Bone marrow-derived mesenchymal stem cells obtained during arthroscopic rotator cuff repair surgery show potential for tendon cell differentiation after treatment with insulin

The addition of mesenchymal stem cells in a bioabsorbable scaffold does not enhance tendon healing after a repair of rotator cuff tear

PURPOSE

The purpose of the study is to evaluate the healing potential of a full-thickness tendon defect in the rotator cuff of rabbits using a bioabsorbable scaffold impregnated with bone marrow-mesenchymal stem cells (BM-MSCs) or rotator cuff-derived mesenchymal stem cells (RC-MSCs).

METHODS

Sixteen adult rabbits were subjected to a full-thickness rotator cuff deficit. Rabbits were randomly assigned to four groups of four animals. In Group 0 (control), the deficit was left untreated. In Group 1, the deficit was treated with a single synthetic scaffold alone. In Group 2, the deficit was treated with the previous scaffold loaded with allogeneic BM-MSCs. In Group 3, the deficit was treated with the previous scaffold loaded with allogenic RC-MSCs. After animal sacrifice, tissue samples were subjected to histological and immunohistochemical analysis.

RESULTS

Group 1 showed the highest mean tendon maturing score (15.3 ± 0.9) postoperatively, being significantly higher, in comparison to groups 0, 2 and 3 (p = 0.01, 0.02 and 0.01, respectively). Group 1 showed the highest mean collagen I/collagen III ratio (1.4 ± 0.8) postoperatively but without any statistical significance.

CONCLUSIONS

The utilization of MSCs in rotator cuff repair in a rabbit model has not been associated with an enhancement in tendon healing in 16 weeks postoperatively, in comparison to controls and bioabsorbable scaffolds. The addition of MSCs does not result in better rotator cuff healing.

LEVEL OF EVIDENCE

Not applicable. This is an animal study.

Bone Marrow Stimulation Does Not Lead to Lower Retear Rates, Better Functional Outcomes, or Higher Complication Rates at Short-Term Follow-Up for Arthroscopic Rotator Cuff Repair: A Meta-analysis of Randomized Controlled Trials

PURPOSE

To determine the effect of bone marrow stimulation (BMS) on retear rates, functional outcomes, and complication rates in patients who underwent arthroscopic rotator cuff repair (RCR) through a meta-analysis of randomized controlled trials.

METHODS

PubMed, EMBASE, Web of Science, and The Cochrane Library were searched on March 25, 2023. Two evaluators independently screened the literature, extracted data, and assessed the methodologic quality of the enrolled studies. Meta-analysis was conducted using RevMan software, version 5.4.

RESULTS

A total of 7 randomized controlled trials with 638 patients were included. The evaluation of rotator cuff tendon integrity was conducted using distinct imaging modalities. Specifically, 259 patients underwent magnetic resonance imaging whereas 208 patients underwent ultrasound. Additionally, a subset of 95 patients underwent either of these modalities; however, the precise distribution between these 2 modalities was not explicitly delineated. Compared with RCR alone, RCR combined with BMS provided similar retear rates (P = .51, I2 = 46%), Constant-Murley scores (P = .14, I2 = 0%), American Shoulder and Elbow Surgeons (standardized shoulder assessment form) scores (P = .56, I2 = 0%), Western Ontario Rotator Cuff Index scores (P = .20, I2 = 0%), visual analog scale scores (P = .19, I2 = 0%), forward flexion (P = .18, I2 = 0%), external rotation (P = .62, I2 = 0%), severe complication rates (P = .56, I2 = 0%), and mild complication rates (P = .10, I2 = 0%).

CONCLUSIONS

Compared with the outcomes observed after isolated arthroscopic RCR, arthroscopic RCR with BMS showed comparable results in terms of retear rate, functional outcomes, and incidence of complications.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level I and II studies.

A network meta-analysis of arthroscopic rotator cuff repair

OBJECTIVE

Rotator cuff tear is a common shoulder injury that often leads to serious limitations in daily life. Herein, a network Meta-analysis using frequency theory was performed to evaluate the clinical outcomes of five rotator cuff repair techniques, including single-row repair, double-row repair, suture bridge repair, platelet-rich plasma therapy, and bone marrow stimulation, thus guiding clinical decision-making on rotator cuff repair.

METHODS

PubMed, EMbase, The Cochrane Library, and Web of Science were searched for randomized controlled trials and cohort studies comparing rotator cuff repair techniques published from inception to May 2022. Combined analysis and quality assessment were performed using software STATA15.1 and Review Manager5.3.

RESULTS

A total of 51 articles were finally included, including 27 randomized controlled trials and 24 cohort studies. Results from the network Meta-analysis showed that: (1) In terms of the American Shoulder and Elbow Surgeons score, platelet-rich plasma therapy, double-row repair, bone marrow stimulation, and single-row repair were significantly better than suture bridge repair. (2) In terms of Constant score, bone marrow stimulation was significantly better than double-row repair, single-row repair, and suture bridge repair. (3) In terms of visual analog scale score, platelet-rich plasma therapy was significantly better than double-row repair and suture bridge repair. (4) In terms of the Shoulder Rating Scale of the University of California at Los Angeles score, platelet-rich plasma therapy and double-row repair were relatively better but not significantly different from the other treatments. (5) In terms of the risk of re-tear, the re-tear rate of platelet-rich plasma therapy and double-row repair was significantly lower than that of single-row repair and suture bridge repair.

CONCLUSION

Based on the results of network Meta-analysis and surface under the cumulative ranking, platelet-rich plasma therapy, bone marrow stimulation, and double-row repair have good overall rehabilitation effects. It is recommended to choose appropriate repair techniques as per the actual clinical situation.

Insulin-Functionalized Bioactive Fiber Matrices with Bone Marrow-Derived Stem Cells in Rat Achilles Tendon Regeneration

Approximately half of annual musculoskeletal injuries in the US involve tendon tears. The naturally hypocellular and hypovascular tendon environment makes tendons injury-prone and heal slowly. Tendon tissue engineering strategies often use biomimetic scaffolds combined with bioactive factors and/or cells to enhance healing. FDA-approved growth factors to promote tendon healing are lacking, which highlights the need for safe and effective bioactive factors. Our previous work evaluated insulin as a bioactive factor and identified an optimal dose to promote in vitro mesenchymal stem cell survival, division, and tenogenesis. The present work evaluates the ability of insulin-functionalized electrospun nanofiber matrices with or without mesenchymal stem cells to enhance tendon repair in a rat Achilles injury model. Electrospun nanofiber matrices were functionalized with insulin, cultured with or without mesenchymal stem cells, and sutured to transected Achilles tendons in rats. We analyzed rat tendons 4 and 8 weeks after surgery for the tendon morphology, collagen production, and mechanical properties. Bioactive insulin-functionalized fiber matrices with mesenchymal stem cells resulted in significantly increased collagen I and III at 4 and 8 weeks postsurgery. Additionally, these matrices supported highly aligned collagen fibrils in the regenerated tendon tissue at 8 weeks. However, treatment- and control-regenerated tissues had similar tensile properties at 8 weeks, which were less than that of the native Achilles tendon. Our preliminary results establish the benefits of insulin-functionalized fiber matrices in promoting higher levels of collagen synthesis and alignment needed for functional recovery of tendon repair.

