Tendon injury and tendinopathy: healing and repair

Amnion-Derived Teno-Inductive Secretomes: A Novel Approach to Foster Tendon Differentiation and Regeneration in an Ovine Model

Regenerative medicine has greatly progressed, but tendon regeneration mechanisms and robust in vitro tendon differentiation protocols remain to be elucidated. Recently, tendon explant co-culture (CO) has been proposed as an in vitro model to recapitulate the microenvironment driving tendon development and regeneration. Here, we explored standardized protocols for production and storage of bioactive tendon-derived secretomes with an evaluation of their teno-inductive effects on ovine amniotic epithelial cells (AECs). Teno-inductive soluble factors were released in culture-conditioned media (CM) only in response to active communication between tendon explants and stem cells (CMCO). Unsuccessful tenogenic differentiation in AECs was noted when exposed to CM collected from tendon explants (CMFT) only, whereas CMCO upregulated SCXB, COL I and TNMD transcripts, in AECs, alongside stimulation of the development of mature 3D tendon-like structures enriched in TNMD and COL I extracellular matrix proteins. Furthermore, although the tenogenic effect on AECs was partially inhibited by freezing CMCO, this effect could be recovered by application of an in vivo-like physiological oxygen (2% O2) environment during AECs tenogenesis. Therefore, CMCO can be considered as a waste tissue product with the potential to be used for the development of regenerative bio-inspired devices to innovate tissue engineering application to tendon differentiation and healing.

Posttraumatic Perfusion Analysis of Quadriceps, Patellar, and Achilles Tendon Regeneration With Dynamic Contrast-Enhanced Ultrasound and Dynamic Contrast-Enhanced Magnetic Resonance Imaging: Preliminary Results

OBJECTIVES

The healing process of tendons after surgical treatment of tendon ruptures mainly depends on the perfusion of the tendon and its surrounding tissue. Dynamic contrast-enhanced ultrasound (DCE-US) and dynamic contrast-enhanced MRI (DCE-MRI) can provide additional information about the local microperfusion. In this pilot study, the feasibility of these techniques to assess the vascularization during tendon regeneration was evaluated.

METHODS

Between 2013 and 2015, 23 patients with surgical treatment of traumatic rupture of quadriceps, patellar, and Achilles tendons were involved. All patients received clinical follow-up examinations at 6, 12, and at least 52 weeks postoperatively. Dynamic contrast-enhanced US and DCE-MRI examinations were performed 6 and 12 weeks postoperatively. Dynamic contrast-enhanced US perfusion was quantified by the parameters peak enhancement, wash-in area under the curve, rise time, and initial area under the curve. Correlations between these parameters were examined via the Spearman rank correlation. The clinical and functional outcomes were assessed via the Lysholm Knee Score and Knee and Osteoarthritis Outcome Score at 12 and 52 weeks postoperatively.

RESULTS

Fourteen patients with quadriceps (n = 8), patellar (n = 4) and Achilles (n = 2) tendon ruptures with complete follow-up were available. The microperfusion could be successful assessed. We could detect a strong correlation of DCE-US (peak enhancement) parameters with DCE-MRI (initial area under the curve) parameters after 6 and 12 weeks.

CONCLUSIONS

In this pilot study, DCE-US was able to visualize the microperfusion of healing tendons with a strong correlation with DCE-MRI. Our initial results are in favor of DCE-US as a potential quantitative imaging tool for evaluating the vascularization in tendon regeneration as a complementary method.

Functional regeneration and repair of tendons using biomimetic scaffolds loaded with recombinant periostin

Tendon injuries disrupt the balance between stability and mobility, causing compromised functions and disabilities. The regeneration of mature, functional tendons remains a clinical challenge. Here, we perform transcriptional profiling of tendon developmental processes to show that the extracellular matrix-associated protein periostin (Postn) contributes to the maintenance of tendon stem/progenitor cell (TSPC) functions and promotes tendon regeneration. We show that recombinant periostin (rPOSTN) promotes the proliferation and stemness of TSPCs, and maintains the tenogenic potentials of TSPCs in vitro. We also find that rPOSTN protects TSPCs against functional impairment during long-term passage in vitro. For in vivo tendon formation, we construct a biomimetic parallel-aligned collagen scaffold to facilitate TSPC tenogenesis. Using a rat full-cut Achilles tendon defect model, we demonstrate that scaffolds loaded with rPOSTN promote endogenous TSPC recruitment, tendon regeneration and repair with native-like hierarchically organized collagen fibers. Moreover, newly regenerated tendons show recovery of mechanical properties and locomotion functions.

The regeneration of functional tendons remains a clinical challenge. Here the authors develop a biomimetic scaffold loaded with recombinant periostin and demonstrate its functionality in promoting tendon stem/progenitor cell recruitment and tenogenic differentiation, and tendon regeneration in a rat full-cut Achilles tendon defect model.

Small extracellular vesicles with LncRNA H19 "overload": YAP Regulation as a Tendon Repair Therapeutic Tactic

Functional healing of tendon injuries remains a great challenge. Small extracellular vesicles (sEVs) have received attention as pro-regenerative agents. H19 overexpression could bring tendon regenerative ability, but the mechanism is still not fully elucidated, and reliable method for delivery of long non-coding RNAs (LncRNAs) was demanded. We identified the downstream mechanism of H19, the activation of yes-associated protein (YAP) via the H19-PP1-YAP axis. We established tendon stem/progenitor cells (TSPCs) stably overexpressing H19 with CRISPR-dCas9-based hnRNP A2/B1 activation (H19-CP-TSPCs). H19-OL-sEVs (H19 “overloading” sEVs) could be produced effectively from H19-CP-TSPCs. Only H19-OL-sEVs were able to significantly load large amounts of H19 rather than other competitors, and the potential of H19-OL-sEVs to promote tendon healing was far better than that of other competitors. Our study established a relatively reliable method for enrichment of LncRNAs into sEVs, providing new hints for modularized sEV-based therapies, and modularized sEVs represented a potential strategy for tendon regeneration.

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H19 overexpression enhances tendon regeneration

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H19 dephosphorylates and activates YAP

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hnRNP A2/B1 assists the enrichment of H19 into sEVs

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H19-OL-sEVs promote tendon regeneration

Advances in the Development of Anti-Adhesive Biomaterials for Tendon Repair Treatment

BACKGROUND

Peritendinous adhesion that simultaneous with tendon healing link the healing tendon to the surrounding tissue. It results in functional disability, and has a significant adverse impact on health as well as social and economic development.

METHODS

Based on a search in the PubMed and Web of Science database, the research articles were screened by their time, main idea, impact factor index, while the ones with no credibility were excluded. Afterwards, we go through the analysis of the reliability and characteristics of the results were further screened from selected articles.

RESULTS

A total of 17 biomaterials used to evaluate the adhesion mechanism and the properties of the material were found. All of these biomaterials contained randomized controlled studies and detailed descriptions of surgical treatment that support the reliability of their results which indicates that biomaterials act as barriers to prevent the formation of adhesion, and most of them exhibit satisfactory biocompatibility, biodegradability or selective permeability. Moreover, a few had certain mechanical strength, anti-inflammatory, or carrier capacities. However, there still existed some defects, such as time, technology, clinical trials, material targeting and different measurement standards which also lowered the reliability of their results.

CONCLUSION

In future, anti-adhesion biomaterials should focus on affordable raw materials with wide sources, and the production process should be simplified, in this way, the versatility and targeting of materials will be improved.

Histological evaluation of the effect of low-frequency electric stimulation on healing Achilles tendons in rats

PURPOSE

Histologically evaluate the effects of low frequency electrical stimulation in the treatment of Achilles tendon injuries in rats.

METHODS

Thirty-four rats underwent Achilles tendon tenotomy and tenorrhaphy. They were randomly allocated in two groups. Half of the sample constituted the experiment group, whose lesions were stimulated with 2 Hz, nonpolarized current and 1 mA, for 14 days. The other animals formed the control group. They were evaluated at 2, 4 and 6 weeks. The histological study was carried out, the collagen density and the wound maturity index were measured.

RESULTS

The healing score was higher in the group stimulated at the 6th week (p = 0.018). The density collagen 1 was higher in the group treated at the three times (p = 0.004) and that collagen 3 was higher in the group treated at 6 weeks (p = 0.004). Together, collagen 1 and 3 were higher in the group stimulated at 4 and 6 weeks (p = 0.009, p = 0.004). The maturity index was higher in this group at the three moments (p = 0.017 p = 0.004 and p = 0.009).

CONCLUSION

Low frequency electric stimulation improved healing and increased the quantity of collagen.

