R399E, A Mutated Form of Growth and Differentiation Factor 5, for Disease Modification of Osteoarthritis

OBJECTIVE

To preclinically characterize a mutant form of growth and differentiation factor 5, R399E, with reduced osteogenic properties as a potential disease-modifying osteoarthritis (OA) drug.

METHODS

Cartilage, synovium, and meniscus samples from patients with OA were used to evaluate anabolic and antiinflammatory properties of R399E. In the rabbit joint instability model, 65 rabbits underwent transection of the anterior cruciate ligament plus partial meniscectomy. Three intraarticular (IA) R399E doses were administered biweekly 6 times, and static incapacitance was determined to assess joint pain. OA was evaluated 13 weeks after surgery. In sheep, medial meniscus transection was performed to induce OA, dynamic weight bearing was measured in-life, and OA was assessed after 13 weeks.

RESULTS

Intermittent exposure to R399E (1 week per month) was sufficient to induce cell proliferation and release of anabolic markers in 3-dimensional chondrocyte cultures. R399E also inhibited the release of interleukin-1β (IL-1β), IL-6, and prostaglandin E₂ from cartilage with synovium, meniscal cell, and synoviocyte cultures. In rabbits, the mean difference (95% confidence interval [95% CI]) in weight bearing for R399E compared to vehicle was -5.8 (95% confidence interval [95% CI] -9.54, -2.15), -7.2 (95% CI -10.93, -3.54), and -7.7 (95% CI -11.49, -3.84) for the 0.6, 6, and 60 μg doses, respectively, 6 hours after the first IA injection, and was statistically significant through the entire study for all doses. Cartilage surface structure improved with the 6-μg dose. Structural and symptomatic improvement with the same dose was confirmed in the sheep model of OA.

CONCLUSION

R399E influences several pathologic processes contributing to OA, highlighting its potential as a disease-modifying therapy.

AB0156 INTRA-ARTICULAR AGRIN PROVIDES DIRECT PAIN RELIEF IN OSTEOARTHRITIS AND CARTILAGE DEFECTS

Background

Osteoarthritis is the leading cause of disability worldwide with a financial burden estimated between 1.5 and 2% of the GDP in all westernised countries. The main driver of progression in osteoarthritis is cartilage loss, which may be associated with bone changes, low degree synovitis and lesions to menisci and ligaments. These pathological features result in pain, which contributes to chronic disability.

Improving cartilage integrity without pain relief does not help patients and results in failure in clinical trials. Therefore, there is a need for therapeutics that induce rapid pain relief and long-term cartilage regeneration.

We previously showed that Agrin results in cartilage regeneration and in this study, following on the serendipitous finding of rapid pain relief after Agrin administration we explore its analgesic effect in animal models of osteochondral defects and osteoarthritis.

Objectives

Test the analgesic potential of Agrin in post-surgical pain associated with osteochondral defects in mice and sheep.

Determine whether Agrin can relieve chronic pain induced by osteoarthritis in mice.

Investigate the therapeutic potential of Agrin in models of primary and injury-induced secondary osteoarthritis.

Methods

Acute post-surgical pain: Surgery was performed on skeletally mature male mice and female sheep to create critical-sized osteochondral defects; defects were filled with collagen gel containing PBS or Agrin. Animals were sacrificed 8 weeks (mice) and 6 months (sheep) after surgery. Pain was measured in mice using von Frey filaments and incapacitance readings. Sheep were fitted with accelerometers for the duration of the study.

Osteoarthritic pain: Osteoarthritis was surgically induced in skeletally mature male mice by menisco-ligament injury (MLI). Control mice received sham surgery. Nine weeks post-surgery, once chronic pain was established, mice were injected intra-articularly with recombinant Agrin. Pain was measured by von Frey filaments and incapacitance.

Treatment in therapeutic regime: Tamoxifen-inducible transgenic mice overexpressing Agrin under the AggrecanCre promotor were generated. Skeletally mature male mice were subjected to menisco-ligament injury surgery. Four weeks later, tamoxifen was administered to overexpress Agrin in the cartilage. Pain was measured by von Frey filaments and incapacitance.

Ex-vivo: MicroCT, X-ray, Kellgren-Laurence scoring, histology, OARSI scoring and immunohistochemistry.

Results

In sheep, Agrin administration induced regeneration in osteochondral defects and, more importantly, reduced the levels of secondary osteoarthritis. This was associated with a rapid and sustained symptomatic relief.

