Evaluation of the Effects of Synovial Multipotent Cells on Deep Digital Flexor Tendon Repair in a Large Animal Model of Intra-Synovial Tendinopathy.

Intra-synovial tendon injuries are a common orthopedic problem with limited treatment options. The synovium is a specialized connective tissue forming the inner encapsulating lining of diarthrodial joints and intra-synovial tendons. It contains multipotent mesenchymal stromal cells that render it a viable source of progenitors for tendon repair. This study evaluated the effects of autologous implantation of cells derived from normal synovium (synovial membrane cells [SMCs]) in augmenting repair in an ovine model of intra-synovial tendon injury. For this purpose, synovial biopsies were taken from the right digital flexor tendon sheath following creation of a defect to the lateral deep digital flexor tendon. Mononuclear cells were isolated by partial enzymatic digestion and assessed for MSC characteristics. Cell tracking and tendon repair were assessed by implanting 5 × 106 cells into the digital flexor tendon sheath under ultrasound guidance with the effects evaluated using magnetic resonance imaging and histopathology. Synovial biopsies yielded an average 4.0 × 105 ± 2.7 × 105 SMCs that exhibited a fibroblastic morphology, variable osteogenic, and adipogenic responses but were ubiquitously strongly chondrogenic. SMCs displayed high expression of CD29 with CD271NEGATIVE and MHC-IILOW cell-surface marker profiles, and variable expression of CD73, CD90, CD105, CD166, and MHC-I. Implanted SMCs demonstrated engraftment within the synovium, though a lack of repair of the tendon lesion over 24 weeks was observed. We conclude healthy synovium is a viable source of multipotent cells, but that the heterogeneity of synovium underlies the variability between different SMC populations, which while capable of engraftment and persistence within the synovium exhibit limited capacity of influencing tendon repair. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 38:128-138, 2020.

Bone mineral health is sensitively related to environmental cadmium exposure- experimental and human data.

Exposure to cadmium (Cd) is recognised as one of the risk factors for osteoporosis, although critical exposure levels and exact mechanisms are still unknown. Here, we first confirmed that in male Wistar rats challenged orally with 6 different levels of Cd (0.3-10 mg/kg b.w.), over 28 days, there was a direct dose relationship to bone Cd concentration. Moreover, bone mineral content was significantly diminished by ∼15% (p < 0.0001) plateauing already at the lowest exposure level. For the other essential bone elements zinc (Zn) loss was most marked. Having established the sensitive metrics (measures of Cd exposure), we then applied them to 20 randomly selected human femoral head bone samples from 16 independent subjects. Bone Cd concentration was inversely proportional to trabecular bone mineral density and mineral (calcium) content and Zn content of bone, but not the donor's age. Our findings, through direct bone analyses, support the emerging epidemiological view that bone health, adjudged by mineral density, is extremely sensitive to even background levels of environmental Cd. Importantly, however, our data also suggest that Cd may play an even greater role in compromised bone health than prior indirect estimates of exposure could reveal. Environmental Cd may be a substantially determining factor in osteoporosis and large cohort studies with direct bone analyses are now merited.

Bone marrow mesenchymal stem cells do not enhance intra-synovial tendon healing despite engraftment and homing to niches within the synovium.

