Effective repair of endometrial injury in rats using enzyme cross-linked gelatin hydrogels with human menstrual blood-derived stem cells

An intact endometrium is critical for zygote implantation and embryonic development, and the recurrence rate after transcervical resection of adhesion surgery is high in patients with endometrial injury. Therefore, there is an urgent need to develop more efficient and stable treatment to solve this problem. In the present study, firstly we used gelatin as a substrate and glutamine transferase as a cross-linking agent to fabricate enzyme cross-linked gelatin hydrogels which have a microporous structure, then implanted human menstrual blood-derived mesenchymal stem cells (MenSCs) in the form of single cells or cell spheres (MenSC_SP/Gel) into enzyme-linked hydrogels. Afterwards cell-hydrogel complexes were transplanted into the injured uterus of rats for the treatment. The results showed that MenSC_SP/Gel could maintain the uterine cavity structure, significantly increase the intimal thickness and the number of endometrial glands, reduce scar formation and promote angiogenesis, leading to an increase in the probability of pregnancy in rats to 91.67%. RNA-seq transcriptome analysis further revealed that the treatment with MenSC_SP/Gel induced immune response-related pathways and estrogen release-related pathways, and significantly increased the expression of Orosomucoid 1 (ORM1) that inhibits fibrosis, and reduced the expressions of H19 and Heme Oxygenase 1 (HOMX1) which promote fibrosis. In conclusion, we successfully developed and used enzyme cross-linked gelatin hydrogels to deliver human MenSCs to repair endometrial injury, and in particular, the use of cell spheres could further improve the repair effect. Therefore, our results represent a significant step towards providing a new technical solution in the clinical treatment of patients with endometrial injury.