Gingery, Anne

ABSTRACT Calcific tendinopathy is a common musculoskeletal disorder marked by calcium deposition within tendons, often accompanied by pain, impaired mobility, and in severe cases, ossification. However, the mechanisms underlying tendon mineralization remain poorly understood. In contrast to pathological human calcification, turkeys naturally develop tendon mineralization during growth without signs of inflammation or ossification. This study had two phases: an observational phase to assess onset and progression of calcification, and an interventional phase to evaluate the role of mechanical loading. In the observational phase, flexor tendons were collected from turkeys aged 1–16 weeks in a serial sacrifice study and analyzed by Von Kossa staining and biomechanical testing. Calcification began at 7 weeks, localized within organized collagen matrices, progressed through Weeks 8–14, and peaked by 16 weeks. In the interventional phase, nine female turkeys were randomized at 4 weeks into a transection group ( n = 3), sham group ( n = 3), and control group ( n = 3). Transection at the muscle–tendon junction eliminated mechanical loading. At 16 weeks, tendons were analyzed by histology, quantitative RT‐PCR, ICP‐MS, and biomechanical testing. Transected tendons showed a near‐complete absence of mineralization, reduced expression of osteogenic markers (osteopontin, osteocalcin, Runx‐2), and significantly lower calcium, magnesium, and phosphorus levels. Biomechanical testing indicated reduced stress relaxation, stiffness, and Young's modulus in the transected group. Tendon calcification in turkeys functioned as a mechanically regulated, nonpathological process. The study established a relevant model for early tendon mineralization and offered a basis for developing load‐dependent therapies for human tendon disease.

Background: The authors present a novel microsurgical model to investigate ischemia-reperfusion (I/R) injury in composite tissue (muscle/skin) using a musculocutaneous flap. I/R was induced in a rodent biceps femoris musculocutaneous flap through collateral ligation and arteriovenous clamping. The authors hypothesized that I/R flaps would show greater tissue damage compared with sham. Methods: Male rats were randomized into I/R ( n = 10) and sham ( n = 9) groups. The I/R group underwent flap elevation, collateral ligation, 3 hours of arteriovenous clamping, followed by reperfusion. The sham group had flap elevation only. Perfusion was monitored using laser-speckle imaging, and flap discoloration was assessed with blinded skin ischemia necrosis scores. Serum and the composite tissue (skin/muscle) were analyzed for injury on postoperative days (PODs) 1 or 3. Results: Clamping reduced perfusion ( P = 0.00), whereas unclamping increased perfusion ( P <0.00). Over time, flaps exposed to I/R were more ischemic (estimate, 0.39; P = 0.02). At POD1, the injury group had higher serum creatine kinase ( P = 0.04) and potassium ( P = 0.00) than the sham group. The injury group had more muscle apoptosis (34.7% versus 5.2%; P = 0.03), myonecrosis (30.3% versus 14.1%; P = 0.04), and inflammation (13.7% versus 4.9%; P = 0.02) than the sham group; myonecrosis and inflammation persisted into POD3. Skin apoptosis and inflammation were similar. Conclusions: This model reliably reproduces I/R injury with a 3-hour ischemic period followed by early reperfusion. Animals subjected to the authors’ technique showed greater tissue damage than the sham group, with muscle being more vulnerable than skin. Serum showed peak muscle injury at 24 hours, and histologic analysis showed myonecrosis and inflammation through 72 hours. This suggests that less than 24 hours’ reperfusion (eg, critical window) may serve as the optimal time for possible intervention. Clinical Relevance Statement: I/R injury is a complex phenomenon affecting vascular composite tissues. The mitochondrial superoxide dismutase may be more specific for I/R injury. There may be a critical window within which to mitigate injury (<24 hours after reperfusion). The authors’ model helps investigate muscle/skin I/R injury.