Mesenchymal Stem Cells From a Hypoxic Culture Can Improve Rotator Cuff Tear Repair

A rotator cuff tear is an age-related common cause of pain and disability. Studies including our previously published ones have demonstrated that mesenchymal stem cells cultured under hypoxic conditions [hypoxic multipotent stromal cells (MSCs)] facilitate the retention of transplanted cells and promote wound healing. However, there are very few, if any, reports targeting the punctured supraspinatus tendons to create more or equally serous wounds as age-related tears of rotator cuff. It remains to be determined whether transplantation of bone-marrow-derived hypoxic MSCs into the punctured supraspinatus tendon improves tendon repair and, when combined with ultrasound-guided delivery, could be used for future clinical applications. In this study, we used a total of 33 Sprague-Dawley rats in different groups for normal no-punched control, hypoxic MSC treatment, nontreated vehicle control, and MSC preparation, and then evaluated treatment outcomes by biomechanical testing and histological analysis. We found that the ultimate failure load of the hypoxic MSC-treated group was close to that of the normal tendon and significantly greater than that of the nontreated vehicle control group. In vivo tracking of cells labeled with superparamagnetic iron oxide (SPIO) nanoparticles revealed an enhanced retention of transplanted cells at the tear site. Our study demonstrates that hypoxic MSCs improve rotator cuff tear repair in a rat model.

Anatomic based microfracture technique of insertion for rotator cuff repair in Vietnamese people: Case series study

Abstract

Postoperative tendon healing is still a matter of concern after rotator cuff repair. Several techniques have been introduced to help improve this healing process. Among them, the bone marrow is commonly used source and a research subject for methods using stem cells to promote wound healing process. A number of studies have shown that bone marrow stem cells can travel up through the holes on the rotator cuff insertion sites, contributing into the rotator cuff repair process, increasing the efficiency of tendon healing and improving clinical results.

Patients and methods

Cross-sectional descriptive study was performed on 41 rotator cuff tear patients. The microfractures for these patients were calculated beforehand, which have great depth but small diameter, based on the anatomical characteristic of the rotator cuff tear insertions of Vietnamese people. Patients' rotator cuff tendon healing processes were evaluated using ultrasound after surgery. Final tendon healing and clinical results ultimately rely on MRI assessments, classified according to Sugaya's classification, UCLA and ASES scale.

Results

No cases of rupture and fracture of the greater tubercle was recorded. There was a clear progression of tendon healing on ultrasound according to postoperative follow-up time-stamps (1 month, 3 months). MRI images evaluation also reveals at the latest follow-up time, according to Sugaya classification, the ratio of tendon healing was 87.8%, while the percentage of re-rupture was 12.2%. ASES and average UCLA scale were collected at the end of the study, respectively as 95.41 ± 5.45 and 32.36 ± 2.53.

Conclusion

The technique's microfractures characteristics based on the rotator cuff tear insertion anatomy ensures a secure, straightforward approach along with promising results in terms of tendon healing rate and postoperative functional outcomes.

Nonoperative and Operative Soft-Tissue, Cartilage, and Bony Regeneration and Orthopaedic Biologics of the Shoulder: An Orthoregeneration Network (ON) Foundation Review

Orthoregeneration is defined as a solution for orthopaedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and optimally, provide an environment for tissue regeneration. Options include drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electro-magnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the shoulder including the rotator cuff tendons, glenohumeral articular cartilage, glenoid labrum, the joint capsule, and bone. Promising and established treatment modalities include hyaluronic acid (HA); platelet-rich plasma (PRP) and platelet rich concentrates (PRC); bone marrow aspirate (BMA) comprising mesenchymal stromal cells (MSCs alternatively termed medicinal signaling cells and frequently, misleadingly labelled "mesenchymal stem cells"); MSC harvested from adipose, umbilical, or placental sources; factors including vascular endothelial growth factors (VEGF), basic fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGFβ), bone morphogenic protein (BMP), and matrix metalloproteinases (MMPs); prolotherapy; pulsed electromagnetic field therapy; microfracture and other marrow-stimulation techniques; biologic resurfacing using acellular dermal allografts, allograft Achilles tendons, allograft lateral menisci, fascia lata autografts, and porcine xenografts; osteochondral autograft or allograft); and autologous chondrocyte implantation (ACI). Studies involving hyaluronic acid, platelet rich plasma, and medicinal signaling cells of various origin tissues have shown mixed results to-date as isolated treatments and as surgical adjuncts. Despite varied results thus far, there is great potential for improved efficacy with refinement of current techniques and translation of burgeoning preclinical work. LEVEL OF EVIDENCE: Level V, expert opinion.

The impact of type 2 diabetes on the development of tendinopathy

Tendinopathy is a chronic and often painful condition affecting both professional athletes and sedentary subjects. It is a multi-etiological disorder caused by the interplay among overload, ageing, smoking, obesity (OB) and type 2 diabetes (T2D). Several studies have identified a strong association between tendinopathy and T2D, with increased risk of tendon pain, rupture and worse outcomes after tendon repair in patients with T2D. Moreover, consequent immobilization due to tendon disorder has a strong impact on diabetes management by reducing physical activity and worsening the quality of life. Multiple investigations have been performed to analyse the causal role of the individual metabolic factors occurring in T2D on the development of tendinopathy. Chronic hyperglycaemia, advanced glycation end-products, OB and insulin resistance have been shown to contribute to the development of diabetic tendinopathy. This review aims to explore the relationship between tendinopathy and T2D, in order to define the contribution of metabolic factors involved in the degenerative process and to discuss possible strategies for the clinical management of diabetic tendinopathy.

The glucagon-like peptide 1 receptor agonist Exendin-4 induces tenogenesis in human mesenchymal stem cells

Tendon injuries are common and account for up to 50% of musculoskeletal injuries in the United States. The poor healing nature of the tendon is attributed to poor vascularization and cellular composition. In the absence of FDA-approved growth factors for tendon repair, engineering strategies using bioactive factors, donor cells, and delivery matrices to promote tendon repair and regeneration are being explored. Growth factor alternatives in the form of small molecules, donor cells, and progenitors offer several advantages and enhance the tendon healing response. Small drug molecules and peptides offer stability over growth factors that are known to suffer from relatively short biological half-lives. The primary focus of this study was to assess the ability of the exendin-4 (Ex-4) peptide, a glucagon-like peptide 1 (GLP-1) receptor agonist, to induce tenocyte differentiation in bone marrow-derived human mesenchymal stem cells (hMSCs). We treated hMSCs with varied doses of Ex-4 in culture media to evaluate proliferation and tendonogenic differentiation. A 20 nM Ex-4 concentration was optimal for promoting cell proliferation and tendonogenic differentiation. Tendonogenic differentiation of hMSCs was evaluated via gene expression profile, immunofluorescence, and biochemical analyses. Collectively, the levels of tendon-related transcription factors (Mkx and Scx) and extracellular matrix (Col-I, Dcn, Bgn, and Tnc) genes and proteins were elevated compared to media without Ex-4 and other controls including insulin and IGF-1 treatments. The tendonogenic factor Ex-4 in conjunction with hMSCs appear to enhance tendon regeneration.

The Effect of Insulin and Insulin-like Growth Factor 1 (IGF-1) on Cellular Proliferation and Migration of Human Subacromial Bursa Tissue

Purpose

To evaluate the effect of a one-time dose of insulin or insulin-like growth factor 1 (IGF-1) on cellular proliferation and migration of subacromial bursa tissue (SBT) over time.

Methods

SBT was harvested from over the rotator cuff tendon in 4 consecutive patients undergoing primary arthroscopic rotator cuff repair. SBT was cultured for 3 weeks in complete media until reaching confluence. The culture dishes were stored in a humidified, low oxygen tension (5% CO₂) incubator at 37°C. SBT of each patient underwent treatment with a one-time dose of insulin or IGF-1, whereas nontreated SBT served as a negative control. Cellular proliferation and migration were evaluated after 24, 48, 72, and 96 hours of incubation. SBT-derived cells migrated in the detection field were visualized using fluorescent microscopy.

