Bonar Score Research Articles

Effect of Sodium selenite administration on the process of tendon healing in Wistar male rats.

Tendon lesions have a great effect on the quality of life and medical spending. Thus is important to investigate the mechanisms responsible for tendon healing and to identify novel treatment options. The aim of the present study was to evaluate the effect of Selenium on the healing processes of injured tendons. A total of 20 Wistar male rats were used and were split into two groups with two different treatment methods. The first group received a normal food administration, while the second group received Na2SeO3. The animals were kept for 28 days. During the eighth day, all animals underwent surgical experimental Achilles tendon lesion and a Kessler-type suture. After three weeks, the animals were sacrificed and the tendon was extracted for histological evaluation in order to do a comparison according to the Movin scale (modified by Bonar). The histological evaluation revealed an even orientation of the collagen fibers in the case of the experimental group (Se) compared with the second group. The Bonar score was 1.62 for the Se group, while the control group had a Bonar score of 1.98. The average number of tenocytes in the Se group was lower which is demonstrated by a lower Bonar score (1.22), compared with the second group (Bonar Score 1.85). In addition, a slightly higher number of tenocytes compared with the intact tendon areas was recorded. In vascularization, a decreased amount of blood vessels in the experimental group (Se) was observed (Bonar Score 1.70), compared with the control group (Bonar score 1.96). The present study demonstrated that Selenium administration on murine models could be beneficial for tendon healing. Further clinical research is required in order for this to be confidently recommended.

Histological, radiological and clinical analysis of the supraspinatus tendon and muscle in rotator cuff tears

BackgroundMacroscopic alterations of the affected rotator cuff (RC) are undoubtedly linked to microscopic changes, but they may underestimate the actual degree of the disease. Moreover, it remains unclear whether preoperative structural RC changes may alter clinical outcomes.MethodsSupraspinatus tendon and muscle samples were collected from 47 patients undergoing RC surgery. Tendons were evaluated histologically according to the Bonar score; fatty infiltration and muscle atrophy were quantified using a software for biomedical image analysis (ImageJ) in percentage of area affected in the observed muscle section. Preoperative shoulder ROM and pain were evaluated. Radiological muscle atrophy was evaluated with the Tangent Sign and Occupation Ratio; fatty infiltration was assessed according to the Goutallier classification. Correlations between histological, radiological and clinical outcomes were assessed. Statistics were performed using the Spearman correlation coefficient. Intraobserver and interobserver agreement was calculated.ResultsHistopathologic fatty infiltration (r = 0.007, p = 0.962), muscle atrophy (r = 0.003, p = 0.984) and the total Bonar score (r = 0.157, p = 0.292) were not correlated to preoperative shoulder pain. Muscle atrophy showed a significant but weak negative correlation with the preoperative movement of abduction (r = -0.344, p = 0.018). A significant but weak positive correlation was found between muscle atrophy and the total Bonar score (r = 0.352, p = 0.015). No correlation between histological and radiological evaluation was found for both fatty infiltration (r = 0.099, p = 0.510) and muscle atrophy (Tangent Sign: r = -0.223, p = 0.131; Occupation Ratio: r = -0.148, p = 0.319). Our histological evaluation showed a modal value of 3 (out of 3) for fatty infiltration and an equal modal value of 2 and 3 (out of 3) for muscle atrophy. In contrast, the modal value of the Goutallier score was 1 (out of 4) and 28 patients out of 47 showed a negative Tangent sign. At histology, intraobserver agreement ranged from 0.59 to 0.81 and interobserver agreement from 0.57 to 0.64. On the MRI intraobserver agreement ranged from 0.57 to 0.71 and interobserver agreement ranged from 0.53 to 0.65.ConclusionsMicroscopic muscle atrophy appeared to negatively correlate with the movement of abduction leading to functional impairment. Shoulder pain did not show any relationship with microscopic changes. Radiological evaluation of the supraspinatus muscle alterations seemed to underestimate the degree of the same abnormalities evaluated at histology.

Absorbable suture knots on the supraspinatus tendon prevent adverse effects of nonabsorbable suture knots in a rat model.