In mice, Agrin expression was lost in the dorsal root ganglia corresponding to the limb subjected to MLI but not in the dorsal root ganglia corresponding to the sham operated limbs.

Intra-articular recombinant Agrin in mice with established OA (9 weeks after MLI surgery) resulted in pain relief as early as three hours after administration. Acute administration of recombinant Agrin does not have any analgesic effects in sham operated mice.

Inducible, cartilage-specific Agrin-overexpression mice were protected from developing pain associated with instability-induced osteoarthritis.

In mice with acute osteochondral defects, intra-articular Agrin administration resulted in pain relief for at least five days.

In humans, the loss of Agrin in the articular cartilage correlated significantly with the Mankin score of patients undergoing knee replacement surgery.

Conclusion

Agrin has analgesic properties in both the acute phases of cartilage damage and in established osteoarthritis. Our findings support the therapeutic use of Agrin for joint surface regeneration and pain relief.

Disclosure of Interests

Suzanne Eldridge: None declared, Aida Barawi: None declared, Anne-Sophie Thorup: None declared, Beatriz F Fernandez: None declared, Sabah Bharde: None declared, Shafaq Sikandar: None declared, Zeyu Guan: None declared, Magdalena Kaneva: None declared, Helen Lydon: None declared, Fran Henson: None declared, Cosimo De Bari: None declared, Andrew McCaskie: None declared, Francesco Dell’Accio Consultant of: Prof Dell’Accio has consulted for Samumed, Grant/research support from: A PhD studentship unrelated to this abstract is funded by UCB

Use of autologous products for the treatment of joint and soft tissue disease in horses: A systematic review

BACKGROUND

Soft tissue injuries and joint disease are the predominate causes of lameness in the equine athlete and these pathologies carry a guarded prognosis for a return to previous performance. Recently the use of autologous products has become more widespread as a treatment in equine sports medicine. However, the efficacy of these products is yet to be fully established.

OBJECTIVE

To evaluate the current published evidence base regarding the efficacy of autologous products in soft tissue injuries and joint disease.

METHODS

A systematic review of English articles using MEDLINE, EMBASE and Web of Science databases from 1980 to 2017. The search strategy identified 1594 papers for review.

RESULTS

Fifty-eight papers were included in this review, 28 of which were randomised controlled trials. Significant benefit was reported under several parameters, most notably in the use of autologous chondrocytes in artificially induced cartilage defects on histology. One paper documented a significant clinical response under lameness examination.

CONCLUSION

The current literature shows that the treatment of soft tissue injury and cartilage disease with autologous products is safe and that the use of some products can give significant benefit on some outcome measures. True clinical significance is yet to be demonstrated with any product.

Using apheresis-derived cells to augment microdrilling in the treatment of chondral defects in an ovine model

The treatment of chondral defects using microdrilling often results in a mechanically weak fibrocartilagenous repair, rather than a more robust hyaline cartilage repair. Many different microfracture/microdrilling augmentation techniques have been described, including the use of cellular products to enhance healing. Autologous peripheral blood progenitor cells can be obtained via apheresis after administration of granulocyte colony-stimulating factor (G-CSF) and have been used successfully to augment microdrilling in clinical patients. The objective of this study was to use apheresis-derived mononuclear blood cells to augment microdrilling treatment of a cartilage defect in an ovine model to determine the effect on healing. Forty adult female sheep were used in this study and were divided into a control group (microdrilling alone) and a treatment group (microdrilling, hyaluronic acid, and apheretic product). Outcome measurements included weight-bearing on the operated limb, macroscopic scoring of the joint, histology, and immunohistochemistry. In addition, magnetic resonance imaging was used to attempt to identify SPION-labeled cells from the apheretic product in the operated limbs. The results showed a significant increase in healing as measured by the modified O'Driscoll sore in the treated group. No evidence of homing of SPION-labeled cells to the defect was found and no correlation was found between the response to G-CSF administration or concentration of CD34⁺  and outcome. A correlation was found between healing and the concentration of white blood cells and peripheral blood mononuclear cell numbers in the apheretic product.

