New perspectives in rotator cuff tendon regeneration: review of tissue engineered therapies

Attachment and Growth of Fibroblasts and Tenocytes Within a Porous Titanium Scaffold: A Bioreactor Approach

Background

Direct attachment of tendons to metallic implants is important in orthopedics. Tissue integration depends on scaffold microstructure and composition. This study evaluated the effect of pore size of titanium on the viability and function of fibroblasts and tenocytes in a dynamic bioreactor.

Methods

Standardized Ti porous cylinders with 3 pore sizes (400, 700, and 1000 μm) were seeded with fibroblasts or tenocytes (4500 cells/μL) in silicon tubes. Cells were analyzed via alamarBlue (AB) assay in addition to scanning electron microscopy at day 7 (fibroblasts) or day 8 (tenocytes) and day 15. AB functions as a cell health indicator where functional living cells reduce the resazurin dye (blue) in the solution to resorufin (pink), and cell viability can be quantified via spectroscopy.

Results

At day 7, fibroblasts cultured on all sizes reduced AB, with significant differences noted between 400 vs 1000 μm (P = .013) and 700 vs 1000 μm (P = .001). At day 15, fibroblasts reduced AB on all sizes with a significant difference noted between 700 vs 1000 μm (P = .004). Fibroblasts on all 3 pore sizes increased AB reduction from day 7 to day 15. Tenocytes reduced AB with significant differences between the 400 vs 700 μm (P = .049) and the 400 vs 1000 μm pore sizes at day 8. In contrast, tenocyte reduction of AB decreased from day 8 to day 15. Scanning electron microscopy performed on fibroblast cylinders showed fibroblasts reached the surface of the cylinders, confirming interconnectivity.

Conclusions

While both fibroblasts and tenocytes penetrated the pores, fibroblasts preferred larger size, whereas tenocytes favored smaller size. Results are encouraging since soft-tissue attachment to a metallic scaffold is difficult but clinically desirable. Future studies could be performed in an in vivo animal model.

A Systematic Summary of Systematic Reviews on the Topic of the Rotator Cuff

BACKGROUND

The number of systematic reviews and meta-analyses published on the rotator cuff (RC) has increased markedly.

PURPOSE

To quantify the number of systematic reviews and meta-analyses published on the RC and to provide a qualitative summary of the literature.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic search for all systematic reviews and meta-analyses pertaining to the RC published between January 2007 and September 2017 was performed with PubMed, MEDLINE, and the Cochrane Database of Systematic Reviews. Narrative reviews and non-English language articles were excluded.

RESULTS

A total of 1078 articles were found, of which 196 met the inclusion criteria. Included articles were summarized and divided into 15 topics: anatomy and function, histology and genetics, diagnosis, epidemiology, athletes, nonoperative versus operative treatment, surgical repair methods, concomitant conditions and surgical procedures, RC tears after total shoulder arthroplasty, biological augmentation, postoperative rehabilitation, outcomes and complications, patient-reported outcome measures, cost-effectiveness of RC repair, and quality of randomized controlled trials.

CONCLUSION

A qualitative summary of the systematic reviews and meta-analyses published on the RC can provide surgeons with a single source of the most current literature.

A Flowable Placental Tissue Matrix Allograft in Lower Extremity Injuries: A Pilot Study

Damaged connective tissue commonly leads to lower extremity injuries. These injuries can result in inflammation, reduced mobility, and chronic pain. Conservative treatment may include orthotics, offloading the injury, physical therapy, and/or NSAIDs. If conservative treatment fails, surgical intervention may be required. Even after successful surgery, these procedures often result in reduced joint mobility and tendon or ligament strength. A novel flowable tissue matrix allograft, derived from human placental connective tissue, has recently been made available for minimally invasive treatment of damaged or inadequate tissue  (PX50®, Human Regenerative Technologies LLC, Redondo Beach, CA). Based on the universal role of connective tissue in the body, and its reported antimicrobial, anti-adhesive, and anti-inflammatory properties, we assessed the effects of using this placental tissue matrix in the treatment of a series of lower extremity injuries. In this pilot study, 9 of 10 patients reported pain levels of 2 or less by week four using the VAS pain scale. This short-term pilot study effectively shows that injectable, flowable amniotic allografts can be used for orthopedic sports injuries of the lower extremities.

