Local rhBMP-12 on an Absorbable Collagen Sponge as an Adjuvant Therapy for Rotator Cuff Repair - A Phase 1, Randomized, Standard of Care Control, Multicenter Study: Safety and Feasibility

Biologic Augmentation of Rotator Cuff Repair: Current Concepts Review

Rotator cuff tears are common in an aging population. Thus far, primary repairs have shown high re-tear rates suggesting the need for improved healing modalities. Current augmentations of rotator cuff repairs include synthetic and biological scaffolds, surgical bone marrow venting, and infusing the repair with a variety of stem cells and growth factors aimed at restoring the native cellular structure and function of the repaired tissue. This current concepts review discusses the anatomy, physical presentation, diagnosis, and treatment of rotator cuff tears; biological adjuvants for rotator cuff repairs; and the current literature on outcomes after biologically augmented rotator cuff repairs. [Orthopedics. 202x;4x(x):xx-xx.].

Effect of Porcine-Derived Absorbable Patch-Type Atelocollagen for Arthroscopic Rotator Cuff Repair: A Prospective Randomized Controlled Trial

BACKGROUND

Even though arthroscopic rotator cuff repair is recognized as a standard treatment option, the risk of postoperative retear is a major concern.

PURPOSE

To evaluate the effect of porcine-derived absorbable patch-type atelocollagen during arthroscopic rotator cuff repair.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 64 patients with rotator cuff tears diagnosed on magnetic resonance imaging (MRI) were enrolled prospectively from November 2020 to December 2021. Both groups had repairs using the suture bridge technique. For the atelocollagen group, before securing the lateral anchors, we inserted porcine-derived absorbable patch-type atelocollagen between the footprint and the tendon. On postoperative day 2, the patients underwent MRI to confirm containment of the patch-type atelocollagen. At 6 months and 1 year postoperatively, the signal intensity of the repaired tendon was assessed using MRI. Patients were evaluated using the Constant score as the primary outcome, along with the visual analog scale for pain; range of motion; American Shoulder and Elbow Surgeons score; University of California, Los Angeles, score; and Korean Shoulder Score preoperatively and at 2, 3, 6, and 12 months postoperatively.

RESULTS

No significant changes in the Constant score as primary outcome, pain or other functional scores, and range of motion were observed between the groups at 1 year postoperatively. The patch-type atelocollagen was confirmed to be contained by the time-zero MRI scan taken 2 days postoperatively. Among the 55 patients included in final analysis, 12 retear cases were recorded (21.8% retear rate). A significantly lower retear rate was found in the atelocollagen group, as 3 cases were observed in this group (10.3%) and 9 cases were observed in the conventional repair group (34.6%) (P = .048).

CONCLUSION

The Constant score was not different between the groups. The retear rate after rotator cuff repair was significantly lower in the group that received porcine-derived absorbable patch-type atelocollagen compared with in the conventional group.

REGISTRATION

KCT0005184 (Clinical Research Information Service [CRIS]; https://cris.nih.go.kr).

Development and Validation of a Predictive Model for Chronic Postsurgical Pain After Arthroscopic Rotator Cuff Repair: A Prospective Cohort Study

Purpose

Chronic pain management continues to present a significant challenge following arthroscopic shoulder surgery. Our purpose was to detect chronic postsurgical pain (CPSP) in patients who had undergone arthroscopic rotator cuff repair (ARCR) and develop a nomogram capable of predicting the associated risk.

Patients and Methods

We collected the demographic and clinical data of 240 patients undergoing ARCR in our hospital from January 2021 to May 2022. The pain level was monitored and evaluated three months after ARCR. LASSO regression was used to screen out pain-predicting factors, which were subsequently used to construct a nomogram. Internal validation was carried out using Bootstrap resampling. The data of 78 patients who underwent ARCR in our hospital from August 2022 to December 2022 were also collected for external verification of the nomogram. The predictive model was evaluated using the receiver operating characteristic curve (ROC), calibration curve, and decision curve analysis (DCA).

Results

Age, duration of preoperative shoulder pain (DPSP), C-reactive protein (CRP), number of tear tendons, and American Shoulder and Elbow Surgical Score (ASES) were screened by LASSO regression as predictive factors for CPSP. These factors were then used to construct a chronic pain risk nomogram. The area under the curve (AUC) of the predictive and validation models were 0.756 (95% CI: 0.6386-0.8731) and 0.806 (95% CI: 0.6825-0.9291), respectively. Furthermore, the calibration curves and decision curve analysis (DCA) for both models indicated strong performance, affirming the reliability of this predictive model.

