Synergistic regenerative therapy of thin endometrium by human placenta-derived mesenchymal stem cells encapsulated within hyaluronic acid hydrogels

Abstract Background: Endometrial injury is one of the major causes of thin endometrium and subfertility. Stem cell-based therapies have made strides towards further efficacious treatment of injured endometrium. However, reported therapeutic stem cells that can be used for thin endometrium are difficult to acquire for large-scale clinical application. The human placenta-derived mesenchymal stem cells (HP-MSCs) are emerging alternative sources of MSCs for their robuster expansion ability, lower immunogenicity as well as extensive sources. To maximize their retention inside the uterus, we loaded HP-MSCs with cross-linked hyaluronic acid hydrogel (HA hydrogel) to investigate their therapeutic efficacy and possible underlying mechanisms.Methods: The murine endometrial injury model was established by ethanol (95%) perfusion, with further intrauterine instillation of treating materials. The retention time of HP-MSCs was detected by in vivo imaging and ex vivo frozen section. Functional restoration of the uterus was assessed by testing embryo implantation rates. The endometrial morphological alteration was observed by H&E staining, Masson staining, and immunohistochemistry (Ki67). The stromal and glandular cells were isolated from the human endometrium to determine proliferation, migration, signaling pathway changes via EdU assay, transwell migration assay, and western blot respectively. Results: Instilled HP-MSCs with HA hydrogel (HP-MSCs-HA) exhibited a prolonged retention time in mouse uteri compared with normal HP-MSCs. In vitro data showed that the HP-MSCs-HA could significantly increase the gland number and endometrial thickness, decrease fibrous area, promote the proliferation of endometrial cells, and improve the embryo implantation rate. In vitro assays indicated that HP-MSCs-HA could not only promote the proliferation and migration of human endometrial stromal via the JNK/Erk1/2-Stat3-VEGF pathway but also promote the proliferation of glandular cells via Jak2-Stat5 and c-Fos-VEGF pathway. Conclusion: Our study suggested the potential therapeutic effects and the underlying mechanisms of HP-MSCs-HA on treating thin endometrium. HA hydrogel could be a preferable delivery method for HP-MSCs and the strategy represents a promising therapeutic approach against endometrial injury in clinical settings.