Results

Cellular proliferation at 24, 48, 72, and 96 hours was 1.40 ± 0.27, 1.00 ± 0.20, 1.47 ± 0.31, and 1.68 ± 0.28 for IGF-1; 1.44 ± 0.24, 1.15 ± 0.27, 1.60 ± 0.36, and 1.61 ± 0.32 for insulin; and 1.51 ± 0.35, 1.29 ± 0.33, 1.53 ± 0.35, and 1.57 ± 0.38 for nontreated SBT. Untreated SBT demonstrated a significantly greater proliferation when compared with IGF-1 and insulin within the first 48 hours, although this effect was found to subside by 96 hours. Cellular migration at 24, 48, 72, and 96 hours was 575.7 ± 45.0, 641.6 ± 77.7, 728.3 ± 122.9, and 752.3 ± 114.5 for IGF-1; 528.4 ± 31.3, 592.5 ± 69.8, 664.2 ± 115.2, and 695.6 ± 148.2 for insulin; and 524.4 ± 41.9, 564.4 ± 49.8, 653.2 ± 81.5, and 685.7 ± 115.5 for nontreated SBT. Insulin showed no difference in migration at each timepoint compared to nontreated SBT (P > .05, respectively).

Conclusions

Insulin and IGF-1 initially inhibit cellular proliferation of human SBT, although this effect was found to subside by 96 hours. Further, neither insulin nor IGF-1 changed the slope of cellular migration over time. However, each treatment group demonstrated a significant increase in cellular proliferation and migration.

Clinical Relevance

In the setting of biologic augmentation of rotator cuff repair, the compatibility and synergistic effect of insulin on human SBT is highly limited.

The Role of Collagen-Based Biomaterials in Chronic Wound Healing and Sports Medicine Applications

Advancements in tissue engineering have taken aim at treating tissue types that have difficulty healing naturally. In order to achieve improved healing conditions, the balance of exogenous matrix, cells, and different factors must be carefully controlled. This review seeks to explore the aspects of tissue engineering in specific tissue types treated in sports medicine and advanced wound management from the perspective of the matrix component. While the predominant material to be discussed is collagen I, it would be remiss not to mention its relation to the other contributing factors to tissue engineered healing. The main categories of materials summarized here are (1) reconstituted collagen scaffolds, (2) decellularized matrix tissue, and (3) non-decellularized tissue. These three groups are ordered by their increase in additional components beyond simply collagen.

Superiority of synovial membrane mesenchymal stem cells in chondrogenesis, osteogenesis, myogenesis and tenogenesis in a rabbit model

Engineering complex tissues is perhaps the most ambitious goal of all tissue engineers. Despite significant advances in tissue engineering, which have resulted in successful engineering of simple tissues such as skin and cartilage, there are a number of challenges that remain in engineering of complex, hybrid tissue structures, such as osteochondral tissue. Mesenchymal stem cells (MSCs) have the capacity to highly proliferate in an undifferentiated state and the potential to differentiate into a variety of different lineages, providing a promising single cell source to produce multiple cell types. MSC obtained from adult human contribute to the regeneration of mesenchymal tissues such as bone, cartilage, fat, muscle, tendon and marrow stroma. In the present study, the regeneration capacity of multipotent MSCs derived from different tissues in the rabbit were compared. Specifically the aim of this study was to isolate and characterize rabbit adult stem cell populations from bone marrow, adipose, synovial membrane, rotator cuff, ligament and tendon and assess their cell morphology, growth rate, cell surface markers and differentiation capacity. MSCs derived from synovial membrane showed superiority in terms of chondrogenesis, osteogenesis, myogenesis and tenogenesis, suggesting that synovial membrane-derived MSCs would be a good candidate for efforts to regenerate musculoskeletal tissues.

Analysis of Time to Form Colony Units for Connective Tissue Progenitor Cells (Stem Cells) Harvested From Concentrated Bone Marrow Aspirate and Subacromial Bursa Tissue in Patients Undergoing Rotator Cuff Repair

Purpose

To evaluate the time required for colonies to develop from concentrated bone marrow aspirate (cBMA) and subacromial bursal tissue samples.

Methods

Samples of cBMA and subacromial bursa tissue were harvested from patients undergoing rotator cuff repair surgery between November 2014 and December 2019. Samples were analyzed for time to form colonies and number of colonies formed. The impact of age, sex, and cellularity (cBMA only) was analyzed. Samples were cultured and evaluated daily for colony formation in accordance with the guidelines of the International Society for Cellular Therapy. Demographic factors were analyzed for impact on time to form colonies and number of colonies formed.

Results

Samples of cBMA were obtained from 92 patients. Subacromial bursa tissue was obtained from 54 patients. For cBMA, older age was associated with more days to form colonies (P = .003), but sex (P = .955) and cellularity (P = .623) were not. For bursa, increased age was associated with longer time to form colonies (P = .002) but not sex (P = .804). Conclusions: Increased age (in cBMA and subacromial bursa tissue) and lower initial cellularity (in cBMA) are associated with longer time to form colonies in culture.

Clinical Relevance

Although connective tissue progenitor cells are widely used in orthopaedic practice, there are few metrics to determine their efficacy. Time to form colonies may serve as an important measurement for determining connective tissue progenitor cell viability for augmentation of rotator cuff repair. Subacromial bursa tissue may represent a viable alternative to cBMA for augmentation of rotator cuff repair, capable of forming colonies expediently in vivo.

Human bone marrow-derived mesenchymal stem cells from different bone sources: a panorama

Regenerative medicine is a promising field in orthopaedic surgery. Although surgical treatments can produce excellent outcomes and may be the best choice for some patients, regenerative medicine can provide with more minimally-invasive treatment options. Mesenchymal stem cells (MSCs) are multipotent cells and are highly capable to differentiate into osteocytes or chondrocytes, while they can be isolated from different bone sources. The bone marrow aspiration from the posterior iliac crest appears to be preferred, as it provided a modestly higher concentration of nucleated cells [(25.1-54.7)×10⁶ cells/mL]. MSCs are also easily obtained from other bone sources, such as humerus, femur, tibia, vertebral body or calcaneus and have their content ranges between 5.8×10⁶ and 38.7×10⁶ nucleated cells. Although, they present a wide range of documented nucleated cells, they can be cultivated and expanded in vitro in multiple cell types, avoiding a second surgical site while preventing post-operative pain and the possible risk for infection. Thus, they represent a promising and encouraging treatment option in orthopaedic surgery.

The Role of Biologic Agents in the Non-operative Management of Elbow Ulnar Collateral Ligament Injuries

PURPOSE OF REVIEW

Injuries to the elbow ulnar collateral ligament (UCL) are especially common in the overhead throwing athlete. Despite preventative measures, these injuries are occurring at increasing rates in athletes of all levels. UCL reconstruction techniques generally require a prolonged recovery period and introduce the potential for intraoperative complications prompting investigations into more conservative treatment measures based on specific patient and injury characteristics. The purpose of this review is to describe the current literature regarding the use of biologic augmentation in the management of UCL injuries. Specifically, this review will focus on the basic science background and clinical investigations pertaining to biologic augmentation utilizing platelet-rich plasma (PRP) and autologous stem cells.