Histopathological and immunohistochemical investigation of the local and systemic effects of tranexamic acid on the healing of the Achilles tendon in rats

OBJECTIVES

This study aims to compare the effects of systemic and local applications of tranexamic acid (TXA) on tendon healing using a rat Achilles tendon injury model.

PATIENTS AND METHODS

Thirty-six adult male albino Wistar rats (aging 3-4 months; weighing 350 to 400 g) were used in this study conducted between December 2019 and January 2020. The Achilles tendon was performed bilateral tenotomy and surgically repaired. Postoperatively, 1 mL of TXA was administered to each leg locally in the local group, whereas 2 mL of TXA was intraperitoneally administered in the systemic group. The control group was left untreated. Half of the rats were sacrificed on Day 15 and the other half on Day 30. Tendon healing was evaluated with the Bonar and the Movin scoring systems and immunohistochemical methods.

RESULTS

The systemic group had the highest Bonar and Movin scores on Day 15. All groups exhibited tendon healing on Day 30, with no significant differences among the groups. The tenocyte morphology was found to be more impaired in both TXA groups on Day 30 (p=0.013). Ground substance scores were lower in the systemic group on Day 30 (p=0.028). The fiber structure and arrangement scores were higher in the systemic group on Day 15 (p=0.007 and p=0.032). Immunohistochemical analyses showed that galectin-3 values exhibited a significant difference in all groups on Day 30 (p=0.020). In all groups, it was determined that type I collagen values showed an increasing trend on Day 30, compared to the values on Day 15, whereas type III collagen values showed a decreasing trend.

CONCLUSION

Our results demonstrated that local and systemic use of TXA does not impair tendon healing. Although advanced studies are needed, our study suggests that TXA application reduces the development of fibrosis.

Moderate and intensive mechanical loading differentially modulate the phenotype of tendon stem/progenitor cells in vivo

To examine the differential mechanobiological responses of specific resident tendon cells, we developed an in vivo model of whole-body irradiation followed by injection of either tendon stem/progenitor cells (TSCs) expressing green fluorescent protein (GFP-TSCs) or mature tenocytes expressing GFP (GFP-TNCs) into the patellar tendons of wild type C57 mice. Injected mice were subjected to short term (3 weeks) treadmill running, specifically moderate treadmill running (MTR) and intensive treadmill running (ITR). In MTR mice, both GFP-TSC and GFP-TNC injected tendons maintained normal cell morphology with elevated expression of tendon related markers collagen I and tenomodulin. In ITR mice injected with GFP-TNCs, cells also maintained an elongated shape similar to the shape found in normal/untreated control mice, as well as elevated expression of tendon related markers. However, ITR mice injected with GFP-TSCs showed abnormal changes, such as cell morphology transitioning to a round shape, elevated chondrogenic differentiation, and increased gene expression of non-tenocyte related genes LPL, Runx-2, and SOX-9. Increased gene expression data was supported by immunostaining showing elevated expression of SOX-9, Runx-2, and PPARγ. This study provides evidence that while MTR maintains tendon homeostasis by promoting the differentiation of TSCs into TNCs, ITR causes the onset of tendinopathy development by inducing non-tenocyte differentiation of TSCs, which may eventually lead to the formation of non-tendinous tissues in tendon tissue after long term mechanical overloading conditions on the tendon.

Tensiometric evaluation of the effect of lowfrequency electric stimulation on healing Achilles tendons in rats

PURPOSE

To evaluate the effects of low-frequency electric stimulation on biomechanics following surgical treatment of the Achilles tendon in rats.

METHODS

Forty-two rats were divided into two groups. One was given electric stimulation and the other was not. All were submitted to Achilles tenotomy and tenorrhaphy performed with a modified Kessler stitch. The experiment group underwent electric stimulation with 2 Hz, a nonpolarized current of 1 mA intensity for 14 days. The animals were euthanized at 2, 4 and 6 weeks for the biomechanical study.

RESULTS

The work performed, that is, the tendon's capacity to absorb energy until rupture, was greater in the electrically stimulated group in the 2nd (p = 0.032) and in the 6th week (p = 0.010). The maximum tension, which is the capacity to support a load, was higher in the treated group in the 2nd (p = 0.030) and the 6th week (p = 024). These results indicate greater resistance of the electrically stimulated tendons. An analysis of the elastic module showed no differences.

CONCLUSION

Low-frequency electric stimulation increased the resistance of the tendons at 2 and 6 weeks of evolution in rats.

The Effects of Hypoxia-Reoxygenation in Mouse Digital Flexor Tendon-Derived Cells

Objective

Ischemia-reperfusion injury refers to the exacerbated and irreversible tissue damage caused by blood flow restoration after a period of ischemia. The hypoxia-reoxygenation (H/R) model in vitro is ideal for studying ischemia-reperfusion injury at the cellular level. We employed this model and investigated the effects of cobalt chloride- (CoCl₂-) induced H/R in cells derived from mouse digital flexor tendons.

Materials and Methods

Various H/R conditions were simulated via treatment of tendon-derived cells with different concentrations of CoCl₂ for 24 h, followed by removal of CoCl₂ to restore a normal oxygen state for up to 96 h. Cell viability was measured using the Cell Counting Kit-8 (CCK-8) assay. Cell growth was determined via observation of cell morphology and proliferation. Oxidative stress markers and mitochondrial activity were detected. The expression levels of hypoxia-inducible factor- (HIF-) 1α, vascular endothelial growth factor-A (VEGF-A), collagen I, and collagen III were determined using Western blot (WB), real-time PCR, and immunofluorescence staining. Cellular apoptosis was analyzed via flow cytometry, and the expression of apoptosis-related proteins Bax and bcl-2 was examined using WB.

Results

The cells treated with low concentrations of CoCl₂ showed significantly increased cell viability after reoxygenation. The increase in cell viability was even more pronounced in cells that had been treated with high concentrations of CoCl₂. Under H/R conditions, cell morphology and growth were unchanged, while oxidative stress reaction was induced and mitochondrial activity was increased. H/R exerted opposite effects on the expression of HIF-1α mRNA and protein. Meanwhile, the expression of VEGF-A was upregulated, whereas collagen type I and type III were significantly downregulated. The level of cellular apoptosis did not show significant changes during H/R, despite the significantly increased Bax protein and reduced bcl-2 protein levels that led to an increase in the Bax/bcl-2 ratio during reoxygenation.

Conclusions

Tendon-derived cells were highly tolerant to the hypoxic environments induced by CoCl₂. Reoxygenation after hypoxia preconditioning promoted cell viability, especially in cells treated with high concentrations of CoCl₂. H/R conditions caused oxidative stress responses but did not affect cell growth. The H/R process had a notable impact on collagen production and expression of apoptosis-related proteins by tendon-derived cells, while the level of cellular apoptosis remained unchanged.

Comparing Absorbable and Nonabsorbable Suture Materials for Repair of Achilles Tendon Rupture: A Magnetic Resonance Imaging-Based Study

We aimed to compare magnetic resonance imaging (MRI) findings and corresponding clinical outcomes of repaired Achilles tendons using absorbable and nonabsorbable sutures. Patients who underwent Achilles tendon repair were divided into 2 groups, with 11 in the absorbable group (group A) and 11 in the nonabsorbable group (group B). For all patients, MRI findings taken 6 months postoperatively were evaluated for morphological changes in the tendon. Concurrently, the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hind foot score and incidence of postoperative complications were evaluated. Regarding MRI findings, the extent to which the cross-sectional area of the repaired tendon was thicker than that of the preoperative tendon was significantly greater in group B than in group A (p = 0.0012). Notably, more stitches remained within the tendon in group B than in group A (p = 0.0063). No other MRI findings showed a significant difference between the two groups. No significant difference was observed in the AOFAS score, and there was one re-rupture each in both groups. Because nonabsorbable suture material in the treatment of Achilles tendon rupture yielded a thicker postoperative MRI cross-sectional area, enhanced rehabilitation is recommended in order to prevent scar formation.

Understanding cellular and molecular mechanisms of pathogenesis of diabetic tendinopathy

There is accumulating evidence of an increased incidence of tendon disorders in people with diabetes mellitus. Diabetic tendinopathy is an important cause of chronic pain, restricted activity, and even tendon rupture in individuals. Tenocytes and tendon stem/progenitor cells (TSPCs) are the dominant cellular components associated with tendon homeostasis, maintenance, remodeling, and repair. Some previous studies have shown alterations in tenocytes and TSPCs in high glucose or diabetic conditions that might cause structural and functional variations in diabetic tendons and even accelerate the development and progression of diabetic tendinopathy. In this review, the biomechanical properties and histopathological changes in diabetic tendons are described. Then, the cellular and molecular alterations in both tenocytes and TSPCs are summarized, and the underlying mechanisms involved are also analyzed. A better understanding of the underlying cellular and molecular pathogenesis of diabetic tendinopathy would provide new insight for the exploration and development of effective therapeutics.

