Phase 1 dose-escalation trial of sub-endometrial injection of human embryonic stem cells-derived immunity-and-matrix-regulatory cells to promote endometrial angiogenesis in refractory intrauterine adhesion.

Clinical application of mesenchymal stem cells for endometrial repair has been hampered by variability in cell quality, large-scale production, and uncertainty regarding the optimal delivery route. In this study, we investigated the therapeutic potential of clinical-grade human embryonic stem cell-derived immunity-and-matrix-regulatory cells (IMRCs) for treating refractory moderate-to-severe intrauterine adhesion (IUA). In a rabbit IUA model, sub-endometrial injection of IMRCs significantly reduced fibrosis and enhanced endometrial angiogenesis, outperforming uterine perfusion. Transcriptomic analysis revealed distinct pro-angiogenic gene expression profiles between the two delivery routes. In vitro, IMRCs co-cultured with endometrial stromal cells (ESCs) markedly enhanced angiogenic potential compared to either cell type alone. Protein array analysis of the co-culture supernatant showed elevated levels of angiogenic factors, with functional assays confirming that inhibition of ANGPTL4, a non-canonical pro-angiogenic mediator, impaired angiogenesis. In a first-in-human, single-center, phase 1 dose-escalation trial involving 18 patients with refractory IUA, high-dose sub-endometrial IMRC injection promoted angiogenesis, reduced uterine scarring, and improved pregnancy outcomes, with no safety concerns observed over 3 years of follow-up. These findings highlight the translational promise of IMRCs as a novel therapeutic strategy for endometrial regeneration in severe IUA.