Cell-based tissue engineering augments tendon-to-bone healing in a rat supraspinatus model

Rotator cuff pathology causes substantial pain/disability and health care costs. Cell-based tissue engineering offers promise for improved outcomes in tendon to bone healing. Cells from the tendon-bone interface were used here to amplify surgical defect healing in a rat model. Cells from tendon-to-bone interface of the rotator cuff were seeded in sponges and implanted into critical rotator cuff defects: Group I, control; II, surgical defect only; III, suture-repaired defect; IV, surgical defect, repair with sponge only; V, surgical defect, repair with sponge with cells. Three, 6-, and 12-week results were assessed for histologic features. At 3 weeks, histologic indices in Group V were significantly increased versus other treatment groups. Group V (12 weeks) showed significantly improved collagen organization versus other treatment groups; there was no difference in collagen organization in Group I versus V. In summary, increased cellularity, inflammation, vascularity, and collagen organization were present at 3 weeks; increased collagen organization at 12 weeks in Group V provides evidence for improved healing with cells. Data further support the utility of tendon-bone interface cells in rotator cuff healing.

Regeneration of rotator cuff tear using electrospun poly(d,l-Lactide-Co-Glycolide) scaffolds in a rabbit model

PURPOSE

The purpose of this study was to evaluate an application of poly(d,l-lactide-co-glycolide) (PLG) scaffold created by electrospinning in a rabbit rotator cuff defect model.

METHODS

Forty-two Japanese white rabbits were used in this study. Defects of the infraspinatus tendon were created, and the PLG scaffolds were implanted. Contralateral infraspinatus tendons were reattached without creating defects. Histologic analyses were performed 4, 8, and 16 weeks after the operation, and mechanical evaluations were performed 0, 4, 8, and 16 weeks after the operation.

RESULTS

Scaffold fibers remained without dissolution and spindle-shaped cells were observed inside of the scaffold at 4 weeks postoperatively. At 8 weeks, the PLG scaffold had dissolved and bone formation was observed at the scaffold-bone interface. At 16 weeks, the scaffold-bone interface matured and expression of type II collagen was observed. A statistical difference in ultimate failure load was not seen between the scaffold group and reattachment group or normal tendon after 8 weeks postoperatively. The stiffness in the scaffold group was not significantly different from that in the reattachment group at each time point. However, it was significantly weaker than normal tendon at each time point.

CONCLUSIONS

Transplantation of cell-free PLG scaffold showed cell migration and type II collagen and proteoglycan expression at the scaffold-bone junction by 16 weeks postoperatively with a sufficient ultimate failure load in a rabbit rotator cuff defect model.

CLINICAL RELEVANCE

The PLG scaffold could be applied to bridge rotator cuff defects. The results showed that bridging with scaffold can be equivalent to reattachment.

Synthetic collagen fascicles for the regeneration of tendon tissue

The structure of an ideal scaffold for tendon regeneration must be designed to provide a mechanical, structural and chemotactic microenvironment for native cellular activity to synthesize functional (i.e. load bearing) tissue. Collagen fibre scaffolds for this application have shown some promise to date, although the microstructural control required to mimic the native tendon environment has yet to be achieved allowing for minimal control of critical in vivo properties such as degradation rate and mass transport. In this report we describe the fabrication of a novel multi-fibre collagen fascicle structure, based on type-I collagen with failure stress of 25-49 MPa, approximating the strength and structure of native tendon tissue. We demonstrate a microscopic fabrication process based on the automated assembly of type-I collagen fibres with the ability to produce a controllable fascicle-like, structural motif allowing variable numbers of fibres per fascicle. We have confirmed that the resulting post-fabrication type-I collagen structure retains the essential phase behaviour, alignment and spectral characteristics of aligned native type-I collagen. We have also shown that both ovine tendon fibroblasts and human white blood cells in whole blood readily infiltrate the matrix on a macroscopic scale and that these cells adhere to the fibre surface after seven days in culture. The study has indicated that the synthetic collagen fascicle system may be a suitable biomaterial scaffold to provide a rationally designed implantable matrix material to mediate tendon repair and regeneration.

