Investigating the histological and structural properties of tendon gel as an artificial biomaterial using the film model method in rabbits

Purpose This study aimed to evaluate the properties of tendon gel by investigating the histological and structural differences among tendon gels under different preservation periods using a rabbit model. Methods Forty mature female rabbits were divided into four groups, each containing ten rabbits, on the basis of in-vivo preservation periods of tendon gels (3, 5, 10, and 15 days). We created the Achilles tendon rupture models using the film model method to obtain tendon gels. Tensile stress was applied to the tendon gel to promote maturation. Histological and structural evaluations of the tendon gel were performed before and after applying the tensile force, and the results obtained from the four groups were compared. Results Although the day-3 and day-5 tendon gels before applying tensile stress were histologically more immature than the day-10 and day-15 gels, type I collagen fibers equivalent to those of normal tendons were observed in all groups after the tensile process. Based on the surface and molecular structural evaluations, the day-3 tendon gels after the tensile process were molecularly cross-linked, and thick collagen fibers similar to those present in normal tendons were observed. Structural maturation observed in the day-3 tendon gels caused by traction was hardly observed in the day-5, -10, and -15 tendon gels. Conclusions The day-3 tendon gel had the highest regenerative potential to become a normal tendon by applying a traction force.

Evaluation of Autologous Protein Solution Injection for Treatment of Superficial Digital Flexor Tendonitis in an Equine Model

Autologous protein solution (APS) has been used anecdotally for intralesional treatment of tendon and ligament injuries, however, its use in these injuries has never been studied in vivo. Our objective was to evaluate the effect of APS on tendon healing in an equine superficial digital flexor (SDF) tendonitis model. We hypothesized intralesional injection of APS would result in superior structural and biomechanical healing. SDF tendonitis was induced in both forelimbs of eight horses using collagenase injection. One forelimb was randomly assigned to receive an intralesional injection of APS, while the other was injected with saline. Ultrasonographic examinations were performed at weeks −1, 0, 2, 4, 8, and 12 following treatment. At 12 weeks, horses were euthanized and SDF samples harvested. Histologic evaluation, biomechanical testing, gene expression analysis, total glycosaminoglycan (GAG) and total DNA quantification were performed. Collagen type III (COL3A1) expression was significantly higher (p = 0.028) in saline treated tendon than in normal tendon. Otherwise, there were no significant differences in gene expression. There were no significant differences in histologic or ultrasonographic scores between groups. Mean total DNA content was significantly higher (p = 0.024) in saline treated tendons than normal tendons, whereas total DNA content was not significantly different between APS treated tendon and normal tendon. Elastic modulus was higher in APS treated than saline treated tendon, but the difference was not significant. Reduced expression of COL3A1 in APS treated tendon may indicate superior healing. Increased total DNA content in saline treated tendon may indicate ongoing healing processes, vs. APS treated tendons which may be in the later stages of healing. Limitations include a relatively short study period and inconsistency in size and severity of induced lesions. Intralesional injection of APS resulted in some improvements in healing characteristics.

Microscopic characterization of local strain field in healing tissue in the central third defect of mouse patellar tendon at early-phase of healing

Tendons exhibit a hierarchical collagen structure, wherein higher-level components, such as collagen fibres and fascicles, are elongated, slid, and rotated during macroscopic stretching. These mechanical behaviours of collagen fibres play important roles in stimulating tenocytes, imposing stretching, compression, and shear deformation. It was hypothesised that a lack of local fibre behaviours in healing tendon tissue may result in a limited application of mechanical stimuli to cells within the tissue, leading to incomplete recovery of tissue structure and functions in regenerated tendons. Therefore, the present study aimed to measure the microscopic strain field in the healing tendon tissue. A central third defect was created in the patellar tendon of mice, and the regenerated tissue in the defect was examined by tensile testing, collagen fibre analysis, and local strain measurement using confocal microscopy at 3 and 6 weeks after surgery. Healing tissue at 3 weeks exhibited a significantly lower strength and disorganised collagen fibre structure compared with the normal tendon. These characteristics at 6 weeks remained significantly different from those of the normal tendon. Moreover, the magnitude of local shear strain in the healing tissue under 4% tissue strain was significantly smaller than that in the normal tendon. Differences in the local strain field may be reflected in the cell nuclear shape and possibly the amount of mechanical stimuli applied to the cells during tendon deformation. Accordingly, restoration of a normal local mechanical environment in the healing tissue may be key to a better healing outcome of tendon injury.