RECENT FINDINGS

Despite some evidence supporting the use of PRP therapy in patients with partial UCL tears, there is no current consensus regarding its true efficacy. Similarly, due to a lack of clinical investigations, no consensus exists regarding the utilization of autologous stem cell treatments in the management of UCL injuries. Management of UCL injuries ranges from non-operative treatment with focused physical therapy protocols to operative reconstruction. The use of biologic augmentation in these injuries continues to be investigated in the orthopedic community. Currently, no consensus exists regarding the efficacy of either PRP or autologous stem cells and further research is needed to further define the appropriate role of these treatments in the management of UCL injuries.

Editorial Commentary: Innovations in Anchor Design-Are Patients Really Benefiting?

Vented open-architecture suture anchors provide theoretical benefits over traditional screw-in solid anchors to include improved osseous ingrowth, elution of marrow elements to enhance biology at the repair site, and easier revision because of reduced anchor material. However, there is no evidence that open-architecture anchors result in improvements in patient-reported outcomes or early cytokine and marrow element release into the subacromial space compared with traditional screw-in solid anchors. Although innovation and evaluation of new technologies are paramount to surgical progress, decisions on implant use should be based on factors including cost, impact on revision, and surgeon familiarity because frequently, clinical differences based on patient-reported outcomes are not appreciated between anchor types or designs.

Examining the Potency of Subacromial Bursal Cells as a Potential Augmentation for Rotator Cuff Healing: An In Vitro Study

PURPOSE

To compare the potency of mesenchymal stem cells between the cells derived from the subacromial bursa to concentrated bone marrow aspirate (cBMA) taken from patients undergoing rotator cuff (RC) repair.

METHODS

Subacromial bursa and cBMA were harvested arthroscopically from 13 patients (age 57.4 ± 5.2 years, mean ± standard deviation) undergoing arthroscopic primary RC repair. Bone marrow was aspirated from the proximal humerus and concentrated using an automated system (Angel System; Arthrex). Subacromial bursa was collected from 2 sites (over the RC tendon and muscle) and digested with collagenase to isolate a single cellular fraction. Proliferation, number of colony-forming units, differentiation potential, and gene expression were compared among the cells derived from each specimen.

RESULTS

The cells derived from subacromial bursa showed significantly higher proliferation compared with the cells derived from cBMA after 5, 7, and 10 days (P = .018). Regarding colony-forming units, the subacromial bursa had significantly more colonies than cBMA (P = .002). Subacromial bursal cells over the RC tendon produced significantly more colonies than cells over both the RC muscle and cBMA (P = .033 and P = .028, respectively). Moreover, when compared with cBMA, cells derived from subacromial bursa showed significantly higher differentiation ability and higher gene expression indicative of chondrogenesis, osteogenesis, and adipogenesis.

CONCLUSION

The subacromial bursa is an easily accessible tissue that can be obtained during RC repair, with significant pluripotent stem cell potency for tendon healing. Compared with cBMA taken from the proximal humerus, bursal cells showed significantly increased differentiation ability and gene expression over time.

CLINICAL RELEVANCE

Failed RC repairs have been partly attributed to a poor healing environment. Biologic augmentation of the repair site may help increase healing potential and incorporation of the cuff at the tendon-bone interface.

Insulin immobilized PCL-cellulose acetate micro-nanostructured fibrous scaffolds for tendon tissue engineering

Use of growth factors as biochemical molecules to elicit cellular differentiation is a common strategy in tissue engineering. However, limitations associated with growth factors, such as short half-life, high effective physiological doses, and high costs, have prompted the search for growth factor alternatives, such as growth factor mimics and other proteins. This work explores the use of insulin protein as a biochemical factor to aid in tendon healing and differentiation of cells on a biomimetic electrospun micro-nanostructured scaffold. Dose response studies were conducted using human mesenchymal stem cells (MSCs) in basal media supplemented with varied insulin concentrations. A dose of 100-ng/mL insulin showed increased expression of tendon markers. Synthetic-natural blends of various ratios of polycaprolactone (PCL) and cellulose acetate (CA) were used to fabricate micro-nanofibers to balance physicochemical properties of the scaffolds in terms of mechanical strength, hydrophilicity, and insulin delivery. A 75:25 ratio of PCL:CA was found to be optimal in promoting cellular attachment and insulin immobilization. Insulin insulin deliveryimmobilized fiber matrices also showed increased expression of tendon phenotypic markers by MSCs similar to findings with insulin supplemented media, indicating preservation of insulin bioactivity. Insulin functionalized scaffolds may have potential applications in tendon healing and regeneration.

Evaluating strategies and outcomes following rotator cuff tears

INTRODUCTION

Rotator cuff tear surgical repair techniques have significantly progressed. However, tendon retear following primary repair persistently occurs at high rates. Rehabilitation protocols, surgical fixation techniques, biologic therapy with scaffolds, platelet-rich plasma, and even stem cell applications are under study to promote adequate tendon healing.

METHODS

A nonsystematic query of the PubMed database was conducted in July 2016 utilizing the search terms "rotator cuff repair," "tear," "rehabilitation," "scaffold," "platelet-rich plasma," and "stem cell" to identify, analyze, and summarize relevant studies.

CONCLUSION

Individualized rehabilitation protocols may be the best approach for small to medium sized tears. Surgical fixation will continue to be debated as modifications to single-row technique and increases in suture number have improved tensile strength. Double-row repairs have been associated with higher costs. Transosseous equivalent technique exhibits comparable subjective and objective outcomes to single- and double-row repair at two-year follow-up. Biocompatible scaffold augmentation has showed inconsistent short-term results. Platelet-rich plasma has lacked uniformity in treatment preparation, administration, and outcome measurement with mixed results. Few human studies have suggested decreased retear rates and improved repair maintenance following bone marrow-derived mesenchymal stem cell augmentation. This review reiterated the necessity of additional high-quality, large-sample studies to develop any final verdict regarding efficacy.

Magnetic Resonance Imaging and Biomechanical Analysis of Adipose-derived Stromal Vascular Fraction Applied on Rotator Cuff Repair in Rabbits

Background:

Adipose-derived stromal vascular fraction (ADSVF) can be applied to repair tendon and ligament tears. ADSVF treatment has a better therapeutic potential than adipose stem cells alone in promoting the healing of connective tissue injury in rabbit models. Magnetic resonance imaging (MRI) and biomechanical testing were used in this study to evaluate the efficiency of SVF in the healing of tendon-bone interface of a rotator cuff injury after reattachment.

Methods:

A total of 36 rabbits were studied between March and June 2016, 18 rabbits received the SVF-fibrin glue (SVF-FG) treatment and the other 18 formed the control group. ADSVF was isolated from each rabbit. A bilateral amputation of the supraspinatus tendon and parallel reconstruction was also performed on all the 36 rabbits. Then, a mixture of SVF and FG was injected into the tendon-bone interface of the SVF-FG group, whereas the control group only received FG. The animals were randomly sacrificed at 4, 8, and 12 weeks after surgery (n = 6 per group), respectively. The shoulders were prepared for MRI scanning and analysis of biomechanical properties. Analyses of variance were performed using SPSS 13.0.

Results:

MRI scanning showed that the signal-to-noise quotient of the SVF-FG group was not significantly higher than that of the control group at either 4 (20.1 ± 3.6 vs. 18.2 ± 3.4, F = 1.570, P = 0.232) or 8 weeks (20.7 ± 3.3 vs. 18.0 ± 3.0, F = 2.162, P = 0.117) posttreatment, and only became significant after 12 weeks (27.5 ± 4.6 vs. 22.1 ± 1.9, F = 4.968, P = 0.009). Biomechanical properties such as the maximum load, maximum strength, and the stiffness for the SVF-FG group were significantly greater than that for the control group at 8 weeks’ posttreatment (maximum load: 166.89 ± 11.62 N vs. 99.40 ± 5.70 N, P < 0.001; maximum strength: 8.22 ± 1.90 N/mm vs. 5.82 ±0.68 N/mm, P < 0.010; and the stiffness: 34.85± 3.00 Pa vs. 24.57± 5.72 Pa, P < 0.010).

