Enhancing Bone Formation Through bFGF-Loaded Mesenchymal Stromal Cell Spheroids During Fracture Healing in Mice

Abstract

This study aimed to evaluate the osteogenic potential of mesenchymal stromal cell (MSC) spheroids combined with the basic fibroblast growth factor (bFGF) in a mouse femur fracture model. To begin, MSC spheroids were generated, and the expression of key trophic factors (bFGF Bmp2, and Vegfa) was assessed using quantitative PCR (qPCR). A binding assay confirmed the interaction between the bFGF and the spheroids’ extracellular matrix. The spheroid cultures significantly upregulated bFGF, Bmp2, and Vegfa expression compared to the monolayers (p p = 0.010; bFGF-spheroids, p = 0.006; bFGF-dSpheroids, p = 0.032) and BMC (bFGF, p = 0.023; bFGF-spheroids, p = 0.004; bFGF-dSpheroids, p = 0.014), compared to the controls. In contrast, a low dose of the bFGF (1 µg) combined with the MSC spheroids significantly increased BV and BMC compared to the control (BV, p = 0.012; BMC, p = 0.015), bFGF alone (BV, p = 0.012; BMC, p = 0.008), and spheroid (BV, p p p > 0.05). The non-viable (frozen) spheroids loaded with a low dose of the bFGF resulted in a higher BV and BMC compared to the spheroids alone (BV, p = 0.003; BMC, p = 0.017), though the effect was less pronounced than in the viable spheroids. These findings demonstrate the synergistic effect of the bFGF and MSC spheroids on bone regeneration. The increased expression of the BMP-2 and VEGF observed in the initial experiments, coupled with the enhanced bone formation in vivo, highlight the therapeutic potential of this combination. Future studies will aim to elucidate the underlying molecular mechanisms and assess the long-term outcomes for bone repair strategies.

Keywords

• mesenchymal stromal cells
• spheroid
• basic fibroblast growth factor
• fracture healing