Cell- and gene-based approaches to tendon regeneration

Repair of rotator cuff tears in experimental models has been significantly improved by the use of enhanced biologic approaches, including platelet-rich plasma, bone marrow aspirate, growth factor supplements, and cell- and gene-modified cell therapy. Despite added complexity, cell-based therapies form an important part of enhanced repair, and combinations of carrier vehicles, growth factors, and implanted cells provide the best opportunity for robust repair. Bone marrow-derived mesenchymal stem cells provide a stimulus for repair in flexor tendons, but application in rotator cuff repair has not shown universally positive results. The use of scaffolds such as platelet-rich plasma, fibrin, and synthetic vehicles and the use of gene priming for stem cell differentiation and local anabolic and anti-inflammatory impact have both provided essential components for enhanced tendon and tendon-to-bone repair in rotator cuff disruption. Application of these research techniques in human rotator cuff injury has generally been limited to autologous platelet-rich plasma, bone marrow concentrate, or bone marrow aspirates combined with scaffold materials. Cultured mesenchymal progenitor therapy and gene-enhanced function have not yet reached clinical trials in humans. Research in several animal species indicates that the concept of gene-primed stem cells, particularly embryonic stem cells, combined with effective culture conditions, transduction with long-term integrating vectors carrying anabolic growth factors, and development of cells conditioned by use of RNA interference gene therapy to resist matrix metalloproteinase degradation, may constitute potential advances in rotator cuff repair. This review summarizes cell- and gene-enhanced cell research for tendon repair and provides future directions for rotator cuff repair using biologic composites.

Decellularized human dermis to treat massive rotator cuff tears: in vitro evaluations

Interest is increasing in biological scaffolds for tissue regeneration such as extracellular matrix membranes, developed through soft tissue decellularization. Extracellular matrix membranes were developed to heal different tendon and soft tissue lesions that are very frequent in the general population with high health-care costs and patient morbidity. The aim of this research was to evaluate a human dermal matrix (HDM) decellularized by a chemico-physical method. A primary culture of rat tenocytes was performed: tenocytes were seeded on HDM samples and on polystyrene wells as controls (CTR). Cell viability and synthetic activity were evaluated at 3 and 7 days. An in vitro microwound model was used to evaluate HDM bioactivity: after tenocyte expansion, artificial wounds were created, HDM extracts were added, and closure time and decorin synthesis were monitored histomorphometrically at 1, 4, 24, and 72 hr. A significant higher amount of collagen I was observed when cells were cultured on HDM in comparison with that on CTR (3 days: p < 0.0001; 7 days: p < 0.05). In HDM group, fibronectin synthesis was significantly higher at both experimental times (p < 0.0001). At 3 days, proteoglycans and transforming growth factor-β1 releases were significantly higher on HDM (p < 0.0001 and p < 0.005, respectively). The artificial microwound closure time and decorin expression were significantly enhanced by the addition of 50% HDM extract (p < 0.05). In vitro data showed that the decellularization technique enabled the development of a matrix with adequate biological and biomechanical properties.

Surgery of subacromial syndrome with application of plasma rich in growth factors

Background

Our objective was to evaluate clinical recovery of patients with subacromial syndrome, after administering them plasma rich in growth factors (PRGF) by means of the Constant, University of California Los Angeles (UCLA) and Dissabilities of Arm, Shoulder and Hand (DASH) tests.

Materials and Methods

Prospective cohort study involving two groups — group A, treated with PRGF (52 patients); and group B, without PRGF treatment (79 patients). We analyzed the clinical situation preoperatively (time 1), at 1 month (time 2) and after rehabilitation (time 3).