BACKGROUND: Intra-synovial tendon injuries display poor healing, which often results in reduced functionality and pain. A lack of effective therapeutic options has led to experimental approaches to augment natural tendon repair with autologous mesenchymal stem cells (MSCs) although the effects of the intra-synovial environment on the distribution, engraftment and functionality of implanted MSCs is not known. This study utilised a novel sheep model which, although in an anatomically different location, more accurately mimics the mechanical and synovial environment of the human rotator cuff, to determine the effects of intra-synovial implantation of MSCs. METHODS: A lesion was made in the lateral border of the lateral branch of the ovine deep digital flexor tendon within the digital sheath and 2 weeks later 5 million autologous bone marrow MSCs were injected under ultrasound guidance into the digital sheath. Tendons were recovered post mortem at 1 day, and 1-2, 4, 12 and 24 weeks after MSC injection. For the 1-day and 1-2-week groups, MSCs labelled with fluorescent-conjugated magnetic iron-oxide nanoparticles (MIONs) were tracked with MRI, histology and flow cytometry. The 4, 12 and 24-week groups were implanted with non-labelled cells and compared with saline-injected controls for healing. RESULTS: The MSCs displayed no reduced viability in vitro to an uptake of 20.0 ± 4.6 pg MIONs per cell, which was detectable by MRI at minimal density of ~ 3 × 104 cells. Treated limbs indicated cellular distribution throughout the tendon synovial sheath but restricted to the synovial tissues, with no MSCs detected in the tendon or surgical lesion. The lesion was associated with negligible morbidity with minimal inflammation post surgery. Evaluation of both treated and control lesions showed no evidence of healing of the lesion at 4, 12 and 24 weeks on gross and histological examination. CONCLUSIONS: Unlike other laboratory animal models of tendon injury, this novel model mimics the failed tendon healing seen clinically intra-synovially. Importantly, however, implanted stem cells exhibited homing to synovium niches where they survived for at least 14 days. This phenomenon could be utilised in the development of novel physical or biological approaches to enhance localisation of cells in augmenting intra-synovial tendon repair.

The Wnt5a Receptor, Receptor Tyrosine Kinase-Like Orphan Receptor 2, Is a Predictive Cell Surface Marker of Human Mesenchymal Stem Cells with an Enhanced Capacity for Chondrogenic Differentiation.

Multipotent mesenchymal stem cells (MSCs) have enormous potential in tissue engineering and regenerative medicine. However, until now, their development for clinical use has been severely limited as they are a mixed population of cells with varying capacities for lineage differentiation and tissue formation. Here, we identify receptor tyrosine kinase-like orphan receptor 2 (ROR2) as a cell surface marker expressed by those MSCs with an enhanced capacity for cartilage formation. We generated clonal human MSC populations with varying capacities for chondrogenesis. ROR2 was identified through screening for upregulated genes in the most chondrogenic clones. When isolated from uncloned populations, ROR2+ve MSCs were significantly more chondrogenic than either ROR2-ve or unfractionated MSCs. In a sheep cartilage-repair model, they produced significantly more defect filling with no loss of cartilage quality compared with controls. ROR2+ve MSCs/perivascular cells were present in developing human cartilage, adult bone marrow, and adipose tissue. Their frequency in bone marrow was significantly lower in patients with osteoarthritis (OA) than in controls. However, after isolation of these cells and their initial expansion in vitro, there was greater ROR2 expression in the population derived from OA patients compared with controls. Furthermore, osteoarthritis-derived MSCs were better able to form cartilage than MSCs from control patients in a tissue engineering assay. We conclude that MSCs expressing high levels of ROR2 provide a defined population capable of predictably enhanced cartilage production. Stem Cells 2017;35:2280-2291.

Spatially offset Raman spectroscopy for photon migration studies in bones with different mineralization levels.

The ability of Spatially Offset Raman Spectroscopy (SORS) to obtain chemically specific information from below the sample surface makes it a promising technique for non-invasive in vivo diagnosis of bone conditions by sampling bone through the skin. The depth below a surface interrogated by SORS depends on the system's optical properties and is difficult to estimate for complex bone material. This paper uses 830 nm laser excitation to investigate the influence of bone mineralization on photon migration properties in deer antler cortex, equine metacarpal cortex and whale tympanic bulla. Thin slices form each type of bone (thickness: 0.6-1.0 mm) were cut and put together on top of each other forming stacks with a total thickness of 4.1-4.7 mm. A 0.38 mm thin slice of polytetrafluoroethylene (PTFE) served as a test material for Raman signal recovery and was placed in between the individual bone slices within the stack. At SORS offsets of 8.0-9.5 mm Raman bands of materials not present in healthy bone (e.g. PTFE as an example) can be recovered through 4.4-4.7 mm of cortical bone tissue, depending on mineralization level and porosity. These findings significantly increase our understanding of SORS analysis through bones of different composition and provide information that is vital to determine the value of SORS as a medical diagnostic technique. The data serve to define which SORS offset is best deployed for the non-invasive detection of chemically specific markers associated with infection, degeneration and disease or cancer within bone.

Repair of Torn Avascular Meniscal Cartilage Using Undifferentiated Autologous Mesenchymal Stem Cells: From In Vitro Optimization to a First-in-Human Study.