AB0039 AGRIN REPAIRS BONE AND CARTILAGE IN VIVO

Background:

Cartilage defects in the joints are reported in 61% of all arthroscopies1&2. The size of the cartilage repair market is estimated to be $2.195 million by 20253. Cartilage defects can evolve into osteoarthritis, in which abnormal load results in cartilage breakdown, joint pain and reduced mobility. Osteoarthritis is the leading cause of permanent disability and absenteeism and affects up to 1/3 of the people over 60yrs. In western countries osteoarthritis costs 1.5-2% of the GDP4. Joint replacement with a prosthesis restores some degree of independence but in up to 20% of patients it does not meet expectations 5 and has a limited life span. There is no pharmacological intervention that arrests or reverts the course of osteoarthritis, despite the desperate need.

We previously published that agrin plays an important role in cartilage homeostasis6. The addition of agrin to chondrocytes in vivo resulted in enhanced cartilage formation, suggesting a potential role for agrin in cartilage repair.

Objectives:

Investigate the potential of agrin for use in cartilage repair.

Methods:

Critical size osteochondral defects were generated in mice and sheep and injected intraarticularly with type I collagen gel containing agrin or vehicle. Animals were monitored for 8 weeks or 6 months respectively. MicroCT, histological analysis, qPCR, linage tracking, reporter assays, chondrogenesis assay, immunohistochemistry were performed.

Results:

A single intraarticular administration of agrin induced regeneration of critical-size osteochondral defects in mice, restoring the tissue architecture and bone-cartilage interface. Agrin stem cells to the site of injury and, through simultaneous activation of CREB and suppression of canonical WNT signalling, induced GDF5 expression and differentiation into stable articular chondrocytes, forming stable articular cartilage. In sheep, agrin treatment resulted in regeneration of bone and cartilage, which promoted increased ambulatory activity.

Conclusion:

Agrin orchestrates repair morphogenesis at the joint surface by modulating multiple signalling pathways, supporting the therapeutic use of agrin for joint surface regeneration.

References:

[1]Curl, W. W. et al. Cartilage injuries: a review of 31,516 knee arthroscopies. Arthrosc. J. Arthrosc. Relat. Surg. Off. Publ. Arthrosc. Assoc. N. Am. Int. Arthrosc. Assoc. 13, 456–460 (1997).

[2]Hjelle, K., Solheim, E., Strand, T., Muri, R. & Brittberg, M. Articular cartilage defects in 1,000 knee arthroscopies. Arthrosc. J. Arthrosc. Relat. Surg. Off. Publ. Arthrosc. Assoc. N. Am. Int. Arthrosc. Assoc. 18, 730–734 (2002).

[3]Cartilage Repair Market Size, Share, Industry Analysis 2018-2025 | AMR. Allied Market Research https://www.alliedmarketresearch.com/cartilage-repair-market.

[4]Hiligsmann, M. et al. Health economics in the field of osteoarthritis: an expert’s consensus paper from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO). Semin. Arthritis Rheum. 43, 303–313 (2013).

[5]Dieppe, P., Lim, K. & Lohmander, S. Who should have knee joint replacement surgery for osteoarthritis? Int. J. Rheum. Dis. 14, 175–180 (2011).

[6]Eldridge, S., et al. Agrin mediates chondrocyte homeostasis and requires both LRP4 and α-dystroglycan to enhance cartilage formation in vitro and in vivo. Annals of the rheumatic diseases 75 (6), 1228-1235 (2016).

Acknowledgements:

We thank the technical staff in the ARM Lab and Staff at the University of Aberdeen’s Animal Facility and Microscopy and Histology Facility for support. Funding: We gratefully acknowledge funding support of this work by the MRC (MR/L022893/1, MR/N010973/1,and MR/P026362/1), Versus Arthritis (19667, 21515, 20886, and 21621), Rosetrees Trust (A1205), the Medical College of St Bartholomew’s Hospital Trust, and the William Harvey Research Foundation.

Disclosure of Interests:

Suzanne Eldridge: None declared, Aida Barawi: None declared, Hui Wang: None declared, Anke Roelofs: None declared, Magdalena Kaneva: None declared, Zeyu Guan: None declared, Helen Lydon: None declared, Bethan Thomas: None declared, Anne-Sophie Thorup: None declared, Beatriz F Fernandez: None declared, Sara Caxaria: None declared, Danielle Strachan: None declared, Ahmed Ali: None declared, Kanatheepan Shanmuganathan: None declared, Costantino Pitzalis: None declared, James Whiteford: None declared, Fran Henson: None declared, Andrew McCaskie: None declared, Cosimo De Bari: None declared, Francesco Dell’Accio Consultant of: F.D. has received consultancy fees from Samumed and UCB.