Conclusion

The CPSP risk model that has been developed exhibits strong predictive capabilities and practical utility. It offers valuable support to clinical healthcare professionals in making informed treatment decisions, reducing the unnecessary use of analgesic drugs, and optimizing the allocation of medical resources.

Bibliometric and visualized analysis of scientific publications on rehabilitation of rotator cuff injury based on web of science

Background

Since the discovery of rehabilitation as an intervention for rotator cuff injury, its impact on the recovery of rotator cuff injury has attracted crucial attention, and the number of related studies is increasing worldwide. There were no bibliometric and visualized analysis studies in this field. This study aimed to investigate the research hotpots and trends in the rehabilitation of rotator cuff injury via bibliometric and visualized analysis and to identify the future development of clinical practice.

Method

The publications regarding rehabilitation of rotator cuff injury from inception to December 2021 were obtained from the Web of Science Core Collection database. The trends of publications, co-authorship and co-occurrence analysis and visualized analysis were carried out using Citespace, VOSviewer, Scimago Graphica software, and R Project.

Results

A total of 795 publications were included in this study. The number of publications significantly increased yearly. The United States published the highest number of related papers and the papers published by the United States had the highest citations. The University of Laval, the University of Montreal and Keele University were the top 3 most contributive institutions. Additionally, the Journal of Shoulder and Elbow Surgery was the journal with the highest number of publications. The most common keywords were "rotator cuff", "rehabilitation", "physical therapy", "management", and "telerehabilitation".

Conclusion

The total number of publications has shown a steady upward trend. The cooperation between countries globally was still relatively lacking, and therefore it is necessary to strengthen cooperation between different countries and regions to provide conditions for multi-center, large sample, and high-quality research. In addition to the relatively mature rehabilitation of rotator cuff injury such as passive motion or exercise therapy, telerehabilitation has also attracted much attention with the progress of science.

Growth Differentiation Factor 7 Prevents Sepsis-Induced Acute Lung Injury in Mice

Objective

Acute lung injury (ALI) is a life-threatening complication during sepsis and contributes to multiple organ failure and high mortality for septic patients. The present study aims to investigate the role and molecular basis of growth differentiation factor 7 (GDF7) in sepsis-induced ALI.

Methods

Mice were subcutaneously injected with recombinant mouse GDF7 Protein (rmGDF7) and then intratracheally injected with lipopolysaccharide (LPS) to generate sepsis-induced ALI. Primary peritoneal macrophages were isolated to further evaluate the role and underlying mechanism of GDF7 in vitro.

Results

GDF7 was downregulated in LPS-stimulated lung tissues, and rmGDF7 treatment significantly inhibited inflammation and oxidative stress in ALI mice, thereby preventing LPS-induced pulmonary injury and dysfunction. Mechanistically, we found that rmGDF7 activated AMP-activated protein kinase (AMPK), and AMPK inhibition significantly blocked the anti-inflammatory and antioxidant effects of rmGDF7 during LPS-induced ALI. Further findings revealed that rmGDF7 activated AMPK through a downregulated stimulator of interferon gene (STING) in vivo and in vitro.

Conclusion

GDF7 prevents LPS-induced inflammatory response, oxidative stress, and ALI by regulating the STING/AMPK pathway. Our findings for the first time identify GDF7 as a potential agent for the treatment of sepsis-induced ALI.

Growth and differentiation factor-7 immobilized, mechanically strong quadrol-hexamethylene diisocyanate-methacrylic anhydride polyurethane polymer for tendon repair and regeneration

