The Impact of Human Placental Tissue-Derived Xenograft on Bone Healing and Pain Behaviors in a Murine Segmental Bone Defect Model.

INTRODUCTION: Segmental bone defects (SBD), frequently resulting from high-energy trauma like military combat injuries and major accidents, represent a significant clinical challenge because of the loss of a large bone segment and associated soft-tissue injury. These injuries often occur in military settings, where blast and ballistic trauma cause complex injuries requiring advanced reconstructive strategies. Similar injuries also occur in the civilian population in car accidents, falls, and workplace injuries. Existing therapies (autografts, allografts, and biomaterials) have limitations, including donor site morbidity and graft rejection, highlighting the need for novel bone regenerative approaches. Human placental tissue-derived xenografts (connective tissue matrix [CTM]), rich in structural proteins and growth factors, are under investigation for enhancing bone repair in severe musculoskeletal injuries. This study investigates the efficacy of placental tissue xenografts in a murine SBD model. MATERIALS AND METHODS: A murine SBD model with a 2 mm defect in the femoral diaphysis of male C57BL/6J mice was used. Mice with SBD were divided into 5 experimental groups: saline control, bone morphogenic protein (BMP-2), and 3 different formulations of CTM (CTM Paste, CTM Membrane, and CTM Membrane+Paste). Treatments were delivered at the defect site at the time of surgery and mice were euthanized 13 weeks postsurgery. Bone healing and pain behaviors were assessed including radiographic scoring, microcomputed tomography (µCT), biomechanical torsion testing, weightbearing, locomotion, and spontaneous nociceptive behaviors. Statistical analyses included one-way or two-way ANOVA and unpaired Student's t-tests. RESULTS: BMP-2-treated groups showed significantly larger callus formation, however, lower bone volume/total volume (BV/TV) % compared to saline control was observed. In contrast, the CTM Membrane+Paste group exhibited significantly higher BV/TV%. Biomechanical tests revealed enhanced ultimate torque in BMP-2 and CTM Membrane+Paste groups versus saline controls. All treatment groups of SBD mice exhibited sustained pain behaviors after fracture, which did not return to baseline levels even when bone healing was complete. CONCLUSION: The CTM Membrane+Paste treatment group exhibited improved bone healing parameters in a murine model of SBD. Specifically, BV/TV and some biomechanical properties were improved. Notably, CTM did not increase pain behaviors. Further studies are needed to optimize graft effects and assess therapeutic value for clinical translation. Overall, the results support continued investigation, including potential combination therapies and trials in larger animal models.