Agrin induces long-term osteochondral regeneration by supporting repair morphogenesis

Cartilage loss leads to osteoarthritis, the most common cause of disability for which there is no cure. Cartilage regeneration, therefore, is a priority in medicine. We report that agrin is a potent chondrogenic factor and that a single intraarticular administration of agrin induced long-lasting regeneration of critical-size osteochondral defects in mice, with restoration of tissue architecture and bone-cartilage interface. Agrin attracted joint resident progenitor cells to the site of injury and, through simultaneous activation of CREB and suppression of canonical WNT signaling downstream of β-catenin, induced expression of the chondrogenic stem cell marker GDF5 and differentiation into stable articular chondrocytes, forming stable articular cartilage. In sheep, an agrin-containing collagen gel resulted in long-lasting regeneration of bone and cartilage, which promoted increased ambulatory activity. Our findings support the therapeutic use of agrin for joint surface regeneration.

The Treatment of Cartilage Damage Using Human Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Systematic Review of in vivo Studies

Damage to joints through injury or disease can result in cartilage loss, which if left untreated can lead to inflammation and ultimately osteoarthritis. There is currently no cure for osteoarthritis and management focusses on symptom control. End-stage osteoarthritis can be debilitating and ultimately requires joint replacement in order to maintain function. Therefore, there is growing interest in innovative therapies for cartilage repair. In this systematic literature review, we sought to explore the in vivo evidence for the use of human Mesenchymal Stem Cell-derived Extracellular Vesicles (MSC-EVs) for treating cartilage damage. We conducted a systematic literature review in accordance with the PRISMA protocol on the evidence for the treatment of cartilage damage using human MSC-EVs. Studies examining in vivo models of cartilage damage were included. A risk of bias analysis of the studies was conducted using the SYRCLE tool. Ten case-control studies were identified in our review, including a total of 159 murine subjects. MSC-EVs were harvested from a variety of human tissues. Five studies induced osteoarthritis, including cartilage loss through surgical joint destabilization, two studies directly created osteochondral lesions and three studies used collagenase to cause cartilage loss. All studies in this review reported reduced cartilage loss following treatment with MSC-EVs, and without significant complications. We conclude that transplantation of MSC-derived EVs into damaged cartilage can effectively reduce cartilage loss in murine models of cartilage injury. Additional randomized studies in animal models that recapitulates human osteoarthritis will be necessary in order to establish findings that inform clinical safety in humans.

Ultra Short Echo Time MRI of Iron-Labelled Mesenchymal Stem Cells in an Ovine Osteochondral Defect Model

Multipotent Mesenchymal Stem/Stromal Cells (MSCs) are widely used in cellular therapy for joint repair. However, the use of MSC therapies is complicated by a lack of understanding of the behaviour of cells and repair within the joint. Current methods of MSC tracking include labelling the cells with Super Paramagnetic Iron Oxide nanoparticles (SPIOs). However, standard acquisition sequences (T2 and T2*) give poor anatomical definition in the presence of SPIOs. To avoid anatomical compromise in the presence of SPIOs, we have investigated the use of Ultra-short Echo Time (UTE) MRI, using a 3D cones acquisition trajectory. This method was used to track SPIO labelled MSC injected into joints containing osteochondral defects in experimental sheep. This study demonstrates that multiple echo times from UTE with 3 T MRI can provide excellent anatomical detail of osteochondral defects and demonstrate similar features to histology. This work also monitors the location of SPIO-labelled cells for regenerative medicine of the knee with MRI, histology, and Prussian blue staining. With these methods, we show that the SPIOs do not hone to the site of defect but instead aggregate in the location of injection, which suggests that any repair mechanism with this disease model must trigger a secondary process.

Ex vivo MRI cell tracking of autologous mesenchymal stromal cells in an ovine osteochondral defect model

BACKGROUND

Osteochondral injuries represent a significant clinical problem requiring novel cell-based therapies to restore function of the damaged joint with the use of mesenchymal stromal cells (MSCs) leading research efforts. Pre-clinical studies are fundamental in translating such therapies; however, technologies to minimally invasively assess in vivo cell fate are currently limited. We investigate the potential of a MRI- (magnetic resonance imaging) and superparamagnetic iron oxide nanoparticle (SPION)-based technique to monitor cellular bio-distribution in an ovine osteochondral model of acute and chronic injuries.