Biological and mechanical cues are both vital for biomaterial aided tendon repair and regeneration. Here, we fabricated mechanically tendon-like (0 s UV) QHM polyurethane scaffolds (Q: Quadrol, H: Hexamethylene diisocyanate; M: Methacrylic anhydride) and immobilized them with Growth and differentiation factor-7 (GDF-7) to produce mechanically strong and tenogenic scaffolds. In this study, we assessed QHM polymer cytocompatibility, amenability to fibrin-coating, immobilization and persistence of GDF-7, and capability to support GDF-7-mediated tendon differentiation in vitro as well as in vivo in mouse subcutaneous and acute rat rotator cuff tendon resection models. Cytocompatibility studies showed that QHM facilitated cell attachment, proliferation, and viability. Fibrin-coating and GDF-7 retention studies showed that mechanically tendon-like 0 s UV QHM polymer could be immobilized with GDF-7 and retained the growth factor (GF) for at least 1-week ex vivo. In vitro differentiation studies showed that GDF-7 mediated bone marrow-derived human mesenchymal stem cell (hMSC) tendon-like differentiation on 0 s UV QHM. Subcutaneous implantation of GDF-7-immobilized, fibrin-coated, QHM polymer in mice for 2 weeks demonstrated de novo formation of tendon-like tissue while implantation of GDF-7-immobilized, fibrin-coated, QHM polymer in a rat acute rotator cuff resection injury model indicated tendon-like tissue formation in situ and the absence of heterotopic ossification. Together, our work demonstrates a promising synthetic scaffold with human tendon-like biomechanical attributes as well as immobilized tenogenic GDF-7 for tendon repair and regeneration. STATEMENT OF SIGNIFICANCE: Biological activity and mechanical robustness are key features required for tendon-promoting biomaterials. While synthetic biomaterials can be mechanically robust, they often lack bioactivity. To biologically augment synthetic biomaterials, numerous drug and GF delivery strategies exist but the large tissue space within the shoulder is constantly flushed with saline during arthroscopic surgery, hindering efficacious controlled release of therapeutic molecules. Here, we coated QHM polymer (which exhibits human tendon-to-bone-like biomechanical attributes) with fibrin for GF binding. Unlike conventional drug delivery strategies, our approach utilizes immobilized GFs as opposed to released GFs for sustained, localized tissue regeneration. Our data demonstrated that GF immobilization can be broadly applied to synthetic biomaterials for enhancing bioactivity, and GDF-7-immobilized QHM exhibit high clinical translational potential for tendon repair.

Clinical perspectives for repairing rotator cuff injuries with multi-tissue regenerative approaches

Background

In the musculoskeletal system, bone, tendon, and muscle form highly integrated multi-tissue units such as the rotator cuff complex, which facilitates functional and dynamic movement of the shoulder joint. Understanding the intricate interplay among these tissues within clinical, biological, and engineering contexts is vital for addressing challenging issues in treatment of musculoskeletal disorders and injuries.

Methods

A wide-ranging literature search was performed, and findings related to the socioeconomic impact of rotator cuff tears, the structure-function relationship of rotator cuff bone-tendon-muscle units, pathophysiology of injury, current clinical treatments, recent state-of-the-art advances (stem cells, growth factors, and exosomes) as well as their regulatory approval, and future strategies aimed at engineering bone-tendon-muscle musculoskeletal units are outlined.

Results

Rotator cuff injuries are a significant socioeconomic burden on numerous healthcare systems that may be addressed by treating the rotator cuff as a single complex, given its highly integrated structure-function relationship as well as degenerative pathophysiology and limited healing in bone-tendon-muscle musculoskeletal tissues. Current clinical practices for treating rotator cuff injuries, including the use of commercially available devices and evolving trends in surgical management have benefited patients while advances in application of stem/progenitor cells, growth factors, and exosomes hold clinical potential. However, such efforts do not emphasize targeted regeneration of bone-tendon-muscle units. Strategies aimed at regenerating bone-tendon-muscle units are thus expected to address challenging issues in rotator cuff repair.

Conclusions

The rotator cuff is a highly integrated complex of bone-tendon-muscle units that when injured, has severe consequences for patients and healthcare systems. State-of-the-art clinical treatment as well as recent advances have resulted in improved patient outcome and may be further enhanced by engineering bone-tendon-muscle multi-tissue grafts as a potential strategy for rotator cuff injuries.

Translational Potential of this Article

This review aims to bridge clinical, tissue engineering, and biological aspects of rotator cuff repair and propose a novel therapeutic strategy by targeted regeneration of multi-tissue units. The presentation of these wide-ranging and multi-disciplinary concepts are broadly applicable to regenerative medicine applications for musculoskeletal and non-musculoskeletal tissues.

Retear rates after rotator cuff surgery: a systematic review and meta-analysis

Background

Rotator cuff retear (RCR) is one of the main postoperative drawbacks. RCR can be considered a multifactorial issue, which causes are related either to biological than biomechanical factors. The aim of this study was to define the incidence of RCR after surgical treatment at different time points and to identify the main factors influencing the postoperative rotator cuff (RC) healing.