Effects and Mechanism of Berberine on the Dexamethasone-Induced Injury of Human Tendon Cells

Objective

To investigate the effects of berberine (Berb) on dexamethasone- (Dex-) induced injury of human tendon cells and its potential mechanism.

Methods

CCK-8 assay was used to explore the appropriate concentration of Dex-induced injury of tendon cells and the doses of Berb attenuates Dex cytotoxicity; cell wound healing assay was used to detect the effects (P < 0.05) of Berb and Dex on the migration ability of tendon cells; flow cytometry was used to measure cell apoptosis; DCF DA fluorescent probe was used to measure the ROS activity of cells. Western blotting was used to detect the expression of phenotype related factors including smooth muscle actin α (SMA-α), type I collagen (Col I), col III, apoptosis-related factors, caspase-3, cleaved caspase-3, caspase-9, cleaved caspase-9, and PI3K/AKT.

Results

CCK-8 assay showed that 1-100 μM Dex significantly inhibited the proliferation of tendon cells in a concentration-dependent manner (P < 0.05), where the inhibitory effect of 100 μM Dex was most significant (P < 0.005), and the pretreatment of 150, 200 μM Berb could reverse those inhibitions (all P < 0.05). Compared with the control group, Dex significantly inhibited cell migration (P < 0.05), while Berb pretreatment could enhance cell migration (P < 0.05). Flow cytometry and ROS assay showed that Dex could induce apoptosis and oxidative stress response of tendon cells (all P < 0.05), while Berb could reverse those responses (P < 0.05). Western blot showed that Dex could inhibit the expression of the col I and III as well as α-SMA (all P < 0.05) and enhance the expression of apoptosis-related factors including cleaved caspase-3 and cleaved caspase-9 (all P < 0.05). Besides, Dex could also inhibit the activation of the PI3K/AKT signaling pathway (all P < 0.05), thus affecting cell function, while Berb treatment significantly reversed the expression of those above proteins (all P < 0.05).

Conclusion

Berb attenuated DEX induced reduction of proliferation and migration, oxidative stress, and apoptosis of tendon cells by activating the PI3K/AKT signaling pathway and regulated the expression of phenotype related biomarkers in tendon cells. However, further studies are still needed to clarify the protective effects of Berb in vivo.

Sustained Exposure of Substance P Causes Tendinopathy

Recently, neuromediators such as substance P (SP) have been found to be important factors in tendon homeostasis. Some studies have found SP to be the cause of inflammation and tendinopathy, whereas others have determined it to be a critical component of tendon healing. As demonstrated by these conflicting findings, the effects of SP on tendinopathy remain unclear. In this study, we hypothesized that the duration of SP exposure determines its effect on the tendons, with repetitive long-term exposure leading to the development of tendinopathy. First, we verified the changes in gene and protein expression using in vitro tenocytes with 10-day exposure to SP. SP and SP + Run groups were injected with SP in their Achilles tendon every other day for 14 days. Achilles tendons were then harvested for biomechanical testing and histological processing. Notably, tendinopathic changes with decreased tensile strength, as observed in the Positive Control, were observed in the Achilles in the SP group compared to the Negative Control. Subsequent histological analysis, including Alcian blue staining, also revealed alterations in the Achilles tendon, which were generally consistent with the findings of tendinopathy in SP and SP + Run groups. Immunohistochemical analysis revealed increased expression of SP in the SP group, similar to the Positive Control. In general, the SP + Run group showed worse tendinopathic changes. These results suggest that sustained exposure to SP may be involved in the development of tendinopathy. Future research on inhibiting SP is warranted to target SP in the treatment of tendinopathy and may be beneficial to patients with tendinopathy.

Expression of alarmins in a murine rotator cuff tendinopathy model

The aim of this study was to investigate the presence of alarmins in a novel murine rotator cuff tendinopathy model. Alarmins have been described as essential early activators of an immune response to tissue damage. Subacromial impingement was induced in both shoulders of 37 male C57Bl/6 mice by placement of a small metal clip in the subacromial space. Animals were allocated to different time points up to 6 weeks. The morphology and cellularity of the supraspinatus tendon were evaluated by hematoxylin-eosin staining, alcian blue, and picrosirius red. The expression and localization of alarmins interleukin-33 (IL-33), c (HMGB1), hypoxia-inducible factor-1 subunit α (HIF1α), and S100A9 were evaluated by immunohistochemical staining and quantitative polymerase chain reaction. The percentage of positively stained cells with HMGB1 and IL-33 was significantly increased in the impingement group at 1w, 4w, and 6w. HIF1α staining was higher in the impingement group at 1w and 6w compared with the control group. HMGB1 gene expression was higher in the 5d impingement group and 6w impingement group. The gene expression of HIF1α was upregulated at all-time points in the impingement group (5d, 2w, 4w, and 6w). The expression of the S100A9 gene was also upregulated in the 5d impingement group. This is the first study to demonstrate the involvement of alarmins in the early phase of tendinopathy using a reproducible animal model. Alarmins may play an important role in the early phases of the development of tendinopathy They may represent potential therapeutic targets for treatment of tendinopathy.

Polysaccharide Extracted from Bletilla striata Promotes Proliferation and Migration of Human Tenocytes

Tendon healing after injury is relatively slow, mainly because of the weak activity and metabolic properties of tendon cells (tenocytes). Bletilla striata polysaccharide (BSP) has been reported to enhance cell proliferation. Here, we aimed to increase tendon cell proliferation by BSP treatment. We isolated tenocytes from the flexor tendon of human origin. Moreover, we improved the process of extracting BSP. When human tenocytes (HTs) were treated with 100 μg/mL BSP, the MEK/ERK1/2 and PI3K/Akt signaling pathways were activated, thereby enhancing the proliferation ability of tenocytes. BSP treatment also increased the migration of HTs and their ability to secrete the extracellular matrix (Col-I and Col-III). In conclusion, BSP was successfully extracted from a natural Chinese herbal extract and was shown to enhance tenocytes proliferation, migration and collagen release ability. This study is the first to demonstrate improved healing of tendons using BSP.

Holistic Approach of Swiss Fetal Progenitor Cell Banking: Optimizing Safe and Sustainable Substrates for Regenerative Medicine and Biotechnology

Safety, quality, and regulatory-driven iterative optimization of therapeutic cell source selection has constituted the core developmental bedrock for primary fetal progenitor cell (FPC) therapy in Switzerland throughout three decades. Customized Fetal Transplantation Programs were pragmatically devised as straightforward workflows for tissue procurement, traceability maximization, safety, consistency, and robustness of cultured progeny cellular materials. Whole-cell bioprocessing standardization has provided plethoric insights into the adequate conjugation of modern biotechnological advances with current restraining legislative, ethical, and regulatory frameworks. Pioneer translational advances in cutaneous and musculoskeletal regenerative medicine continuously demonstrate the therapeutic potential of FPCs. Extensive technical and clinical hindsight was gathered by managing pediatric burns and geriatric ulcers in Switzerland. Concomitant industrial transposition of dermal FPC banking, following good manufacturing practices, demonstrated the extensive potential of their therapeutic value. Furthermore, in extenso, exponential revalorization of Swiss FPC technology may be achieved via the renewal of integrative model frameworks. Consideration of both longitudinal and transversal aspects of simultaneous fetal tissue differential processing allows for a better understanding of the quasi-infinite expansion potential within multi-tiered primary FPC banking. Multiple fetal tissues (e.g., skin, cartilage, tendon, muscle, bone, lung) may be simultaneously harvested and processed for adherent cell cultures, establishing a unique model for sustainable therapeutic cellular material supply chains. Here, we integrated fundamental, preclinical, clinical, and industrial developments embodying the scientific advances supported by Swiss FPC banking and we focused on advances made to date for FPCs that may be derived from a single organ donation. A renewed model of single organ donation bioprocessing is proposed, achieving sustained standards and potential production of billions of affordable and efficient therapeutic doses. Thereby, the aim is to validate the core therapeutic value proposition, to increase awareness and use of standardized protocols for translational regenerative medicine, potentially impacting millions of patients suffering from cutaneous and musculoskeletal diseases. Alternative applications of FPC banking include biopharmaceutical therapeutic product manufacturing, thereby indirectly and synergistically enhancing the power of modern therapeutic armamentariums. It is hypothesized that a single qualifying fetal organ donation is sufficient to sustain decades of scientific, medical, and industrial developments, as technological optimization and standardization enable high efficiency.

