Supraspinatus detachment causes musculotendinous degeneration and a reduction in bone mineral density at the enthesis in a rat model of chronic rotator cuff degeneration

BACKGROUND: To evaluate biological strategies that enhance tendon-bone healing in humans, it is imperative that suitable animal models accurately reproduce the pathological changes observed in the clinical setting following a tear. The purpose of the present study was to investigate rotator cuff degeneration in a rat, as well as assess the development of osteopenia at the enthesis following tendon detachment. METHODS: Eighteen female Wistar rats underwent unilateral detachment of the supraspinatus tendon. Specimens were retrieved at 4 weeks (n = 6), 6 weeks (n = 6) and 9 weeks (n = 6) postoperatively for histological analysis and peripheral quantitative computer tomography. RESULTS: Three weeks following tendon detachment, there was a significant increase in the modified Movin score, characterized by a loss of muscle mass, fatty infiltration, an increase in musculotendinous cellularity, loss of normal collagen fibre structure/arrangement, rounded tenocyte nuclei and an increase in the number of vascular bundles. This was accompanied by a reduction in bone mineral density at the tendon insertion site. After 3 weeks however, these changes were less prominent. CONCLUSIONS: The rotator cuff tendon-muscle-bone unit in a rat model 3 weeks after detachment of supraspinatus represents a valid model for investigating rotator cuff degeneration

Stem Cell Interventions for Bone Healing: Fractures and Osteoporosis

With the ageing population, musculoskeletal conditions are becoming more inherent. Delayed union is defined as a slower than normal fracture healing response, with no healing after 4 to 6 months; however, union is anticipated given sufficient time. In the context of delayed/non-union, fragility fractures in osteoporotic populations carry significant patient morbidity and socioeconomic costs. Multiple mechanisms hinder fracture healing in osteoporotic patients, imbalanced bone remodelling leads to impaired bone microarchitecture due to reduced osteoblast number and activity and as such, callus formation is diminished. Since stem cells can self-renew and differentiate into various tissue lineages, they are becoming very popular in tissue regeneration in musculoskeletal conditions. In this review we discuss the role of stem cells in physiological fracture healing and their potential therapeutic use following a fracture. We explore the potential of stem cells, the release of chemokines and cytokines to reduce fracture risk in osteoporosis

The influence of parathyroid hormone 1-34 on the osteogenic characteristics of adipose- and bone-marrow-derived mesenchymal stem cells from juvenile and ovarectomized rats

Mesenchymal stem cells (MSCs) are of growing interest in terms of bone regeneration. Most preclinical trials utilize bone-marrow-derived mesenchymal stem cells (bMSCs), although this is not without isolation and expansion difficulties. The aim of this study was: to compare the characteristics of bMSCs and adipose-derived mesenchymal stem cells (AdMSCs) from juvenile, adult, and ovarectomized (OVX) rats; and to assess the effect of human parathyroid hormone (hPTH) 1-34 on their osteogenic potential and migration to stromal cell-derived factor-1 (SDF-1)

The influence of age and osteoporosis on bone marrow stem cells from rats

OBJECTIVES: This study aimed to assess the effect of age and osteoporosis on the proliferative and differentiating capacity of bone-marrow-derived mesenchymal stem cells (MSCs) in female rats. We also discuss the role of these factors on expression and migration of cells along the C-X-C chemokine receptor type 4 (CXCR-4) / stromal derived factor 1 (SDF-1) axis. METHODS: Mesenchymal stem cells were harvested from the femora of young, adult, and osteopenic Wistar rats. Cluster of differentiation (CD) marker and CXCR-4 expression was measured using flow cytometry. Cellular proliferation was measured using Alamar Blue, osteogenic differentiation was measured using alkaline phosphatase expression and alizarin red production, and adipogenic differentiation was measured using Oil red O. Cells were incubated in Boyden chambers to quantify their migration towards SDF-1. Data was analyzed using a Student’s t-test, where p-values < 0.05 were considered significant. RESULTS: CD marker expression and proliferation of the MSCs from the three groups was not significantly different. The young MSCs demonstrated significantly increased differentiation into bone and fat and superior migration towards SDF-1. The migration of SDF-1 doubled with young rats compared with the adult rats (p = 0.023) and it was four times higher when compared with cells isolated from ovariectomized (OVX) osteopenic rats (p = 0.013). CONCLUSION: Young rat MSCs are significantly more responsive to osteogenic differentiation, and, contrary to other studies, also demonstrated increased adipogenic differentiation compared with cells from adult and ostopenic rats. Young-rat-derived cells also showed superior migration towards SDF-1 compared with MSCs from OVX and adult control rats

