Development of mechanically optimized biomimetic hybrid scaffold–stem cell constructs for functional tendon regeneration and restoration of mechanical integrity

Tendon ruptures heal poorly due to hypocellularity, disorganized extracellular matrix (ECM), and inadequate mechanical loading. Current scaffold-stem cell strategies lack integration of dynamic mechanical cues and sustained growth factor delivery. The objective of this study is to engineer a mechanically tuned, bioactive hybrid scaffold system that integrates tendon-derived stem cells (TDSCs) and mesenchymal stem cells (MSCs), controlled growth factor release, and progressive mechanical stimulation to achieve functional tendon regeneration with enhanced structural and mechanical recovery. Scaffolds were fabricated with controlled pore architecture and fiber alignment. TDSCs were seeded dynamically and cultured under cyclic uniaxial strain (5%, 1 Hz, 4 h/day) with TGF-β3-loaded PLGA microspheres (release >21 days). In vitro assays assessed viability, proliferation, scleraxis/tenomodulin expression, collagen I/III ratio, and GAG content. In vivo evaluation used a rat Achilles tendon defect model (6 mm gap) with four groups: scaffold-only, scaffold+TDSCs, scaffold+TDSCs + TGF-β3, and scaffold+TDSCs + TGF-β3 + mechanical preconditioning (the full composite). Outcomes at 6 and 12 weeks included biomechanical testing, histology (collagen alignment, vascularity), and immunohistochemistry. The full composite group achieved 92% cell viability at 14 days, 8-fold upregulation of scleraxis, and organized collagen I deposition (60 ± 6 µg/mg). Cyclic strain improved collagen alignment by 3.5-fold versus static controls. In vivo, the full composite restored 88% of native tendon tensile strength by week 6 and 95% by week 12, with minimal adhesion formation and near-native ECM organization. The preconditioned groups showed significantly lower inflammatory scores and higher tenomodulin expression. Mechano-activated, growth factor-eluting scaffolds with TDSCs achieve superior tendon regeneration by combining biochemical and biophysical cues. This strategy offers a scalable, off-the-shelf, or autologous solution for clinical tendon repair.