To compare the absorbable and nonabsorbable suture knots on the tendon on bone-to-tendon healing during the early phase in a rat rotator cuff tear (RCT) model. Fifty-two male Sprague-Dawley rats (10weeks old; mean weight, 380g) were used in this study, and 51 of them were randomly assigned into three groups: absorbable suture group (ASG, n = 22), nonabsorbable suture group (NSG, n = 22), and sham surgery group (SSG, n = 7), and the remaining rat was used to take surgical pictures. Bilateral supraspinatus tendon tears were created and repaired immediately in ASG and NSG. Three rats from ASG and NSG were killed for Western blot and histological evaluation at 3days, 1week, and 4weeks after surgery. At 4weeks, four rats from each group were killed for biomechanical test, and three rats from SSG were used for histological evaluation. Absorbable suture knots on the tendon completely degraded at 4weeks. However, nonabsorbable suture knots remained intact between the tendon and articular side. ASG showed a stronger inflammatory reaction at 3days and 1week, but a weaker reaction at 4weeks as confirmed by gross observation and Western blot. Besides, ASG showed superior biomechanical properties in terms of maximum load to failure and stiffness at 4weeks. Modified Bonar score revealed superior maturity for tissue healing in ASG to that in NSG at 4weeks. Furthermore, inferior bone-to-tendon interface and weakest link formation were observed in NSG on histologic images. Absorbable suture knots on the tendon contributed to better mechanical properties compared with the nonabsorbable one after rotator cuff repair.

Evaluating the role of type 2 diabetes mellitus in rotator cuff tendinopathy: Development and analysis of a novel rat model.

ObjectiveTo establish and validate an intact rotator cuff rat model for exploring the pathophysiological effects of type 2 diabetes on the rotator cuff tendon in vivo.MethodsA total of 45 adult male rats were randomly divided into a control group (n = 9) and type 2 diabetes group (n=36). The rats were sacrificed at 2 weeks (T2DM-2w group, n=9), 4 weeks (T2DM-4w group, n=9), 8 weeks (T2DM-8w group, n=9), and 12 weeks (T2DM-12w group, n=9) after successful modeling of type 2 diabetes. Bilateral shoulder samples were collected for gross observation and measurement, protein expression(enzyme-linked immunosorbent assay,ELISA), histological evaluation, biomechanical testing, and gene expression (real-time quantitative polymerase chain reaction, qRT-PCR).ResultsProtein expression showed that the expression of IL-6 and Advanced glycation end products (AGEs)in serum increased in type 2 diabetic group compared with the non-diabetic group. Histologically, collagen fibers in rotator cuff tendons of type 2 diabetic rats were disorganized, ruptured, and with scar hyperplasia, neovascularization, and extracellular matrix disturbances, while Bonar score showed significant and continuously aggravated tendinopathy over 12 weeks. The biomechanical evaluation showed that the ultimate load of rotator cuff tendons in type 2 diabetic rats gradually decreased, and the ultimate load was negatively correlated with AGEs content. Gene expression analysis showed increased expression of genes associated with matrix remodeling (COL-1A1), tendon development (TNC), and fatty infiltration (FABP4) in tendon specimens from the type 2 diabetic group.ConclusionPersistent type 2 diabetes is associated with the rupture of collagen fiber structure, disturbance in the extracellular matrix, and biomechanical decline of the rotator cuff tendon. The establishment of this new rat model of rotator cuff tendinopathy provides a valuable research basis for studying the cellular and molecular mechanisms of diabetes-induced rotator cuff tendinopathy.

The effects of percutaneous ultrasound tenotomy on chronic tendinopathy in a rabbit Achilles’ tendon model

Objective: Chronic tendinopathy is debilitating and significantly limits physical function and quality-of-life. For chronic tendinopathy recalcitrant to conservative approaches, percutaneous ultrasound tenotomy (PUT) has become a common minimally-invasive therapy. To clarify the histopathological effects of PUT, we assessed the cellular and tissue-level effects of PUT in an animal model of chronic tendinopathy.Design: This within-subject randomized-controlled study treated the bilateral Achilles’ tendons of 10 skeletally-mature, male New Zealand white rabbits with Kartogenin (KGN) beads to mimic chronic tendinopathy and allowed free cage activity for six weeks. One randomly-selected Achilles’ tendon per rabbit underwent sonographically-guided PUT, using 60 s of ultrasound energy. Six weeks post-procedure, the bilateral Achilles’ tendons were harvested and histologically graded.Results: Treated and untreated sides were compared using paired t-tests and mixed models. There were no statistically-significant differences in collagen arrangement, cellularity, or ground substance deposition (all p>0.16). Bonar scores for the most superficial level (95% CI) and the whole tendon (95% CI) were 1.7 (0.6, 2.8) and 0.9 (0.0, 1.9) points lower on the PUT side compared with the untreated side (p=0.037 and p=0.059 respectively). Conclusion: These findings provide evidence that PUT stimulates Histopathologic improvement in collagen formation and organization in the setting of chronic tendinopathy.

Feasibility of Neovessel Embolization in a Large Animal Model of Tendinopathy: Safety and Efficacy of Various Embolization Agents.

