Injectable Bioactive Hydrogel Enhances Endometrial Regeneration for Recurrent Pregnancy Loss via Angiogenesis and Immunomodulation

Background: Recurrent pregnancy loss (RPL) associated with endometrial dysfunction remains clinically challenging due to the lack of localized, multifunctional therapeutic strategies.Restoring endometrial receptivity, vascularization, and immune balance is key to successful intervention.Methods: An injectable bioactive hydrogel was developed by crosslinking aldehyde-modified hyaluronic acid (HA-CHO) with chitosan.The hydrogel was loaded with LIF (Leukemia Inhibitory Factor), VEGF (Vascular Endothelial Growth Factor), IL-11 (Interleukin-11), and valproic acid to enhance regenerative activity.Its effects were assessed in vitro via cell proliferation (CCK-8), tube formation (HUVEC assay), cytokine expression (THP-1 qPCR), and endometrial gene profiling (hEMSC qPCR).Results: The hydrogel exhibited rapid gelation, good biocompatibility, and factor-loading capacity.It significantly enhanced hEMSC proliferation and HUVEC tube formation.Pro-inflammatory cytokines (TNF-α, IL-6) were downregulated, while IL-10 (Interleukin-10) was upregulated in macrophages.The hydrogel also increased expression of LIF and IGFBP1 (Insulin-like Growth Factor Binding Protein 1), but not PRL, indicating enhanced receptivity without full decidualization.Conclusion: This HA-CHO/chitosan hydrogel supports endometrial regeneration through coordinated promotion of proliferation, angiogenesis, immune modulation, and receptivity.It holds strong potential for localized treatment of RPL with endometrial insufficiency.