Methods

A systematic review and meta-analysis were performed following the PRISMA guidelines. A comprehensive search of the literature was carried out in July 2020, using PubMed and Cochrane Library databases. Only level 1 and 2 clinical evidence studies were included. Studies were included if patients with preoperative repairable full-thickness RC tears were treated surgically, and if studies reported postoperative RCR confirmed by imaging diagnostic. The association between timing of retear and follow-up time points were investigated using an inverse-variance method of pooling data. A subgroup meta-analysis was performed using the DerSimonian and Laird method for the estimation of the between-study variance, i.e., τ². The association between retear rate after surgery and patients’ age, preoperative tear size, fatty infiltration, postoperative rehabilitation protocol, surgical techniques, and RC repairs was determined by expressing the effect measure in terms of odds ratio (OR) with 95% confidence interval (CI). The Mantel-Haenszel method with 95% CIs was used.

Results

Thirty-one articles were included in this study. The percentage of RCR after surgery was 15% at 3 months follow-up, 21% at 3–6 months follow-up, 16% at 6–12 months follow-up, 21% at 12–24 months follow-up, 16% at follow-up longer than 24 months. The main factors influencing RC healing are both patient-related (i.e., age, larger tear size, fatty infiltration) and not patient-related (i.e., postoperative rehabilitation protocol, surgical techniques, and procedures).

Conclusions

Postoperative RC healing is influenced by patient-related and non-patient-related factors. Further high-level clinical studies are needed to provide highly relevant clinical results.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04634-6.

Reporting and Analyzing Race and Ethnicity in Orthopaedic Clinical Trials: A Systematic Review

BACKGROUND

The distinction between race and ethnicity should be carefully understood and described for demographic data collection. Racial healthcare differences have been observed across many orthopaedic subspecialties. However, the frequency of reporting and analyzing race and ethnicity in orthopaedic clinical trials has not been determined. Therefore, the primary purpose of this systematic review was to determine how frequently race and ethnicity are reported and analyzed in orthopaedic clinical trials.

METHODS

The top 10 journals by impact factor in the field of orthopaedics were manually screened from 2015 to 2019. All randomized controlled trials related to orthopaedics and assessing clinical outcomes were included. Eligible studies were evaluated for bias using the Cochrane risk-of-bias tool and for whether the trial reported and analyzed several demographics, including age, sex, height, weight, race, and ethnicity. The frequency of reporting and analyzing by each demographic was accessed. In addition, comparisons of reporting and analyzing race/ethnicity were made based on orthopaedic subspecialty and journal of publication.

RESULTS

A total of 15,488 publications were screened and 482 met inclusion criteria. Of these 482 trials, 460 (95.4%) reported age and 456 (94.6%) reported sex, whereas 35 (7.3%) reported race and 15 (3.1%) reported ethnicity for the randomized groups; 79 studies (16.4%) analyzed age and 72 studies (14.9%) analyzed sex, whereas 6 studies (1.2%) analyzed race and 1 study (0.2%) analyzed ethnicity. The orthopaedic subspecialty of spine was found to report race (23.5%) and ethnicity (17.6%) more frequently than all the other subspecialties, whereas sports medicine reported race and/or ethnicity in only 3 of 150 trials (2.0%).

CONCLUSIONS

Race and ethnicity are not frequently reported or analyzed in orthopaedic randomized controlled trials. Social context, personal challenges, and economic challenges should be considered while analyzing the effect of race and ethnicity on outcomes.

Cell-Free Book-Shaped Decellularized Tendon Matrix Graft Capable of Controlled Release of BMP-12 to Improve Tendon Healing in a Rat Model

BACKGROUND

Achilles tendon (AT) defects often occur in traumatic and chronic injuries. Currently, no graft can satisfactorily regenerate parallel tendinous tissue at the defect site to completely restore AT function.

PURPOSE

To develop a cell-free functional graft by tethering bone morphogenetic protein 12 (BMP-12) on a book-shaped decellularized tendon matrix (BDTM) and to determine whether this graft is more beneficial for AT defect healing than an autograft.

STUDY DESIGN

Controlled laboratory study.

METHODS

Canine patellar tendon was sectioned into a book shape and decellularized to fabricate a BDTM. The collagen-binding domain (CBD) was fused into the N-terminus of BMP-12 to synthesize a recombinant BMP-12 (CBD-BMP-12), which was tethered to the BDTM to prepare a cell-free functional graft (CBD-BMP-12/BDTM). After its tensile resistance, tenogenic inducibility, and BMP-12 release dynamics were evaluated, the efficacy of the graft for tendon regeneration was determined in a rat model. A total of 140 mature male Sprague-Dawley rats underwent AT tenotomy. The defect was reconstructed with reversed AT (autograft group), native BMP-12 tethered to an intact decellularized tendon matrix (IDTM; NAT-BMP-12/IDTM group), native BMP-12 tethered to a BDTM (NAT-BMP-12/BDTM group), CBD-BMP-12 tethered on an IDTM (CBD-BMP-12/IDTM group), and CBD-BMP-12 tethered on a BDTM (CBD-BMP-12/BDTM group). The rats were sacrificed 4 or 8 weeks after surgery to harvest AT specimens. Six specimens from each group at each time point were used for histological evaluation; the remaining 8 specimens were used for biomechanical testing.