Targeting neovessels in chronic tendinopathies has emerged as a new therapeutic approach and several embolization agents have been reported. The aim of this study was to investigate the feasibility of embolization with different agents in a porcine model of patellar tendinopathy and evaluate their safety and efficacy. Eight 3-month-old male piglets underwent percutaneous injection of collagenase type I to induce patellar tendinopathies (n = 16 tendons). They were divided into four groups (2 piglets, 4 tendons/group): the control group, 50–100 µm microspheres group, 100–300 µm microspheres group, and the Imipenem/Cilastatin (IMP/CS) group. Angiography and embolization were performed for each patellar tendon on day 7 (D7). The neovessels were evaluated visually with an angiography on day 14. The pathological analysis assessed the efficacy (Bonar score, number of neovessels/mm2) and safety (off-target persistent cutaneous ischemic modifications and presence of off-target embolization agents). The technical success was 92%, with a failed embolization for one tendon due to an arterial dissection. Neoangiogenesis was significantly less important in the embolized groups compared to the control group angiographies (p = 0.04) but not with respect to histology (Bonar score p = 0.15, neovessels p = 0.07). Off-target cutaneous embolization was more frequently depicted in the histology of the 50–100 µm microspheres group (p = 0.02). Embolization of this animal model with induced patellar tendinopathy was technically feasible with different agents and allowed assessing the safety and efficacy of neovessel destruction. Particles smaller than 100 µm seemed to be associated with more complications.

SS-31 as a Mitochondrial Protectant in the Treatment of Tendinopathy: Evaluation in a Murine Supraspinatus Tendinopathy Model.

Prior studies have demonstrated mitochondrial dysfunction in tendinopathy. The objective of this investigation was to explore the potential of SS-31 (elamipretide), a mitochondrial protectant, to improve mitochondrial function and promote tendon healing in a murine supraspinatus tendinopathy model. One hundred and twenty-six mice (252 limbs) were divided into 6 groups (42 limbs/group) that received (I) 4 weeks of impingement; (II) 8 weeks of impingement; (III) 8 weeks of impingement including 4 weeks of SS-31 treatment (5 mg/kg/d) starting after 4 weeks of impingement; (IV) 4 weeks of impingement ending with clip removal, followed by harvesting 4 weeks later; and (V) 4 weeks of impingement ending with clip removal, followed by 4 weeks of SS-31 treatment and harvesting; and a control group. Specimens were prepared for biomechanical testing, histological analysis, transmission electron microscopy, measurement of superoxidative dismutase (SOD) activity, and measurement of gene expression. Failure force decreased after impingement, compared with the intact tendon, and the decrease was partially reversed after clip removal, SS-31 treatment, and the 2 treatments combined. A similar pattern was observed for stiffness. Histological analysis demonstrated higher modified Bonar scores in the impingement groups; however, the changes in tendon morphology were partially reversed following all treatments, especially the combined treatment. Decreased mitochondrial number and altered organization and density of cristae were observed in the impingement groups. Mitochondrial structure and number became more normal, with improvement in morphology of the cristae, after clip removal and/or SS-31 treatment. SOD activity decreased after impingement, compared with the control group, then increased significantly again after treatment, especially in the combined treatment group. Mitochondria-related gene expression decreased in the impingement groups and increased again after treatment. The mitochondrial protectant SS-31 improved mitochondrial function, promoting tendon healing, especially when combined with removal of subacromial impingement. Improving mitochondrial function with agents such as SS-31 may represent an effective treatment to promote healing in the setting of supraspinatus tendinopathy.

Paper 90: Histopathology of Rotator Cuff Tendons in Elderly Patients with Glenohumeral Arthritis without Cuff Tears

Paper 90: Histopathology of Rotator Cuff Tendons in Elderly Patients with Glenohumeral Arthritis without Cuff Tears

Poster 100: Evaluation of SS-31 as a Potential Therapeutic in the Treatment of Tendinopathy

Poster 100: Evaluation of SS-31 as a Potential Therapeutic in the Treatment of Tendinopathy

Poster 163: Evaluating the Role of Subacromial Impingement in Rotator Cuff Tendinopathy: Development and Analysis of a Novel Rat Model