Meniscal cartilage tears are common and predispose to osteoarthritis (OA). Most occur in the avascular portion of the meniscus where current repair techniques usually fail. We described previously the use of undifferentiated autologous mesenchymal stem cells (MSCs) seeded onto a collagen scaffold (MSC/collagen-scaffold) to integrate meniscal tissues in vitro. Our objective was to translate this method into a cell therapy for patients with torn meniscus, with the long-term goal of delaying or preventing the onset of OA. After in vitro optimization, we tested an ovine-MSC/collagen-scaffold in a sheep meniscal cartilage tear model with promising results after 13 weeks, although repair was not sustained over 6 months. We then conducted a single center, prospective, open-label first-in-human safety study of patients with an avascular meniscal tear. Autologous MSCs were isolated from an iliac crest bone marrow biopsy, expanded and seeded into the collagen scaffold. The resulting human-MSC/collagen-scaffold implant was placed into the meniscal tear prior to repair with vertical mattress sutures and the patients were followed for 2 years. Five patients were treated and there was significant clinical improvement on repeated measures analysis. Three were asymptomatic at 24 months with no magnetic resonance imaging evidence of recurrent tear and clinical improvement in knee function scores. Two required subsequent meniscectomy due to retear or nonhealing of the meniscal tear at approximately 15 months after implantation. No other adverse events occurred. We conclude that undifferentiated MSCs could provide a safe way to augment avascular meniscal repair in some patients. Registration: EU Clinical Trials Register, 2010-024162-22. Stem Cells Translational Medicine 2017;6:1237-1248.

Large animal in vivo evaluation of a binary blend polymer scaffold for skeletal tissue-engineering strategies; translational issues.

Binary blend polymers offer the opportunity to combine different desirable properties into a single scaffold, to enhance function within the field of tissue engineering. Previous in vitro and murine in vivo analysis identified a polymer blend of poly(l-lactic acid)-poly(ε-caprolactone) (PLLA:PCL 20:80) to have characteristics desirable for bone regeneration. Polymer scaffolds in combination with marrow-derived skeletal stem cells (SSCs) were implanted into mid-shaft ovine 3.5 cm tibial defects, and indices of bone regeneration were compared to groups implanted with scaffolds alone and with empty defects after 12 weeks, including micro-CT, mechanical testing and histological analysis. The critical nature of the defect was confirmed via all modalities. Both the scaffold and scaffold/SSC groups showed enhanced quantitative bone regeneration; however, this was only found to be significant in the scaffold/SSCs group (p = 0.04) and complete defect bridging was not achieved in any group. The mechanical strength was significantly less than that of contralateral control tibiae (p < 0.01) and would not be appropriate for full functional loading in a clinical setting. This study explored the hypothesis that cell therapy would enhance bone formation in a critical-sized defect compared to scaffold alone, using an external fixation construct, to bridge the scale-up gap between small animal studies and potential clinical translation. The model has proved a successful critical defect and analytical techniques have been found to be both valid and reproducible. Further work is required with both scaffold production techniques and cellular protocols in order to successfully scale-up this stem cell/binary blend polymer scaffold. © 2015 The Authors. Journal of Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.

Counteracting bone fragility with human amniotic mesenchymal stem cells.

The impaired maturation of bone-forming osteoblasts results in reduced bone formation and subsequent bone weakening, which leads to a number of conditions such as osteogenesis imperfecta (OI). Transplantation of human fetal mesenchymal stem cells has been proposed as skeletal anabolic therapy to enhance bone formation, but the mechanisms underlying the contribution of the donor cells to bone health are poorly understood and require further elucidation. Here, we show that intraperitoneal injection of human amniotic mesenchymal stem cells (AFSCs) into a mouse model of OI (oim mice) reduced fracture susceptibility, increased bone strength, improved bone quality and micro-architecture, normalised bone remodelling and reduced TNFα and TGFß sigalling. Donor cells engrafted into bones and differentiated into osteoblasts but importantly, also promoted endogenous osteogenesis and the maturation of resident osteoblasts. Together, these findings identify AFSC transplantation as a countermeasure to bone fragility. These data have wider implications for bone health and fracture reduction.

