the abdominal cavity. Aside from epithelial cells, these lesions consist of stromal cells that have the capacity to migrate, adhere, proliferate, and induce neuro- and lymphangiogenesis, which allows them to survive at ectopic locations. However, the exact underlying mechanisms that regulate these changes are yet to be elucidated. The common ground of these processes, however, is the second messenger, calcium. In this regard, members of the superfamily of transient receptor potential (TRP) ion channels, which are known to be calcium-permeable and expressed in the endometrium, have emerged as key regulators. Here, we assessed the molecular and functional expression of TRP channels in stromal cells isolated from the eutopic endometrium of endometriosis patients and controls. Using RT-qPCR, high mRNA levels of TRPV2, TRPV4, TRPM4, TRPM7, TRPC1, TRPC3, TRPC4, and TRPC6 were observed in the whole endometrium throughout the menstrual cycle. Additionally, and in line with previous reports of control patients, TRPV2, TRPV4, TRPC1/4, and TRPC6 were present in human endometrial stromal cells (hESC) from endometriosis patients both at the molecular and functional level. Moreover, proliferation and migration assays illustrated that these parameters were not affected in stromal cells from endometriosis patients. Furthermore, comparison between eutopic and ectopic endometrial samples revealed that the RNA expression pattern of TRP channels did not differ significantly. Collectively, although a functional expression of specific ion channels in hESCs was found, their expression did not correlate with endometriosis.