Conclusion:

Local application of ADSVF might lead to better tendon-bone healing in rabbit models.

Characterization of Tendon-Specific Markers in Various Human Tissues, Tenocytes and Mesenchymal Stem Cells

Background

Unlike bone, cartilage, or muscle, tendon-specific markers are not well established. The purpose of the study was to investigate expression pattern and level of 6 well-known tendon-specific markers, in various human musculoskeletal tissues, tenocytes, and mesenchymal stem cells (MSCs).

Methods

Musculoskeletal tissue samples of tendon, bone, cartilage, nerve, muscle, and fat were obtained from patients undergoing orthopedic surgery. Tenocytes, MSCs from bone marrow, adipose tissue, and umbilical cord were isolated from each tissue and cultured. Six tendon-specific markers, scleraxis (Scx), tenomodulin (TNMD), thrombospondin-4 (TSP-4), tenascin-C (TNC), type I collagen (Col I), and type III collagen (Col III) were investigated in tendon tissue, tenocytes, and MSCs.

Results

mRNA levels of 6 tendon-specific markers were significantly higher in tendon tissue that in other connective tissues levels of Scx, TNMD, TSP-4, and Col III immediately decreased after plating tenocytes in culture dishes whereas those of TNC and Col I did not. In comparison with tendon tissue, mRNA levels pattern of Scx, TNMD, and TSP-4 in tenocytes were significantly higher than that in MSCs, but lower than in tendon tissue whereas expression pattern of TNC, Col I and III showed different pattern with each other.

Conclusion

This study demonstrated that 6 commonly used tendon-specific markers were mainly expressed in tendon tissue, but that expression level and pattern of the tendon-specific markers with respect to kinds of tissues, culture duration of tenocytes and sources of MSCs.

Editorial Commentary: Paving a Road Requires a Well-Mixed Cement Stem Cells, Platelet-Rich Plasma, and Shoulder Rotator Cuff Healing

The process of healing in musculoskeletal tissues is complex, and the addition of devices, including platelet-rich plasma and mesenchymal stem cells, to biologically enhance it may favor its optimization. This work shows in a compelling fashion that it is possible to produce the right admixture of physical and biological factors to make it happen in rotator cuff repair.

Regenerative Engineering of the Rotator Cuff of the Shoulder

Rotator cuff tears often heal poorly, leading to re-tears after repair. This is in part attributed to the low proliferative ability of the resident cells (tendon fibroblasts and tendon-stem cells) upon injury to the rotator cuff tissue and the low vascularity of the tendon insertion. In addition, surgical outcomes of current techniques used in clinical settings are often suboptimal, leading to the formation of neo-tissue with poor biomechanics and structural characteristics, which results in re-tears. This has prompted interest in a new approach, which we term as "Regenerative Engineering", for regenerating rotator cuff tendons. In the Regenerative Engineering paradigm, roles played by stem cells, scaffolds, growth factors/small molecules, the use of local physical forces, and morphogenesis interplayed with clinical surgery techniques may synchronously act, leading to synergistic effects and resulting in successful tissue regeneration. In this regard, various cell sources such as tendon fibroblasts and adult tissue-derived stem cells have been isolated, characterized, and investigated for regenerating rotator cuff tendons. Likewise, numerous scaffolds with varying architecture, geometry, and mechanical characteristics of biologic and synthetic origin have been developed. Furthermore, these scaffolds have been also fabricated with biochemical cues (growth factors and small molecules), facilitating tissue regeneration. In this Review, various strategies to regenerate rotator cuff tendons using stem cells, advanced materials, and factors in the setting of physical forces under the Regenerative Engineering paradigm are described.

Mechanical Actuation Systems for the Phenotype Commitment of Stem Cell-Based Tendon and Ligament Tissue Substitutes

High tensile forces transmitted by tendons and ligaments make them susceptible to tearing or complete rupture. The present standard reparative technique is the surgical implantation of auto- or allografts, which often undergo failure.Currently, different cell types and biomaterials are used to design tissue engineered substitutes. Mechanical stimulation driven by dedicated devices can precondition these constructs to a remarkable degree, mimicking the local in vivo environment. A large number of dynamic culture instruments have been developed and many appealing results collected. Of the cells that have been used, tendon stem cells are the most promising for a reliable stretch-induced tenogenesis, but their reduced availability represents a serious limitation to upscaled production. Biomaterials used for scaffold fabrication include both biological molecules and synthetic polymers, the latter being improved by nanotechnologies which reproduce the architecture of native tendons. In addition to cell type and scaffold material, other variables which must be defined in mechanostimulation protocols are the amplitude, frequency, duration and direction of the applied strain. The ideal conditions seem to be those producing intermittent tension rather than continuous loading. In any case, all physical parameters must be adapted to the specific response of the cells used and the tensile properties of the scaffold. Tendon/ligament grafts in animals usually have the advantage of mechanical preconditioning, especially when uniaxial cyclic forces are applied to cells engineered into natural or decellularized scaffolds. However, due to the scarcity of in vivo research, standard protocols still need to be defined for clinical applications.

Bones Morphogenic Protein-4 and retinoic acid combined treatment comparative analysis for in vitro differentiation potential of murine mesenchymal stem cells derived from bone marrow and adipose tissue into germ cells

Nowadays, infertility is no longer considered as an unsolvable disorder due to progresses in germ cells derived from stem lineage with diverse origins. Technical and ethical challenges push researchers to investigate various tissue sources to approach more efficient gametes. The purpose of the current study is to investigate the efficacy of a combined medium, retinoic acid (RA) together with Bone Morphogenic Protein-4 (BMP4), on differentiation of Bone Marrow Mesenchymal Stem Cells (BMMSCs) and adipose-derived mesenchymal stem cells (ADMSCs) into germ cells. Murine MSCs were obtained from both Bone Marrow (BM) and Adipose Tissue (AT) samples and were analyzed for surface markers to get further verification of their nature. BMMSCs and ADMSCs were induced into osteogenic and adipogenic lineage cells respectively, to examine their multipotency. They were finally differentiated into germ cells using media enriched with BMP4 for 4 days followed by addition of RA for 7 days (11 days in total). Analyzing of differentiation potential of BMMSCs- and ADMSCs were performed via Immunofluorescence, Flowcytometry and Real time-PCR techniques for germ cell-specific markers (Mvh, Dazl, Stra8 and Scp3). Mesenchymal surface markers (CD90 and CD44) were expressed on both BMMSCs and ADMSCs, while endothelial and hematopoietic cell markers (CD31 and CD45) had no expression. Finally, all germ-specific markers were expressed in both BM and AT. Although germ cells differentiated from ADMSCs showed faster growth and proliferation as well as easy collection, they significantly expressed germ-specific markers lower than BMMSCs. This suggests stronger differentiation potential of murine BMMSCs than ADMSCs.

Clinical application of concentrated bone marrow aspirate in orthopaedics: A systematic review

AIM

To examine the evidence behind the use of concentrated bone marrow aspirate (cBMA) in cartilage, bone, and tendon repair; establish proof of concept for the use of cBMA in these biologic environments; and provide the level and quality of evidence substantiating the use of cBMA in the clinical setting.

