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Tendons play an important role in the maintenance of motor function by connecting muscles and bones and transmitting forces. Particularly, the role of mechanical stress has primarily focused on the key mechanism of tendon homeostasis, with much research on this topic. With the recent development of molecular biological techniques, the mechanisms of mechanical stress sensing and signal transduction have been gradually elucidated with the identification of mechanosensor in tendon cells and the master regulator in tendon development. This review provides a comprehensive overview of the structure and function of tendon tissue, including the role for physical performance and the detailed mechanism of mechanotransduction in its regulation. An important lesson is that the role of mechanotransduction in tendon tissue is only partially clarified, indicating the complexity of the mechanisms of motor function and fueling increasing interest in uncovering these mechanisms. Lay Summary: This review summarizes current knowledge of the mechanobiology of tendons. Appropriate mechanical stress can enhance the anabolic effects of tenocytes via the activation of PIEZO1-MKX/SCX cascade, which can alter the mechanical properties of tendon tissue and may also affect physical performance. However, the elucidation of the mechanisms by which structural changes in tendons affect physical performance appears to be still partial. Further clarification of tendon function is anticipated to lead to applications in enhancing physical performance and the extension of healthy life expectancy. [ABSTRACT FROM AUTHOR]

Background: It is not clear whether rehabilitation after surgery for trigger finger is effective. The aim of this study was to reveal its effectiveness for trigger finger. Methods: This study was a randomized, controlled trial that included patients who underwent operations for trigger fingers. The patients in the rehabilitation group had postoperative occupational therapy (OT) for 3 months, while the patients in the control group were not referred for rehabilitation but received advice for a range of motion exercises. We evaluated the severity of trigger finger, Disability of Arm-Shoulder-Hand (DASH) score, pain-visual analogue scale (VAS), grip strength, whether they gained a full range of motion (ROM), and complications before and after surgery. Results: Finally, 29 and 28 patients were included in the control and rehabilitation groups, respectively. At final follow-up, the DASH score, grip strength, and ROM were significantly improved in the rehabilitation group compared to that preoperatively. At final follow-up, pain was significantly improved in both groups from that preoperatively. There were no significant differences in the results, including the DASH score, grip strength, ROM and pain-VAS between the control and rehabilitation groups at the final follow-up. Subgroup analysis showed that there is a significant difference in the DASH score of patients doing housework or light work and those with a duration of symptoms >12 months between the control and rehabilitation groups at the final follow-up. [ABSTRACT FROM AUTHOR]

Tendons and ligaments are jointed to bones via an enthesis that is essential to the proper function of the muscular and skeletal structures. The aim of the study is to investigate the effect of mechanical stress on the enthesis. We used ex vivo models in organ cultures of rat Achilles tendons with calcaneus including the enthesis. The organ was attached to a mechanical stretching apparatus that can conduct cyclic tensile strain. We made the models of 1‐mm elongation (0.5 Hz, 3% elongation), 2‐mm elongation (0.5 Hz, 5% elongation), and no stress. Histological evaluation by Safranin O staining and Toluidin Blue and Picro Sirius red staining was conducted. Expression of sex‐determining region Y‐box 9 (Sox9), scleraxis (Scx), Runt‐related transcription factor 2 (Runx2), and matrix metalloproteinase 13 (Mmp13) were examined by real‐time polymerase chain reaction and immunocytochemistry. Terminal deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate biotin nick end‐labeling and live/dead staining and was conducted for evaluation of the apoptosis and cell viability. The structure of the enthesis was most maintained in the model of 1‐mm elongation. The electronic microscope showed that the enthesis of the no stress model had ill‐defined borders between fibrocartilage and mineralized fibrocartilage, and that calcification of mineralized fibrocartilage occurred in the model of 2‐mm elongation. Sox9 and Scx was upregulated by 1‐mm elongation, whereas Runx2 and Mmp13 were upregulated by 2‐mm elongation. Apoptosis was inhibited by low stress. The results of this study suggested that 1‐mm elongation can maintain the structure of the enthesis, while 2‐mm elongation promotes degenerative changes. [ABSTRACT FROM AUTHOR]