The correlations between dimensions of the normal tendon and tendinopathy changed Achilles tendon in routine magnetic resonance imaging

This comparative study aimed to investigate how tendinopathy-related lesions change correlations in the dimensions of the Achilles tendon. Our experimental group included 74 patients. The mean age was 52.9 ± 10.4 years. The control group included 81 patients with a mean age was 35.2 ± 13.6 years, p < .001. The most significant difference in correlation was the thickness of the tendon and the midportion's width, which was more significant in the tendinopathy (r = .49 vs. r = .01, p < .001). The correlation was positive between width and length of the insertion but negative in normal tendons (r = .21 vs. r = − .23, p < .001). The correlation was between the midportions width in tendinopathy and the tendon's length but negative in the normal tendon (r = .16 vs. r = − .23, p < .001). The average thickness of the midportion in tendinopathy was 11.2 ± 3.3 mm, and 4.9 ± 0.5 mm in the control group, p < .001. The average width of the midportion and insertion was more extensive in the experimental group, 17.2 ± 3.1 mm vs. 14.7 ± 1.8 mm for the midportion and 31.0 ± 3.9 mm vs. 25.7 ± 3.0 mm for insertion, respectively, p < .001. The tendon's average length was longer in tendinopathy (83.5 ± 19.3 mm vs. 61.5 ± 14.4 mm, p < .001). The dimensions correlations in normal Achilles tendon and tendinopathic tendon differ significantly.

Autologous Heterogeneous Skin Construct Closes Traumatic Lower Extremity Wounds in Pediatric Patients: A Retrospective Case Series

Lower extremity traumatic wounds pose unique challenges in pediatric patients, including vessel caliber, compliance with postoperative instructions, parental concerns about multiple operations, and long-term function. An autologous heterogeneous skin construct (AHSC) has demonstrated the ability to cover avascular structures and regenerate full-thickness functional skin. The objective of this study is to report our experience using AHSC in a cohort of pediatric trauma patients. This study is a noncontrolled, retrospective cohort analysis of all pediatric patients (<19 years of age) treated with AHSC for lower extremity traumatic wounds with at least one exposed deep structure (tendon, bone, and/or joint) at a single institution between May 1, 2018, and April 1, 2019. Seven patients with 10 traumatic wounds met inclusion criteria. The median follow-up time was 11.8 months. Five patients were male (71%); the median age was 7 years (range = 2-15 years). Average wound size was 105 cm2. All wounds achieved coverage of exposed structures and epithelial closure in a median of 13 and 69 days, respectively. There were no donor site complications and no reoperations required. All patients returned to normal activity, ambulate without limp, can wear shoes normally, and have normal tendon gliding. AHSC covered exposed structures and achieved closure within a single application in complex traumatic lower extremity wounds in a pediatric cohort.

Autologous hematopoietic stem cell transplantation for Stiff Person Spectrum Disorder: A clinical trial

