Subacromial Bursa-Derived Cells Demonstrate High Proliferation Potential Regardless of Patient Demographics and Rotator Cuff Tear Characteristics

The role of injections of mesenchymal stem cells as an augmentation tool in rotator cuff repair: a systematic review

Background

Arthroscopic repair is currently the gold standard for the surgical treatment of rotator cuff tears, but the retear rates remain unacceptably high. Mesenchymal stem cells (MSCs) may play a role in the local biology and enhance tendon-to-bone healing during rotator cuff repair. However, the scientific literature is still not well systematized on the effects of injection of MSCs as an augmentation tool for rotator cuff repair. Our goal was to investigate the effect of injections of MSCs to augment rotator cuff repair in patients with rotator cuff tear.

Methods

PubMed and EMBASE were searched up to June 2022 for clinical studies that applied MSCs injections to augment rotator cuff repair. Imaging, patient-reported outcomes measures, shoulder range of motion and strength were collected. Quantitative synthesis included within- and between-group mean differences with the within-group percentage of minimal clinically important difference for each study and continuous outcomes, and relative risks (RR) for retears and adverse events. Quantitative synthesis was computed with 95% confidence intervals (CIs).

Results

We included 5 studies comprising a total of 228 individuals with a weighted mean age of 59.3 ± 1.2 years. Three studies used bone marrow MSCs and two studies applied adipose-derived MSCs. Patient-reported outcomes measures, shoulder range of motion, and strength improved significantly in all MSCs groups, with minimal clinically important differences ranging from 120% to 679% of established cut-off. When compared to rotator cuff repair alone, the MSCs groups did not result in improved outcomes. The MSCs group showed significant protective effect at the mid-term (RR = 0.52, 95% CI 0.27-0.98) and long-term (RR = 0.24, 95% CI 0.11-0.53).

Conclusion

There are no differences in clinical and functional outcomes between rotator cuff repair with or without augmentation with MSCs. However, there may be a protective effect against retear at the mid-term and long-term follow-up when augmenting the repair with MSCs. The literature on this topic is still preliminary and the quality and certainty of evidence is limited.

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.].

Biologic augmentation of rotator cuff repair with microfragmented autologous subacromial bursal tissue enveloped in a patch of compressed autologous long head of biceps tendon tissue: the Bio-Ravioli technique

Background

Rotator cuff repair is one of the most frequently performed procedures in orthopedic surgery. However, considering the limited healing potential of rotator cuff tendons, several augmentation strategies have evolved to enhance tendon healing. The purpose of this article was to present a new surgical technique called Bio-Ravioli.

Methods

Patients with repairable full-thickness posterosuperior rotator cuff tear and a moderate-to-high risk of healing failure were chosen as candidates for the Bio-Ravioli procedure. It is a biologic augmentation strategy to increase healing potential of arthroscopic rotator cuff repair by use of a biologic graft fixed at the bone-tendon interface. The Bio-Ravioli consists of microfragmented autologous subacromial bursal tissue enveloped in a patch of compressed autologous long head of biceps tendon tissue. The rotator cuff is then repaired to the bone and over the graft using a transosseus equivalent configuration.

Conclusion

The Bio-Ravioli technique represents an easy and reliable way to increase the healing potential at the bone-tendon interface by using autologous mesenchymal stem cells from different sources: subacromial bursa and long head of the biceps tendon.

Bursal Tissue Harvested During Rotator Cuff Repair Contains Viable Mesenchymal Stem Cells

Purpose

To evaluate the effect of intraoperative ablation on the viability, distribution, phenotype, and potential for culture expansion of bursal cells harvested during arthroscopic rotator cuff surgery.

