Harnessing Molecular Signals and Biologic Synergies in Bone and Cartilage Regeneration.

ABSTRACT Bone and cartilage regeneration represent multifactorial biological processes orchestrated by complex networks of signaling pathways, cellular interactions and extracellular matrix remodeling. Despite remarkable intrinsic regenerative potential, impaired bone healing and cartilage degeneration remain major clinical challenges, highlighting the need for innovative strategies that integrate molecular modulation with biologically active cues. This study explored two complementary approaches aimed at enhancing osteogenic and chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBM-MSCs). The first focused on the activation of the Hedgehog (Hh) signaling pathway through specific agonists to delineate its contribution to osteogenic commitment and matrix mineralization. The second investigated the regenerative potential of platelet-rich plasma (PRP) and its composite formulation with hyaluronic acid (PRP-HA) as biologic enhancers of stem cell differentiation and tissue-specific matrix deposition. The experiments were performed under two-dimensional (2D), three-dimensional (3D spheroid), and scaffold-based culture conditions to mimic different microenvironmental architectures and to evaluate cell-matrix interactions. A comprehensive set of assays was employed, including Alizarin Red and Alcian Blue staining, calcium and alkaline phosphatase (ALP) quantifications, Live/Dead viability analysis, immunostaining for lineage-specific markers (RUNX2, SOX9, COL1A1, Aggrecan), and gene expression profiling of osteogenic and Hedgehog related targets (RUNX2, COL1A1, PTCH1, GLI1). Activation of the Hedgehog pathway significantly upregulated osteogenic markers and enhanced matrix mineralization in both 2D and scaffold-based cultures. In parallel, PRP and PRP-HA treatments markedly accelerated the osteogenic and chondrogenic differentiation process compared with conventional culture conditions, representing the most striking outcome of this study. This rapid commitment was accompanied by robust lineage-specific marker expression, improved extracellular matrix organization, and enhanced cellular integration, effects that were particularly pronounced in 3D and scaffold-based systems. Collectively, these findings provide mechanistic and translational insights into the combined use of molecular pathway modulation and biologic bioactive factors, supporting their potential as synergistic tools in the development of advanced therapeutic strategies for bone and cartilage regeneration.