RESULTS

In vitro CBD-BMP-12/BDTM was noncytotoxic, showed high biomimetics with native tendons, was suitable for cell adhesion and growth, and had superior tenogenic inducibility. In vivo the defective AT in the CBD-BMP-12/BDTM group regenerated more naturally than in the other groups, as indicated by more spindle-shaped fibroblasts embedded in a matrix of parallel fibers. The biomechanical properties of the regenerated AT in the CBD-BMP-12/BDTM group also increased more significantly than in the other groups.

CONCLUSION

CBD-BMP-12/BDTM is more beneficial than autograft for healing AT defects in a rat model.

CLINICAL RELEVANCE

The findings of this study demonstrate that CBD-BMP-12/BDTM can serve as a practical graft for reconstructing AT defects.

Engineering multi-tissue units for regenerative Medicine: Bone-tendon-muscle units of the rotator cuff

Our body systems are comprised of numerous multi-tissue units. For the musculoskeletal system, one of the predominant functional units is comprised of bone, tendon/ligament, and muscle tissues working in tandem to facilitate locomotion. To successfully treat musculoskeletal injuries and diseases, critical consideration and thoughtful integration of clinical, biological, and engineering aspects are necessary to achieve translational bench-to-bedside research. In particular, identifying ideal biomaterial design specifications, understanding prior and recent tissue engineering advances, and judicious application of biomaterial and fabrication technologies will be crucial for addressing current clinical challenges in engineering multi-tissue units. Using rotator cuff tears as an example, insights relevant for engineering a bone-tendon-muscle multi-tissue unit are presented. This review highlights the tissue engineering strategies for musculoskeletal repair and regeneration with implications for other bone-tendon-muscle units, their derivatives, and analogous non-musculoskeletal tissue structures.

Reconstruction of large chronic rotator cuff tear can benefit from the bone-tendon composite autograft to restore the native bone-tendon interface

Purpose

We designed a paired controlled study to investigate the advantages of using bone–tendon composite autograft to reconstruct chronic rotator cuff tear compared with primary repair and provide some evidence to use the bone–tendon composite autograft.

Method

Thirty-eight Sprague–Dawley rats were used. The native bone–tendon junctions of supraspinatus and Achilles tendon insertion from two rats were harvested for gross and histological observation. Another thirty-six rats had bilateral supraspinatus tenotomy from the great tuberosity. Three weeks later, primary repair (simple tendon pullout direct repair to bone) was performed on one side and the other side was reconstructed using an Achilles–calcaneus composite autograft from the ipsilateral leg. Nine rats were sacrificed for biomechanical testing and another three were sacrificed for histological evaluation at 3, 6, and 9 weeks after surgery, respectively.

Results

The Achilles–calcaneus composite autograft group showed significantly better biomechanical characteristics at 3 and 6 weeks in terms of maximum load and stiffness. Tissue histology demonstrated an organised extracellular matrix, a clear tidemark, and distinct fibrocartilage layers in the composite graft group, similar to those of the native bone–tendon interface. Additionally, clear bone-to-bone healing and tendon-to-tendon healing were observed. By contrast, the conventional primary repair could not regenerate the structure of the native bone–tendon interface.

Conclusions

Bone–tendon autograft for chronic rotator cuff reconstruction is superior to the primary repair regarding biomechanical property and histological structure. Our study may provide some evidence in support of the reconstruction of a chronic rotator cuff tear using bone–tendon composite autografts in clinical practice.

The Translational potential of this article

The current study finds the bone-tendon autograft can restore the normal bone-tendon interface, which can not regenerate after repair and is the key factor affecting re-tear. The bone-tendon autografts from our body can be the candidates for rotator cuff tear reconstruction especially the large to massive rotator cuff tear in the future to reduce the re-tear after rotator cuff tear.

