Poster Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

Introduction: Tendon is a mechanosensitive tissue which bears loading from muscle contraction to bone. Compared to excessive mechanical loading, which can cause rupture or tendinopathy, insufficient loading also has adverse effect on tendon tissue. However, less studies were involved in investigation of cellular and extracellular changes in loading deprived tendon. In our study, we investigated cellular function of tendon derived stem cells (TDSCs) and collagen component changes in patella tendon under insufficient loading. The results showed collagen degeneration and compromised TDSCs regarding differentiations and proliferation. Also, we interestingly found that the inflammatory cytokines and MMP- 13 were increased in loading deprived tendon. The results are promising to develop therapeutic strategies for degenerative tendinopathy in relative patients.

Methods: Patella tendons of 12-week aged mice were subjected to no mechanical loading by injection of Botulinum Toxin (botox) in quadricep. Histological examinations were performed by H&E staining and polarized microscopic image. Collagen degenerations were detected by Collagen Hybridizing Peptides. Tri-lineage differentiations of TDSCs (osteogenesis, chondrogenesis and adipogenesis) and tenogenesis were examined by qPCR, western blot and relevant staining. MMP- 13 and TNF-Alpha were examined by western blot and qPCR.

Results and discussions: Our results showed that tendon without mechanical loading was atrophic and had collagen fibers disorientated (Figure 1A, B) and more collagen degeneration was detected in botox group as well (Figure 1C). Colony formation and proliferation ability of TDSC was diminished (Figure 2A, B). Furthermore, differentiation capacity of TDSCs was compromised in botox group (Figure 3, 4 and 5) towards osteogenesis, chondrogenesis and adipogenesis. Besides, tenogenesis of TDSC was also downregulated which was evidenced by low mRNA expression of TNMD and MKX. Interestingly, inflammatory cytokines TNF-a were up-regulated in mRNA level and protein level in botox group. Also, MMP-13 but not MMP-9, was increased and might be responsible for collagen degenerations.