Tensile Stimulation in Biorelevant Culture Conditions Enhances MSC and TPSC Tenogenesis on Aligned Electrospun Scaffolds

This study developed an aligned electrospun poly(ε-caprolactone) (PCL) scaffold that combines topographical guidance with sustained biochemical cue delivery and mechanical loading to promote tenogenic differentiation. The scaffold was functionalized by encapsulating GDF-7 into mesoporous silica nanoparticles (MSNs) (reported ~99.9% encapsulation efficiency) and incorporating these MSNs into aligned PCL fibers, producing controlled growth-factor release over ~46 days with non-Fickian kinetics. The authors then compared static versus dynamic culture of human mesenchymal stromal cells (MSCs) and porcine tendon progenitor stem cells (TPSCs) on the aligned scaffolds under either atmospheric oxygen (21% O2) or physoxia (2% O2) to mimic the tendon niche. Dynamic mechanical stimulation promoted cell alignment along the fiber axis and increased proliferation (approximately ~2× higher DNA content versus static), with physoxia further enhancing viability and proliferation. Importantly, the combination of aligned topography, cyclic tensile loading, and physoxia synergistically increased tenogenic commitment, including increased tenomodulin (Tnmd) expression at the protein level (immunofluorescence) and elevated tendon-marker gene expression by RT-qPCR in both MSCs and TPSCs. Mechanical characterization of the electrospun mats showed MSN incorporation reduced modulus/ultimate strength (especially in dry samples), while hydration reduced mechanical properties of polymer-only fibers; however, after 10 days of culture, cell-mediated matrix deposition partially recovered scaffold mechanical performance, indicating cellular reinforcement of the construct. Overall, the work presents a multi-cue tendon tissue engineering strategy in which biorelevant oxygen tension and controlled cyclic strain substantially improve tenogenic outcomes on aligned electrospun scaffolds.