Is the Collagen Primed for Mineralization in Specific Regions of the Turkey Tendon? An Investigation of the Protein-Mineral Interface Using Raman Spectroscopy.

The tendons in the turkey leg have specific well-defined areas which become mineralized as the animal ages and they are a thoroughly characterized model system for studying the mineralization process of bone. In this study, nondestructive Raman spectroscopic analysis was used to explore the hypothesis that regions of the turkey tendon that are associated with mineralization exhibit distinct and observable chemical modifications of the collagen prior to the onset of mineralization. The Raman spectroscopy features associated with mineralization were identified by probing (on the micrometer scale) the transition zone between mineralized and nonmineralized regions of turkey leg tendons. These features were then measured in whole tendons and identified in regions of tendon which are destined to become rapidly mineralized around 14 weeks of age. The data show there is a site-specific difference in collagen prior to the deposition of mineral, specifically the amide III band at 1270 cm(-1) increases as the collagen becomes more ordered (increased amide III:amide I ratio) in regions that become mineralized compared to collagen destined to remain nonmineralized. If this mechanism were present in materials of different mineral fraction (and thus material properties), it could provide a target for controlling mineralization in metabolic bone disease.

Peak strain magnitudes and rates in the tibia exceed greatly those in the skull: An in vivo study in a human subject.

Bone mass and architecture are the result of a genetically determined baseline structure, modified by the effect of internal hormonal/biochemical regulators and the effect of mechanical loading. Bone strain is thought to drive a feedback mechanism to regulate bone formation and resorption to maintain an optimal, but not excessive mass and organisation of material at each skeletal location. Because every site in the skeleton has different functions, we have measured bone strains induced by physiological and more unusual activities, at two different sites, the tibia and cranium of a young human male in vivo. During the most vigorous activities, tibial strains were shown to exceed 0.2%, when ground reaction exceeded 5 times body weight. However in the skull the highest strains recorded were during heading a heavy medicine/exercise ball where parietal strains were up to 0.0192%. Interestingly parietal strains during more physiological activities were much lower, often below 0.01%. Strains during biting were not dependent upon bite force, but could be induced by facial contortions of similar appearance without contact between the teeth. Rates of strain change in the two sites were also very different, where peak tibial strain rate exceeded rate in the parietal bone by more than 5 fold. These findings suggest that the skull and tibia are subject to quite different regulatory influences, as strains that would be normal in the human skull would be likely to lead to profound bone loss by disuse in the long bones.

Towards the in vivo prediction of fragility fractures with Raman spectroscopy.

Fragility fractures, those fractures which result from low level trauma, have a large and growing socio-economic cost in countries with aging populations. Bone-density-based assessment techniques are vital for identifying populations that are at higher risk of fracture, but do not have high sensitivity when it comes to identifying individuals who will go on to have their first fragility fracture. We are developing Spatially Offset Raman Spectroscopy (SORS) as a tool for retrieving chemical information from bone non-invasively in vivo. Unlike X-ray-based techniques SORS can retrieve chemical information from both the mineral and protein phases of the bone. This may enable better discrimination between those who will or will not go on to have a fragility fracture because both phases contribute to bone's mechanical properties. In this study we analyse excised bone with Raman spectroscopy and multivariate analysis, and then attempt to look for similar Raman signals in vivo using SORS. We show in the excised work that on average, bone fragments from the necks of fractured femora are more mineralised (by 5-10%) than (cadaveric) non-fractured controls, but the mineralisation distributions of the two cohorts are largely overlapped. In our in vivo measurements, we observe similar, but as yet statistically underpowered, differences. After the SORS data (the first SORS measurements reported of healthy and diseased human cohorts), we identify methodological developments which will be used to improve the statistical significance of future experiments and may eventually lead to more sensitive prediction of fragility fractures. © 2015 The Authors. Journal of Raman Spectroscopy Published by John Wiley & Sons, Ltd.

The scale-up of a tissue engineered porous hydroxyapatite polymer composite scaffold for use in bone repair: an ovine femoral condyle defect study.