Methods

Tissue was collected during primary arthroscopic rotator cuff repair on 6 healthy, randomly selected patients from a fellowship-trained surgeon's practice between September 2020 and January 2021. There were 3 women (aged 60 ± 8 years) and 3 men (aged 61 ± 10 years). At the time of surgery, subacromial bursal tissue was subjected to no ablation, 1 second of ablation, or 3 seconds of ablation. Tissues were collected by an autograft harvesting system connected to an arthroscopic shaver and a pituitary grasper. Tissue fragments from each condition were sampled for viability testing or cell isolation. A viability kit with confocal microscopy was used to assess live and dead cells. Cell isolation consisted of collagenase digestion or placing tissue fragments onto tissue culture-treated plates that induced migration of cells out of the tissue. Cell proliferation rates were monitored and surface markers for mesenchymal stem cells (MSC) and pericytes were analyzed via multicolor flow cytometry.

Results

Increased ablation time significantly reduced cell viability. The mean percentage of live cells was 55.2% ± 27.2% (range, 26%-90% live) in the control group, 46.8% ± 23.8% (range, 9.6%-69.6%, P = .045) in the short-ablation group, and 35.5% ± 19% (range, 11%-54%, P = .03) in the long-ablation group. No significant differences in population doubling level (1.6 ± 0.5 days) and population doubling time (6.7 ± 2.4 days) were observed in cells from any treatment. The surface marker profile indicated an MSC phenotype with absence of a pericyte population. Ablation or cell isolation procedure had no significant effect on the surface marker profile of isolated cells.

Conclusions

Radiofrequency ablation significantly reduced the overall tissue viability but had no significant effect on cell proliferation or expression of surface markers on isolated subacromial bursal cells harvested arthroscopically.

Clinical Relevance

Analysis of the viability and performance of cells harvested after the use of ablation devices using mechanical surgical collection during rotator cuff repair surgery could further our understanding of subacromial bursal tissue and its potential role in augmenting rotator cuff repair healing.

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.

Unrepaired Trochanteric Bursae as a Risk Factor for Deep Gluteal Syndrome After Total Hip Arthroplasty: A Prospective Randomized Controlled Trial

BACKGROUND

The trochanteric bursae are often left unrepaired after total hip arthroplasty (THA) and they retract posteriorly over the muscle belly of the piriformis. Deep gluteal syndrome (DGS) is a multifactorial condition presenting as buttock pain and is attributed to nondiscogenic sciatic nerve irritation or impingement causes. The purpose of this study was to investigate the relationship between bursal repair and incidence of DGS in patients undergoing THA.

METHODS

This prospective randomized trial included patients treated with a THA between January and December 2022 for a diagnosis of primary osteoarthritis. Patients were randomized into 2 groups: group 1 underwent a routine bursal repair, while group 2 did not, leaving the bursae unrepaired. Follow-up was performed on the 15th, 30th, and 90th day postoperatively with clinical scores, physical examinations, and laboratory tests. In this cohort of 104 patients, mean age was 55 years (range, 26 to 88). Demographic variables as well as range of motion and overall clinical results showed no significant difference between the groups.

RESULTS

DGS rates were significantly more common in the patients who had an unrepaired bursa (group 2) both on the 30th and 90th postoperative days, while comparison of lateral trochanteric pain on palpation showed similar results between the groups.

CONCLUSIONS

DGS is common in individuals who have unrepaired trochanteric bursal tissue following a THA. Despite its higher frequency, these symptoms did not have a substantial impact on the overall clinical scores, which remained consistent across the study groups.

The effect of augmenting suture material with magnesium and platelet-rich plasma on the in vitro adhesion and proliferation potential of subacromial bursa-derived progenitor cells

Background

Connective tissue subacromial bursa-derived progenitor cells (SBDCs) have been suggested as a potent biologic augment to promote healing of the repaired rotator cuff tendon. Maximizing the amount of retained progenitor cells at the tendon repair site is essential for ensuring an optimal healing environment, warranting a search for proadhesive and proliferative adjuvants. The purpose was to evaluate the effect of magnesium (Mg), platelet-rich plasma (PRP), and a combination of both adjuvants on the in vitro cellular adhesion and proliferation potential of SBDCs on suture material commonly used in rotator cuff surgery.