Objective:To test the hypothesis that autologous non-myeloablative hematopoietic stem cell transplantation (HSCT) is safe and shows efficacy in the treatment of stiff person spectrum disorder (SPSD).Methods:Twenty-three participants were treated in a prospective open-label cohort study of safety and efficacy. Following stem cell mobilization with cyclophosphamide (2 g/m2) and filgrastim (5–-10 ug/kg/day), participants were treated with cyclophosphamide (200 mg/kg) divided as 50 mg/kg IV on day −-5 to day −-2, rATG (thymoglobulin) given IV at 0.5 mg/kg on day −-5, 1 mg/kg on day −-4 and −-3, and 1.5 mg/kg on days −-2, and −-1 (total dose 5.5 mg/kg), and rituximab 500 mg IV on days −-6 and +1. Unselected peripheral blood stem cells were infused on day 0. Safety was assessed by survival and NCI common toxicity criteria for adverse events during HSCT. Outcome was assessed by ≥ 50% decrease or discontinuation of anti-spasmodic drugs and by quality of life instruments.Results:There was no treatment-related mortality. One participant died 1 year after transplant from disease progression. 74% of participants responded, 47% have stayed in remission for a mean of 3.5 years, and 26% did not respond. When compared to non-responders, responders were more likely to have pre-transplant intermittent muscle spasms (16/17 vsversus 0/6), normal reflexes (12/17 vsversus 0/6) and positive cerebrospinal fluid anti-GAD serology (12/14 vsversus 2/6). Compared to responders, non-responders were more likely to have lead pipe rigidity (4/6 vsversus 0/17), and EMG documented simultaneous contraction of agonist / antagonist limb muscles (4/6 vsversus 1/17). Pre-HSCT use of prescription SSRI and or SNRI was more common in those who relapsed or never responded (9/12) compared to those responders who never relapsed (0/11).Conclusion:In this cohort, HSCT was safe, but beneficial effect of HSCT was variable and predominately confined to participants with episodic spasms, normal tendon reflexes, without simultaneous co-contraction of limb agonist antagonist muscles, and who were not taking SSRI or SNRI antidepressants.Classification of eEvidence:This study provides Class IV evidence that for a subset of people with SPSD, autologous non-myeloablative HSCT improves outcomes.Clinical trial registry:ClinicalTrials.gov Identifier: NCT02282514.

2020 J. Leonard Goldner Award Winner: Inhibition of HMGB1 by Metformin Prevents Mechanical Overloading-Induced Tendinopathy

Category: Basic Sciences/Biologics; Sports Introduction/Purpose: Tendinopathy is a debilitating tendon disorder that affects millions of Americans and costs billions of healthcare dollars every year. Mechanical overloading is considered to cause the development of tendinopathy, but the underlying molecular mechanisms of tendinopathy remain unclear. High mobility group box-1 (HMGB1), an upstream potent inflammatory mediator, has been identified in high levels in early stage tendinopathy patients [1]. However, whether HMGB1 mediates tendinopathy development due to mechanical overloading is completely unknown. Metformin (Met), a hypoglycemic drug commonly used for the treatment of type II diabetes, has shown to inhibit the activity of HMGB1 via binding the acidic tail of HMGB1 [2]. In this study, we tested the hypothesis that Met prevents mechanical overloading-induced tendinopathy by inhibiting HMGB1. Methods: A total of 24 mice were divided into 4 groups and treated for 24 weeks as follows: Group 1 (Cage) with cage activities; Group 2 (Met) received daily IP injection of metformin (50 mg/kg body weight); Group 3 (ITR) ran on treadmill at 15 meters/min for 3 h/ day, 5 days a week; Group 4 (ITR+Met) ran the same protocol as that of ITR group but with daily IP injection of metformin. Six mice/group were sacrificed at 24 weeks and the Achilles and patellar tendon tissues were harvested. The tendons from the left legs were used for histochemical staining and the right for immunostaining. Results: We found that mechanical overloading induced HMGB1 release into tendon matrix (Fig. 1G, K, O). Metformin inhibited HMGB1 release (Fig. 1H, L, P). ITR induced degenerative tendinopathy as evidenced by the cell morphological changes from elongated shape in normal tendon (Fig. 2A, E, I, M) to round shape (Fig. 2C, G, K, O) and the accumulation of proteoglycans (Fig. 2K, O) in ITR tendon. Metformin injection inhibited ITR effect, which is shown by less round shaped cells and low proteoglycan levels found in metformin injected ITR tendons (Fig. 2D, H, L, P). ITR promoted the expression of chondrogenic markers (collagen II and SOX-9) in tendon (Fig. 3C, G, K, O), and metformin inhibited the expression of chondrogenic makers (Fig. 3D, H, L, P). Conclusion: Our study demonstrated that mechanical overloading induced degenerative changes in mouse tendons characterized by the presence of chondrocyte-like cells, accumulation of proteoglycans, high levels of chondrogenic marker SOX-9 and Collagen II expression. Administration of metformint reduced the degenerative responses in overloaded tendon and blocked the development of tendinopathy. These findings support the notion that mechanical overloading induces tendinopathy development by initiation of tendon inflammation via HMGB1, which leads to eventual tendon degeneration. Thus, metformin, a commonly prescribed and FDA approved drug that specifically inhibits HMGB1, can be used to prevent tendinopathy development due to mechanical overloading placed on the tendon.