METHODS

We conducted a systematic review according to PRISMA guidelines. EMBASE, MEDLINE, and Web of Knowledge databases were screened for the use of cBMA in the repair of cartilage, bone, and tendon repair. We extracted data on tissue type, cBMA preparation, cBMA concentration, study methods, outcomes, and level of evidence and reported the results in tables and text.

RESULTS

A total of 36 studies met inclusion/exclusion criteria and were included in this review. Thirty-one of 36 (86%) studies reported the method of centrifugation and preparation of cBMA with 15 (42%) studies reporting either a cell concentration or an increase from baseline. Variation of cBMA application was seen amongst the studies evaluated. Twenty-one of 36 (58%) were level of evidence IV, 12/36 (33%) were level of evidence III, and 3/36 (8%) were level of evidence II. Studies evaluated full thickness chondral lesions (7 studies), osteochondral lesions (10 studies), osteoarthritis (5 studies), nonunion or fracture (9 studies), or tendon injuries (5 studies). Significant clinical improvement with the presence of hyaline-like values and lower incidence of fibrocartilage on T2 mapping was found in patients receiving cBMA in the treatment of cartilaginous lesions. Bone consolidation and time to bone union was improved in patients receiving cBMA. Enhanced healing rates, improved quality of the repair surface on ultrasound and magnetic resonance imaging, and a decreased risk of re-rupture was demonstrated in patients receiving cBMA as an adjunctive treatment in tendon repair.

CONCLUSION

The current literature demonstrates the potential benefits of utilizing cBMA for the repair of cartilaginous lesions, bony defects, and tendon injuries in the clinical setting. This study also demonstrates discrepancies between the literature with regards to various methods of centrifugation, variable cell count concentrations, and lack of standardized outcome measures. Future studies should attempt to examine the integral factors necessary for tissue regeneration and renewal including stem cells, growth factors and a biologic scaffold.

The Influence of Trocar Fenestration and Volume on Connective Tissue Progenitor Cells (Stem Cells) in Arthroscopic Bone Marrow Aspiration From the Proximal Humerus

PURPOSE

To evaluate the number of connective tissue progenitor cells (CTPs) and nucleated cells obtained during bone marrow aspiration (BMA) from the proximal humerus using either a fenestrated or a nonfenestrated trocar and determine differences in varying amounts of aspiration volume. The first hypothesis was that the number of CTPs extracted with the fenestrated trocar would be greater due to its potential to extract more cells through its fenestrations. The second hypothesis was that using consecutive aspirations with either trocar would provide a consistent number of CTPs and nucleated cells throughout the aspiration with no significant decrease of cells at the end.

METHODS

Patients were eligible for inclusion if they underwent primary or revision arthroscopic rotator cuff surgery, were between 18 and 75 years of age, and signed the informed consent. Between January 2011 and September 2013, 24 patients underwent BMA from the proximal humerus during arthroscopic surgery. They were grouped according to which of 3 different trocars were used for aspiration: (1) nonfenestrated, (2) fenestrated trocar A, and (3) fenestrated trocar H. Four consecutive 12 mL double syringes were used for each aspiration: 1 (0-12 mL), 2 (12-24 mL), 3 (24-36 mL), and 4 (36-48 mL). One milliliter was removed from each syringe (nonconcentrated BMA). The remainder of the BMA was then spun using a centrifuge. BMA and concentrated BMA were brought to the laboratory, counted for nucleated cells (million cells/mL BMA) and cultured for 7 days to obtain colony-forming units (CTPs/million cells).

RESULTS

No significant differences were observed in tubes 1 to 4 in the number of nucleated cells in the nonconcentrated and concentrated BMA using the nonfenestrated trocar compared with the fenestrated trocars A and H (all P > .05), except for concentrated BMA tube 3 (P = .014) and tube 4 (P = .003). Nonconcentrated and concentrated BMA from tubes 1 to 4 had a significantly higher CTP prevalence using the nonfenestrated trocar compared with the fenestrated trocars A and H (all P < .05). Most of the times the first tube of each aspiration showed a significantly greater amount of cells and a greater CTP prevalence compared with tubes 2, 3, and 4.

CONCLUSIONS

Aspiration from the proximal humerus with the nonfenestrated trocar during BMA was associated with higher prevalence of CTPs, suggesting that more CTPs can be obtained using a nonfenestrated trocar. Furthermore, CTPs can be obtained through all consecutive aspirations with a greater amount in the first tubes.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

* An Engineered Multiphase Three-Dimensional Microenvironment to Ensure the Controlled Delivery of Cyclic Strain and Human Growth Differentiation Factor 5 for the Tenogenic Commitment of Human Bone Marrow Mesenchymal Stem Cells

At present, injuries or rupture of tendons are treated by surgical repair or conservative approaches with unpredictable clinical outcome. Alternative strategies to repair tendon defects without the undesirable side effects associated with the current options are needed. With this in mind, a tissue engineering approach has gained considerable attention as a promising strategy. Here we investigated a synthetic three-dimensional (3D) microenvironment able to interact with stem cells and inducing, via coupled biochemical and physical signals, their early commitment toward the tenogenic lineage. This multiphase 3D construct consisted of a braided hyaluronate elastic band merged with human bone marrow mesenchymal stem cells (hBMSCs) and poly-lactic-co-glycolic acid microcarriers loaded with human growth differentiation factor 5 (hGDF-5) by means of fibrin hydrogel. The multiphase structure allowed hBMSC culture under cyclic strain within a microenvironment where a controlled amount of hGDF-5 was regularly delivered. The cooperative biochemical and physical stimuli induced significantly increased expression of tenogenic markers, such as collagen type I and III, decorin, scleraxis, and tenascin-C, within only 3 days of dynamic hBMSC culture. This approach opens exciting perspectives for future development of engineered tendon tissue substitutes.

Effectiveness of Biologic Factors in Shoulder Disorders

Background:

Shoulder pathology can cause significant pain, discomfort, and loss of function that all interfere with activities of daily living and may lead to poor quality of life. Primary osteoarthritis and rotator cuff diseases with its sequalae are the main culprits. Management of shoulder disorders using biological factors gained an increasing interest over the last years. This interest reveals the need of effective treatments for shoulder degenerative disorders, and highlights the importance of a comprehensive and detailed understanding of the rapidly increasing knowledge in the field.

Methods:

This study will describe most of the available biology-based strategies that have been recently developed, focusing on their effectiveness in animal and clinical studies.

Results:

Data from in vitro work will also be briefly presented; in order to further elucidate newly acquired knowledge regarding mechanisms of tissue degeneration and repair that would probably drive translational work in the next decade. The role of platelet rich-plasma, growth factors, stem cells and other alternative treatments will be described in an evidence-based approach, in an attempt to provide guidelines for their clinical application. Finally, certain challenges that biologic treatments face today will be described as an initiative for future strategies.

Conclusion:

The application of different growth factors and mesenchymal stem cells appears as promising approaches for enhancing biologic repair. However, data from clinical studies are still limited, and future studies need to improve understanding of the repair process in cellular and molecular level and evaluate the effectiveness of biologic factors in the management of shoulder disorders.