Methods

SBDCs were isolated from subacromial bursa samples harvested during rotator cuff repair and cultured in growth media. Commercially available collagen-coated nonabsorbable flat-braided suture was cut into 1-inch pieces, placed into 48-well culture dishes, and sterilized under ultraviolet light. Either a one-time dose of 5 mM sterile Mg, 0.2 mL of PRP, or a combination of both adjuvants was added, while a group without treatment served as a negative control. Cellular proliferation and adhesion assays on suture material were performed for each treatment condition.

Results

Augmenting the suture with Mg resulted in a significantly increased cellular adhesion (total number of attached cells) of SBDCs compared to PRP alone (31,527 ± 19,884 vs. 13,619 ± 8808; P < .001), no treatment (31,527 ± 19,884 vs. 21,643 ± 8194; P = .016), and combination of both adjuvants (31,527 ± 19,884 vs. 17,121 ± 11,935; P < .001). Further, augmentation with Mg achieved a significant increase in cellular proliferation (absorbance) of SBDCs on suture material when compared to the PRP (0.516 ± 0.207 vs. 0.424 ± 0.131; P = .001) and no treatment (0.516 ± 0.207 vs. 0.383 ± 0.094; P < .001) group. The combination of Mg and PRP showed a significantly higher proliferation potential compared to PRP alone (0.512 ± 0.194 vs. 0.424 ± 0.131; P = .001) and no treatment (0.512 ± 0.194 vs. 0.383 ± 0.094; P < .001). There were no significant differences in the remaining intergroup comparisons (P > .05, respectively).

Conclusion

Augmenting suture material with Mg resulted in a significantly increased cellular adhesion of SBDCs compared to untreated suture material, as well as augmentation with PRP alone or a combination of both adjuvants. Further, Mg with or without PRP augmentation achieved a significant increase in the cellular proliferation of SBDCs on suture material compared to untreated sutures and augmentation with PRP alone. Application of Mg may be a clinically feasible approach to optimizing the use of SBDCs as a biological augment in rotator cuff repair, while combined augmentation with PRP may harness the full potential for optimized tissue recovery due to the high concentration of PRP-derived growth factors.

Clinical outcomes of rotator cuff repair with subacromial bursa reimplantation: a retrospective cohort study

Background

The subacromial bursa has been found to be a rich, local, source of mesenchymal stem cells but is removed for visualization during rotator cuff repair. Reimplantation of this tissue may improve rotator cuff healing. The purpose of this study is to evaluate clinical outcomes of rotator cuff repair with and without subacromial bursa reimplantation.

Methods

Patients aged 37-77 with a full-thickness or near full-thickness supraspinatus tears underwent arthroscopic transosseous-equivalent double row rotator cuff repair. In patients prior to July 2019, the subacromial bursa was resected for visualization, and discarded. In patients after July 2019, the subacromial bursa was collected using a filtration device connected to an arthroscopic shaver and reapplied to the bursal surface of the tendon at the completion of the rotator cuff repair. Rotator cuff integrity was evaluated via magnetic resonance imaging on bursa patients at 6 months postoperatively. Minimum 18-month clinical outcomes (Single Assessment Numeric Evaluation, American Shoulder and Elbow Surgeons, patient satisfaction) were compared between bursa and nonbursa cohorts.

Results

A total of 136 patients were included in the study (control n = 110, bursa n = 26). Preoperative demographics and tear characteristics were not different between groups. Average follow-up was significantly longer in the control group (control: 3.2 ± 0.7 years; bursa: 1.8 ± 0.3 years; P < .001). The control group showed a significantly higher Single Assessment Numeric Evaluation score (control: 87.9 ± 15.8, bursa: 83.6 ± 15.1, P = .037) that did not meet minimum clinically important difference. The American Shoulder and Elbow Surgeons and patient satisfaction scores were similar between the groups. Symptomatic retears were not significantly different between groups (control: 9.1%, bursa 7.7%, P = .86). Seven patients in the control group underwent reoperation (6.4%), compared to 0 patients in the bursa group (0%, P = .2). Six-month postoperative magnetic resonance images obtained on bursa patients demonstrated 85% rotator cuff continuity (n = 17/20) as defined via Sugaya classification.