METHODS

MSCs were isolated, expanded and labelled with Nanomag, a 250-nm SPION, and using a novel cell-penetrating technique, glycosaminoglycan-binding enhanced transduction (GET). MRI visibility thresholds, cellular toxicity and differentiation potential post-labelling were assessed in vitro. A single osteochondral defect was created in the medial femoral condyle in the left knee joint of each sheep with the contralateral joint serving as the control. Cells, either GET-Nanomag labelled or unlabelled, were delivered 1 week or 4.5 weeks later. Sheep were sacrificed 7 days post implantation and immediately MR imaged using a 0.2-T MRI scanner and validated on a 3-T MRI scanner prior to histological evaluation.

RESULTS

MRI data demonstrated a significant increase in MRI contrast as a result of GET-Nanomag labelling whilst cell viability, proliferation and differentiation capabilities were not affected. MRI results revealed evidence of implanted cells within the synovial joint of the injured leg of the chronic model only with no signs of cell localisation to the defect site in either model. This was validated histologically determining the location of implanted cells in the synovium. Evidence of engulfment of Nanomag-labelled cells by leukocytes is observed in the injured legs of the chronic model only. Finally, serum c-reactive protein (CRP) levels were measured by ELISA with no obvious increase in CRP levels observed as a result of P21-8R:Nanomag delivery.

CONCLUSION

This study has the potential to be a powerful translational tool with great implications in the clinical translation of stem cell-based therapies. Further, we have demonstrated the ability to obtain information linked to key biological events occurring post implantation, essential in designing therapies and selecting pre-clinical models.

Peripheral mononuclear blood cell apheresis in a preclinical ovine model

Background

Recent research has demonstrated that circulating peripheral blood mononuclear fractions (PBMC) containing haematopoietic stem (HSC)/progenitor cells have the potential to play a crucial role in regenerative medicine strategies. Work in our laboratory has shown that a peripheral blood mononuclear cell fraction (PBMC) enhances cartilage repair in an osteochondral defect model in sheep and has a significant effect on cells in the joint niche. In order to obtain PBMC rich blood containing HSCs for further studies, we have performed, for the first time, apheresis on adult sheep.

Results

Subcutaneous granulocyte-colony stimulating factor (G-CSF) was used to mobilise white blood cells and continual flow apheresis was performed on 8 sheep under general anaesthetic. There were no observable side effects, although a marked tendency for blood clotting during the procedure was noted. The administration of G-CSF for 3 days increased the white blood cell (WBC) count in the peripheral blood from to 6.7 ± 2.1 × 10⁶/ml to 16.1 ± 5.0 × 10⁶/ml. Following apheresis, the WBC numbers in the apheretic product increased to 38.5 ± 27.6 × 10⁶/ml, comprised of a significant increase in neutrophils and PBMC (from 5.25 ± 1.8 × 10⁶/ml following G-CSF stimulation to 27.5 5 ± 27.6 × 10⁶/ml). There was a mean of 2.1% CD34 + ve cells and 95.5% CD45 + ve cells in the apheretic product.

Conclusions

This study describes the administration of G-CSF and subsequent apheresis in adult sheep. The technique is safe when performed as described with no observable side effects. The technique permits collection of an increased WBC fraction containing neutrophils and PBMC in adult sheep. This apheretic product contains CD34 + ve cells, representing an HSC/progenitor population for use in in vivo and in vitro experiments.

Increased sclerostin associated with stress fracture of the third metacarpal bone in the Thoroughbred racehorse

Objectives

The exact aetiology and pathogenesis of microdamage-induced long bone fractures remain unknown. These fractures are likely to be the result of inadequate bone remodelling in response to damage. This study aims to identify an association of osteocyte apoptosis, the presence of osteocytic osteolysis, and any alterations in sclerostin expression with a fracture of the third metacarpal (Mc-III) bone of Thoroughbred racehorses.

Methods

A total of 30 Mc-III bones were obtained; ten bones were fractured during racing, ten were from the contralateral limb, and ten were from control horses. Each Mc-III bone was divided into a fracture site, condyle, condylar groove, and sagittal ridge. Microcracks and diffuse microdamage were quantified. Apoptotic osteocytes were measured using TUNEL staining. Cathepsin K, matrix metalloproteinase-13 (MMP-13), HtrA1, and sclerostin expression were analyzed.