Objectives:Subacromial impingement of the rotator cuff caused by variations in acromial anatomy is an extrinsic factor that leads to inflammation and degeneration of the rotator cuff, ultimately contributing to the development of tendinopathy. However, microscopic and molecular changes in the impinged tendon remain poorly understood, and a robust rat model for studying rotator cuff tendinopathy is still lacking.Methods:Our study was approved by the Institutional Animal Care and Use Committee. A total of 44 adult male Sprague-Dawley rats were included in the study. Animals were randomly allocated to one of four study groups: intact control group (Group 1, n=11); bilateral subacromial surgical clip placement to induce supraspinatus impingement for 2 weeks (Group 2, n=11), 4 weeks (Group 3, n=11) and 8 weeks (Group 4, n=11). At time of sacrifice, bilateral shoulder specimens were harvested for biomechanical testing, histological and quantitative real-time polymerase chain reaction (qRT-PCR) analysis. One-way analysis of variance (ANOVA) with the post-hoc Tukey test was used to analyze differences among groups.Results:Radiography confirmed that all microvascular clips remained in stable position in the subacromial space. Gross inspection of supraspinatus tendon specimens in the impingement groups revealed frayed and hazy tendon discoloration at the enthesis and mid-substance. Biomechanical evaluation demonstrated decreased supraspinatus tendon failure force and tissue stiffness at all time points compared to control group. Histologic specimens demonstrated significant, persistent tendinopathic changes over 8 weeks, with the mean modified Bonar scores significantly increased in the clip impingement groups compared to the control group (control: 1.56±0.86; 2 weeks group: 9.17±0.76; 4 weeks group: 9.11±0.65; and 8 weeks group: 6.56±0.50. P <0.001 for all comparisons). qRT-PCR analysis of impinged tendon specimens demonstrated upregulation of gene expression for Col3 and MMP14 in the impingement groups compared with control groups (P =0.001 and 0.015 respectively). In muscle samples, significant upregulation was seen in the expression of genes that are commonly associated with muscle atrophy (MURF1: P <0.001 and UBE2B: P <0.001) and fatty infiltration (FABP4: P =0.002, PPARγ2: P =0.006, and KLF15: P =0.001).Conclusions:In conclusion, we developed a novel rat model of subacromial impingement and found consistent and sustained histologic, biomechanical, and gene expression changes that are consistent with findings in human tendinopathy. This model will allow future studies to further evaluate the underlying cellular and molecular mechanisms of tendinopathy, as well as evaluation of novel therapeutic approaches for treatment of this common problem.Figure 1.Gross insepction nof the specismen at all time points.Figure 2.RadiographyFigure 3.

Selective Serotonin Reuptake Inhibitor Promotes Bone-Tendon Interface Healing in a Rotator Cuff Tear Rat Model.

Selective serotonin reuptake inhibitor (SSRI) is believed to accelerate wound healing, and thus expected to have a positive effect on rotator cuff repair. We hypothesized that SSRI has a positive effect on the healing of the bone-tendon interface (BTI), and improved rotator cuff tear healing would be confirmed by mechanical strength measurements and histological assessment of the restored tendon. The study used 40 adult male Sprague-Dawley wild-type rats. The animals were divided into two groups: group-SSRI, the supraspinatus repair with SSRI injection group, and group-C, conventional supraspinatus repair only without SSRI. Biomechanical and histological analyses were performed 8weeks after index rotator cuff surgery. The ultimate load (N) was significantly higher in group-SSRI than in group-C (54.8 ± 56.9 Vs 25.1 ± 11.1, p = .031). In the histological evaluation, the Bonar score confirmed significant differences in collagen fiber density (group-C: 0.6 ± 0.5, group-SSRI: 1.1 ± 0.6, p = .024), vascularity (group-C: 0.1 ± 0.2, group-SSRI: 0.3 ± 0.4, p = .024) and cellularity (group-C: 1.7 ± 0.4, group-SSRI: 2.0 ± 0.0, p = .023) between the groups. Based on the total score, group-SSRI was significantly better compared with group-C (6.3 ± 2.7 Vs 4.3 ± 1.9, p = .019). Our study demonstrated that SSRI could facilitate improved biomechanical and histological outcomes 8weeks after rotator cuff repair in a rat model. Consequently, SSRI may improve healing after rotator cuff repair.

Advances in Microscopic Studies of Tendinopathy: Literature Review and Current Trends, with Special Reference to Neovascularization Process

Tendinopathy is a process of chaotic extracellular matrix remodeling followed by increased secretion of enzymes and mediators of inflammation. The histopathological assessment of tendinous tissue is crucial to formulate the diagnosis and establish the severity of tendon degeneration. Nevertheless, the microscopic analysis of tendinous tissue features is often challenging. In this review, we aimed to compare the most popular scales used in tendon pathology assessment and reevaluate the role of the neovascularization process. The following scores were evaluated: the Bonar score, the Movin score, the Astrom and Rausing Score, and the Soslowsky score. Moreover, the role of neovascularization in tendon degeneration was reassessed. The Bonar system is the most commonly used in tendon pathology. According to the literature, hematoxylin and eosin with additional Alcian Blue staining seems to provide satisfactory results. Furthermore, two observers experienced in musculoskeletal pathology are sufficient for tendinopathy microscopic evaluation. The control, due to similar and typical alterations in tendinous tissue, is not necessary. Neovascularization plays an ambiguous role in tendon disorders. The neovascularization process is crucial in the tendon healing process. On the other hand, it is also an important component of the degeneration of tendinous tissue when the regeneration is incomplete and insufficient. The microscopic analysis of tendinous tissue features is often challenging. The assessment of tendinous tissue using the Bonar system is the most universal. The neovascularization variable in tendinopathy scoring systems should be reconsidered due to discrepancies in studies.

