Intrauterine Injection of Umbilical Cord Mesenchymal Stem Cell Exosome Gel Significantly Improves the Pregnancy Rate in Thin Endometrium Rats.

Human umbilical cord mesenchymal stem cell (HUMSC)-exosome gel played a significant role in promoting thin endometrial receptivity and improving the pregnancy rate by inhibiting endometrial fibrosis and accelerating subendometrial microangiogenesis. High-quality HUMSC-exosome were obtained by pretreating HUMSC with transforming growth factor-β₁ (TGF-β₁). Exosome gel mixture has good biocompatibility and physical rheological properties, stabilizing the structure of exosomes and prolonging the action of exosomes in the uterine cavity. HUMSC or HUMSC-derived exosomes were used to treat rat model of thin endometrium. In animal experiments, four groups, including the HUMSC, HUMSC-exosome, model (negative control), and sham operation groups, were designed. The therapeutic effects were evaluated by the thickness of the endometrium, the number of glands, the subendometrial vessel density, the markers of endometrial receptivity, and the pregnancy rate. In an <i>in vivo</i> study, three groups, involving HUMSC-coculture, HUMSC-exosome, and the control, were explored. The proliferation and migration of the human endometrial stromal cells (HESCs) were further determined by cell scratch and 5-ethynyl-2'-deoxyuridine (EdU) assays. The protein expression of the TGF-β₁/smad2/3 signaling pathway was determined by Western blot. After treatment, the thickness of the endometrium, the number of glands, and the subendometrial microangiogenesis were obviously increased, and the level of inhibition of endometrial fibrosis, molecular markers of endometrial receptivity, and the pregnancy rate were also significantly improved. HUMSC-exosome and HUMSC significantly promoted the migration and proliferation of HESCs. And it was confirmed that HUMSC-exosome were superior to HUMSC in inhibiting HESCs fibrosis through TGF-β₁/smad2/3 signaling pathway at the protein expression level.