Objective We aimed to assess the occurrence of carpal tunnel syndrome (CTS) before and after rheumatoid arthritis (RA) incidence and by serologic status. Methods This population‐based study included residents of a geographically defined area meeting the 1987 American College of Rheumatology classification criteria for RA in 1980 to 2019 matched 1:1 with individuals without RA. At least two diagnosis codes ≥30 days apart were used to identify CTS. Cumulative incidence of CTS adjusting for competing risk of death was assessed. Logistic regression and Cox proportional hazard models were used, adjusting for age, sex, calendar year, smoking, obesity, diabetes mellitus, and hypothyroidism. Results We included 1,335 patients with RA and 1,331 individuals without RA. The overall prevalence of CTS before or on RA incidence or index was 179 patients with RA (13%) and 85 individuals without RA (6%), respectively (odds ratio [OR] 2.23; 95% confidence interval [CI] 1.69–2.94). Most previous incidences of CTS occurred ≥2 years before the index date (112 events in patients with RA and 75 events in individuals without RA, respectively). Following RA incidence or index, individuals with RA (vs those without RA) had ~80%‐higher risk of CTS (hazard ratio [HR] 1.78; 95% CI 1.38–2.30). The risk estimates of CTS in patients with seronegative (vs seropositive) RA were OR 1.33 (95% CI 0.96–1.84) before RA incidence and HR 1.37 (95% CI 0.99–1.88) after RA incidence. In RA, obesity (HR 1.42, 95% CI 1.02–1.99) and seronegative cyclic citrullinated peptide antibody status (HR 1.79, 95% CI 1.07–2.99), but not other risk factors, were associated with increased CTS risk. Conclusion We found a more than two‐fold increase in risk of CTS in the years preceding RA and a 1.8‐fold increased risk of incident CTS following RA onset. image

Abstract Senescent osteocytes are key contributors to age‐related bone loss and fragility; however, the impact of mechanobiological changes in these cells remains poorly understood. This study provides a novel analysis of these changes in primary osteocytes following irradiation‐induced senescence. By integrating subcellular mechanical measurements with gene expression analyses, we identified significant, time‐dependent alterations in the mechanical properties of senescent bone cells. Increases in classical markers such as SA‐β‐Gal activity and p16 Ink4a expression levels confirmed the senescence status post‐irradiation. Our key findings include a time‐dependent increase in cytoskeletal Young's modulus and altered viscoelastic properties of the plasma membrane, affecting the contractility of primary osteocytes. Additionally, we observed a significant increase in Sclerostin ( Sost ) expression 21 days post‐irradiation. These biophysical changes may impair osteocyte mechanosensation and mechanotransduction, contributing to bone fragility. This is the first study to time‐map senescence‐associated mechanical changes in the osteocyte cytoskeleton. Our findings highlight the potential of biophysical markers as indicators of cellular senescence, providing more specificity than traditional, variable biomolecular markers. We believe these results may support biomechanical stimulation as a potential therapeutic strategy to rejuvenate aging osteocytes and enhance bone health.

AbstractChordae tendineae, referred to as heart tendinous cords, act as tendons connecting the papillary muscles to the valves in the heart. Their role is analogous to tendons in the musculoskeletal system. Despite being exposed to millions of cyclic tensile stretches over a human's lifetime, chordae tendineae rarely suffer from overuse injuries. On the other hand, musculoskeletal tendinopathy is very common and remains challenging in clinical treatment. The objective of this study was to investigate the mechanism behind the remarkable durability and resistance to overuse injuries of chordae tendineae, as well as to explore their effects on flexor tenocyte biology. The messenger RNA expression profiles of chordae tendineae were analyzed using RNA sequencing and verified by quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Interestingly, we found that periostin (Postn) and fibroblast growth factor 7 (FGF7) were expressed at significantly higher levels in chordae tendineae, compared to flexor tendons. We further treated flexor tenocytes in vitro with periostin and FGF7 to examine their effects on the proliferation, migration, apoptosis, and tendon‐related gene expression of flexor tenocytes. The results displayed enhanced cell proliferation ability at an early stage and an antiapoptotic effect on tenocytes, while treated with periostin and/or FGF7 proteins. Furthermore, there was a trend of promoted tenocyte migration capability. These findings indicated that Postn and FGF7 may represent novel cytokines to target flexor tendon healing. Clinical significance: The preliminary discovery leads to a novel idea for treating tendinopathy in the musculoskeletal system using specific molecules identified from chordae tendineae.