Histopathology of long head of biceps tendon removed during tenodesis demonstrates degenerative histopathology and not inflammatory changes

BackgroundThe aim of this study is to describe and quantitatively analyze the histopathology of proximal long head biceps (LHB) tendinopathy in patients who have undergone LHB tenodesis. The hypothesis is that severe histopathologic changes of the LHB tendon (LHBT) will most likely be reflected with improved postoperative clinical outcomes.MethodsThe study included patients with isolated LHB tendinopathy or LHB tendinopathy associated with concomitant shoulder pathologies. All had failed conservative treatment (12 months) and had a positive pain response (> 50% reduction) pre-operatively after LHB tendon injection with local anesthetic. All underwent biceps tenodesis procedure between 2008 and 2014. Tendon specimens were collected and histologically analyzed with the semi-quantitative Bonar scoring system. Minimum follow-up time was 1 year. A subset of patients was retrospectively reviewed postoperatively and evaluated employing visual analogue score (VAS), short form survey (SF-12), American Shoulder and Elbow Surgeon (ASES) score, Disability of Arm, Shoulder and Hand (DASH) score, and Oxford Shoulder Score (OSS) and postoperative return to work status.ResultsForty-five biceps tendon specimens were obtained from 44 patients (mean age 50 ± 9.6 years). Histopathological analyses demonstrated advanced degenerative changes with myxoid degeneration and marked collagen disorganization. Minimal inflammation was identified. There were no regional differences in histopathological changes. Clinical outcomes did not correlate significantly with severity of histopathologic changes.ConclusionsThis study confirms that LHBT specimens in patients undergoing tenodesis demonstrate with the use of the Bonar score histopathologic changes of chronic degeneration and not inflammation. The correct histopathologic terminology for this process is LHB tendinosis. The histopathological changes appear uniform throughout the entire length of the LHBT which may inform the nature of the procedure performed.

No differences in histopathological degenerative changes found in acute, trauma-related rotator cuff tears compared with chronic, nontraumatic tears

PurposeAcute trauma-related rotator cuff tears are believed to have better healing potential than chronic tears due to less degenerative changes of the tendons. However, the histopathological condition of tendons from trauma-related tears is not well investigated. The purpose of this study was to explore specific histopathological features in tendons from acute trauma-related full-thickness rotator cuff tears and to compare them to findings in tendons from nontraumatic, chronic tears.MethodsIn a prospective cohort study, 62 previously asymptomatic patients [14 women, median age 61 years (range 42–75)] with trauma-related full-thickness rotator cuff tears were consecutively included. Arthroscopic repair was performed within 30 (median, IQR 25–37) days after the injury. During surgery, tissue biopsies were harvested from the supraspinatus tendons in 53 (86%) of the patients. In addition, similar biopsies were harvested from 10 patients undergoing surgery for chronic tears without history of trauma. All tissue samples were examined by a well-experienced pathologist under light microscope. Tendon degeneration was determined using the Bonar score whereas immunostaining was used for proliferation (Ki67), inflammation (CD45), apoptosis (p53) and haemosiderin staining to study traces of bleeding.ResultsThe median (IQR) Bonar score for the acute trauma-related biopsies was 10.5 (7.5–14.5) compared to 11 (5–12.8) for the control group with no statistically significant difference between the groups. No statistically significant between-group difference was found for the inflammatory index whereas tendons from patients with trauma-related full-thickness rotator cuff tears had statistically significantly higher apoptosis [3.1 (0.5–8.9) vs. 0.1 (0–1.5), p = 0.003] and proliferation [4.0 (1.8–6.9) vs. 0.4 (0–2.0), p = 0.001) indices than those undergoing surgery for chronic tears. Positive haemosiderin staining was found in 34% of tissue samples from patients with trauma-related tears compared to 10% in the control group (n.s).ConclusionThis study suggests that there is no difference with regard to degenerative changes between supraspinatus tendons harvested from patients with acute, trauma-related rotator cuff tears and patients with nontraumatic, chronic tears.Level of evidenceII.

