Speaker
Description
"In tendon biology, considerable progress has been made in identifying tendon-specific genes. However, despite the comprehensive knowledge of the tendon mechanical function, neither the ontogeny of the tenogenic lineage nor signalling cascades are fully understood (Citeroni et al., 2020). For this reason, it is important to define the main actors in the developmental pathway that induces the sequential differentiation of MSCs into Tendon Progenitor Stem Cells and then Tenocytes. The main objective of this study was to define the best and-logic system in which the biological signal power and its presentation cooperate to drive specific differentiation paths.
TSPCs and tenocytes were isolated from pig-derived tendon tissue (Yang et al., 2018). MSCs were obtained from human bone marrow (Kay et al., 2015). We showed that TPSCs, similarly to MSCs and differently than tenocytes, have stem cell characteristics such as clonogenicity, multipotency and self-renewal capacity. Stem cells and tendon-specific markers, Scleraxis, Oct-4, Nanog, Nestin, Tenomodulin and Thrombospondin-4 were investigated in parallel in all three cell lines to establish cell-specific peculiarities in their genetic profiles. Cell characterization and functionality were evaluated through surface marker expression, analysed via flow cytometry. BMP12/BMP13/BMP14 were used as media supplementation, individually and in combination, to induce hBMSCs and TPSCs differentiation, and the expression of tenolineage transcription factors and matrix proteins was compared.
hBMSCs expressed surface markers CD73, CD90 and CD105 and stained negative for CD14, CD19, CD34, CD45 and HLA-DR. Multi-lineage differentiation potential of hBMSCs was demonstrated for osteogenic, chondrogenic and adipogenic induction media. Conversely, when extracted from the tendon, TPSCs rapidly lost their differentiation potential starting to express more tendon-related markers. The marker CD44 has been proved to be a discriminative element between TPSCs and tenocytes. The independent exposure of three different growth factors outlined the time-dependent role of any growth factor in any specific phase of the differentiation, allowing us to optimize their synergic effect.
MSCs can improve tissue regeneration and healing by three main mechanisms: differentiation, promotion of angiogenesis, and inflammatory response control. All these mechanisms can be induced by specific growth factors. An in vitro evaluation of tenogenesis in two-dimensional culture is always based only on relative changes in the set of molecules expression, for this reason, there is no unequivocal method to recognize completed tenogenic differentiation. We selected a specific subset of BMPs growth factors that are specifically recognized for their ability to induce tenogenic differentiation. These growth factors have been selected because they represent different areas of growth factor-mediated effect and so they allow us to retrace the developmental tenogenic pathway. The use of bioactive molecules in tenogenesis may have critical implications for the early phase of tendon tissue engineering. Indeed, a better understanding of the effect of bioactive molecules in tenogenesis will lead to more complex systems in which the transcriptional differentiation could be supported by composite living fibre able to improve the synaptic effect related to cells capability to sense each other. Future challenges will involve the design of three-dimensional systems capable to reproduce the native environment of tendon tissue."
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