The American Society of Shoulder and Elbow Therapists' consensus statement on rehabilitation for anatomic total shoulder arthroplasty

Anatomic total shoulder arthroplasty is the gold standard shoulder replacement procedure for patients with an intact rotator cuff and sufficient glenoid bone to accommodate prosthetic glenoid implant and offers reliable patient satisfaction, excellent implant longevity, and a low incidence of complications. Disparity exists in the literature regarding rehabilitation strategies following anatomic total shoulder arthroplasty. This article presents a consensus statement from experts in the field on rehabilitation following anatomic total shoulder arthroplasty. The goal of this consensus statement is to provide a current evidence-based foundation to inform the rehabilitation process after anatomic total shoulder arthroplasty. These guidelines apply to anatomic total shoulder arthroplasty (replacement of the humeral head and glenoid), hemiarthroplasty (replacing only the humeral head), and hemiarthroplasty with glenoid reaming or resurfacing. The consensus statement integrates an extensive literature review, as well as survey results of the practice patterns of members of the American Society of Shoulder and Elbow Therapists and the American Shoulder and Elbow Surgeons. Three stages of recovery are proposed, which initially protect and then gradually load soft tissue affected by the surgical procedure, such as the subscapularis, for optimal patient outcomes. The proposed guidelines should be used in collaboration with surgeon preferences and patient-specific factors.

Mechanotransduction of stem cells for tendon repair

Tendon is a mechanosensitive tissue that transmits force from muscle to bone. Physiological loading contributes to maintaining the homeostasis and adaptation of tendon, but aberrant loading may lead to injury or failed repair. It is shown that stem cells respond to mechanical loading and play an essential role in both acute and chronic injuries, as well as in tendon repair. In the process of mechanotransduction, mechanical loading is detected by mechanosensors that regulate cell differentiation and proliferation via several signaling pathways. In order to better understand the stem-cell response to mechanical stimulation and the potential mechanism of the tendon repair process, in this review, we summarize the source and role of endogenous and exogenous stem cells active in tendon repair, describe the mechanical response of stem cells, and finally, highlight the mechanotransduction process and underlying signaling pathways.

In Vitro Innovation of Tendon Tissue Engineering Strategies

Tendinopathy is the term used to refer to tendon disorders. Spontaneous adult tendon healing results in scar tissue formation and fibrosis with suboptimal biomechanical properties, often resulting in poor and painful mobility. The biomechanical properties of the tissue are negatively affected. Adult tendons have a limited natural healing capacity, and often respond poorly to current treatments that frequently are focused on exercise, drug delivery, and surgical procedures. Therefore, it is of great importance to identify key molecular and cellular processes involved in the progression of tendinopathies to develop effective therapeutic strategies and drive the tissue toward regeneration. To treat tendon diseases and support tendon regeneration, cell-based therapy as well as tissue engineering approaches are considered options, though none can yet be considered conclusive in their reproduction of a safe and successful long-term solution for full microarchitecture and biomechanical tissue recovery. In vitro differentiation techniques are not yet fully validated. This review aims to compare different available tendon in vitro differentiation strategies to clarify the state of art regarding the differentiation process.

Dose-Response Tendon-Specific Markers Induction by Growth Differentiation Factor-5 in Human Bone Marrow and Umbilical Cord Mesenchymal Stem Cells

Mesenchymal stem cells derived from human bone marrow (hBM-MSCs) are utilized in tendon tissue-engineering protocols while extra-embryonic cord-derived, including from Wharton's Jelly (hWJ-MSCs), are emerging as useful alternatives. To explore the tenogenic responsiveness of hBM-MSCs and hWJ-MSCs to human Growth Differentiation Factor 5 (hGDF-5) we supplemented each at doses of 1, 10, and 100 ng/mL of hGDF-5 and determined proliferation, morphology and time-dependent expression of tenogenic markers. We evaluated the expression of collagen types 1 (COL1A1) and 3 (COL3A1), Decorin (DCN), Scleraxis-A (SCX-A), Tenascin-C (TNC) and Tenomodulin (TNMD) noting the earliest and largest increase with 100 ng/mL. With 100 ng/mL, hBM-MSCs showed up-regulation of SCX-A (1.7-fold) at Day 1, TNC (1.3-fold) and TNMD (12-fold) at Day 8. hWJ-MSCs, at the same dose, showed up-regulation of COL1A1 (3-fold), DCN (2.7-fold), SCX-A (3.8-fold) and TNC (2.3-fold) after three days of culture. hWJ-MSCs also showed larger proliferation rate and marked aggregation into a tubular-shaped system at Day 7 (with 100 ng/mL of hGDF-5). Simultaneous to this, we explored the expression of pro-inflammatory (IL-6, TNF, IL-12A, IL-1β) and anti-inflammatory (IL-10, TGF-β1) cytokines across for both cell types. hBM-MSCs exhibited a better balance of pro-inflammatory and anti-inflammatory cytokines up-regulating IL-1β (11-fold) and IL-10 (10-fold) at Day 8; hWJ-MSCs, had a slight expression of IL-12A (1.5-fold), but a greater up-regulation of IL-10 (2.5-fold). Type 1 collagen and tenomodulin proteins, detected by immunofluorescence, confirming the greater protein expression when 100 ng/mL were supplemented. In the same conditions, both cell types showed specific alignment and shape modification with a length/width ratio increase, suggesting their response in activating tenogenic commitment events, and they both potential use in 3D in vitro tissue-engineering protocols.

The absence of oestrogen receptor beta disturbs collagen I type deposition during Achilles tendon healing by regulating the IRF5-CCL3 axis

Achilles tendon healing (ATH) remains an unanswered question in the field of sports medicine because it does not produce tissue with homology to the previously uninjured tissue. Oestrogen receptor β (ERβ) is involved in the injury and repair processes of tendons. Our previous study confirmed that ERβ plays a role in the early stage of ATH by affecting adipogenesis, but its role in extracellular matrix (ECM) remodelling is unknown. We established a 4‐week Achilles tendon repair model to investigate the mechanism through which ERβ affects ATH at the very beginning of ECM remodelling phase. In vitro studies were performed using tendon‐derived stem cells (TDSCs) due to their promising role in tendon healing. Behavioural and biomechanical tests revealed that ERβ‐deficient mice exhibit weaker mobility and inferior biomechanical properties, and immunofluorescence staining and qRT‐PCR showed that these mice exhibited an erroneous ECM composition, as mainly characterized by decreased collagen type I (Col I) deposition. The changes in gene expression profiles between ERβ‐knockout and WT mice at 1 week were analysed by RNA sequencing to identify factors affecting Col I deposition. The results highlighted the IRF5‐CCL3 axis, and this finding was verified with CCL3‐treated TDSCs. These findings revealed that ERβ regulates Col I deposition during ATH via the IRF5‐CCL3 axis.

Muscle Fascicles Exhibit Limited Passive Elongation Throughout the Rehabilitation of Achilles Tendon Rupture After Percutaneous Repair

Achilles tendon rupture (ATR) results in long-term functional and structural deficits, characterized by reduced ankle mobility and plantarflexor muscle atrophy. However, it remains unclear how such functional impairments develop after surgical repair. While it is known that this injury negatively affects the tendon’s function, to date, limited work has focused on the short-term effect of ATR on the structure of the muscles in series. The aim of this study was to characterize changes in medial gastrocnemius architecture and its response to passive lengthening during the post-surgical rehabilitative period following ATR. Both injured and contralateral limbs from 10 subjects (1 female, BMI: 27.2 ± 3.9 kg/m²; age: 46 ± 10 years) with acute, unilateral ATR were assessed at 8, 12, and 16 weeks after percutaneous surgical repair. To characterize the component tissues of the muscle-tendon unit, resting medial gastrocnemius muscle thickness, fascicle length, and pennation angle were determined from ultrasound images with the ankle in both maximal plantarflexion and dorsiflexion. The ankle range of motion (ROM) was determined using motion capture; combined ultrasound and motion capture determined the relative displacement of the musculotendinous junction (MTJ) of the AT with the medial gastrocnemius. The ATR-injured gastrocnemius muscle consistently exhibited lower thickness, regardless of time point and ankle angle. Maximal ankle plantarflexion angles and corresponding fascicle lengths were lower on the injured ankle compared to the contralateral throughout rehabilitation. When normalized to the overall ankle ROM, both injured fascicles and MTJ displacement exhibited a comparably lower change in length when the ankle was passively rotated. These results indicate that when both ankles are passively exposed to the same ROM following ATR surgery, both ipsilateral Achilles tendon and gastrocnemius muscle fascicles exhibit limited lengthening compared to the contralateral MTU tissues. This appears to be consistent throughout the rehabilitation of gait, suggesting that current post-operative rehabilitative exercises do not appear to induce muscle adaptations in the affected MTU.