Influence of Local Chemokine Delivery and Postoperative Peripheral Blood Mobilization on Achilles Tendon Repair

Category:Basic Sciences/Biologics; Sports; TraumaIntroduction/Purpose:Mesenchymal stem cells (MSCs) have demonstrated promise in augmenting the surgical repair of full thickness tendon tears. Despite this promise, obtaining a therapeutic concentration of MSCs is time-, labor- and resource intensive, and is subject to ever-tightening governmental regulations. Our group recently demonstrated that postoperative mobilization of MSCs from the marrow compartment and into peripheral blood via subcutaneous granulocyte- colony stimulating factor administration enhanced tendon-bone healing in a rat model of surgical repair of a full-thickness supraspinatus tendon tear. We hypothesized that combining postoperative stem cell mobilization with local delivery of a chemokine that stimulates MSC chemotaxis would enhance the surgical repair of a mid-substance Achilles tendon transection.Methods:Following IACUC approval, Achilles tendons were unilaterally frayed via multiple longitudinal scalpel blade nicks in 24 Lewis rats. Tendons were then surgically transected, followed by repair with braided non-absorbable suture in a modified-Kessler pattern. Based on randomization (n=6/group), the tendon anastomosis was coated with a resorbable chitosan hydrogel containing 100 ng of the chemokine, CCL5 (RANTES), or hydrogel without RANTES. Skin closure and anesthesia recovery were then performed; rats were allowed ad libitum activity. Beginning 24 hours postoperatively, rats received a daily subcutaneous injection of either a peripheral blood mobilizing agent, AMD3100 (5 mg/kg), or saline; dosing was repeated at 48 and 72 hours. At the 4- week endpoint, Achilles tendons harvested en bloc. Decalcified histologic sections were stained with H&E and Alcian Blue as well as immunostained for Collagen III, CD163, and CD68. Slides were digitized (40x magnification) and graded by blinded reviewers via modified-Bonar score to assess tendon integrity.Results:Rats that received local application of RANTES-loaded chitosan hydrogel had worse (higher) modified-Bonar subscores with respect to tenocyte morphology, collagen orientation, and ground substance staining, though none of these comparisons were statistically significant (p=0.068, p=0.672, and p=0.407, respectively). Animals that received subcutaneous AMD3100 alone, or in conjunction with RANTES-loaded chitosan hydrogel displayed the best (lowest) total modified Bonar scores, though these comparisons were also not statistically significant (p = 0.498). No significant differences were found with respect to CD163 (p=0.132) and CD68 (p=0.104) staining. Despite a lack of statistical significance, animals that received AMD3100 displayed a higher number of both macrophage subtypes. No differences were found with respect to Collagen III immunostaining (p=0.808).Conclusion:Tendon repair and regeneration remains a significant clinical challenge, which may be aided by MSC transplantation. The mobilization of endogenous marrow-derived MSCs into peripheral blood and subsequent recruitment via local chemokine delivery may be an efficacious way to enhance tendon repair without the need for ex vivo processing. We failed to demonstrate significant effects of stem cell mobilization via AMD3100 injections, and chemokine-directed recruitment, though trends were present indicating that AMD3100 alone may be beneficial. Additional work is required to draw any translatable conclusions from this research.

Collagenase-Induced Patellar Tendinopathy with Neovascularization: First Results towards a Piglet Model of Musculoskeletal Embolization

Background: Therapeutic strategies targeting neovessels responsible for musculoskeletal chronic pain have emerged, including neovessels embolization. Our study aimed to develop a large animal model of patellar tendinopathy with neovascularization. Methods: Nine 3-month-old male piglets (18 patellar tendons) received percutaneous injections of increasing doses of collagenase (0 to 50 mg) at day 0 (D0). Tendinopathy was evaluated by ultrasound (D7 and D14). Neovascularization was evaluated visually and on angiographies. Bonar score was used for histological analysis (D14). Correlations were evaluated using Spearman’s rank (Rs) test. Results: Research protocol was well tolerated. All tendons were enlarged with a median increase of 31.58% [25–40.28] at D7 (p = 0.244) at D7 and 57.52% [48.41–91.45] at D14 (p = 0.065). Tendons with collagenase injection had more hypoechoic changes, with one tendon rupture (p = 0.012). Neovascularization was reported above 5 mg collagenase (p < 0.01) at D7 and D14 with dose-related neovessels induction (Rs = 0.8, p < 0.001). The Bonar score increased above 5 mg collagenase, correlated with the dose (Rs = 0.666, p = 0.003). Conclusions: The study shows the feasibility, safety and reproducibility of this new large animal model of patellar tendinopathy with neovascularization after collagenase injection. It will allow studying new treatments on direct embolization of neovessels by endovascular approach.

