Journal of Anatomy最新文献

Tendon injuries and disorders associated with mechanical tendon overuse are common musculoskeletal problems. Even though tendons play a central role in human movement, the intrinsic healing process of tendon is very slow. So far, it is known that tendon cell activity is supported by several interstitial cells within the tendon. However, the interplay between the tendon and the adjacent muscle for tendon regeneration and development processes has not been fully investigated. Here, we tested whether factors released from muscle derived myogenic cells (myoblasts) enhance tenogenic progressions of human tendon derived cells (tendon fibroblasts) using two-dimensional (2D) culture model and a three-dimensional (3D)-engineered tendon construct culture model, which mimics tendon regeneration and development. The conditioned media from myoblasts and unconditioned media as control were applied to tendon fibroblasts. In 2D, immunofluorescence analysis revealed increased collagen type I expressing area and increased migration potential when conditioned media from myoblasts were applied. In the 3D-engineered human tendon construct model, wet weight, diameter, and cross-sectional area of the tendon constructs were increased in response to the application of conditioned media from myoblasts, whereas the collagen density was lower and mechanical function was reduced both at the functional level (maximum stiffness) and the material level (maximum stress and modulus). These results indicate that myoblast-derived factors extend collagen expressing area and enhance migration of tendon fibroblasts, while factors involved in the robustness of extra-cellular matrix deposition of tissue-engineered tendon constructs are lacking. Our findings suggest that adjacent muscle affects the signaling interplay in tendons.

The enthesis, the specialized junction between tendon and bone, is a common site of injury. Although notoriously difficult to repair, advances in interfacial tissue engineering techniques are being developed for restorative function. Most notably are 3D in vitro co-culture models, built to recreate the complex heterogeneity of the native enthesis. While cell and matrix properties are often considered, there has been little attention given to native enthesis anatomical morphometrics and replicating these to enhance clinical relevance. This study focuses on the flexor digitorum profundus (FDP) tendon enthesis and, by combining anatomical morphometrics with computer-aided design, demonstrates the design and construction of an accurate and scalable model of the FDP enthesis. Bespoke 3D-printed mould inserts were fabricated based on the size, shape and insertion angle of the FDP enthesis. Then, silicone culture moulds were created, enabling the production of bespoke anatomical culture zones for an in vitro FDP enthesis model. The validity of the model has been confirmed using brushite cement scaffolds seeded with osteoblasts (bone) and fibrin hydrogel scaffolds seeded with fibroblasts (tendon) in individual studies with cells from either human or rat origin. This novel approach allows a bespoke anatomical design for enthesis repair and should be applied to future studies in this area.

Diabetes mellitus type 2 (DMT2) promotes Achilles tendon (AS) degeneration and exercise could modulate features of DMT2. Hence, this study investigated whether tenocytes of non DMT2 and DMT2 rats respond differently to normo- (NG) and hyperglycemic (HG) conditions in the presence of tumor necrosis factor (TNF)α or cyclic stretch. AS tenocytes, isolated from DMT2 (fa/fa) or non DMT2 (lean, fa/+) adult Zucker Diabetic Fatty (ZDF) rats, were treated with 10 ng/mL TNFα either under NG or HG conditions (1 g/L vs. 4.5 g/L glucose) and were exposed to cyclic stretch (14%, 0.3 Hz, 48 h). Tenocyte survival, metabolic activity, gene and/or protein expression of tendon extracellular matrix component collagen type 1, alpha smooth muscle actin (αSMA, Acta2), the stress defense enzyme heme oxygenase-1 (Hmox1) as well as suppressors of cytokine signaling (Socs)1 and Socs3 were analyzed. Tenocyte vitality remained high, but metabolic activity was slightly impaired by HG conditions irrespectively of cell origin. Collagen type 1 alpha protein and gene expression was suppressed by TNFα, but only in cells of non DMT2 animals in NG culture medium. Higher amounts of αSMA were visualized in tendons/tenocytes of diabetic rats or those exposed to TNFα. Cyclic stretch caused cell alignment in zero stretch direction. In addition, it led to a significant reduction of cell perimeters, particularly in cells of DMT2 donor rats under HG conditions. Hmox1, Socs1 and Socs3 were induced by HG, but only in tenocytes of diabetic rats (4 h). Stretch induced significantly Hmox1 transcriptional activity under NG conditions and Socs3 under HG conditions especially in tenocytes of DMT2 rats. The response of tenocytes to TNFα and cyclic stretch depends on glucose supply and origin suggesting their irreversible impairment by DMT2.

Normal function of the hand and, in particular, the finger joints is fundamental to the activities of daily life. Deterioration of hand and finger function can be detrimental and lead to poor quality of life. There are multiple causes of hand and finger dysfunction that can lead to pain and disability. In this review, we will consider the role of collagen and its organization within the finger joint capsules and adjacent entheses, particularly in the proximal interphalangeal joints, and aim to address three questions: (1) What are the main collagen orientations in the interphalangeal joint capsules of the human hand? (2) Is there a relationship between collagen orientation and joint function? (3) How could altering the orientation of collagen fibers affect the functional performance of the joint following injury or surgical intervention? To answer these questions, we will consider the evidence for the main collagen orientations in the finger joint capsules and entheses and investigate the relationships between structure and function. We will then consider how collagen organization is disrupted following injury and what may be potential modulators. This will provide a better understanding of how common surgical interventions affect collagen orientation in the joint capsules and highlight some implications for post-surgical outcomes.