Results

We considered 131 patients (71.2% were men, with median age of 53.7 years). Different approaches were used — traditional (62.5%), mini-open (22.5%) and arthroscopic (15%), without significant differences (P= .71). We observed improvement in the Constant test results at time 2 (59.8 ± 11.5 points in group A vs. 13.2 ± 7.1 points in group B; P < .05) and at time 3 (79.3 ± 11.6 points in group A vs. 59.7 ± 20.1 points in group B; P ¼ .05). We found improvement in the UCLA test results at time 2 (23.2 ± 5.8 points in group A vs. 4.72 ± 1.1 points in group B; P < .05) and at time 3 (32.1 ± 5.3 points in group A vs. 22.1 ± 7.35 points in group B; P < .05). We also observed improvement in the DASH test results at time 2 (45.2 ± 17.2 points in group A vs. 118.3 ± 7.6 points in group B, P < .05) and at time 3 (37.3 ± 12.6 points in group A vs. 69 ± 25.7 points in group B). Time of rehabilitation reduced significantly: 2.53 months in group A vs. 4.96 months in group B (P < .05). No significant differences were observed in surgical times: 88 minutes (group A) vs. 97 minutes (group B).

Conclusion

In our experience, PRGF should be indicated in subacromial syndrome and cuff involvement, as shown by the improvement in our results in terms of better results of tests, reduction in rehabilitation time and no increase in operation time.

Human dermal matrix scaffold augmentation for large and massive rotator cuff repairs: preliminary clinical and MRI results at 1-year follow-up

The high incidence of recurrent tendon tears after repair of massive cuff lesions is prompting the research of materials aimed at mechanically or biologically reinforcing the tendon. Among the materials studied upto now, the extracellular matrix (ECM) scaffolds of human origin have proved to be the safest and most efficient, but the current laws about grafts and transplants preclude their use in Europe. In order to overcome this condition in 2006, we started a project regarding the production of an ECM scaffold of human origin which could be implanted in Europe too. In 2009, the clinical study began with the implantation of dermal matrix scaffolds in 7 middle-aged patients affected with large/massive cuff lesions and tendon degeneration. Out of 5 cases, followed for at least 1 year in which the scaffold was employed as an augmentation device, there were 3 patients with complete healing, 1 partial re-tear, and 1 total recurrence. The absence of adverse inflammatory or septic complications allows to continue this line of research with a prospective controlled study in order to define the real advantages and correct indications offered by scaffold application.

Culture of human rotator cuff cells on orthobiologic support (porcine small intestinal submucosa)

Outcomes obtained in patients with two-tendon rotator cuff tear submitted to repair reinforced with porcine small intestinal submucosa (SIS) have not been as encouraging as those observed in animal models. We verify the capacity of SIS to be used as a physical support for a culture of cuff cells. During arthroscopic repairs of large rotator cuff tears, we removed a fragment of supraspinatus tendon. Samples were treated for obtaining a cuff cell culture. Daily microscopic analysis, to observe adhesion to substrate, replication and cell shape was performed. A confluent monolayer was obtained in 1 week. Cells at the second passage were collected and seeded onto scaffold and cultured for 7-30 days. A morphological and immunohistochemical evaluation was performed. After 1 week, a monolayer of tendinous-like cells lay along the surface of the SIS. Within two weeks, a multicellular layer was observable in many foci of the scaffold. After a month, the cells completely invaded the numerous splits of the SIS and were positive to monoclonal anti-type I collagen antibody. Our experimental study has proved that a cuff cell culture can be performed using SIS as substrate. The culture covers the SIS surface, therefore it may reduce immune or non-specific inflammatory reactions.

The natural and engineered 3D microenvironment as a regulatory cue during stem cell fate determination

The concept of using stem cells as self-renewing sources of healthy cells in regenerative medicine has existed for decades, but most applications have yet to achieve clinical success. A main reason for the lack of successful stem cell therapies is the difficulty in fully recreating the maintenance and control of the native stem cell niche. Improving the performance of transplanted stem cells therefore requires a better understanding of the cellular mechanisms guiding stem cell behavior in both native and engineered three-dimensional (3D) microenvironments. Most techniques, however, for uncovering mechanisms controlling cell behavior in vitro have been developed using 2D cell cultures and are of limited use in 3D environments such as engineered tissue constructs. Deciphering the mechanisms controlling stem cell fate in native and engineered 3D environments, therefore, requires rigorous quantitative techniques that permit mechanistic, hypothesis-driven studies of cell-microenvironment interactions. Here, we review the current understanding of 2D and 3D stem cell control mechanisms and propose an approach to uncovering the mechanisms that govern stem cell behavior in 3D.