The development of an osteogenic bone graft substitute has important practical and cost implications in many branches of medicine where bone regeneration is required. Previous in vitro and small animal (murine) in vivo studies highlighted a porous hydroxyapatite/poly (DL-lactic acid) composite scaffold in combination with skeletal stem cells (SSCs) as a potential bone graft substitute candidate. The aim of the current study was to scale up the bone cell-scaffold construct to large animals and examine the potential for repair of a critical-sized defect via an ovine model. SSC seeded scaffolds (and unseeded scaffold controls) were implanted bilaterally into ovine femoral condyle critical defects for 3 months. A parallel in vitro analysis of ovine SSC seeded scaffolds was also performed. Post mortem mechanical indentation testing showed the bone strengths of the defect sites were 20% (controls) and 11% (SSC seeded scaffolds) those of normal cancellous bone (p < 0.01). MicroCT analysis demonstrated new bone formation within all defects with a mean increase of 13.4% in the control scaffolds over the SSC seeded scaffolds (p = 0.14). Histological examination confirmed these findings, with enhanced quality new bone within the control defects. This study highlights important issues and steps to overcome in scale-up and translation of tissue engineered products. The scaffold demonstrated encouraging results as an osteoconductive matrix; however, further work is required with cellular protocols before any human trials.

Functional adaptation of long bone extremities involves the localized "tuning" of the cortical bone composition; evidence from Raman spectroscopy.

In long bones, the functional adaptation of shape and structure occurs along the whole length of the organ. This study explores the hypothesis that adaptation of bone composition is also site-specific and that the mineral-to-collagen ratio of bone (and, thus, its mechanical properties) varies along the organ's length. Raman spectroscopy was used to map the chemical composition of long bones along their entire length in fine spatial resolution (1 mm), and then biochemical analysis was used to measure the mineral, collagen, water, and sulfated glycosaminoglycan content where site-specific differences were seen. The results show that the mineral-to-collagen ratio of the bone material in human tibiae varies by <5% along the mid-shaft but decreases by >10% toward the flared extremities of the bone. Comparisons with long bones from other large animals (horses, sheep, and deer) gave similar results with bone material composition changing across tens of centimeters. The composition of the bone apatite also varied with the phosphate-to-carbonate ratio decreasing toward the ends of the tibia. The data highlight the complexity of adaptive changes and raise interesting questions about the biochemical control mechanisms involved. In addition to their biological interest, the data provide timely information to researchers developing Raman spectroscopy as a noninvasive tool for measuring bone composition in vivo (particularly with regard to sampling and measurement protocol).

Low dose of propranolol does not affect rat osteotomy healing and callus strength.

Experimental studies suggest that the ß-blocker propranolol stimulates bone formation but little work has investigated its effect on fracture healing. In this study, we examined if a low dose of propranolol, previously shown to be preventive against bone loss in rats, improves bone repair. Female Wistar rats were injected with saline or propranolol (0.1 mg/kg/day) (n = 20/group), 5 days a week for 8 weeks. Three weeks after the beginning of treatment, all rats underwent a mid-diaphyseal transverse osteotomy in the left femur. Radiographic analysis of ostetomy healing was performed 2 and 5 weeks after osteotomy. Rats were sacrificed at 5 weeks and femora collected for measurements of fracture strength by torsional testing, callus volume, and mineral content by micro-CT analysis and histology of fracture callus. Eighty nine percent of osteotomies achieved apparent radiological union by 5 weeks in both groups. Propranolol treatment did not significantly alter the torsional strength of the fractured femur compared with controls. The volume and mineralization of fracture callus at 5 weeks were not significantly different in both groups. Histology showed that endochondral ossification was not affected by propranolol. Altogether, our results demonstrate that propranolol using the regimen described does not significantly improve or inhibit rat osteotomy healing and mechanical strength.

Millimeter-scale mapping of cortical bone reveals organ-scale heterogeneity.

