Targeting CD14 to Inhibit Macrophage Senescence and Regulate the Microenvironment for Enhanced Tendon-Bone Healing.

Abstract

To date, no targeted pharmacological agents have been clinically available specifically for postoperative management after anterior cruciate ligament reconstruction (ACLR). To elucidate the role of macrophage senescence in the tendon-bone interface microenvironment and assess whether targeting CD14 can mitigate senescence, thereby enhancing tendon-bone healing. Controlled laboratory study. A murine ACLR model was used to evaluate the tendon-bone healing. Healing was assessed 8 weeks postsurgery through histological staining, micro-computed tomography analysis of neoplastic bone formation within bone tunnels, and biomechanical testing of tendon grafts. Cellular senescence was evaluated using β-galactosidase staining, while immunofluorescence and immunohistochemistry were used to analyze protein expression levels. Macrophage heterogeneity at the tendon-bone interface was assessed via t-distributed stochastic neighbor embedding projection, and senescent macrophage characteristics were investigated using CellChat, KEGG, and GO analyses. Alkaline phosphatase and Alizarin Red S staining were used to evaluate osteogenic differentiation of bone marrow mesenchymal stem cells. Early inflammatory responses triggered by apoptotic cells at the tendon-bone interface resulted in macrophage senescence, activation of inflammatory pathways, increased secretion of pro-inflammatory factors, and elevated CD14 expression. Targeting CD14 reduced macrophage senescence and the inflammatory response at the tendon-bone interface, thereby increasing tendon-bone healing. The findings indicate that excessive inflammation within the tendon-bone interface microenvironment promotes macrophage senescence, thereby impairing tendon-bone healing. Targeting CD14 effectively prevents macrophage senescence, facilitating improved tendon-bone healing. Currently, targeted therapeutics to enhance tendon-bone healing post-ACLR are lacking in clinical practice. The findings demonstrate that microenvironmental inflammation leading to macrophage senescence is a critical factor contributing to impaired tendon-bone healing. CD14-targeted therapy may inhibit macrophage senescence, accelerate tendon-bone healing, and offer significant translational potential for clinical application.