Recombinant humanized collagen remodels endometrial immune microenvironment of chronic endometritis through macrophage immunomodulation

Recently, evidence has suggested that chronic endometritis (CE) is a crucial factor associated with infertility and failure of assisted reproductive techniques, prompting concern in the reproductive field. Studies have shown that persistent infiltered immune cells stimulation result in the disturbance of endometrial immune microenvironment could lead to the infertility of CE patients finally. Conventional treatments are limited because they lack immune regulation, so it is urgent to develop a novel approach to treat CE and promote embryo implantation in patients with CE. Herein, we prepared recombinant humanized type III collagen (rhCol III) with high cell adhesion activity to regulate macrophages and repair the endometrium. In this study, M1 macrophages and M1 macrophages cultured medium and lipopolysaccharide (LPS) co-stimulated inflammatory endometrium stromal cells (ESCs) were established in vitro to mimic CE condition. rhCol III promoted M1 macrophages toward M2 phenotype, improved cell migration, viability and collagen components of inflammatory ESCs. Also, the inflammatory response of inflammatory ESCs was downregulated after rhCol III treatment. Subsequently, LPS was used for CE rat model and a 28-day observation was performed; inflammatory cells' infiltration, endometrium repair, extracellular matrix (ECM) remodeling and pregnancy outcomes were promoted after rhCol III endometrial infusion. In conclusion, rhCol III promoted (i) macrophage polarization toward M2 macrophages, (ii) pro-inflammatory cytokine production and anti-inflammatory cytokine reduction, (iii) ECM remodeling and (iv) fertility restoration. Meanwhile, rhCol III enhanced cell biological functions by interacting with discoidin domain receptors, regulated cell metabolism and reduced the inflammatory response through the inhibition of the NF-κB/YAP signaling pathway. Overall, the results illustrated the potential therapeutic prospects of rhCol III for CE treatment.