Clinical outcomes following intra-articular injection of autologous adipose-derived mesenchymal stem cells for the treatment of osteoarthritis in dogs characterized by weight-bearing asymmetry

Aims: This study investigates the effects of intra-articular injection of adipose-derived mesenchymal stem cells (AdMSCs) and platelet-rich plasma (PRP) on lameness, pain, and quality of life in osteoarthritic canine patients. Methods: With informed owner consent, adipose tissue collected from adult dogs diagnosed with degenerative joint disease was enzymatically digested and cultured to passage 1. A small portion of cells (n = 4) surplus to clinical need were characterized using flow cytometry and tri-lineage differentiation. The impact and degree of osteoarthritis (OA) was assessed using the Liverpool Osteoarthritis in Dogs (LOAD) score, Modified Canine Osteoarthritis Staging Tool (mCOAST), kinetic gait analysis, and diagnostic imaging. Overall, 28 joints (25 dogs) were injected with autologous AdMSCs and PRP. The patients were followed up at two, four, eight, 12, and 24 weeks. Data were analyzed using two related-samples Wilcoxon signed-rank or Mann-Whitney U tests with statistical significance set at p < 0.05. Results: AdMSCs demonstrated stem cell-like characteristics. LOAD scores were significantly lower at week 4 compared with preinjection (p = 0.021). The mCOAST improved significantly after three months (p = 0.001) and six months (p = 0.001). Asymmmetry indices decreased from four weeks post-injection and remained significantly lower at six months (p = 0.025). Conclusion: These improvements in quality of life, reduction in pain on examination, and improved symmetry in dogs injected with AdMSCs and PRP support the effectiveness of this combined treatment for symptom modification in canine OA for six months

Mesenchymal Stromal Cells and Platelet-Rich Plasma Promote Tendon Allograft Healing in Ovine Anterior Cruciate Ligament Reconstruction

Purpose The effect of bone marrow mesenchymal stromal cells (BMSCs) and platelet-rich plasma (PRP) on tendon allograft maturation in a large animal anterior cruciate ligament (ACL) reconstruction model was reported for the first time. It was hypothesised that compared with non-augmented ACL reconstruction, BMSCs and PRP would enhance graft maturation after 12 weeks and this would be detected using magnetic resonance imaging (MRI). Methods Fifteen sheep underwent unilateral tendon allograft ACL reconstruction using aperture fixation and were randomised into three groups (n = 5). Group 1 received 10 million allogeneic BMSCs in 2 ml fibrin sealant; Group 2 received 12 ml PRP in a plasma clot injected into the graft and bone tunnels; and Group 3 (control) received no adjunctive treatment. At autopsy at 12 weeks, a graft maturation score was determined by the sum for graft integrity, synovial coverage and vascularisation, graft thickness and apparent tension, and synovial sealing at tunnel apertures. MRI analysis (n = 2 animals per group) of the signal–noise quotient (SNQ) and fibrous interzone (FIZ) was used to evaluate intra-articular graft maturation and tendon–bone healing, respectively. Spearman’s rank correlation coefficient (r) of SNQ, autopsy graft maturation score and bone tunnel diameter were analysed. Results The BMSC group (p = 0.01) and PRP group (p = 0.03) had a significantly higher graft maturation score compared with the control group. The BMSC group scored significantly higher for synovial sealing at tunnel apertures (p = 0.03) compared with the control group. The graft maturation score at autopsy significantly correlated with the SNQ (r = − 0.83, p < 0.01). The tunnel diameter of the femoral tunnel at the aperture (r = 0.883, p = 0.03) and mid-portion (r = 0.941, p = 0.02) positively correlated with the SNQ. Conclusions BMSCs and PRP significantly enhanced graft maturation, which indicates that orthobiologics can accelerate the biologic events in tendon allograft incorporation. Femoral tunnel expansion significantly correlated with inferior maturation of the intra-articular graft. The clinical relevance of this study is that BMSCs and PRP enhance allograft healing in a translational model, and biological modulation of graft healing can be evaluated non-invasively using MRI