How mechanical stress affects physical performance via tendons is not fully understood. Piezo1 is a mechanosensitive ion channel, and E756del PIEZO1 was recently found as a gain-of-function variant that is common in individuals of African descent. We generated tendon-specific knock-in mice using R2482H Piezo1, a mouse gain-of-function variant, and found that they had higher jumping abilities and faster running speeds than wild-type or muscle-specific knock-in mice. These phenotypes were associated with enhanced tendon anabolism via an increase in tendon-specific transcription factors, Mohawk and Scleraxis, but there was no evidence of changes in muscle. Biomechanical analysis showed that the tendons of R2482H Piezo1 mice were more compliant and stored more elastic energy, consistent with the enhancement of jumping ability. These phenotypes were replicated in mice with tendon-specific R2482H Piezo1 replacement after tendon maturation, indicating that PIEZO1 could be a target for promoting physical performance by enhancing function in mature tendon. The frequency of E756del PIEZO1 was higher in sprinters than in population-matched nonathletic controls in a small Jamaican cohort, suggesting a similar function in humans. Together, this human and mouse genetic and physiological evidence revealed a critical function of tendons in physical performance, which is tightly and robustly regulated by PIEZO1 in tenocytes. Potentiating physical performance: Tendons connect muscle to bone and are important for musculoskeletal function, including athletic performance. Here, Nakamichi et al. used a mouse model to study the effects of a gain-of-function variant in Piezo1, a mechanosensitive ion channel, in tendon. Mutant tendons were wider, with larger collagen fibril cross-sectional diameter, and had increased compliance and greater storage of elastic energy. Tendon-specific mutant mice demonstrated greater jumping ability and faster running. The authors also observed increased frequency of a gain-of-function PIEZO1 deletion in a cohort of Jamaican sprinters, supporting a role for tendon expression of PIEZO1 in potentiating physical performance. [ABSTRACT FROM AUTHOR]

Tendons and ligaments are essential connective tissues that connect the muscle and bone. Their recovery from injuries is known to be poor, highlighting the crucial need for an effective therapy. A few reports have described the development of artificial ligaments with sufficient strength from human cells. In this study, we successfully generated a tendon-like tissue (bio-tendon) using human induced pluripotent stem cells (iPSCs). We first differentiated human iPSCs into mesenchymal stem cells (iPSC-MSCs) and transfected them with Mohawk (Mkx) to obtain Mkx-iPSC-MSCs, which were applied to a newly designed chamber with a mechanical stretch incubation system. The embedded Mkx-iPSC-MSCs created bio-tendons and exhibited an aligned extracellular matrix structure. Transplantation of the bio-tendons into a mouse Achilles tendon rupture model showed host-derived cell infiltration with improved histological score and biomechanical properties. Taken together, the bio-tendon generated in this study has potential clinical applications for tendon/ligament-related injuries and diseases. [ABSTRACT FROM AUTHOR]

Damage to the intervertebral discs (IVDs) occurs due to aging or excessive mechanical stress, causing a series of IVD‐related degenerative diseases, such as spinal disc herniation and spondylosis. These IVD‐related diseases are difficult to cure, partially because the regeneration ability of IVDs is not sufficient. As a novel strategy for treatment of IVD‐related diseases, mesenchymal stem cell transplantation to the damaged discs has been reported in animal studies. To further develop and improve this approach, it is necessary to gain a better understanding of the molecular network regulating IVD development by critical transcription factors. Recent findings reveal that during IVD development, nucleus pulposus and annuls fibrosus differentiation is coordinated by a series of transcription factors, such as Mkx, Pax1, 9, Shh, Foxa1, 2, T‐Brachyury, and Sox5, 6, 9. The combination of mesenchymal stem cell transplantation with the regulation of these molecules may provide a novel strategy for treatment of degenerative disc diseases. [ABSTRACT FROM AUTHOR]