A Historical Analysis of Randomized Controlled Trials in Rotator Cuff Tears

Background and objectives: Our research aimed to evaluate the quality of reporting of randomized controlled trials (RCTs) linked to rotator cuff (RC) tears. The present study analyzed factors connected to the quality of the RCTs and trends in the quality of reporting through time. Materials and Methods: The online databases used to search all RCTs on the topic of RC surgery completed until March 2020 were PubMed and Ovid (MEDLINE). The quality of reporting was evaluated using the modified Coleman methodology score (MCMS) and the consolidated standards of reporting trials (CONSORT). Results: The online search found 957 articles. Finally, 183 studies were included in the quantitative synthesis. A total of 97 (53%) of 183 studies had a level of evidence I and 86 (47%) of 183 studies had a level of evidence II, according to the Oxford Center of Evidence Based Medicine (EBM). A statistically significant difference in MCMS between articles written before 2010 and articles written after 2010 was found. Articles written after 2010 had, on average, the highest Coleman score. The average number of CONSORT checklist items for each article across all analyzed RCTs was 21.67. The 37 studies completed up to 2010 averaged a number of checklist items of 19.97 and the studies completed between 2011 and 2019 averaged a number of checklist items of 22.10. A statistically significant difference in the number of checklist items between articles written before 2010 and articles written after 2010 was found. Articles written after 2010 had on average more checklist items. However, low correlation (0.26) between the number of checklist items for each article and the respective Coleman score was found. On the other hand, articles with the CONSORT diagram had a significantly high Coleman score. Conclusions: An improvement in the quantity and quality of RCTs relating to RC surgery over the analyzed period was found.

Atelocollagen Injection Improves Tendon Integrity in Partial-Thickness Rotator Cuff Tears: A Prospective Comparative Study

Background:

Ongoing controversy surrounds the best treatment modality for partial-thickness rotator cuff tears.

Purpose:

To investigate the effects of atelocollagen injection in patients with small, symptomatic, intratendinous rotator cuff tears.

Study Design:

Randomized controlled trial; Level of evidence, 1.

Methods:

From January 2014 to December 2017, 94 patients who had small, symptomatic, intratendinous rotator cuff tears were enrolled and randomly allocated to 1 of 3 groups: intratendinous injection with 0.5 mL of type I atelocollagen (group 1, n = 32), intratendinous injection with 1 mL of type I atelocollagen (group 2, n = 30), and no injection of type I atelocollagen (group 3, n = 32). American Shoulder and Elbow Surgeons score, Constant Shoulder Score, visual analog scale pain score, and range of motion were evaluated before injection; at 3, 6, and 12 months after injection; and at final follow-up. Magnetic resonance imaging (MRI) was performed at least 6 months after injection to evaluate rotator cuff integrity.

Results:

Demographic data did not differ significantly among the 3 groups before injection (P > .05). The mean follow-up period was 24.7 months. The functional and pain scores in groups 1 and 2 were significantly improved at final follow-up (P < .05). No significant improvement was seen in functional or pain scores at final follow-up in group 3 (P > .05). Groups 1 and 2 had significantly better functional scores compared with group 3 at final follow-up (P < .05). The proportion of patients with a decrease in size of the torn tendon on follow-up MRI at least 6 months after atelocollagen injection was significantly higher in group 1 (28.1%; P = .02) and group 2 (36.7%; P = .003) compared with group 3 (6.3%).

Conclusion:

Atelocollagen injection can improve the functional outcome and integrity of the tendon in intratendinous rotator cuff tears.

The Behavior of Tendon Progenitor Cells from Tendinopathic Tendons: Implications for Treatment