Raman spectroscopy was used to show that across 10 cm of diaphyseal (mid-shaft) cortical bone the phosphate-to-amide I ratio (a measure of the mineral to collagen ratio) can vary by as much as 8%, and the phosphate-to-carbonate ratio (a measure of carbonate inclusion in mineral crystals) by as much as 5%. The data are preliminary but are important because they reveal a spatial variation at a scale that is much larger than many of the spectral maps reported in the literature to date. Thus they illustrate natural variation in chemical composition that could have been overlooked in such studies or could have appeared as an undue error where the overall composition of the bone was investigated. Quantifying the variation in mid-shaft cortical bone at the millimeter/centimeter scale reduces the possibility of natural heterogeneity obscuring the average bone composition, or being mistaken for experimental signal, and results in an improvement in the sampling accuracy analogous to that obtained by switching from micrometer-size point spectra of bones to spectral images obtained across hundreds of micrometers. Although the study was carried out using Raman spectroscopy, the underlying cause of the variation is ascribed to the variation of the chemical composition of the bone; therefore the findings have direct implications for other chemically specific analytical methods such as Fourier transform infrared spectroscopy or nuclear magnetic resonance spectroscopy.

Do progenitor cells from different tissue have the same phenotype?

The purpose of this work was to validate isolation methods for sheep mesenchymal stem cells (MSC) from different sources and to explore the hypothesis that MSC exhibit markers of the same phenotype independent from tissue source. Cells derived from ovine bone marrow, synovial membrane and adipose tissue were characterized using the following markers: CD44, CD45, CD11b and MHC-I. The isolated MSC were cultivated, went through osteogenic, chondrogenic and adipogenic differentiation, and were characterized by flow cytometry using mouse anti-ovine CD44, CD45 and MHC-I monoclonal antibody (mAb), and mouse anti-bovine CD11b mAb. Ovine MSC from all three sources differentiated under chondorgenic, osteogenic and adipogenic conditions. Also, MSC from the three tissues were found to express CD44 and MHC-I but lack of CD11b and CD45. The results obtained revealed that our isolation methods for the different tissues tested are valid and that MSC from the three sources studied have same immunophenotic characteristics.

Evidence from Raman spectroscopy of a putative link between inherent bone matrix chemistry and degenerative joint disease.

OBJECTIVE: Osteoarthritis (OA) is a common debilitating disease that results in degeneration of cartilage and bone in the synovial joints. Subtle changes in the molecular structure of the subchondral bone matrix occur and may be associated with cartilage changes. The aim of this study was to explore whether the abnormal molecular changes observed in the matrix of OA subchondral bone can be identified with Raman spectroscopy. METHODS: Tibial plateaus from patients undergoing total knee replacement for OA (n = 10) were compared with healthy joints from patients undergoing leg amputation (n = 5; sex- and laterality-matched) and with non-OA cadaveric knee specimens (n = 5; age-matched). The samples were analyzed with Raman spectroscopy, peripheral quantitative computed tomography, and chemical analysis to compare changes in defined load-bearing sites in both the medial and lateral compartments. RESULTS: OA subchondral bone matrix changes were detected by Raman spectroscopy. Within each cohort, there was no spectral difference in bone matrix chemistry between the medial and lateral compartments, whereas a significant spectral difference (P < 0.001) was observed between the non-OA and OA specimens. Type I collagen chain ratios were normal in the non-OA specimens but were significantly elevated in the OA specimens. CONCLUSION: In comparing the results of Raman spectroscopy with those obtained by other standard techniques, these findings show, for the first time, that subchondral bone changes, or inherent differences, exist in both the medial and lateral (beneath intact cartilage) compartments of OA knees. The development of Raman spectroscopy as a screening tool, based on molecular-specific modifications in bone, would facilitate the identification of clinical disease, including early molecular changes.

Beneficial effects of autologous bone marrow-derived mesenchymal stem cells in naturally occurring tendinopathy.