Use of Platelet-Rich Plasma for the Improvement of Pain and Function in Rotator Cuff Tears: A Systematic Review and Meta-analysis With Bias Assessment

BACKGROUND

Many clinical trials have investigated the use of platelet-rich plasma (PRP) to treat rotator cuff-related abnormalities. Several meta-analyses have been published, but none have focused exclusively on level 1 randomized controlled trials.

PURPOSE

To assess the efficacy of PRP for rotator cuff-related abnormalities and evaluate how specific tendon involvement, the inclusion of leukocytes, and the use of gel/nongel formulations affect pain and functional outcomes.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

The literature was screened following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Baseline, short-term, and long-term data were extracted for the Constant score, University of California, Los Angeles (UCLA) score, visual analog scale (VAS) for pain, retear rate, Simple Shoulder Test (SST), and American Shoulder and Elbow Surgeons (ASES) score. The 100-point modified Coleman Methodology Score (CMS) was used to assess methodological quality. Funnel plots and the Egger test were used to screen for publication bias, and sensitivity analysis was performed to evaluate the effect of potential outliers.

RESULTS

A total of 18 level 1 studies were included in this review, 17 (1116 patients) of which could be included in quantitative analysis. The mean modified CMS was 79.4 ± 10.39. The Constant scores of patients who received PRP were significantly better short term (weighted mean difference [WMD], 2.89 [95% CI, 0.89-4.90]; P < .01) and long term (WMD, 2.66 [95% CI, 1.13-4.19]; P < .01). The VAS scores were significantly improved short term (WMD, -0.45 [95% CI, -0.75 to -0.15]; P < .01). Sugaya grade IV and V retears in PRP-treated patients were significantly reduced long term (odds ratio [OR], 0.34 [95% CI, 0.20-0.57]; P < .01). In PRP-treated patients with multiple tendons torn, there were reduced odds of retears (OR, 0.28 [95% CI, 0.13-0.60]; P < .01). Patients who received leukocyte-rich PRP had significantly better Constant scores compared with the leukocyte-poor PRP group, but there was no difference in VAS scores. Patients receiving PRP gel reported higher Constant scores compared with the controls, whereas those receiving nongel PRP treatments did not, although there was no difference in VAS scores. Long-term odds of retears were decreased, regardless of leukocyte content (leukocyte-poor PRP: OR, 0.36 [95% CI, 0.16-0.82]; leukocyte-rich PRP: OR, 0.32 [95% CI, 0.16-0.65]; all P < .05) or usage of gel (nongel: OR, 0.42 [95% CI, 0.23-0.76]; gel: OR, 0.17 [95% CI, 0.05-0.51]; all P < .01).

CONCLUSION

Long-term retear rates were significantly decreased in patients with rotator cuff-related abnormalities who received PRP. Significant improvements in PRP-treated patients were noted for multiple functional outcomes, but none reached their respective minimal clinically important differences. Overall, our results suggest that PRP may positively affect clinical outcomes, but limited data, study heterogeneity, and poor methodological quality hinder firm conclusions.

Complete resolution of a hamstring intramuscular tendon injury on MRI is not necessary for a clinically successful return to play

BACKGROUND

Clinical decision-making around intramuscular tendon injuries of the hamstrings is a controversial topic in sports medicine. For this injury, MRI at return to play (RTP) might improve RTP decision-making; however, no studies have investigated this.

OBJECTIVE

Our objectives were to describe MRI characteristics at RTP, to evaluate healing and to examine the association of MRI characteristics at RTP with reinjury for clinically recovered hamstring intramuscular tendon injuries.

METHODS

We included 41 athletes with hamstring intramuscular tendon injuries and an MRI at baseline and RTP. For both MRIs, we used a standardised scoring form that included intramuscular tendon injury characteristics. We recorded reinjuries during 1-year follow-up.

RESULTS

At RTP, 56% of the intramuscular tendons showed a partial or complete thickness tendon discontinuity. Regarding healing from injury to RTP, 18 of 34 (44% overall) partial-thickness tendon discontinuities became continuous and 6 out of 7 (15% overall) complete thickness tendon discontinuities became partial-thickness tendon discontinuities. Waviness decreased from 61% to 12%, and 88% of tendons became thickened. We recorded eight (20%) reinjuries within 1 year. Intramuscular tendon characteristics at RTP between participants with or without a reinjury were similar.

CONCLUSION

Complete resolution of an intramuscular tendon injury on MRI is not necessary for clinically successful RTP. From injury to RTP, the intramuscular tendon displayed signs of healing. Intramuscular tendon characteristics of those with or without a reinjury were similar.

Advances in the development of gene therapy, noncoding RNA, and exosome-based treatments for tendinopathy

Tendinopathy is a common musculoskeletal disorder characterized by chronic low-grade inflammation and tissue degeneration. Tendons have poor innate healing ability and there is currently no cure for tendinopathy. Studies elucidating mechanisms underlying the pathogenesis of tendinopathy and mechanisms mediating the genesis of tendons during development have provided novel targets and strategies to enhance tendon healing and repair. This review summarizes the current understanding and treatments for tendinopathy. The review also highlights recent advances in gene therapy, the potential of noncoding RNAs, such as microRNAs, and exosomes, which are nanometer-sized extracellular vesicles secreted from cells, for the treatment of tendinopathy.

Comparison of surgical outcomes between rotator cuff repair with and without rotator interval capsular release for rotator cuff tears to prevent and improve postoperative stiffness: a meta-analysis

BACKGROUND

A common complication of rotator cuff (RC) repair is a postoperative stiffness. Postoperative stiffness may develop and lead to inferior functional outcomes. Rotator cuff repair with additional rotator interval (RI) capsular release can be done to prevent postoperative stiffness in rotator cuff tears. However, routine rotator interval capsular release in rotator cuff repair is controversial. Therefore, we conducted a systematic review and meta-analysis to compare the postoperative outcomes between RC repair with and without RI capsular release for RC tears with and without concomitant stiffness.

METHOD

We searched all comparative studies that compared postoperative outcomes (VAS, CS, ASES, complications and ROM at 3, 6 and 12 months) of RC repair with and without RI capsular release for RC tears with and without concomitant stiffness from PubMed and Scopus databases from inception to the February 1, 2020.

RESULTS

Seven of 255 studies (six comparative studies and one RCT) (N = 803 patients) were eligible; 2 and 5 studies were included in the pooling of RC repair and RI release without concomitant stiffness and stiffness, respectively; 2, 6, 3, 6, 3, 5, 7, 7, and 7 studies were included in pooling of VAS, CS, ASES at 6 and 12 months and range of motion (internal, external rotation and forward flexion) at 3, 6 and 12 months, respectively. The UMD of VAS, CS and ASES scores at 6- and 12-month follow-up for the RC repair and RI release group was 0.48 (95% CI: 0.05, 0.90), 0.93 (-1.70, 3.56), -2.27 (-5.30, 0.76), -0.04 (-0.24, 0.15), 1.66 (0.77, 2.55) and 1.58 (0.21, 2.96) scores when compared to RC repair alone with and without concomitant stiffness. In terms of ROM, forward flexion for the RC repair and RI release group was -4.60 (-10.61, 1.41), -7.11 (-15.47, 1.25) and -0.70 (-2.51, -1.11) degrees at 3, 6 and 12 months, respectively, when compared to RC repair alone. For external rotation, RC repair and RI release were -0.12 (-8.27, 8.03), -3.98 (-12.09, 4.14) and -2.65 (-5.35, 0.04) degrees at 3, 6 and 12 months, respectively, when compared to RC repair alone. For internal rotation in RC repair and RI release, the values were -1.22 (-1.97, - 0.48), -1.01 (-1.79, -0.23) and -0.19 (-1.13, 0.74) degrees at 3, 6 and 12 months, respectively, when compared to RC repair alone. There were no differences with a RR of 0.92 (0.46, 1.84) between the two groups in terms of complications. After subgroup analysis, RC repair with RI release had no clinically significant differences for pain, function and ROM when compared to RC repair alone in RC tear patients with and without preoperative stiffness.

CONCLUSIONS

RC repair with RI release in patients with and without preoperative stiffness had no statistically significant differences for pain, function (CS and ASES) and range of motion (FF, ER and IR) when compared to RC repair alone in RC injury patients.

LEVEL OF EVIDENCE

II.

In vitro analysis of the effect of Flightless I on murine tenocyte cellular functions

BACKGROUND

Healing of tendons after injury involves the proliferation of tenocytes and the production of extracellular matrix; however, their capacity to heal is limited by poor cell density and limited growth factor activity. Flightless I (Flii) has previously been identified as an important regulator of cellular proliferation and migration, and the purpose of this study was to evaluate the effect of differential Flii gene expression on tenocyte function in vitro.