The Role of Indian Hedgehog Signaling in Tendon Response to Subacromial Impingement: Evaluation Using a Mouse Model

Background: The underlying cellular and molecular mechanisms involved in the development of tendinopathy due to subacromial supraspinatus tendon (SST) impingement and the response to subsequent removal of impingement remain unknown. Purpose: To investigate the involvement of Indian hedgehog (IHH) signaling in the development of SST tendinopathy and the subsequent healing process after the relief of subacromial impingement in a novel mouse shoulder impingement model. Study Design: Controlled laboratory study. Methods: A total of 48 male wild-type C57BL/6 mice were used in this study. Supraspinatus tendinopathy was induced by inserting a microsurgical clip into the subacromial space bilaterally. Eleven mice were sacrificed at 4 weeks after surgery to establish impingement baseline; 24 mice underwent clip removal at 4 weeks after surgery and then were euthanized at 2 or 4 weeks after clip removal. Thirteen mice without surgical intervention were utilized as the control group. All SSTs were evaluated with biomechanical testing; quantitative histomorphometry after staining with hematoxylin and eosin, Alcian blue, and picrosirius red; and immunohistochemical staining (factor VIII, IHH, Patched1 [PTCH1], and glioma-associated oncogene homolog 1 [GLI1]). Results: The mean failure force and stiffness in the 4-week impingement group decreased significantly compared with the control group (P < .001) and gradually increased at 2 and 4 weeks after clip removal. Histological analysis demonstrated increased cellularity and disorganized collagen fibers in the SST, with higher modified Bonar scores at 4 weeks, followed by gradual improvement after clip removal. The IHH-positive area and PTCH1- and GLI1-positive cell percentages significantly increased after 4 weeks of clip impingement (20.64% vs 2.06%, P < .001; 53.9% vs 28.03%, P = .016; and 30% vs 12.19%, P = .036, respectively) and continuously increased after clip removal. Conclusion: The authors’ findings suggest that the hedgehog signaling pathway and its downstream signaling mediator and target GLI1 may play a role in the development and healing process of rotator cuff tendinopathy due to extrinsic rotator cuff impingement. Clinical Relevance: This study suggests the potential for the hedgehog pathway, together with its downstream targets, as candidates for further study as potential therapeutic targets in the treatment of supraspinatus tendinopathy.

Tendon midsubstance trauma as a means for the development of translatable chronic rotator cuff degeneration in an ovine model.

BackgroundChronic degeneration of rotator cuff tendons is a major contributing factor to the unacceptably high prevalence of rotator cuff repair surgery failures. The etiology of chronic rotator cuff degeneration is not well understood, and current therapies are not effective, necessitating preclinical research to fill this knowledge gap. Unfortunately, current large animal models rely on enthesis disruption as a means of model generation, which is not representative of human patients with chronic rotator cuff degeneration prior to full-thickness tears. Following, the goal of this study was to develop and characterize a translational large-animal model of chronic rotator cuff degeneration without enthesis release.MethodsA midsubstance damage model [i.e., “combed fenestration” (CF)] in adult sheep was generated by creating 16 longitudinal cuts within the top third of the infraspinatus tendon thickness. Tendon integrity was characterized through exhaustive non-destructive biomechanical stress relaxation testing [peak stress, peak load, percent relaxation, and cross-sectional area (CSA)], followed by histopathological degeneration scoring and analysis (Bonar score), histomorphological analysis of collagen organization and fatty atrophy (percent adipose area), and gene expression analyses.ResultsThe CF model tendons exhibited significantly decreased mechanical properties as evidenced by decreased peak stress (P<0.025) and increased percent relaxation (18-week vs. Control, P<0.035) at multiple strain magnitudes and across all timepoints. At all timepoints, the CF tendons exhibited pathological changes aligned with tendon degeneration, as evidenced by increased Bonar scoring (P<0.001) and decreased collagen organization (6-week vs. Control, P=0.013). Increases in intramuscular adipose content were also documented through histomorphology analysis (6- and 18-week vs. Control, P<0.077). Significant changes in gene expression were noted at all timepoints.ConclusionsThese data reveal that this new ovine CF model of chronic rotator cuff degeneration results in tendons with decreased mechanical properties, degenerative pathology characteristics, and gene expression profiles that aligned with the degenerative changes that have been noted in humans with tendinopathy. For these reasons, we believe this novel large animal model of chronic rotator cuff degeneration is a translational platform in which to test devices, therapies, and/or technologies aimed at repairing damage to the shoulder.