Results

In the fracture group, microdamage was elevated 38.9% (sd 2.6) compared with controls. There was no difference in the osteocyte number and the percentage of apoptotic cells between contralateral limb and unraced control; however, there were significantly fewer apoptotic cells in fractured samples (p < 0.02). Immunohistochemistry showed that in deep zones of the fractured samples, sclerostin expression was significantly higher (p < 0.03) than the total number of osteocytes. No increase in cathepsin K, MMP-13, or HtrA1 was present.

Conclusion

There is increased microdamage in Mc-III bones that have fractured during racing. In this study, this is not associated with osteocyte apoptosis or osteocytic osteolysis. The finding of increased sclerostin in the region of the fracture suggests that this protein may be playing a key role in the regulation of bone microdamage during stress adaptation.

Cite this article: N. Hopper, E. Singer, F. Henson. Increased sclerostin associated with stress fracture of the third metacarpal bone in the Thoroughbred racehorse. Bone Joint Res 2018;7:94–102. DOI: 10.1302/2046-3758.71.BJR-2016-0202.R4.

Peripheral blood derived mononuclear cells enhance osteoarthritic human chondrocyte migration

Introduction

A major problem in cartilage repair is the lack of chondrogenic cells migrating from healthy tissue into defects. Cartilage is essentially avascular and therefore its healing is not considered to involve mononuclear cells. Peripheral blood derived mononuclear cells (PBMC) offer a readily available autologous cell source for clinical use and therefore this study was designed to evaluate the effects of PBMCs on chondrocytes and cartilage.

Methods

Human primary chondrocytes and cartilage tissue explants were taken from patients undergoing total knee replacement (n = 17). Peripheral blood samples were obtained from healthy volunteers (n = 12) and mononuclear cells were isolated by density-gradient centrifugation. Cell migration and chemokinetic potential were measured using a scratch assay, xCELLigence and CyQuant assay. PCR array and quantitative PCR was used to evaluate mRNA expression of 87 cell motility and/or chondrogenic genes.

Results

The chondrocyte migration rate was 2.6 times higher at 3 hour time point (p < 0.0001) and total number of migrating chondrocytes was 9.7 times higher (p < 0.0001) after three day indirect PBMC stimulus and 8.2 times higher (p < 0.0001) after three day direct co-culture with PBMCs. A cartilage explant model confirmed that PBMCs also exert a chemokinetic role on ex vivo tissue. PBMC stimulation was found to significantly upregulate the mRNA levels of 2 chondrogenic genes; collagen type II (COL2A1 600–fold, p < 0.0001) and SRY box 9 (SOX9 30–fold, p < 0.0001) and the mRNA levels of 7 genes central in cell motility and migration were differentially regulated by 24h PBMC stimulation.

Conclusion

The results support the concept that PBMC treatment enhances chondrocyte migration without suppressing the chondrogenic phenotype possibly via mechanistic pathways involving MMP9 and IGF1. In the future, peripheral blood mononuclear cells could be used as an autologous point-ofcare treatment to attract native chondrocytes from the diseased tissue to aid in cartilage repair.

Peripheral Blood Mononuclear Cells Enhance Cartilage Repair in in vivo Osteochondral Defect Model

This study characterized peripheral blood mononuclear cells (PBMC) in terms of their potential in cartilage repair and investigated their ability to improve the healing in a pre-clinical large animal model. Human PBMCs were isolated with gradient centrifugation and adherent PBMC’s were evaluated for their ability to differentiate into adipogenic, chondrogenic and osteogenic lineages and also for their expression of musculoskeletal genes. The phenotype of the PBMCs was evaluated using Stro-1, CD34, CD44, CD45, CD90, CD106, CD105, CD146 and CD166 cell surface markers. Osteochondral defects were created in the medial femoral condyle (MFC) of 24 Welsh mountain sheep and evaluated at a six month time point. Four cell treatment groups were evaluated in combination with collagen-GAG-scaffold: (1) MSC alone; (2) MSCs and PBMCs at a ratio of 20:1; (3) MSCs and PBMC at a ratio of 2:1 and (4) PBMCs alone. Samples from the surgical site were evaluated for mechanical properties, ICRS score and histological repair. Fresh PBMC samples were 90% positive for hematopoietic cell surface markers and negative for the MSC antibody panel (<1%, p = 0.006). However, the adherent PBMC population expressed mesenchymal stem cell markers in hypoxic culture and lacked CD34/45 positive cells (<0.2%). This finding demonstrated that the adherent cells had acquired an MSC-like phenotype and transformed in hypoxia from their original hematopoietic lineage. Four key genes in muskuloskeletal biology were significantly upregulated in adherent PBMCs by hypoxia: BMP2 4.2-fold (p = 0.0007), BMP6 10.7-fold (p = 0.0004), GDF5 2.0-fold (p = 0.002) and COL1 5.0-fold (p = 0.046). The monolayer multilineage analysis confirmed the trilineage mesenchymal potential of the adherent PBMCs. PBMC cell therapy was equally good as bone marrow MSC therapy for defects in the ovine large animal model. Our results show that PBMCs support cartilage healing and oxygen tension of the environment was found to have a key effect on the derivation of a novel adherent cell population with an MSC-like phenotype. This study presents a novel and easily attainable point-of-care cell therapy with PBMCs to treat osteochondral defects in the knee avoiding any cell manipulations outside the surgical room.

