Compound design of a patient-derived 3D cell culture system modelling early peritoneal endometriosis.

Peritoneal endometriosis causes pelvic pain and infertility, but the underlying mechanisms related to these symptoms are not fully understood. Endometriosis diagnosis is typically delayed; thus, patient samples are unsuitable to study early endometriosis formation in situ. We generated a 3D co-culture model of early peritoneal endometriosis using patient-derived primary cells, providing unique opportunities to examine endometriotic lesion initiation and progression. The successful assembly of a simple peritoneum layer model comprising a mesothelial monolayer, basement membrane and underlying fibroblasts was achieved by embedding human peritoneal fibroblasts in a Matrigel-collagen I matrix and subsequent seeding with a layer of donor-matched human peritoneal mesothelial cells, while secretion of tissue plasminogen activator demonstrated functional mesothelial physiology. Endometrial epithelial organoids were co-cultured with endometrial stromal cells to form endometrial assembloids mimicking shed endometrial tissue fragments at menstruation, which adhered onto the peritoneal layer model, simulating early endometriotic lesion formation. Our modifiable superficial endometriosis model allows for further refinement to determine the underlying molecular mechanism(s) involved in endometriotic lesion formation.