Adipose Stem Cell-Derived Exosomes As a Macrophage-Based Treatment for Chronic Rotator Cuff Tendinopathy: From a Mouse Model to a Study in Human Tissue

Objectives:Chronic rotator cuff tendinopathy is one of the most prevalent causes of shoulder pain. Growing evidence suggests that macrophages play a significant role in the pathogenesis of tendinopathy. Therefore, a treatment that targets macrophages would be useful for patients with this common musculoskeletal disorder. To investigate whether adipose stem cell-derived exosomes (ASC-Exos) mediate polarization of macrophages and contribute to the healing of chronic rotator cuff tendinopathy.Methods:First, we compared the effects of ASC-Exos on polarization of mouse bone marrow-derived macrophages between a classically activated phenotype (M1φ) and an alternatively activated phenotype (M2φ) in vitro. Seventy-two C57Bl/6 mice were assigned to normal cage activity (n=24) or 5 weeks of treadmill overuse (n=48). The enthesis of supraspinatus in each mouse was then injected with ASC-Exos (ASC-Exos group, n=24) or saline (saline group, n=24). Histological and biomechanical outcomes were assessed 4 weeks after treatment. Finally, tissue samples from human patients with rotator cuff tendinopathy were obtained to determine the effect of ASC-Exos on the M1φ/M2φ balance in tissue-resident macrophages.Results:ASC-Exos inhibited M1φ polarization and augmented M2φ polarization both in mouse bone marrow-derived macrophages, mouse in vivo model and human tissue-resident macrophages. Mice in the ASC-Exos group showed less severe pathological changes than the saline group, including less cellular infiltration, disorganization of collagen, and ground substance deposition. The mean modified Bonar score was significantly lower in the ASC-Exos group than in the saline group (9.81 ± 0.96 vs 7.69 ± 1.03; P<.05). Furthermore, the maximum failure load was significantly higher in the ASC-Exos group than in the saline group (4.23 ± 0.66 N vs 3.86 ± 0.65 N; P<.05) as was stiffness (3.38 ± 0.34 N/m vs. 2.68 ± 0.49 N/m; P<.05).Conclusions:ASC-Exos-mediated balance of M1φ/M2φ contributes to healing of tendinopathy. Regulation of the M1φ/M2φ balance could be a new target for treatment of chronic rotator cuff tendinopathy.

Adipose Stem Cell–Derived Exosomes Ameliorate Chronic Rotator Cuff Tendinopathy by Regulating Macrophage Polarization: From a Mouse Model to a Study in Human Tissue

Background: Chronic rotator cuff (RC) tendinopathy is one of the most prevalent causes of shoulder pain. Growing evidence suggests that macrophages play a significant role in the proinflammatory response, resolution of inflammation, and tissue healing of tendinopathy. In particular, enhancement of M2 macrophage (M2φ) activity contributes to the accelerated healing of tendinopathy. Therefore, a treatment that enhances M2φ polarization would be useful for patients with this common musculoskeletal disorder. Purpose: To investigate whether adipose stem cell–derived exosomes (ASC-Exos) enhance M2φ polarization and ameliorate chronic RC tendinopathy. Study Design: Controlled laboratory study. Methods: First, we compared the effects of ASC-Exos on polarization of mouse bone marrow–derived macrophages between a classically activated phenotype (M1φ) and an alternatively activated phenotype (M2φ) in vitro. In total, 72 C57BL/6 mice were assigned to normal cage activity (n = 24) or 5 weeks of treadmill overuse (n = 48). The supraspinatus tendon of each treadmill overuse mouse was treated with ASC-Exos (n = 24) or saline (n = 24). Histological and biomechanical outcomes were assessed 4 weeks after treatment. Finally, tissue samples from human patients with RC tendinopathy were obtained to assay the effect of ASC-Exos on the M1φ/M2φ balance in tissue-resident macrophages. Results: ASC-Exos inhibited M1φ polarization and augmented M2φ polarization in vitro and in vivo. Mice in the ASC-Exos group showed less severe pathological changes than those in the saline group, including less cellular infiltration, disorganization of collagen, and ground substance deposition. The modified Bonar score of the ASC-Exos group (mean ± SD, 7.68 ± 1.03) was significantly lower than that of the saline group (9.81 ± 0.96; P < .05). Furthermore, the maximum failure load was significantly higher in the ASC-Exos group than in the saline group (4.23 ± 0.66 N vs 3.86 ± 0.65 N; P < .05), as was stiffness (3.38 ± 0.34 N/m vs 2.68 ± 0.49 N/m; P < .05). Conclusion: ASC-Exos–mediated polarization balance of M1φ/M2φ contributes to the amelioration of chronic RC tendinopathy. Regulation of the M1φ/M2φ balance could be a new target for the treatment of chronic RC tendinopathy. Clinical Relevance: Administration of ASC-Exos is a cell-free approach that may become a novel treatment option for chronic RC tendinopathy and should be explored further.