Tendinopathy remains a significant clinical challenge. Although there is some evidence that leukocyte-rich platelet-rich plasma can improve the symptoms of tendinopathy, more efficacious treatments will be required in the future to improve probability of successfully resolving this condition in athletes. Because optimal treatments are not currently available, there is a need to better understand the pathology of tendinopathy from the perspective of tendon progenitor cells (TPCs). TPCs isolated from normal and tendinopathy donors were characterized by their stem cell properties and proliferation capacities, along with their ability to become tenocytes under mechanical loading. The results showed a significant 2.6-fold increase in the viable cell population in tendinopathy versus normal donors. Although the percentage of self-renewing cells was similar, the total number of TPCs in tendinopathy was significantly higher (1.6-fold) than normal TPCs based on the colony formation assays. In contrast, TPCs from tendinopathy tissue showed significantly lower cellular proliferation rate by cumulative population doublings. Next, the expanded TPCs from both tissues successfully demonstrated the trilineage differentiation capabilities with specific gene markers, staining, and biochemical assays. To induce tenogenic differentiation, stretchable silicone wells were designed and fabricated, plus the creation of an adaptor platform used on a syringe pump for mechanical stretch. This economic design provided the adequate cyclic loading to drive tenogenic differentiation. With these devices, the stretch duration was optimized and showed the significant increase in scleraxis (SCX) and tenomodulin (TNMD) expression at 2.60 (fold change) and 3.86 (fold change in logarithm), respectively, by reverse transcription-quantitative polymerase chain reaction in normal TPCs after stretch. This assay also demonstrated the widespread cell reorientation following stretch in normal TPCs. In contrast, the mechanical loading did not increase the SCX gene expression; TNMD expression remained undetectable, and cell realignment was significantly less in tendinopathy TPCs. In addition, western blot analysis confirmed the elevated TNMD protein expression in normal TPCs following stretch and the lack of expression in tendinopathy TPCs. In summary, tendinopathy TPCs were unable to differentiate into tenocytes following mechanical stretch. Future studies may aim to reprogram tendinopathy TPCs to allow tenogenic induction. Impact Statement This article presents a model to distinguish between normal and tendinopathy progenitor cell behavior, which reveals insight into the pathophysiology of tendinopathy. With the design of a platform adaptor, mechanical stretch was applied to tendon progenitor cells (TPCs) that promoted tenogenic differentiation. This design provided programmable features for more flexible application with low cost. These devices successfully stimulated tenogenic differentiation of TPCs from normal, but not tendinopathic tendons under cyclic stretch. The scientific method provided in this article will allow testing of biologics, exosomes, and other treatment strategies to derive new, more efficient treatment of tendinopathy in the future.

Enhancement of rotator cuff tendon-bone healing using bone marrow-stimulating technique along with hyaluronic acid

Objective

The purpose of this study was to investigate the effect of hyaluronic acid (HA) in the tendon–bone healing process after rotator cuff repair in a rabbit model.

Methods

In vitro, rat bone marrow stromal cells (rBMSCs) were cultured in media for cartilage-related and inflammation-related gene expression levels examination at 1.0 mg/mL of HA. In vivo, 48 New Zealand white rabbits underwent rotator cuff repair surgery, and they were randomly divided into three groups: (1) control group (n = 16), (2) microfracture (MF) group accepting MF treatment (n = 16) and (3) MF/HA group accepting MF with HA treatment (n = 16). Four rabbits from each group were sacrificed at 6 and 12 weeks postoperatively for histological evaluation and biomechanical testing.

Results

In vitro experiments reveal that HA significantly decreased inflammation-related mRNA expression (IL-1, TNFα) compared with the control group. At 6 weeks after surgery, there was no significant difference of load-to-failure between groups. At 12 weeks after surgery, the mean failure load of the MF/HA group was significantly higher than that of the control group (100.5 ± 10.1 N vs. 68.0 ± 6.2 N; p = 0.0115). The mean failure load of the MF group appeared higher than that of the control group, whereas there was no significant difference (p > 0.05). Histologically, more chondrocytes were clustered at the tendon–bone interface, and more extracellular matrixes were produced in the MF/HA group. The interface of the MF/HA group appeared similar with the normal tendon–bone interface.

Conclusion

HA may play a crucial role in the acceleration of tendon-to-bone healing which might be through inhibiting inflammation. Rotator cuff repair using MF along with HA led to better tendon–bone healing and a subsequent increase of biomechanical strength at the repair site.

The translational potential of this article

HA injection is very common for patients with rotator cuff disease because of its antiinflammatory action and adhesion prevention preoperatively. The HA injection during surgery provides an antiinflammatory effect during tendon–bone healing process and leads to better tendon–bone healing postoperatively.

The Collagen Suprafamily: From Biosynthesis to Advanced Biomaterial Development

Collagen is the oldest and most abundant extracellular matrix protein that has found many applications in food, cosmetic, pharmaceutical, and biomedical industries. First, an overview of the family of collagens and their respective structures, conformation, and biosynthesis is provided. The advances and shortfalls of various collagen preparations (e.g., mammalian/marine extracted collagen, cell-produced collagens, recombinant collagens, and collagen-like peptides) and crosslinking technologies (e.g., chemical, physical, and biological) are then critically discussed. Subsequently, an array of structural, thermal, mechanical, biochemical, and biological assays is examined, which are developed to analyze and characterize collagenous structures. Lastly, a comprehensive review is provided on how advances in engineering, chemistry, and biology have enabled the development of bioactive, 3D structures (e.g., tissue grafts, biomaterials, cell-assembled tissue equivalents) that closely imitate native supramolecular assemblies and have the capacity to deliver in a localized and sustained manner viable cell populations and/or bioactive/therapeutic molecules. Clearly, collagens have a long history in both evolution and biotechnology and continue to offer both challenges and exciting opportunities in regenerative medicine as nature's biomaterial of choice.