METHODS

The role of Flii on tenocyte proliferation, migration, and contraction was assessed using established assays. Tenocytes from Flii^+/-, wild-type, and Flii overexpressing mice were obtained and the effect of differential Flii expression on migration, proliferation, contraction, and collagen synthesis determined in vitro. Statistical differences were determined using unpaired Student's t test and statistical outliers were identified using the Grubbs' test.

RESULTS

Flii overexpressing tenocytes showed significantly improved migration and proliferation as well as increased collagen I secretion. Explanted tendons from Flii overexpressing mice also showed significantly elevated tenocyte outgrowth compared to Flii^+/- mice. In contrast to its role in dermal wound repair, Flii positively affects cellular processes in tendons.

CONCLUSIONS

These findings suggest that Flii could be a novel target for modulating tenocyte activity and improving tendon repair. This could have significant clinical implications as novel therapeutic targets for improved healing of tendon injuries are urgently needed.

Management of Lateral Epicondylitis: A Narrative Literature Review

Lateral epicondylitis, also termed as "tennis elbow," is the most common cause of elbow pain and dysfunction, mainly resulting from repetitive gripping or wrist extension during various activities. The exact pathogenesis remains largely elusive with putative tendinosis, a symptomatic degenerative process of the local tendon. It is usually diagnosed by clinical examinations. Sometimes, additional imaging is required for a specific differential diagnosis. Although most cases can be self-healing, the optimal treatment strategy for chronic lateral epicondylitis remains controversial. This article presents a landscape of emerging evidence on lateral epicondylitis and focuses on the pathogenesis, diagnosis, and management, shedding light on the understandings and treatment for healthcare professionals.

Common Musculoskeletal Disorders in the Elderly: The Star Triad

Musculoskeletal disorders are debilitating conditions that significantly impair the state of health, especially in elderly subjects. A pathological triad of inter-related disorders that are highly prevalent in the elderly consists of the following main “components”: sarcopenia, tendinopathies, and arthritis. The aim of this review is to critically appraise the literature relative to the different disorders of this triad, in order to highlight the pathophysiological common denominator and propose strategies for personalized clinical management of patients presenting with this combination of musculoskeletal disorders. Their pathophysiological common denominator is represented by progressive loss of (focal or generalized) neuromuscular performance with a risk of adverse outcomes such as pain, mobility disorders, increased risk of falls and fractures, and impaired ability or disability to perform activities of daily living. The precise management of these disorders requires not only the use of available tools and recently proposed operational definitions, but also the development of new tools and approaches for prediction, diagnosis, monitoring, and prognosis of the three disorders and their combination.

[Advance of diagnosis and treatment of Haglund syndrome]

OBJECTIVE

To review the current research on the diagnosis and treatment of Haglund syndrome.

METHODS

The domestic and foreign literature about Haglund syndrome in recent years was extensively reviewed to summarize and analyze the etiology, anatomy, clinical manifestations, diagnosis, and treatment of Haglund syndrome.

RESULTS

The etiology of Haglund syndrome is not very clear, and it may be related to local friction and high gastrocnemius muscle tension, and there may be a certain genetic tendency. The local anatomy is more complex and there are many adjacent tissue structures. Haglund malformation may cause the impingement of the posterior heel bursa and Achilles tendon insertion, lead to wear of the posterior heel bursa and the Achilles tendon insertion, and finally result in pain. The FPA (Fowler-Philipp angle), CPA (calcaneal pith angle), PPL (parallel pitch lines), CLA (Chauveaux-Liet angle), and X/Y ratios (ratio of total calcaneal length to calcaneal tuberosity length) measured on X-ray film can be used for the diagnostic measurement of Haglund malformation. Treatment includes conservative and surgical treatment (open Haglund ostectomy, dorsal closed wedge osteotomy of the calcaneus, and arthroscopic Haglund osteotomy).

CONCLUSION

Both open and arthroscopic Haglund ostectomy and dorsal closed wedge osteotomy of the calcaneus can achieve satisfactory results, but minimally invasive treatment is the current development trend. Surgeons should pay attention to the management of the calcification of Achilles tendon insertion and reconstruction of Achilles tendon insertion.

Adverse Impact of Corticosteroids on Rotator Cuff Tendon Health and Repair: A Systematic Review of Basic Science Studies

Purpose

To evaluate the in vitro effects of corticosteroid injections (CSIs) on rotator cuff tendon (RCT).

Methods

A systematic review of the MEDLINE database was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for all studies reporting on adverse biochemical and biomechanical effects of CSIs on RCT.

Results

Sixteen studies were identified that had been published in the last 15 years on the effects of corticosteroids on RCTs. Eight of these studies were on human RCTs, 6 were on rat tendons, 1 considered both human and rat tendons, and 1 was on dog tendon. Five studies analyzed the effects of corticosteroids on the biomechanical properties of RCT or rotator cuff repair, whereas the remaining observed the cellular and molecular effects of CSIs on RCT. Corticosteroids suppress an inflammatory response, induce apoptosis, and have negative effects on collagen and tendon cell viability in RCTs. The mechanical properties, including load to failure of RCTs and rotator cuff repair anchor pull-out strength, also are decreased by CSIs. These in vitro effects appear to be transient as well as frequency and dose dependent.

Conclusions

On a molecular level, CSIs decrease cellular proliferation, alter collagen and extracellular matrix composition, impede inflammatory pathways, decrease cellular viability, increase adipocyte differentiation, and increase apoptosis. These changes can be seen as early as 24 hours after corticosteroid exposure, last as long as 2 to 3 weeks, and are exacerbated by increased doses and decreased latency between doses. Biomechanical studies demonstrate that these changes result in decreased maximal load to failure, tendon stiffness, and suture anchor pull-out strength in rat shoulders up to 2 weeks but not at 3 and 4 weeks, post-CSI.

Clinical Relevance

Shoulder subacromial steroid injection is common, and practitioners should be aware of results both positive and deleterious.

Optimization of tenocyte lineage-related factors from tonsil-derived mesenchymal stem cells using response surface methodology

BACKGROUND

In order to optimize the tenogenic differentiation of mesenchymal stem cells (MSCs), researchers should consider various factors. However, this requires testing numerous experimental settings, which is costly and time-consuming. We aimed to assess the differential effects of transforming growth factor beta-3 (TGF-β3) on the tenogenesis of tonsil-derived MSCs (T-MSCs) and bone marrow-derived MSCs (BM-MSCs) using response surface methodology (RSM).

METHODS

Bone marrow and tonsillar tissue were collected from four patients; mononuclear cells were separated and treated with 5 or 10 ng/mL of TGF-β3. A full factorial experimental design with a categorical factor of 0 was employed to study the effect of tension based on T-MSCs. Eighty-four trials were fitted with RSM and then used to obtain mathematical prediction models.

RESULTS

Exposure of T-MSCs and BM-MSCs to TGF-β3 increased the expression of scleraxis (SCX), tenomodulin (TNMD), decorin, collagen I, and tenascin C. Expression of most of these factors reached a maximum after 2-3 days of treatment. The model predicted that the values of the tenocyte lineage-related factors assessed would be significantly increased at 2.5 days of culture with 2.7 ng/mL of TGF-β3 for T-MSCs and at 2.3 days of culture regardless of TGF-β3 concentration for BM-MSCs.

CONCLUSIONS

This study demonstrated that the RSM prediction of the culture time necessary for the tenogenic differentiation of T-MSCs and BM-MSCs under TGF-β3 stimulation was similar to the experimentally determined time of peak expression of tenocyte-related mRNAs, suggesting the potential of using the RSM approach for optimization of the culture protocol for tenogenesis of MSCs.

Impact of PDGF-BB on cellular distribution and extracellular matrix in the healing rabbit Achilles tendon three weeks post-operation

Current methods for tendon rupture repair suffer from two main drawbacks: insufficient strength and adhesion formation, which lead to rerupture and impaired gliding. A novel polymer tube may help to overcome these problems by allowing growth factor delivery to the wound site and adhesion reduction, and by acting as a physical barrier to the surrounding tissue. In this study, we used a bilayered DegraPol® tube to deliver PDGF-BB to the wound site in a full-transection rabbit Achilles tendon model. We then performed histological and immunohistochemical analysis at 3 weeks postoperation. Sustained delivery of PDGF-BB to the healing Achilles tendon led to a significantly more homogenous cell distribution within the healing tissue. Lower cell densities next to the implant material were determined for +PDGF-BB samples compared to -PDGF-BB. PDGF-BB application increased proteoglycan content and reduced alpha-SMA+ areas, clusters of different sizes, mainly vessels. Finally, PDGF-BB reduced collagens I and III in the extracellular matrix. The sustained delivery of PDGF-BB via an electrospun DegraPol® tube accelerated tendon wound healing by causing a more uniform cell distribution with higher proteoglycan content and less fibrotic tissue. Moreover, the application of this growth factor reduced collagen III and alpha-SMA, indicating a faster and less fibrotic tendon healing.

