Summary

our study has highlighted the importance of applying appropriate mechanical stimulation when dissecting the molecular pathways involved in tendon development and function, and demonstrated that our bioreactor model provides a physiologically relevant environment for such studies.

Abstract

Background

and Aims: Tendon injury is one of the most common musculoskeletal injuries and causes pain, discomfort or even disability. Tendons are mechanosensitive fibro connective tissue but little is known about the role of mechanical loading in tendon development, homeostasis and regeneration. In this study, we compare the impact of uniaxial and biaxial mechanical stimulation on tendon derived stem cells isolated from mouse and human.

Method

Tendon derived stem cells (TDSC) were isolated from human and mice tendon tissue and characterized by flow cytometry, colony unit formation and multipotent differentiation assay. Uniaxial and biaxial mechanical loading (6% strain, 0.25Hz, 8h/d for 6 day) were applied on monolayer cultured tendon derived stem cells. QPCR and western blotting were perform to assess the differentiation effect and molecular pathway induced by the loading. Then the same uni-axial loading was applied on the scaffold-free engineered tendon QPCR, western blot analysis, histology and immunohistochemistry and immunofluorescence confocal microscopy were used to investigate the formation of tendon-like tissue.

Results

We show that biaxial loading mainly induced ERK activation, whereas AKT signal pathway is trigged by uni-axial loading. Distinct differentiation effect of various loading is observed, but tenogenic differentiation can only be induced by uni-axial mechanical stimulation. Furthermore, The loading regime verified in the monolayer cell system was used to stimulate the 3D engineered tendon formation, tendon-specific microstructure, protein and gene expression profiles were exhibited after 6 days cultured in the bioreactor system.

Conclusion

Our study demonstrates that the mechanical loading generated in our system mimics the physiological conditions for tenogenic differentiation and development and highlights the importance of applying appropriate mechanical stimulation when dissecting the molecular pathways involved in tendon development and function.