Conclusion

Augmentation of rotator cuff repair with bursal tissue does not appear to have negative effects, and given the accessibility and ease of harvest of this tissue, further research should be performed to evaluate its potential for improved tendon healing or clinical outcomes.

Arthroscopy and Musculoskeletal Biologics

Orthopaedic biologics holds great promise. Absent peer-reviewed clinical musculoskeletal research, orthobiologics indications and treatment recommendations will remain opaque. In a Call for Papers, Arthroscopy; Arthroscopy Techniques; and Arthroscopy, Sports Medicine, and Rehabilitation editors invite authors to submit clinical musculoskeletal biologics original scientific research, and technical notes with video. Each year, the top articles will be awarded inclusion in an annual Biologics Special Issue. Future investigators and current readers could follow the science while being mindful of the regulatory environment.

Orthopaedic Musculoskeletal Biologics Research Impacts Patient Care: The First Annual Arthroscopy Orthobiologics Virtual Special Issue

Orthobiologics can modify symptoms and improve healing in a variety of musculoskeletal conditions as a part of office-based care or as an adjunct to surgery. Orthobiologics harness the benefits of naturally derived blood components, autologous tissue, and growth factors to reduce inflammation and optimize the host-healing environment. The Arthroscopy family of journals seeks to positively influence evidence-based clinical decision-making by publishing peer-reviewed biologics research. This special issue contains recent influential articles strategically chosen to positively impact patient care.

Advances in Stem Cell Therapies for Rotator Cuff Injuries

Rotator cuff injury is a common upper extremity musculoskeletal disease that may lead to persistent pain and functional impairment. Despite the clinical outcomes of the surgical procedures being satisfactory, the repair of the rotator cuff remains problematic, such as through failure of healing, adhesion formation, and fatty infiltration. Stem cells have high proliferation, strong paracrine action, and multiple differentiation potential, which promote tendon remodeling and fibrocartilage formation and increase biomechanical strength. Additionally, stem cell-derived extracellular vesicles (EVs) can increase collagen synthesis and inhibit inflammation and adhesion formation by carrying regulatory proteins and microRNAs. Therefore, stem cell-based therapy is a promising therapeutic strategy that has great potential for rotator cuff healing. In this review, we summarize the advances of stem cells and stem cell-derived EVs in rotator cuff repair and highlight the underlying mechanism of stem cells and stem cell-derived EVs and biomaterial delivery systems. Future studies need to explore stem cell therapy in combination with cellular factors, gene therapy, and novel biomaterial delivery systems.

Significant Improvement in Shoulder Function and Pain in Patients Following Biologic Augmentation of Revision Arthroscopic Rotator Cuff Repair Using an Autologous Fibrin Scaffold and Bone Marrow Aspirate Derived From the Proximal Humerus

Purpose

To clinically evaluate patients who underwent a biologic augmentation technique in revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated stem cells isolated from bone marrow aspirate (BMA) obtained from the proximal humerus.

Methods

This is a retrospective review of prospectively collected data from patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and BMA obtained from the proximal humerus between 2014 and 2015. Minimum follow-up was 12 months. Outcome measures were collected preoperatively and postoperatively including range of motion as well as American Shoulder and Elbow Surgeons Shoulder Form, Simple Shoulder Test, single assessment numeric evaluation, and visual analog score. In addition, BMA samples of each patient were assessed for the number of nucleated cells and colony-forming units. Regression analysis was performed to investigate whether the number of nucleated cells and colony-forming units had an influence on outcome and failure.

