The role of physiological mechanical cues on mesenchymal stem cell differentiation in an airway tract-like dense collagen-silk fibroin construct

Airway tracts serve as a conduit of transport in the respiratory system. Architecturally, these are composed of cartilage rings that offer flexibility and prevent collapse during normal breathing. To this end, the successful regeneration of an airway tract requires the presence of differentiated chondrocytes and airway smooth muscle cells. This study investigated the role of physiological dynamic mechanical stimulation, in vitro, on the differentiation of mesenchymal stem cells (MSCs), three-dimensionally seeded within a tubular dense collagen matrix construct-reinforced with rings of electrospun silk fibroin mat (TDC-SFC). In particular, the role of either shear stress supplied by laminar fluid flow or cyclic shear stress in combination with circumferential strain, provided by pulsatile flow, on the chondrogenic differentiation, and contractile lineage of MSCs, and their effects on TDC-SFC morphology and mechanical properties were analysed. Chondrogenic differentiation of MSCs was observed in the presence of chondrogenic supplements under both static and laminar flow cultures. In contrast, physiological pulsatile flow resulted in preferential cellular orientation within TDC-SFC, as dictated by dynamic circumferential strain, and induced MSC contractile phenotype expression. In addition, pulsatile flow decreased MSC-mediated collagen matrix remodelling and increased construct circumferential strength. Therefore, TDC-SFC demonstrated the central role of a matrix in the delivery of mechanical stimuli over chemical factors, by providing an in vitro niche to control MSC differentiation, alignment and its capacity to remodel the matrix.