Synthesis and Formulation of Four-Arm PolyDMAEA-siRNA Polyplex for Transient Downregulation of Collagen Type III Gene Expression in TGF-β1 Stimulated Tenocyte Culture

The natural healing process for tendon repair is associated with high upregulation of collagen type III, leading to scar tissue and tendon adhesions with functionally deficient tendons. Gene delivery systems are widely reported as potential nanotherapeutics to treat diseases, providing a promising approach to modulate collagen type III synthesis. This work investigates a proof-of-concept four-arm cationic polymer-siRNA polyplex to mediate a transient downregulation of collagen type III expression in a tendon cell culture system. The tendon culture system was first supplemented with TGF-β1 to stimulate the upregulation of collagen type III prior to silencing experiments. The four-arm poly[2-(dimethylamino) ethyl acrylate] (PDMAEA) polymer was successfully synthesized via RAFT polymerization and then mixed with siRNA to formulate the PDMAEA-siRNA polyplexes. The formation of the polyplex was optimized for the N:P ratio (10:1) and confirmed by agarose gel electrophoresis. The size and solution behavior of the polyplex were analyzed by dynamic light scattering and zeta potential, showing a hydrodynamic diameter of 155 ± 21 nm and overall positive charge of +30 mV at physiological pH. All the polyplex concentrations used had a minimal effect on the metabolic activity of cultured cells, indicating good biocompatibility. The dose and time effects of the TGF-β1 on collagen type III gene expressions were analyzed by qPCR, showing an optimal dose of 10 ng mL^-1 TGF-β1 and 3-fold increase of COL3α1 expression at 48 h in cultured tenocytes. The PDMAEA-siRNA polyplex concept observed a limited yet successful and promising efficiency in silencing collagen type III at 48 h compared to PEI-siRNA. Therefore, this concept is a promising approach to reduce tissue scarring and adhesion following injuries.

Elasticity of torn supraspinatus tendons measured by shear wave elastography: a potential surrogate marker of chronicity?

PURPOSE

This study investigated whether shear wave elastography (SWE) could be used to estimate the chronicity of supraspinatus tendon (SST) tears.

METHODS

A retrospective study was performed. From November 2015 to July 2016, 113 patients (52 men, 61 women; age range, 21 to 79 years) with persistent shoulder pain underwent 119 rotator cuff tendon examinations by routine B-mode ultrasonography, while SST elasticity was measured using SWE. Following the exclusion of eight suboptimal examinations, four examinations with missing SST measurements, and 27 examinations of patients with other conditions, 80 examinations were analyzed. A torn SST was found in 54 examinations (27 with a partial-thickness tear and 27 with a full-thickness tear). Elasticity values were compared in multiple ways. The results were analyzed using the Mann-Whitney U test or Kruskal-Wallis test.

RESULTS

No statistically significant difference in elasticity values (in kPa) was found between normal (median, 94.65; interquartile range [IQR], 87.43 to 105.47) and torn SSTs (median, 96.79; IQR, 86.71 to 108.56) or between full-thickness tears (median, 93.80; IQR, 82.50 to 108.33) and partial-thickness tears (median, 96.83; IQR, 90.60 to 112.20). However, there was a statistically significant difference in elasticity according to whether the duration of symptoms was 1 year or less (median, 92.20; IQR, 84.01 to 104.38) or longer than 1 year (median, 105.10; IQR, 100.41 to 116.03; P=0.032).

CONCLUSION

Elasticity values were significantly higher in torn SSTs in patients with chronic shoulder pain that had persisted for more than 1 year. Further studies with larger samples seem warranted to determine whether elasticity values measured by SWE can be used preoperatively as a surrogate marker of the chronicity of a rotator cuff tendon tear.

Effects of rabbit pinna-derived blastema cells on tendon healing

OBJECTIVES

Tendon healing is substantially slow and often associated with suboptimal repair. Cell therapy is one of the promising methods to improve tendon repair. Blastema, a population of undifferentiated cells, represents characteristics of pluripotent mesenchymal stem cells and has the potentials to be used in regenerative medicine. The aim of this study was to investigate the use of blastema allotransplantation in rabbit tendon healing.

MATERIALS AND METHODS

In this study, one rabbit was used as a blastema donor, and twenty-four rabbits were divided into control and treatment groups. Blastema cells were obtained from ear pinna upon punch hole injury in the donor rabbit. Under general anesthesia, a complete transverse tenotomy was performed on the midsubstance of deep digital flexor tendon followed by suture-repair. In the treatment group, 1 × 106 blastema cells suspended in buffer saline were injected intratendinously at the repair site, while the control group received only the buffer saline. Cast coaptation was maintained for two weeks. Eight weeks after the operation, tendons were harvested, and histopathological, biomechanical, and biochemical assays were performed on samples.

RESULTS

Mechanical testing showed a significant increase in ultimate load, energy absorption, stiffness, yield load, stress, and strain in blastema-treated tendons compared to controls. Also, higher hydroxyproline content and improved collagen alignment along with lower inflammatory cell infiltration and decreased angiogenesis were observed in blastema-treated tendons.

CONCLUSION

Increased levels of hydroxyproline and improved histopathological and biomechanical parameters in the treatment group suggest that blastema cells could be considered an adjunct to tendon repair in rabbits.

Power Doppler to investigate superficial digital flexor tendinopathy in the horse

Background:

Recent advances in tendinopathy research have focused on tendon vascularization detected with Color Doppler (CD) ultrasound. The use of CD has also been described in horses in a study on chronic lesions of superficial digital flexor tendon and suspensory ligament.

Aim:

The aim of this study was to investigate the occurrence and distribution of power Doppler (PD) signal in horses with superficial digital flexor tendinopathy.

Methods:

Twenty-five horses with tendinopathy were included and 10 healthy horses with no lameness and no ultrasonographic abnormalities were used for comparison.

Results:

In all horses with tendinopathy, the PD signal was visible while normal tendons with no abnormalities in B-mode were PD signal-free.

Conclusion:

We can speculate that PD could provide essential information about the healing process than the grayscale ultrasound.

Conservative treatment of Achilles tendon partial tear in a futsal player: A case report

Background and purpose: Achilles tendon is the most commonly injured part in the lower limb, especially in athletes. Treatment options for Achilles tendinopathy and total rupture are well described; however, there is a lack of information regarding treatment protocols for partial tears. Thus, the purpose of this case report was to describe the examination, intervention and outcomes of patient who suffered an acute Achilles tendon partial tear. Case description: A case is described here, in which the diagnosis of Achilles tendon partial tear was based on both magnetic resonance imaging and physical evaluation. Both the patient and the physical therapy team opted for non-surgical treatment. A 12-week course of conservative treatment including exercise, tendon loading, electrical stimulation, and photobiomodulation is described. Outcomes: Ankle dorsiflexion range of motion and hop tests. Discussion: This case report demonstrated that non-surgical treatment for Achilles tendon partial tear was effective for this patient and enabled the athlete to return to pre-injury levels of activity 6 months following the injury.

Restoration of Cellular Proliferation and Characteristics of Human Tenocytes by Vitamin D

Vitamin D (Vit D) increases calcium absorption in the intestine after binding to the Vit D receptor (VDR). The VDR has also been identified in muscle cells. Vit D supplementation resulted in improved muscle strength. However, there is a paucity of studies of the role of Vit D on tenocytes. We investigated the effects of Vit D on damaged tenocytes. Human tenocytes were treated with dexamethasone (Dex) to induce cell injury. Expression of the tenocyte-related markers tenomodulin (Tnmd), tenascin C (Tnc), scleraxis (Scx), mohawk (Mkx), and collagen (Col) 1 and 3 were measured. Then, tenocytes were cotreated with Vit D. 1-α-Hydroxylase and VDR were explored in tenocytes. With 10 μM Dex, the growth of tenocytes was significantly inhibited, and the gene expression of Tnmd, Tnc, Scx, Mkx, Col 1 and 3 also decreased. When tenocytes were cotreated with Vit D, cell proliferation recovered in a dose-dependent manner, and the expression of TNMD and Col 1 improved. When studying the mechanisms of the effects of Vit D on tenocytes, reactive oxygen species produced by Dex decreased with Vit D, and the phosphorylation of extracellular signal-regulated kinase and p38 was stimulated by Vit D cotreatment. 1-α-Hydroxylase and VDR were found in tenocytes, indicating that the cells have the ability to use an inactive form of Vit D and interact with it. Vit D is known to perform diverse actions and its protective effects on tenocytes suggest its beneficial role in tendon in addition to muscle and bone. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2241-2248, 2019.