Results

Ten patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated BMA obtained from the proximal humerus between 2014 and 2015 were included. The mean follow-up time was 30.7 (range: 12-49) months. Four patients were revised at final follow-up. Postoperative clinical scores improved significantly: American Shoulder and Elbow Surgeons (28.1 ± 5.4 to 60.9 ± 9.0; P < .01), single assessment numeric evaluation (6.6 ± 2.3 to 65.1 ± 10.9; P < .01), visual analog scale (7.2 ± 0.9 to 3.1 ± 0.9; P < .01), and Simple Shoulder Test (1.6 ± 0.5 to 10.3 ± 5.7; P < .01). Postoperative range of motion increased significantly with regard to flexion (97.0 ± 13.6 to 151.0 ± 12.2; P < .01) and abduction (88.0 ± 14.0 to 134.0 ± 15.1; P = .038) but not with external rotation (38.0 ± 5.7 to 50.5 ± 6.5; P = .16). Less pain was correlated to an increased number of nucleated cells (P = .026); however, there was no correlation between failure rate and number of nucleated cells (P = .430).

Conclusions

Patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated BMA demonstrated a significant improvement in shoulder function along with reduction of pain. However, the overall revision rate for this procedure was 40%.

Level of Evidence

Level IV, therapeutic case series.

Trochanteric Bursa Is a Source of Connective Tissue Progenitor Cells

Purpose

To investigate the presence of connective tissue progenitor cells (CTPs) in the trochanteric bursa harvested over the gluteus medius muscle belly and tendon during open hip procedures.

Methods

Trochanteric bursa samples from nine patients (63.1 ± 8.6 years) undergoing total hip arthroplasty for primary osteoarthritis were obtained from 2 sites: over the gluteus medius tendon at the greater trochanter and over the muscle belly. Bursal tissue was digested with collagenase and grown in culture. The nucleated cell count, cellular concentration, cellular proliferation, fluorescence-activated cell sorting (FACS) analysis, and differentiation using immunostaining and quantitative polymerase chain reaction (PCR) were used to determine and quantify the presence of CTPs.

Results

Bursa-derived CTPs were identified in all harvested samples. At t = 0, there was no difference in nucleated cell count over muscle and tendon (1.69 ± 1.26 × 10⁸ and 1.41 ± 1.12 × 10⁸ cells/g, respectively; P = .162). Similarly, the cellular concentration at 3 weeks was not significantly different between bursa harvested over muscle and tendon (6.61 ± 5.14 × 10⁶ and 5.58 ± 4.70 × 10⁶ cells/g, respectively; P = .532). High cellular proliferation was identified for both bursal tissue overlying muscle and tendon (2.28 ± .95 and 1.66 ± 1.05, respectively; P = .194). FACS analysis revealed high positivity rates (>95%) of CTP-specific surface epitopes (CD105, CD90, and CD73) and low positivity rates (<1.3%) of negative markers (CD45, CD31). Osteogenic, adipogenic, and chondrogenic differentiation potential was demonstrated with immunostaining and quantitative PCR for gene expression.

Conclusions

Connective tissue progenitor cells are found in the trochanteric bursa overlying the muscle and tendon of the hip abductors.

Clinical Relevance

During open hip procedures, the trochanteric bursa is often partially excised to identify muscular boundaries and tissue planes for surgical exposure. The function of the trochanteric bursa remains largely unknown. However, this tissue is a source of connective tissue progenitor cells, which may be important in the healing response of surgically repaired abductor tendons.

The Subacromial Bursa: Current Concepts Review

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The subacromial bursa is a distinct anatomic structure with distinct histologic features; it plays a critical role in the symptoms of the painful shoulder and in the local healing capacity of the rotator cuff tendon.

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Treatment of pain from bursitis of the subacromial bursa largely involves nonoperative interventions; however, operative treatment may be considered in certain instances.

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Preservation of the subacromial bursa should occur whenever possible given its intrinsic trophic and pluripotent factors, which have been shown to play important roles in rotator cuff tendon pathology.