Osteoporosis and ageing affects the migration of stem cells and this is ameliorated by transfection with CXCR4

OBJECTIVES: Cellular movement and relocalisation are important for many physiologic properties. Local mesenchymal stem cells (MSCs) from injured tissues and circulating MSCs aid in fracture healing. Cytokines and chemokines such as Stromal cell-derived factor 1(SDF-1) and its receptor chemokine receptor type 4 (CXCR4) play important roles in maintaining mobilisation, trafficking and homing of stem cells from bone marrow to the site of injury. We investigated the differences in migration of MSCs from the femurs of young, adult and ovariectomised (OVX) rats and the effect of CXCR4 over-expression on their migration. METHODS: MSCs from young, adult and OVX rats were put in a Boyden chamber to establish their migration towards SDF-1. This was compared with MSCs transfected with CXCR4, as well as MSCs differentiated to osteoblasts. RESULTS: MSCs from OVX rats migrate significantly (p < 0.05) less towards SDF-1 (9%, sd 5%) compared with MSCs from adult (15%, sd 3%) and young rats (25%, sd 4%). Cells transfected with CXCR4 migrated significantly more towards SDF-1 compared with non-transfected cells, irrespective of whether these cells were from OVX (26.5%, sd 4%), young (47%, sd 17%) or adult (21%, sd 4%) rats. Transfected MSCs differentiated to osteoblasts express CXCR4 but do not migrate towards SDF-1. CONCLUSIONS: MSC migration is impaired by age and osteoporosis in rats, and this may be associated with a significant reduction in bone formation in osteoporotic patients. The migration of stem cells can be ameliorated by upregulating CXCR4 levels which could possibly enhance fracture healing in osteoporotic patients

Application of a Demineralized Cortical Bone Matrix and Bone Marrow-Derived Mesenchymal Stem Cells in a Model of Chronic Rotator Cuff Degeneration

BACKGROUND: The success of rotator cuff repair is primarily dependent on tendon-bone healing. Failure is common because weak scar tissue replaces the native enthesis, rendering it prone to reruptures. A demineralized bone matrix (DBM) consists of a network of collagen fibers that provide a sustained release of growth factors such as bone morphogenetic proteins. Previous studies have demonstrated that it can regenerate a fibrocartilaginous enthesis. HYPOTHESIS: The use of a DBM and mesenchymal stem cells (MSCs) at the healing enthesis will result in a higher bone mineral density at the tendon insertion and will enhance the regeneration of a morphologically superior enthesis when compared with an acellular human dermal matrix. STUDY DESIGN: Controlled laboratory study. METHODS: Eighteen female Wistar rats underwent unilateral detachment of the supraspinatus tendon. Three weeks later, tendon repair was carried out in animals randomized into 3 groups: group 1 received augmentation of the repair with a cortical allogenic DBM (n = 6); group 2 received augmentation with a nonmeshed, ultrathick, acellular human dermal matrix (n = 6); and group 3 underwent tendon-bone repair without a scaffold (n = 6). All animals received 1 × 10(6) MSCs delivered in fibrin glue to the repair site. Specimens were retrieved at 6 weeks postoperatively for histological analysis and the evaluation of bone mineral density. RESULTS: All groups demonstrated closure of the tendon-bone gap with a fibrocartilaginous enthesis. Although there were no significant differences in the enthesis maturation and modified Movin scores, repair augmented with a dermal matrix + MSCs exhibited a disorganized enthesis, abnormal collagen fiber arrangement, and greater cellularity compared with other MSC groups. Only repairs augmented with a DBM + MSCs reached a bone mineral density not significantly lower than nonoperated controls. CONCLUSION: A DBM enhanced with MSCs can augment rotator cuff healing at 6 weeks and restore bone mineral density at the enthesis to its preinjury levels. CLINICAL RELEVANCE: Biological augmentation of rotator cuff repair with a DBM and MSCs may reduce the incidence of retears, although further studies are required to determine its effectiveness

