Tenure Track Assistant Professor University of Maryland Eastern Shore Princess Anne, Maryland, United States
Abstract: Osteoporosis, a prevalent disorder among aging populations, is characterized by impaired bone remodeling largely due to increased marrow fat and reduced bone density. Bone marrow mesenchymal stem cells (MSCs) in osteoporosis favor adipogenesis over osteogenesis, exacerbating bone loss. Modulating aberrant MSC differentiation presents a promising therapeutic strategy for bone regeneration. Tribble 3 (Trb3), a critical regulator of MSC lineage commitment, has emerged as a potential therapeutic target for restoring osteogenic balance. This study aims to develop Trb3-enriched exosome mimetics (EM-B3) with enhanced bone-targeting property to promote osteoporotic bone regeneration. EM-B3 were generated from hMSCs treated with small molecules using an extrusion method. Comprehensive characterization of EM-B3, including structural and functional analyses, was conducted. To augment their bone-targeting efficiency, EM-Trb3 were metabolically engineered with alendronate (bEM-B3). Bone-binding capabilities of bEM-Trb3 were evaluated ex vivo using labeled particles on mouse bone chips. Their in vivo therapeutic efficacy was subsequently assessed in an ovariectomized (OVX) mouse model of osteoporosis through µCT imaging and quantitative analyses. TEM revealed the intact and spherical EM-B3 with an average size of ~100 nm, as confirmed by nanoparticle tracking analysis. Confocal microscopy demonstrated efficient cellular uptake of EM-B3. ELISA assay showed a significant upregulation of endogenous Trb3 within EM-B3. Functional assays highlighted that EM-TB3 enhanced osteogenic differentiation, evidenced by increased osteogenic gene expression, ALP activities, and mineral deposition. Conversely, EM-TB3 suppressed adipogenic differentiation, as indicated by reduced expression of adipogenic markers. Ex vivo studies confirmed the high bone-binding affinity of bEM-B3. In vivo µCT analysis revealed that bEM-B3 treatment significantly improved bone regeneration in OVX mice, as demonstrated by increased bone mineral density and bone volume fraction. Overall, bEM-B3 represent a novel and effective therapeutic strategy for addressing osteoporotic bone loss. This exosome-mimetic platform holds promise for clinical translation and offers a potential breakthrough in stem cell treatment.