Arthroscopic Biological Augmentation for Massive Rotator Cuff Tears: The Biceps-Cuff-Bursa Composite Repair

Surgical repair of massive and chronic rotator cuff tears is difficult due to tendon retraction and severe atrophy, and the resultant retear rate in the structurally weak tendons is high. Commercially available patches and bioinductive scaffolds have been used to provide strength and superior healing environment in partial and complete rotator cuff tears. Biological biceps autograft has been used for superior capsular reconstruction, and the subacromial bursa has been shown to have significant pluripotent stem cell potency for tendon healing. We describe our technique for combined use of the long biceps tendon (LBT) and vasculature-preserved subacromial bursa as autografts in rotator cuff repair augmentation. The technique involves obtaining a LBT graft of sufficient length using a "traction and tenodesis" technique. The subacromial bursa is mobilized as a continuous layer (vascular bursal duvet) by maintaining its medial and lateral vascularity. All-suture anchors are used to minimize the insertion apertures (3 mm) in tuberosity. The bursa is advanced laterally, and the mobilized cuff is repaired together as a biceps-cuff-bursa composite unit. Combined use of the biceps and bursa as biological autografts has the advantage of structural and regenerative augmentation, and the autografts are easily accessible without added cost.

Analysis of Patient Factors Affecting In Vitro Characteristics of Subacromial Bursal Connective Tissue Progenitor Cells during Rotator Cuff Repair

Unsatisfactory failure rates following rotator cuff (RC) repair have led orthopaedic surgeons to explore biological augmentation of the healing enthesis. The subacromial bursa (SB) contains abundant connective tissue progenitor cells (CTPs) that may aid in this process. The purpose of the study was to investigate the influence of patient demographics and tear characteristics on the number of colony-forming units (CFUs) and nucleated cell count (NCC) of SB-derived CTPs. In this study, we harvested SB tissue over the supraspinatus tendon and muscle in 19 patients during arthroscopic RC repair. NCC of each sample was analyzed on the day of the procedure. After 14 days, CFUs were evaluated under a microscope. Spearman’s rank correlation coefficient was then used to determine the relationship between CFUs or NCC and patient demographics or tear characteristics. The study found no significant correlation between patient demographics and the number of CFUs or NCC of CTPs derived from the SB (p > 0.05). The study did significantly observe that increased tear size was negatively correlated with the number of CFUs (p < 0.05). These results indicated that increased tear size, but not patient demographics, may influence the viability of CTPs and should be considered when augmenting RCrepairs with SB.

Editorial Commentary: Point-of-Care Harvest and Application of Resident Stem Are Practical and Cost-Effective

Point-of-care harvest and application of residence stem cells are practical and cost-effective. Tissue formerly considered waste contains these biologically potent cells, and use of such tissue may represent a big part of biologics going forward. The practical application of orthobiologics has slowed because of 3 hurdles: the regulatory requirements of stem cell technologies; the energy, time, and money required to develop a clinical evidence base; and the expense that they present to patients and institutions. Orthobiologic technologies that are simple and cheap and that leverage tissues that are already readily available at the point of care (i.e., the surgical procedure) solve many of these challenges. Cell sources could include knee synovium, shoulder subacromial bursa, bone marrow aspirate, and anterior cruciate ligament injury effusion fluid and stump tissue. A current concern is that collagenase processing and culture expansion are steps resulting in regulatory hurdles in the United States.

Decreased Colony-Forming Ability of Subacromial Bursa-Derived Cells During Revision Arthroscopic Rotator Cuff Repair

Purpose

To compare the cellular viability and differentiation potential of subacromial bursa-derived cells (SBDCs) located over the rotator cuff muscle and tendon of patients undergoing primary versus revision arthroscopic rotator cuff repair (ARCR).

Methods

Subacromial bursa was harvested from 18 primary (57.1 ± 4.6 years) and 12 revision ARCRs (57.3 ± 6.7 years). Bursa was collected from 2 sites (over rotator cuff tendon and muscle), digested with collagenase, and grown in culture. The number of nucleated cells, colony-forming units (CFUs), differentiation potential, and mesenchymal stem cell surface markers were compared in primary and revision cases.