Biomaterials for the Treatment of Tendon Injury

Background

Most tendon injuries are occurring from a gradual wearing and tearing of the tendon tissues from overuse. Such injuries are usually seen in sports, exercising, or daily activities that involve a high mechanical load and weight bearing. However, owing to the lack of both cellularity and blood vessels in tendons, the process of tendon repair is slow and inefficient. Although various conservative (non-surgical) and surgical management options are conducted by the clinicians, a gold standard of these approaches does not exist. In this regard, the treatment of tendon injuries is challenging.

Method

Here, we describe the recent advances of biomaterial-based approaches for the treatment of injured tendons.

Results

Regenerative medicine is an emerging multidisciplinary research that specializes in the repair of damaged tendon tissues through the delivery of regenerative factors by biomaterials.

Conclusion

Although current biomaterial-based treatment strategies have shown their potential for tendon healing, future research and clinical applications should focused on finding the optimum combinations of regenerative factors with ideal biomaterials for the repair of tendons.

Hydroxycamptothecin Inhibits Peritendinous Adhesion via the Endoplasmic Reticulum Stress-Dependent Apoptosis

Traumatic peritendinous fibrosis is a worldwide clinical problem resulting in severe limb disability. Hydroxycamptothecin (HCPT) is an anti-neoplastic drug widely exploited in clinical practice. It has shown potential of anti-fibrosis in recent years. We previously demonstrated that HCPT inhibited the characterization of fibrosis in vitro. However, it is still unclear whether it ameliorates peritendinous adhesion in an in vivo animal tendon injury model. The underlying mechanism is also worth investigating. The present study aims to determine whether HCPT inhibits tendon adhesion and to explore the underlying mechanisms. In a rat tendon injury model, we observed that topical application of HCPT significantly attenuated peritendinous adhesion as revealed by the results of macroscopic observation, biomechanical, histological, immunohistochemical evaluation, western blot, and quantitative PCR (q-PCR) analyses. Furthermore, western blot and q-PCR analyses revealed that this phenomenon is correlated with HCPT activation of endoplasmic reticulum (ER) stress. In addition, in vitro studies show that HCPT significantly inhibits fibroblast proliferation and induces apoptosis by reducing the expression of extracellular matrix (ECM) proteins COL3A1 and α-smooth muscle actin (α-SMA). Finally, we employed small interfering RNA (siRNA) to target inositol requiring kinase 1 (IRE1) and activated transcription factor 6 (ATF-6) to verify that the effect of inhibitory fibrosis of HCPT disappears after knockdown of ATF-6 and IRE1, thereby suggesting that an anti-fibrotic effect of HCPT is mediated by the ER-dependent apoptotic pathway. In conclusion, our results indicate that HCPT inhibits peritendinous fibrosis through the ER-dependent apoptotic pathway and might serve as a potential solution to prevent traumatic peritendinous adhesion.

Absence of estrogen receptor beta leads to abnormal adipogenesis during early tendon healing by an up-regulation of PPARγ signalling

Achilles tendon injury is one of the challenges of sports medicine, the aetiology of which remains unknown. For a long time, estrogen receptor β (ERβ) has been known as a regulating factor of the metabolism in many connective tissues, such as bone, muscle and cartilage, but little is known about its role in tendon. Recent studies have implicated ERβ as involved in the process of tendon healing. Tendon-derived stem cells (TDSCs) are getting more and more attention in tendon physiological and pathological process. In this study, we investigated how ERβ played a role in Achilles tendon healing. Achilles tendon injury model was established to analyse how ERβ affected on healing process in vivo. Cell proliferation assay, Western blots, qRT-PCR and immunocytochemistry were performed to investigate the effect of ERβ on TDSCs. Here, we showed that ERβ deletion in mice resulted in inferior gross appearance, histological scores and, most importantly, increased accumulation of adipocytes during the early tendon healing which involved activation of peroxisome proliferator-activated receptor γ (PPARγ) signalling. Furthermore, in vitro results of ours confirmed that the abnormity might be the result of abnormal TDSC adipogenic differentiation which could be partially reversed by the treatment of ERβ agonist LY3201. These data revealed a role of ERβ in Achilles tendon healing for the first time, thereby providing a new target for clinical treatment of Achilles tendon injury.

Multi-Scale Loading and Damage Mechanisms of Plantaris and Rat Tail Tendons

Tendinopathy, degeneration of the tendon that leads to pain and dysfunction, is common in both sports and occupational settings, but multi-scale mechanisms for tendinopathy are still unknown. We recently showed that micro-scale sliding (shear) is responsible for both load transfer and damage mechanisms in the rat tail tendon; however, the rat tail tendon is a specialized non-load-bearing tendon, and thus the load transfer and damage mechanisms are still unknown for load-bearing tendons. The objective of this study was to investigate the load transfer and damage mechanisms of load-bearing tendons using the rat plantaris tendon. We demonstrated that micro-scale sliding is a key component for both mechanisms in the plantaris tendon, similar to the tail tendon. Namely, the micro-scale sliding was correlated with applied strain, demonstrating that load was transferred via micro-scale sliding in the plantaris and tail tendons. In addition, while the micro-scale strain fully recovered, the micro-scale sliding was non-recoverable and strain-dependent, and correlated with tissue-scale mechanical parameters. When the applied strain was normalized, the % magnitudes of non-recoverable sliding was similar between the plantaris and tail tendons. Statement of clinical significance: Understanding the mechanisms responsible for the pathogenesis and progression of tendinopathy can improve prevention and rehabilitation strategies and guide therapies and the design of engineered constructs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1827-1837, 2019.

Relaxin inhibits patellar tendon healing in rats: a histological and biochemical evaluation

BACKGROUND

Female patients are more likely to have tendon injuries than males, especially those who has a higher concentration of relaxin. Previous studies have demonstrated that relaxin attenuates extracellular matrix (ECM) formation. However, the mechanism of relaxin on tendon repair remains unclear. We hypothesize that relaxin inhibits tendon healing by disrupting collagen synthesis.

METHODS

A patellar tendon window defect model was established using Sprague-Dawley rats. The center of the patellar tendon was removed from the patella distal apex and inserted to the tibia tuberosity in width of 1 mm. Then, the rats were injected with saline (0.2 μg/kg/day) or relaxin (0.2 μg/kg/day) for two and four weeks, which was followed by biomechanical analysis and histological and histochemical examination.

RESULTS

Mechanical results indicated that relaxin induces a significant decrease in tear resistance, stiffness, and Young's modulus compared to those rats without relaxin treatment. In addition, it was shown that relaxin activates relaxin family peptide receptor 1(RXFP1), disturbs the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs), and reduces the deposition of collagen in injury areas.

CONCLUSIONS

Relaxin impairs tendon healing in rats. Also, relaxin might lead to tendon injury more commonly for females than males.

Characterization of moderate tendinopathy in ex vivo stress-deprived rat tail tendons

Background

Stress deprivation (SD) has frequently been used as a model to study tendinopathy. Most of these studies have investigated either short-term (early tendinopathy) or long-term SD (advanced tendinopathy), while the transient mid-term SD has been given less attention. Therefore, the main objective of this study was to characterize mid-term SD.

Methods

To this end, live, healthy rat tail tendons (RTTs) were harvested and cultured without mechanical stress and then were divided into five groups based on their culture time (fresh, 2-day SD, 4-day SD, 6-day SD, and 10-day SD). For each group, the tendons were subjected to traction testing and pathohistology, immunohistochemistry, and viability assays.

Results

Our results showed that 4 days of SD resulted in moderate pathological changes in RTTs. These changes included increases in the space area between fibers, cell density, and fiber tortuosity as well as a decrease in collagen density and elongation of cell nuclei. No changes in the stress at failure of tendons were observed at this time point.

Conclusions

This simple ex vivo model is expected to be useful for studying the progression of tendinopathy as well as for testing potential mechanobiological or pharmacological therapy strategies to stop or reverse the progression of the pathology.

Ultrasound-guided percutaneous irrigation of calcific tendinopathy: technical developments

Rotator cuff calcific tendinopathy (RCCT) is a common and painful shoulder disease characterised by deposition of calcium into the rotator cuff’s tendond. Different therapeutic options have been proposed, but the ultrasound-guided percutaneous irrigation (US-PICT) is been proved as an effective and safe first-line treatment. It can be performed with a single- of a double-needle tecnique, using warm saline solution to improve the dissolution of the calcific deposit. The procedure is ended with an intrabursal injection of local anaesthetics and slow-release steroids to improve the pain relief and to prevent complications. US-PICT leads to significative improvement in the shoulder funtion and pain relief in the short and long term, with a low complications rate. (www.actabiomedica.it)