Tendon injuries are a common age-related degenerative condition where current treatment strategies fail to restore functionality and normal quality of life. This disease also occurs naturally in horses, with many similarities to human tendinopathy making it an ideal large animal model for human disease. Regenerative approaches are increasingly used to improve outcome involving mesenchymal stem cells (MSCs), supported by clinical data where injection of autologous bone marrow derived MSCs (BM-MSCs) suspended in marrow supernatant into injured tendons has halved the re-injury rate in racehorses. We hypothesized that stem cell therapy induces a matrix more closely resembling normal tendon than the fibrous scar tissue formed by natural repair. Twelve horses with career-ending naturally-occurring superficial digital flexor tendon injury were allocated randomly to treatment and control groups. 1X10(7) autologous BM-MSCs suspended in 2 ml of marrow supernatant were implanted into the damaged tendon of the treated group. The control group received the same volume of saline. Following a 6 month exercise programme horses were euthanized and tendons assessed for structural stiffness by non-destructive mechanical testing and for morphological and molecular composition. BM-MSC treated tendons exhibited statistically significant improvements in key parameters compared to saline-injected control tendons towards that of normal tendons and those in the contralateral limbs. Specifically, treated tendons had lower structural stiffness (p<0.05) although no significant difference in calculated modulus of elasticity, lower (improved) histological scoring of organisation (p<0.003) and crimp pattern (p<0.05), lower cellularity (p<0.007), DNA content (p<0.05), vascularity (p<0.03), water content (p<0.05), GAG content (p<0.05), and MMP-13 activity (p<0.02). Treatment with autologous MSCs in marrow supernatant therefore provides significant benefits compared to untreated tendon repair in enhancing normalisation of biomechanical, morphological, and compositional parameters. These data in natural disease, with no adverse findings, support the use of this treatment for human tendon injuries.

Cytotoxic agents are detrimental to bone formed by distraction osteogenesis.

UNLABELLED: Distraction osteogenesis can be used to replace segmental bone loss when treating malignant bone tumors in children and adolescents. These patients often receive cytotoxic chemotherapy as part of their treatment regimen. The effect of cytotoxic drugs on the cellular processes during distraction osteogenesis and the structural and mechanical properties of regenerate bone is unknown. We therefore used a rabbit model of distraction osteogenesis to determine that cytotoxic agents had a detrimental effect on regenerate bone formed by this technique. We administered adriamycin and cisplatinum to 20 rabbits using two different simulated chemotherapy regimens. All rabbits underwent an osteotomy at 12 weeks of age. Distraction osteogenesis began 24 h later at a rate of 0.75 mm a day for 10 days, followed by 18 days without correction to allow for consolidation. Regenerate bone was assessed using plain radiographs, bone densitometry, and mechanical testing. Peri-operative chemotherapy decreased the mechanical properties of the regenerate with regard to yield strain (3.7 × 10(-2) vs. 5.2 × 10(-2)) and energy at yield (2.73 × 10(7) vs. 3.92 × 10(7)). Preoperative chemotherapy in isolation reduced bone mineral density (0.38 vs. 0.5 g/cm(2)), bone mineral content (0.24 vs. 0.36 g), and volumetric bone mineral density (0.57 vs. 0.65 g/cm(2)) with no alterations in the mechanical properties. CONCLUSIONS: Preoperative chemotherapy appears to decrease the volume of regenerate bone, without affecting structural integrity, suggesting that the callus formed is of good quality. The converse appears true for peri-operative chemotherapy.

A biomechanical evaluation of a Hybrid Dynamic Compression Plate and a CastLess Arthrodesis Plate for pancarpal arthrodesis in dogs.

OBJECTIVE: To determine mechanical differences between two plates with different requirements for supplementary casting after pancarpal arthrodesis (PCA): the Veterinary Instrumentation Hybrid Dynamic Compression Plate (HDCP), and the OrthoMed CastLess Arthrodesis Plate (CLP). STUDY DESIGN: In vitro mechanical analysis. SAMPLE POPULATION: HDCP(n = 10), CLP(10). METHODS: Single-cycle load to failure using a materials-testing machine and cyclic loading between 38 and 380 N ± 5% to simulate estimated in vivo loads until failure or 10(6) cycles. RESULTS: Single-cycle to failure: bending stiffness was significantly higher for the HDCP(2269 ± 175 N/mm) than CLP(1754 ± 88 N/mm; P < .001). Bending structural stiffness was higher for the HDCP(3.8 ± 0.3 Nm(2) ) versus CLP(2.9 ± 0.2 Nm(2) ; P= .0022). A difference between the 2 plates for bending strength was not demonstrated; HDCP= 13.9 ± 1.4 Nm, CLP13.2 ± 0.5 Nm (P= .24). Cyclic Loading: no failures occurred with either plate type when plates were cycled to 10(6) cycles. CONCLUSION: There is no mechanical advantage in bending resistance afforded by the CLPover the HDCP. Fatigue failure of either plate during the convalescent period of an estimated 150,000-250,000 cycles is unlikely. Based on the bending performance, there is no evidence to support the use of the CLPover the HDCPfor castless PCA.