Results

There was no difference in the number of nucleated cells between primary and revision ARCR harvested from the subacromial bursa overlying the tendon (3019.3 ± 1420.6 cells/mg and 3541.7 ± 2244.2 cells/mg, respectively; P = .912) or muscle (2753.5 ± 1547.1 cells/mg and 2989.0 ± 2231.4 cells/mg, respectively; P = .777). There was no difference in the number of CFUs between primary and revision ARCR over the rotator cuff tendon (81.5 ± 49.5 CFUs and 53.0 ± 36.9 CFUs, respectively; P = .138), but there were significantly fewer CFUs over the muscle in revision cases (28.1 ± 22.7 CFUs) compared with primary cases (55.7 ± 34.5 CFUs) (P = .031). SBDCs from revision ARCR expressed characteristic mesenchymal stem cell surface epitopes and had multidifferentiation potentials for chondrogenesis, osteogenesis, and adipogenesis.

Conclusions

SBDCs harvested over the rotator cuff muscle demonstrated significantly decreased colony-forming abilities in revision arthroscopic rotator cuff repairs compared with primary repairs. However, the subacromial bursa retains its pluripotent differentiation potential for chondrogenic, osteogenic, and adipogenic lineages in the revision setting.

Clinical Relevance

The subacromial bursa may play a role in the healing response of the repaired rotator cuff. This capacity is not necessarily diminished in the revision setting and may be harnessed as an orthobiologic.

Arthroscopic Rotator Cuff Repair Augmented with Autologous Subacromial Bursa Tissue, Concentrated Bone Marrow Aspirate, Platelet-Rich Plasma, Platelet-Poor Plasma, and Bovine Thrombin

As recurrent rotator cuff tears following repair remain a significant problem, improving healing potential using biologic adjuvants, including concentrated bone marrow aspirate (cBMA), platelet-rich plasma (PRP), or subacromial bursa tissue (SBT), has become increasingly popular in recent years. In an attempt to combine the benefits of these various biologic adjuvants and maximize the healing potential of the repaired tendon, an arthroscopic rotator cuff repair technique biologically augmented with autologous SBT, cBMA, PRP, platelet-poor plasma (PPP), and bovine thrombin has been developed. The created clot is used as a biologic scaffold for sufficient delivery, and it is stabilized using bovine thrombin in order to ensure maximum stability and retainment of the applied biologic augments at the repair site.

CLASSIFICATIONS

I: shoulder; II: rotator cuff.

Current Biological Strategies to Enhance Surgical Treatment for Rotator Cuff Repair

Rotator cuff tear is one of the most common shoulder problems encountered by orthopedic surgeons. Due to the slow healing process and high retear rate, rotator cuff tear has distressed millions of people all around the world every year, especially for the elderly and active athletes. This disease significantly impairs patients' motor ability and reduces their quality of life. Besides conservative treatment, open and arthroscopic surgery contributes a lot to accelerate the healing process of rotator cuff tear. Currently, there are many emerging novel treatment methods to promote rotator cuff repair. A variety of biological stimulus has been utilized in clinical practice. Among them, platelet-rich plasma, growth factors, stem cells, and exosomes are the most popular biologics in laboratory research and clinical trials. This review will focus on the biologics of bioaugmentation methods for rotator cuff repair and tendon healing, including platelet-rich plasma, growth factors, exosomes and stem cells, etc. Relevant studies are summarized in this review and future research perspectives are introduced.

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.

Editorial Commentary: Mesenchymal Stem Cell Preparation Methods Affect the Properties of Shoulder Subacromial Bursa-Derived Cells

Augmentation of mesenchymal stem cells (MSCs) from the subacromial bursa in the setting of irreparable rotator cuff tears is a powerful candidate for future regenerative medicine. However, little is known about whether the preparation technique affects the individual differences and potentials of subacromial bursa-derived MSCs. The yields obtained by chopping or cell-expansion techniques with a high-density of initial nucleated cells seem to be lower than those obtained with low-density cell-expansion techniques. Differences in cell-preparation methods may affect whether individual differences in their properties exist. Further studies are required using a low-density cell-expansion technique to establish a new regenerative treatment using subacromial bursa-derived MSCs for irreparable rotator cuff tears.