Abstract
Current cell-based tissue engineering strategies have limited clinical applicability due to the need for large cell numbers and prolonged culture periods that lead to phenotypic drift. In vitro microenvironmental modulators have been proposed to mimic the native tendon. Standard in vitro culture conditions result in delayed extracellular matrix (ECM) deposition, impairing the development of scaffold-free approaches. ECM deposition can be enhanced by macromolecular crowding (MMC), a biophysical phenomenon that governs the milieu of multicellular organisms. We assessed a multifactorial biophysical approach, using MMC and mechanical loading, on different cell sources to determine their suitability for in vitro fabrication of tendon-like tissue. Human dermal fibroblasts (DFs), tenocytes (TCs) and bone marrow mesenchymal stem cells (BMSCs) were cultured with MMC under static and uniaxial strain culture conditions. TCs and DFs exhibited alignment perpendicular to the load, whilst BMSCs did not show preferential alignment. When MMC was used, DFs and BMSCs showed increased deposition of collagen I, the main component in tendon ECM. DFs presented ECM composition similar to TCs with collagen types III, V and VI present. Gene expression analysis revealed upregulation of tenogenic markers by TCs and DFs, such as scleraxis and thrombospondin-4, under both loading and MMC. The combined use of MMC and mechanical stimulation is suitable for TCs phenotype maintenance and can modulate the phenotype of DFs and BMSCs differentially. This study provides insight into response of different cell sources to biophysical cues and contributes to further development of cell therapies for tendon repair and regeneration.