Mechanical Loading Improves Tendon-Bone Healing in a Rabbit Anterior Cruciate Ligament Reconstruction Model by Promoting Proliferation and Matrix Formation of Mesenchymal Stem Cells and Tendon Cells

Background/Aims: This study investigated the effect of mechanical stress on tendon-bone healing in a rabbit anterior cruciate ligament (ACL) reconstruction model as well as cell proliferation and matrix formation in co-culture of bone-marrow mesenchymal stem cells (BMSCs) and tendon cells (TCs). Methods: The effect of continuous passive motion (CPM) therapy on tendon-bone healing in a rabbit ACL reconstruction model was evaluated by histological analysis, biomechanical testing and gene expressions at the tendon-bone interface. Furthermore, the effect of mechanical stretch on cell proliferation and matrix synthesis in BMSC/TC co-culture was also examined. Results: Postoperative CPM therapy significantly enhanced tendon-bone healing, as evidenced by increased amount of fibrocartilage, elevated ultimate load to failure levels, and up-regulated gene expressions of Collagen I, alkaline phosphatase, osteopontin, Tenascin C and tenomodulin at the tendon-bone junction. In addition, BMSC/TC co-culture treated with mechanical stretch showed a higher rate of cell proliferation and enhanced expressions of Collagen I, Collagen III, alkaline phosphatase, osteopontin, Tenascin C and tenomodulin than that of controls. Conclusion: These results demonstrated that proliferation and differentiation of local precursor cells could be enhanced by mechanical stimulation, which results in enhanced regenerative potential of BMSCs and TCs in tendon-bone healing.

The biology of rotator cuff healing

Despite advances in surgical reconstruction of chronic rotator cuff (RC) tears leading to improved clinical outcomes, failure rates of 13-94% have been reported. Reasons for this rather high failure rate include compromised healing at the bone-tendon interface, as well as the musculo-tendinous changes that occur after RC tears, namely retraction and muscle atrophy, as well as fatty infiltration. Significant research efforts have focused on gaining a better understanding of these pathological changes in order to design effective therapeutic solutions. Biological augmentation, including the application of different growth factors, platelet concentrates, cells, scaffolds and various drugs, or a combination of the above have been studied. It is important to note that instead of a physiological enthesis, an abundance of scar tissue is formed. Even though cytokines have demonstrated the potential to improve rotator cuff healing in animal models, there is little information about the correct concentration and timing of the more than 1500 cytokines that interact during the healing process. There is only minimal evidence that platelet concentrates may lead to improvement in radiographic, but not clinical outcome. Using stem cells to biologically augment the reconstruction of the tears might have a great potential since these cells can differentiate into various cell types that are integral for healing. However, further studies are necessary to understand how to enhance the potential of these stem cells in a safe and efficient way. This article intends to give an overview of the biological augmentation options found in the literature.

Tendinopathy in diabetes mellitus patients-Epidemiology, pathogenesis, and management

Chronic tendinopathy is a frequent and disabling musculo-skeletal problem affecting the athletic and general populations. The affected tendon is presented with local tenderness, swelling, and pain which restrict the activity of the individual. Tendon degeneration reduces the mechanical strength and predisposes it to rupture. The pathogenic mechanisms of chronic tendinopathy are not fully understood and several major non-mutually exclusive hypotheses including activation of the hypoxia-apoptosis-pro-inflammatory cytokines cascade, neurovascular ingrowth, increased production of neuromediators, and erroneous stem cell differentiation have been proposed. Many intrinsic and extrinsic risk/causative factors can predispose to the development of tendinopathy. Among them, diabetes mellitus is an important risk/causative factor. This review aims to appraise the current literature on the epidemiology and pathology of tendinopathy in diabetic patients. Systematic reviews were done to summarize the literature on (a) the association between diabetes mellitus and tendinopathy/tendon tears, (b) the pathological changes in tendon under diabetic or hyperglycemic conditions, and (c) the effects of diabetes mellitus or hyperglycemia on the outcomes of tendon healing. The potential mechanisms of diabetes mellitus in causing and exacerbating tendinopathy with reference to the major non-mutually exclusive hypotheses of the pathogenic mechanisms of chronic tendinopathy as reported in the literature are also discussed. Potential strategies for the management of tendinopathy in diabetic patients are presented.

A proteomic analysis of chondrogenic, osteogenic and tenogenic constructs from ageing mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) have prospective applications in regenerative medicine and tissue engineering but to what extent phenotype and differentiation capacity alter with ageing is uncertain. Consequently, any loss in functionality with age would have profound consequences for the maintenance of tissue viability and the quality of tissues. Proteomics enables the set of proteins responsible for a particular cell phenotype to be identified, as well as enabling insights into mechanisms responsible for age-related alterations in musculoskeletal tissues. Few proteomic studies have been undertaken regarding age-related effects on tissue engineered into cartilage and bone, and none for tendon. This study provides a proteome inventory for chondrogenic, osteogenic and tenogenic constructs synthesised from human MSCs, and elucidates proteomic alterations as a consequence of donor age.

Methods

Human bone-marrow derived MSCs from young (n = 4, 21.8 years ± 2.4SD) and old (n = 4, 65.5 years ± 8.3SD) donors were used to make chondrogenic, osteogenic and tenogenic tissue-engineered constructs. We utilised an analytical method relying on extracted peptide intensities as a label-free approach for peptide quantitation by liquid chromatography–mass spectrometry. Results were validated using western blotting.

Results

We identified proteins that were differentially expressed with ageing; 128 proteins in chondrogenic constructs, 207 in tenogenic constructs and four in osteogenic constructs. Differentially regulated proteins were subjected to bioinformatic analysis to ascertain their molecular functions and the signalling pathways. For all construct types, age-affected proteins were involved in altered cell survival and death, and antioxidant and cytoskeletal changes. Energy and protein metabolism were the principle pathways affected in tenogenic constructs, whereas lipid metabolism was strongly affected in chondrogenic constructs and mitochondrial dysfunction in osteogenic constructs.

Conclusions

Our results imply that further work on MSC-based therapeutics for the older population needs to focus on oxidative stress protection. The differentially regulated proteome characterised by this study can potentially guide translational research specifically aimed at effective clinical interventions.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0384-2) contains supplementary material, which is available to authorized users.

Scaffold-free Scleraxis-programmed tendon progenitors aid in significantly enhanced repair of full-size Achilles tendon rupture

Aim: Currently there is no effective approach to enhance tendon repair, hence we aimed to identify a suitable cell source for tendon engineering utilizing an established clinically relevant animal model for tendon injury. Materials & methods: We compared, by in-depth histomorphometric evaluation, the regenerative potential of uncommitted human mesenchymal stem cells (hMSC) and Scleraxis (Scx)-programmed tendon progenitors (hMSC-Scx) in the healing of a full-size of rat Achilles tendon defect. Results: Our analyses clearly demonstrated that implantation of hMSC-Scx, in contrast to hMSC and empty defect, results in smaller diameters, negligible ectopic calcification and advanced cellular organization and matrix maturation in the injured tendons. Conclusion: Scaffold-free delivery of hMSC-Scx aids in enhanced repair in a clinically translatable Achilles tendon injury model.

The effect of acoustic radiation force on osteoblasts in cell/hydrogel constructs for bone repair

Ultrasound, or the application of acoustic energy, is a minimally invasive technique that has been used in diagnostic, surgical, imaging, and therapeutic applications. Low-intensity pulsed ultrasound (LIPUS) has been used to accelerate bone fracture repair and to heal non-union defects. While shown to be effective the precise mechanism behind its utility is still poorly understood. In this study, we considered the possibility that LIPUS may be providing a physical stimulus to cells within bony defects. We have also evaluated ultrasound as a means of producing a transdermal physical force that could stimulate osteoblasts that had been encapsulated within collagen hydrogels and delivered to bony defects. Here we show that ultrasound does indeed produce a measurable physical force and when applied to hydrogels causes their deformation, more so as ultrasound intensity was increased or hydrogel stiffness decreased. MC3T3 mouse osteoblast cells were then encapsulated within hydrogels to measure the response to this force. Statistically significant elevated gene expression for alkaline phosphatase and osteocalcin, both well-established markers of osteoblast differentiation, was noted in encapsulated osteoblasts (p < 0.05), suggesting that the physical force provided by ultrasound may induce bone formation in part through physically stimulating cells. We have also shown that this osteoblastic response is dependent in part on the stiffness of the encapsulating hydrogel, as stiffer hydrogels resulted in reducing or reversing this response. Taken together this approach, encapsulating cells for implantation into a bony defect that can potentially be transdermally loaded using ultrasound presents a novel regenerative engineering approach to enhanced fracture repair.