The intrinsic healing following tendon injury is ideal, in which tendon progenitor cells proliferate and migrate to the injury site to directly bridge or regenerate tendon tissue. However, the mechanism determining why and how those cells are attracted to the injury site for tendon healing is not understood. Since the tenocytes near the injury site go through apoptosis or necrosis following injury, we hypothesized that secretions from injured tenocytes might have biological effects on cell proliferation and migration to enhance tendon healing. Tenocyte apoptosis was induced by 24 h cell starvation. Apoptotic body-rich media (T-ABRM) and apoptotic body-depleted media (T-ABDM) were collected from culture media after centrifuging. Tenocytes and bone marrow-derived stem cells (BMDSCs) were isolated and cultured with the following four media: (1) T-ABRM, (2) T-ABDM, (3) GDF-5, or (4) basal medium with 2% fetal calf serum (FCS). The cell activities and functions were evaluated. Both T-ABRM and T-ABDM treatments significantly stimulated the cell proliferation, migration, and extracellular matrix synthesis for both tenocytes and BMDSCs compared to the control groups (GDF-5 and basal medium). However, cell proliferation, migration, and extracellular matrix production of T-ABRM-treated cells were significantly higher than the T-ABDM, which indicates the apoptotic bodies are critical for cell activities. Our study revealed the possible mechanism of the intrinsic healing of the tendon in which apoptotic bodies, in the process of apoptosis, following tendon injury promote tenocyte and stromal cell proliferation, migration, and production. Future studies should analyze the components of the apoptotic bodies that play this role, and, thus, the targeting of therapeutics can be developed.

Abstract Rotator cuff injuries increase with age. The enthesis is the most frequent site of rotator cuff injury and degeneration. Understanding age‐related changes of the enthesis are essential to determine the mechanism of rotator cuff injuries, degeneration, and to guide mechanistically driven therapies. In this study, we explored age‐related cellular changes of the rotator cuff enthesis in young, mature, and aged rats. Here we found that the aged enthesis is typified by an increased mineralized zone and decreased nonmineralized zone. Proliferation, migration, and colony‐forming potential of rotator cuff derived cells (RCECs) was attenuated with aging. The tenogenic and chondrogenic potential were significantly reduced, while the osteogenic potential increased in aged RCECs. The adipogenic potential increased in RCECs with age. This study explores the cellular differences found between young, mature, and aged rotator cuff enthesis cells and highlights the importance of using age‐appropriate models, as well as provides a basis for further delineation of mechanisms and potential therapeutics for rotator cuff injuries.

Background: The retear rate after rotator cuff repair remains unacceptably high. Various biological engineered scaffolds have been proposed to reduce the retear rate. We have developed a double rip-stop repair with medial row knot (DRSK) technique to enhance suture-tendon strength and a novel engineered tendon-fibrocartilage-bone composite (TFBC) for rotator cuff repair. Hypothesis: DRSK rotator cuff repair augmented with TFBC will have better biomechanical properties than that of DRSK repair with an acellular dermal graft (DG). Study Design: Controlled laboratory study. Methods: Fresh-frozen canine shoulders (n = 30) and knees (n = 10) were used. TFBCs were harvested from the patellar tendon–tibia complex and prepared for rotator cuff repair. The infraspinatus tendon was sharply detached from its bony attachment and randomly assigned to the (1) control group: DRSK repair alone, (2) TFBC group: DRSK repair with TFBC, and (3) DG group: DRSK repair with DG. All specimens were tested to failure, and videos were recorded. The footprint area, tendon thickness, load to create 3-mm gap formation, failure load, failure modes, and stiffness were recorded and compared. Data were recorded as mean ± SD. Results: The mean load to create a 3-mm gap in both the control group (206.8 ± 55.7 N) and TFBC group (208.9 ± 39.1 N) was significantly higher than that in the DG group (157.7 ± 52.3 N) ( P < .05 for all). The failure load of the control group (275.7 ± 75.0 N) and TFBC group (275.2 ± 52.5 N) was significantly higher compared with the DG group (201.5 ± 49.7 N) ( P < .05 for both comparisons). The stiffness of the control group (26.4 ± 4.7 N/mm) was significantly higher than of the TFBC group (20.4 ± 4.4 N/mm) and the DG group (21.1 ± 4.8 N/mm) ( P < .05 for both comparisons). Conclusion: TFBC augmentation showed superior biomechanical performance to DG augmentation in rotator cuff tears repaired using the DRSK technique, while there was no difference between the TFBC and control groups. Clinical Relevance: TFBC may help to reduce retear or gap formation after rotator cuff repair using the DRSK technique.