Antibacterial PMMA Composite Cements with Tunable Thermal and Mechanical Properties

PMMA-based cements are the most used bone cements in vertebroplasty and total hip arthroplasty. However, they present several drawbacks, including susceptibility to bacterial infection, monomer leakage toxicity, and high polymerization temperature, which can all lead to damage to the surrounding tissues and their failure. In the present study, silver nanowires (AgNWs) have been introduced to bestow antibacterial properties; chitosan (CS) to promote porosity and to reduce the polymerization temperature, without negatively affecting the mechanical performance; and methacryloyl chitosan (CSMCC) to promote cross-linking with methyl methacrylate (MMA) and reduce the quantity of monomer required for polymerization. Novel PMMA cements were formulated containing AgNWs (0 and 1% w/w) and CS or CSMCC at various concentrations (0, 10, 20, and 30% w/w), testing two different ratios of powder and MMA (P/L). Mechanical, thermal, antibacterial, and cytotoxic properties of the resulting composite cements were tested. Cements with concentrations of CS &gt; 10% presented a significantly reduced polymerization temperature. The mechanical performances were affected for concentrations &gt; 20% with a P/L concentration equal to 2:1. Concentrations of AgNWs as low as 1% w/w conferred antimicrobial activity against S. aureus, whereas biofilm formation on the surface of the cements was increased when CS was included in the preparation. The combination of CS and AgNWs allowed a higher concentration of Ag+ to be released over time with enhanced antimicrobial activity. Inclusion of AgNWs did not affect cell viability on the scaffolds. In conclusion, a combination of CS and AgNWs may be beneficial for reducing both polymerization temperature and biofilm formation, without significantly affecting mesenchymal stem cell proliferation on the scaffolds. No advantages have been noticed as a result of the reducing P/L ratio or using CSMCC instead of CS

The effectiveness of demineralized cortical bone matrix in a chronic rotator cuff tear model.

BACKGROUND: The purpose of this study was to assess the effect of demineralized bone matrix (DBM) on rotator cuff tendon-bone healing. The hypothesis was that compared with a commercially available dermal matrix scaffold, DBM would result in a higher bone mineral density and regenerate a morphologically superior enthesis in a rat model of chronic rotator cuff degeneration. METHODS: Eighteen female Wistar rats underwent unilateral detachment of the supraspinatus tendon. Three weeks later, tendon repair was carried out in animals randomized into 3 groups: group 1 animals were repaired with DBM (n = 6); group 2 received augmentation with the dermal scaffold (n = 6); and group 3 (controls) underwent nonaugmented tendon-bone repair (n = 6). Specimens were retrieved at 6 weeks postoperatively for histologic analysis and evaluation of bone mineral density. RESULTS: No failures of tendon-bone healing were noted throughout the study. All groups demonstrated closure of the tendon-bone gap with a fibrocartilaginous interface. Dermal collagen specimens exhibited a disorganized structure with significantly more abnormal collagen fiber arrangement and cellularity than in the DBM-based repairs. Nonaugmented repairs exhibited a significantly higher bone mineral density than in DBM and the dermal collagen specimens and were not significantly different from control limbs that were not operated on. CONCLUSION: The application of DBM to a rat model of chronic rotator cuff degeneration did not improve the composition of the healing enthesis compared with nonaugmented controls and a commercially available scaffold. However, perhaps the most important finding of this study was that the control group demonstrated a similar outcome to augmented repairs