High levels of S1P in fact have been found in the peritoneal environment of women suffering of endometriosis, showing the capability to induce differentiation of macrophages into CD163 + M2 type, which secretes pro-inflammatory cytokines such as IL-6, COX-2, and TGF-β contributing to the inflammation and fibrosis underlying these lesions [45]. This evidence concerns the gene TGFB1 and endometriosis.