Concise Review: Stem Cell Fate Guided By Bioactive Molecules for Tendon Regeneration

Tendon disorders, which are commonly presented in the clinical setting, disrupt the patients' normal work and life routines, and they damage the careers of athletes. However, there is still no effective treatment for tendon disorders. In the field of tissue engineering, the potential of the therapeutic application of exogenous stem cells to treat tendon pathology has been demonstrated to be promising. With the development of stem cell biology and chemical biology, strategies that use inductive tenogenic factors to program stem cell fate in situ are the most easily and readily translatable to clinical applications. In this review, we focus on bioactive molecules that can potentially induce tenogenesis in adult stem cells, and we summarize the various differentiation factors found in comparative studies. Moreover, we discuss the molecular regulatory mechanisms of tenogenesis, and we examine the various challenges in developing standardized protocols for achieving efficient and reproducible tenogenesis. Finally, we discuss and predict future directions for tendon regeneration. Stem Cells Translational Medicine 2018;7:404-414.

Local rhBMP-12 on an Absorbable Collagen Sponge as an Adjuvant Therapy for Rotator Cuff Repair-A Phase 1, Randomized, Standard of Care Control, Multicenter Study: Part 2-A Pilot Study of Functional Recovery and Structural Outcomes

BACKGROUND

The high failure rate of rotator cuff repairs requires the development of methods to enhance healing at the tendon-bone junction of the repair site.

PURPOSE

To assess functional recovery and structural outcomes in detail after implanting recombinant human bone morphogenetic protein-12 (rhBMP-12)/absorbable collagen sponge (ACS) as adjuvant treatment during open rotator cuff repair in patients over a 1-year postoperative follow-up.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 20 patients were randomized into 2 groups, rhBMP-12/ACS and standard-of-care (SOC) control, with 16 and 4 patients, respectively. The patients underwent open repair of a rotator cuff tear at least 2 to 4 cm wide; in the rhBMP-12/ACS group, this was augmented with a bioscaffold containing rhBMP-12. Follow-up assessments were conducted with a 100-mm visual analog scale (VAS) for pain and active and passive ranges of motion (ROMs) including forward flexion, elevation in the scapular plane, abduction, and external rotation at 12, 16, 26, 39, and 52 weeks after surgery; isometric strength in scapular abduction and external rotation at 16, 26, 39, and 52 weeks; and magnetic resonance imaging (MRI) at 12 and 52 weeks.

RESULTS

The mean VAS score decreased from 37.9 mm preoperatively to 13.8 mm at week 52, and ROM and isometric strength recovered at week 52 in the rhBMP-12/ACS group. The mean VAS score decreased from 48.3 mm preoperatively to 1.5 mm at week 52, and ROM (excluding external rotation) and isometric strength recovered by week 52 in the SOC control group. Of the 16 patients in the rhBMP-12/ACS group, 14 showed an intact repair at week 12; the MRI scans of the other 2 patients could not be evaluated because of artifacts. In the SOC control group, 1 patient showed repair failure. At week 52, 14 repairs in the rhBMP-12/ACS group and 2 repairs with available MRI scans in the SOC control group remained intact.

CONCLUSION

Functional recovery and structural outcomes in patients in whom rhBMP-12/ACS was used as adjuvant therapy in rotator cuff repair justify conducting future, larger, multicenter, prospective studies.

REGISTRATION

NCT00936559, NCT01122498 (ClinicalTrials.gov identifier).

Current concepts on tenogenic differentiation and clinical applications

Tendon is a tissue that transmits force from muscle to bone. Chronic or acute tendon injuries are very common, and are always accompanied by pain and a limited range of motion in patients. In clinical settings, management of tendon injuries still remains a big challenge. Cell therapies, such as the application of stem cells for tenogenic differentiation, were suggested to be an ideal strategy for clinical translation. However, there is still a lack of specific methods for tenogenic differentiation due to the limited understanding of tendon biology currently. This review focuses on the summary of current published strategies for tenogenic differentiation, such as the application of growth factors, mechanical stimulation, biomaterials, coculture, or induced pluripotent stem cells. Current clinical applications of stem cells for treatment of tendon injuries and their limitations have also been discussed in this review.