Biologic Treatments for Sports Injuries II Think Tank-Current Concepts, Future Research, and Barriers to Advancement, Part 2: Rotator Cuff

Rotator cuff tears are common and result in considerable morbidity. Tears within the tendon substance or at its insertion into the humeral head represent a considerable clinical challenge because of the hostile local environment that precludes healing. Tears often progress without intervention, and current surgical treatments are inadequate. Although surgical implants, instrumentation, and techniques have improved, healing rates have not improved, and a high failure rate remains for large and massive rotator cuff tears. The use of biologic adjuvants that contribute to a regenerative microenvironment have great potential for improving healing rates and function after surgery. This article presents a review of current and emerging biologic approaches to augment rotator cuff tendon and muscle regeneration focusing on the scientific rationale, preclinical, and clinical evidence for efficacy, areas for future research, and current barriers to advancement and implementation.

Efficacy of platelet-rich plasma in arthroscopic repair of full-thickness rotator cuff tears: a meta-analysis

BACKGROUND

The use of platelet-rich plasma (PRP) is an innovative clinical therapy, especially in arthroscopic rotator cuff repair. The purpose of this study was to compare the clinical improvement and tendon-to-bone healing with and without PRP therapy in arthroscopic rotator cuff repair.

METHODS

A systematic search was done in the major medical databases to evaluate the studies using PRP therapy (PRP+) or with no PRP (PRP-) for the treatment of patients with rotator cuff tears. We reviewed clinical scores such as the Constant score, the American Shoulder and Elbow Surgeons score, the University of California at Los Angeles (UCLA) Shoulder Rating Scale, the Simple Shoulder Test, and the failure-to-heal rate by magnetic resonance imaging between PRP+ and PRP- groups.

RESULTS

Five studies included in this review were used for a meta-analysis based on data availability. There were no statistically significant differences between PRP+ and PRP- groups for overall outcome scores (P > .05). However, the PRP+ group exhibited better healing rates postoperatively than the PRP- group (P = .03) in small/moderate full-thickness tears.

CONCLUSION

The use of PRP therapy in full-thickness rotator cuff repairs showed no statistically significant difference compared with no PRP therapy in clinical outcome scores, but the failure-to-heal rate was significantly decreased when PRP was used for treatment of small-to-moderately sized tears. PRP therapy may improve tendon-to-bone healing in patients with small or moderate rotator cuff tears.

Umbilical Cord Tissue Offers the Greatest Number of Harvestable Mesenchymal Stem Cells for Research and Clinical Application: A Literature Review of Different Harvest Sites

PURPOSE

Recent years have seen dramatic increases in the techniques used to harvest and isolate human mesenchymal stem cells. As the potential therapeutic aspects of these cells further develop, informative data on the differences in yields between tissue harvest sites and methods will become increasingly valuable. We collected and compared data on cell yields from multiple tissue harvest sites to provide insight into the varying levels of mesenchymal stem cells by tissue and offer primary and alternative tissue types for harvest and clinical application.

METHODS

The PubMed and Medline databases were searched for articles relating to the harvest, isolation, and quantification of human mesenchymal stem cells. Selected articles were analyzed for relevant data, which were categorized according to tissue site and, if possible, standardized to facilitate comparison between sites.

RESULTS

Human mesenchymal stem cell levels in tissue varied widely according to tissue site and harvest method. Yields for adipose tissue ranged from 4,737 cells/mL of tissue to 1,550,000 cells/mL of tissue. Yields for bone marrow ranged from 1 to 30 cells/mL to 317,400 cells/mL. Yields for umbilical cord tissue ranged from 10,000 cells/mL to 4,700,000 cells/cm of umbilical cord. Secondary tissue harvest sites such as placental tissue and synovium yielded results ranging from 1,000 cells/mL to 30,000 cells/mL.

CONCLUSIONS

Variations in allogeneic mesenchymal stem cell harvest levels from human tissues reflect the evolving nature of the field, patient demographic characteristics, and differences in harvest and isolation techniques. At present, Wharton's jelly tissue yields the highest concentration of allogeneic mesenchymal stem cells whereas adipose tissue yields the highest levels of autologous mesenchymal stem cells per milliliter of tissue.

CLINICAL RELEVANCE

This comparison of stem cell levels from the literature offers a primer and guide for harvesting mesenchymal stem cells. Larger mesenchymal stem cell yields are more desirable for research and clinical application.

Editorial Commentary: Stem Cell Research in Arthroscopy Is Scant and Requires Basic Science Review

Stem cell research in Arthroscopy is rare, but review of journals beyond orthopaedics yields many interesting highlights. The key points are that sources of stem cells vary with regard to cellular yield, but manipulation to improve the yield is severely limited by the United States Food and Drug Administration.

Use of biomimetic microtissue spheroids and specific growth factor supplementation to improve tenocyte differentiation and adaptation to a collagen-based scaffold in vitro

Tenocytes represent a valuable source of cells for the purposes of tendon tissue engineering and regenerative medicine and as such, should possess a high degree of tenogenic differentiation prior to their use in vivo in order to achieve maximal efficacy. In the current report, we identify an efficient means by which to maintain differentiated tenocytes in vitro by employing the hanging drop technique in combination with defined growth media supplements. Equine tenocytes retained a more differentiated state when cultured as scaffold-free microtissue spheroids in low serum-containing medium supplemented with L-ascorbic acid 2-phosphate, insulin and transforming growth factor (TGF)-β1. This was made evident by significant increases in the expression levels of pro-tenogenic markers collagen type I (COL1A2), collagen type III (COL3A1), scleraxis (SCX) and tenomodulin (TNMD), as well as by enhanced levels of collagen type I and tenomodulin protein. Furthermore, tenocytes cultured under these conditions demonstrated a typical spindle-like morphology and when embedded in collagen gels, became highly aligned with respect to the orientation of the collagen structure following their migration out from the microtissue spheroids. Our findings therefore provide evidence to support the use of a biomimetic microtissue approach to culturing tenocytes and that in combination with the defined growth media described, can improve their differentiation status and functional repopulation of collagen matrix.

Rotator cuff biology and biomechanics: a review of normal and pathological conditions

The glenohumeral joint is a complex anatomic structure commonly affected by injury such as tendinopathy and rotator cuff tears. This review presents an up-to-date overview of research on tendon biology and structure, shoulder joint motion and stability, tendon healing, and current and potential future repair strategies. Recent studies have provided information demonstrating the serious impact on uninjured tissues after a rotator cuff tear or other cause of altered shoulder joint mechanics. Another major focus of recent research is biological augmentation of rotator cuff repair with the goal of successfully reinstating normal tendon-to-bone structure. To effectively treat shoulder pathologies, clinicians need to understand normal tendon biology, the healing process and environment, and whole shoulder stability and function.

Editorial Commentary: Biomechanical Data Does Not Translate to Clinical Rerupture Rates After Shoulder Rotator Cuff Repair Using Different Suture Techniques

Biomechanical data does not translate to clinical re-rupture rates after shoulder rotator cuff repair using different suture techniques stratified by method of repair and tear size. Explanations include reporting and selection bias.