Enhanced Expansion of Bone Marrow-Derived Mesenchymal Stem Cells on Collagen-Coated Microcarriers Functionalized with Chimeric IGF-1–bFGF Proteins

Human mesenchymal stem cells (hMSCs) are promising for cell transplantation therapies. Nevertheless, their limited yield necessitates large-scale ex vivo expansion. Microcarrier-based culture offers a scalable platform, but efficient functionalization strategies are not available. Here, we engineered collagen-binding chimeric proteins by fusing insulin-like growth factor-1 (IGF-1) and basic fibroblast growth factor (bFGF) with an osteopontin-derived collagen-binding peptide and immobilized them on type I collagen-coated poly-(vinyl alcohol) microcarriers. This single-molecule design provides the unique advantage where the surface is functionalized with a fixed molar ratio of IGF-1 to bFGF, avoiding the stoichiometric uncertainty inherent to the coimmobilization of separate proteins. Structural characterization confirmed proper folding of the chimeras, and functional assays demonstrated that dual-domain constructs markedly enhanced hMSC proliferation compared with single-factor controls, with the IGF-1-bFGF chimera yielding the highest effect. Expanded cells retained osteogenic differentiation potential. These findings demonstrate that chimeric growth factors with defined stoichiometry offer a practical and robust strategy for scalable hMSC expansion, with significant implications for regenerative medicine and cell therapy.