Infiltration of synovitis into the flexor tendon: a case report

Synovitis is a type of aseptic inflammation that occurs within joints or surrounding tendons. No previous reports have described a hypertrophic synovium eroding the tendon sheath and manifesting as synovitis within the flexor tendon. We herein report a case involving a 10-year-old girl who presented to our hospital with a 1-month history of a swollen mass and progressive inability to completely flex her left index finger. The active flexion angle of the proximal interphalangeal joint was limited to 85°. A longitudinal incision of the flexor digitorum profundus tendon was surgically performed. The synovium inside and outside the flexor digitorum profundus tendon was completely removed. After the surgical excision, normal tendon gliding returned without recurrence by the 1-year follow-up. The active flexion angle of the proximal interphalangeal joint improved to 100°. To the best of our knowledge, this is the first case of synovitis affecting the flexor tendon and leading to limited flexion of a finger. The manifestation of a double ring sign on magnetic resonance imaging is quite characteristic. Early diagnosis and monitoring of the hyperproliferation and invasiveness of the synovial tissue are required. Surgical excision can be a simple and effective tool when necessary.

Targeted pathological collagen delivery of sustained-release rapamycin to prevent heterotopic ossification

Heterotopic ossification (HO) in connective tissues like tendons and ligaments severely damages tissue structure. The pathogenesis of HO remains unclear but may involve mTOR. The results presented here indicate that tendon stem/progenitor cells do not undergo osteochondrogenic differentiation when mTOR signaling is inactivated by gene knockout or rapamycin (RAPA) treatment. Meanwhile, it is necessary to deliver RAPA to the injured sites and avoid disturbing the normal tendon. A RAPA delivery system, developed using collagen hybrid peptide (CHP) to modify the surface of poly(lactic-co-glycolic acid) (PLGA) nanoparticles, targeted RAPA specifically to pathological tendon collagen. The CHP-PLGA-RAPA nanoparticles showed excellent pathological collagen affinity, sustained-release ability, and bioactivity. In a mouse model of tendon HO, CHP-PLGA-RAPA nanoparticles specifically bound to pathological tendon and strongly suppressed HO progression. The mTOR signaling pathway appears to be a viable therapeutic target for tendon HO, and CHP-PLGA nanoparticles may be valuable for the treatment of tendon-related diseases.

Stem cell therapies for equine tendinopathy

Tendons can be injured through over-strain at a number of different sites. When injured outside a synovial cavity (extra-thecal), injuries frequently repair by fibrosis, but this tissue is functionally deficient compared to normal tendon. Stem cells offer the prospect of improving this repair to restore function and enable a successful restoration of activity while minimizing the risk of re-injury. Naturally occurring equine Superficial Digital Flexor Tendon (SDFT) overstrain injuries usually have a contained lesion, thereby enabling simple intra-tendinous injection and, by the time of stem cell implantation, is filled with granulation tissue which acts as a vascularized scaffold. An anabolic drive is provided by mechanical loading of the tendon and the suspension of mesenchymal stem cells (MSCs) in bone marrow supernatant, which we have shown to have significant anabolic effects in vitro. To test the hypothesis that stem cells will enhance tendon healing, a controlled experimental study of naturally occurring SDFT injuries (n=12) has been performed (Smith et al. 2013). MSC treatment appeared to ‘normalize’ the tissue parameters so that they were closer to the contralateral, relatively normal, and untreated tendons than saline-injected controls, in spite of labelling experiments showing the majority of cells being lost within 24 hours (Becerra et al. 2013; Sole et al. 2013). A second adequately powered and independently analyzed study evaluated the clinical outcome of naturally occurring SDFT injuries treated using this technique (n=113), which showed a significantly reduced re-injury rate (Godwin et al. 2012). Intrasynovial (intra-thecal) tendon tears usually communicate with the synovial cavity where the synovial environment is particularly challenging for successful repair. However, MSCs administered intra-synovially failed to improve healing in either equine (naturally occurring) and ovine (induced) deep digital flexor tendon (DDFT) tears (Khan et al. 2018). Labelling of the implanted cells showed them to lodge within the synovium with no cells present in the tendon defect. Scaffolds are likely to offer better advantages for enhancing repair of intra-thecal tendon tears.