Understanding the role of tendons in muscle function and proprioception is crucial for enhancing amputation surgery. Muscle spindles and Golgi tendon organs provide essential feedback for muscle control. Preservation of tendon function in amputation surgery and the development of the agonist-antagonist myoneural interface (AMI) have shown promising results restoring muscle-tendon proprioception and in improving prosthetic control. However, challenges remain in constructing AMI due to anatomical limitations in residual limbs. A total of 25 lower legs from fresh-frozen human Caucasian donors were dissected, and the muscles relevant to the AMI technique, such as the gastrocnemius complex, the tibialis posterior, the tibialis anterior, and the peroneus longus, were analyzed. Demographic and anthropometric measurements, muscle preparation and weight, markings, imaging, and statistical analysis methods were described in detail. In all muscles examined, the intramuscular course of the tendon extended over more than 75% of the distal muscle belly. The muscle belly length of the peroneus longus muscle and the medial head of the gastrocnemius muscle showed a significant positive correlation with the weight and height of the donors. There were no significant correlations between the ratio of the intramuscular course of the tendon to muscle belly length and the weight or height of the donor. The AMI technique can enhance proprioceptive feedback for transtibial amputees wearing prostheses. The study indicates that gender does not impact muscle characteristics, but weight and height show correlations. These results offer valuable insights into muscle anatomy for informing future research on the functional effects of AMI and prosthetic limb design.

This review celebrates the work of Professor Mike Benjamin, whose anatomical research transformed our understanding of entheses - the sites where tendons, ligaments and other connective tissues attach to bone. This review aims to provide an overview of Professor Benjamin's foundational concepts, including the enthesis organ, functional entheses and the synovio-entheseal complex and their relevance to musculoskeletal health and disease. Entheses are biomechanically complex regions that accommodate the transition between compliant soft connective tissues and rigid bone by natural macroscopic and microscopic adaptations that reduce stress concentration. Macroscopically, tendons and ligaments often flare near their attachment sites, increasing surface area. Microscopically, entheses are classified as fibrous or fibrocartilaginous, with the latter displaying a zonal organisation that includes uncalcified and calcified fibrocartilage. These zones provide a graded transition in stiffness, reducing the risk of tissue failure and enables gradual bending of collagen fibres. Mechanical loading is essential for the normal development of the enthesis and is required to maintain its biomechanical properties in the adult. The enthesis organ concept, one of Professor Benjamin's most significant contributions, recognises that entheses are rarely isolated structures. Instead, they are part of a functional unit comprising adjacent tissues including sesamoid and periosteal fibrocartilages, bursae, fat pads and retinaculae which collectively dissipate mechanical stress. Adipose tissue and synovium at these sites may also play immunological and proprioceptive roles, and its involvement in neurovascular invasion has implications for pain and pathology. However, beyond direct tendon-bone attachments, functional entheses describe regions where tendons and ligaments interact with bone at a distance from the insertion but share structural and functional characteristics with classical entheses. The development of these concepts highlights Professor Benjamin's integrative approach to research and will continue to underpin research in musculoskeletal biology, pathology and tissue engineering, as well as inspire generations of anatomists.

Physical activity can activate extracellular matrix (ECM) protein synthesis and influence the size and mechanical properties of tendon. In this study, we aimed to investigate whether different training histories of horses would influence the synthesis of collagen and other matrix proteins and alter the mechanical properties of tendon. Samples from superficial digital flexor tendon (SDFT) from horses that were either (a) currently race trained (n = 5), (b) previously race trained (n = 5) or (c) untrained (n = 4) were analysed for matrix protein abundance (mass spectrometry), collagen and glycosaminoglycan (GAG) content, ECM gene expression and mechanical properties. It was found that ECM synthesis by tendon fibroblasts in vitro varied depending upon the previous training history. In contrast, fascicle morphology, collagen and GAG content, mechanical properties and ECM gene expression of the tendon did not reveal any significant differences between groups. In conclusion, although we could not identify any direct impact of the physical training history on the mechanical properties or major ECM components of the tendon, it is evident that horse tendon cells are responsive to loading in vivo, and the training background may lead to a modification in the composition of newly synthesised matrix.

Calcaneal spurs are shown to be increasingly prevalent in modern populations and often contribute to forming heel and foot pain. There are multiple hypotheses for their formation, including exercise, prolonged standing and obesity. The impact of these spurs on foot biomechanics remains unclear; it is suggested that their presence may contribute to enthesial avulsion forces. This study aimed to determine the avulsion properties of the plantar aponeurosis enthesis with and without spurs. Twenty-four feet from 15 cadavers donated to the Department of Anatomy at the University of Otago were used for this study. Tissues were X-rayed to determine the presence of spurs. The donor feet were dissected to isolate the calcanei. These were then mounted in a custom-developed 3D-printed clamping rig to perform tensile testing of the plantar calcaneal enthesis to determine pull-out forces of the central band of the plantar fascia. Biomechanical testing showed no statistically significant differences in avulsion properties between the spur (n = 7) and non-spur (n = 14) samples in any of the avulsion parameters investigated: F_max (1121 ± 358 N vs. 953 ± 283 N, mean ± SD, p = 0.302) and εF_max (53 ± 11% vs. 51 ± 13%, mean ± SD, p = 0.660). Despite this, the avulsion parameters were highly variable. The results of this study indicate that the pull-out force of the central band of the plantar fascia is unrelated to the presence of spurs. Therefore, it is less likely that plantar spurs fulfill a biomechanical function within the plantar fascia complex.