Delivering rhFGF-18 via a bilayer collagen membrane to enhance microfracture treatment of chondral defects in a large animal model

Augmented microfracture techniques use growth factors, cells, and/or scaffolds to enhance the healing of microfracture-treated cartilage defects. This study investigates the effect of delivering recombinant human fibroblastic growth factor 18 (rhFHF18, Sprifermin) via a collagen membrane on the healing of a chondral defect treated with microfracture in an ovine model. Eight millimeter diameter chondral defects were created in the medial femoral condyle of 40 sheep (n = 5/treatment group). Defects were treated with microfracture alone, microfracture + intra-articular rhFGF-18 or microfracture + rhFGF-18 delivered on a membrane. Outcome measures included mechanical testing, weight bearing, International Cartilage Repair Society repair score, modified O'Driscoll score, qualitative histology, and immunohistochemistry for types I and II collagen. In animals treated with 32 μg rhFGF-18 + membrane and intra-articularly, there was a statistically significant improvement in weight bearing at 2 and 4 weeks post surgery and in the modified O'Driscoll score compared to controls. In addition, repair tissue stained was more strongly stained for type II collagen than for type I collagen. rhFGF-18 delivered via a collagen membrane at the point of surgery potentiates the healing of a microfracture treated cartilage defect.

Osteochondral tissue engineering using a biphasic collagen/GAG scaffold containing rhFGF18 or BMP-7 in an ovine model

BACKGROUND

The aim of this study was to investigate the effect of combining rhFGF18 or BMP-7 with a biphasic collagen/GAG osteochondral scaffold (Chondromimetic) on the repair of osteochondral defects in sheep.

METHODS

Osteochondral defects (5.8x6mm) were created in the medial femoral condyle (MFC) and the lateral trochlea sulcus (LTS) of the stifle joint of 24 female sheep. Sheep were randomly assigned to four groups (n = 6); 1) empty defect, 2) scaffold only, 3) scaffold + rhFGF-18 (30 μg) and 4) scaffold + BMP-7 (100 μg). At 6 months the defects underwent non-destructive mechanical testing, gross assessment of repair tissue (ICRS score) and histological analysis (Modified O'Driscoll score).

RESULTS

ICRS repair score: Defects treated with scaffold + rhFGF18 (mean 9.83, 95% CI 8.43-11.23) and scaffold + BMP-7 (10, 9.06-10.94) in the MFC had significantly improved ICRS scores compared to empty defects (4.2, 0-8.80) (p = 0.002). Mechanical properties: BMP-7 treated defects (mean 64.35, 95% CI 56.88-71.82) were significantly less stiff than both the rhFGF18 (mean 84.1, 95% CI 76.8-91.4) and empty defects in the LTS, compared to both contralateral limb (p = 0.003), and the perilesional articular cartilage (p < 0.001).

HISTOLOGY

A statistically significant improvement in the modified O'Driscoll score was observed in the rhFGF18 treated group (mean 16.83, 95% CI 13.65-20.61) compared to the empty defects (mean 9, 95% CI 4.88-13.12) (p = 0.039) in the MFC. Excellent tissue fill, lateral integration and proteoglycan staining was observed. Only the rhFGF18 defects showed pericellular type VI collagen staining with positive type II collagen and reduced positive type I collagen staining. The majority of defects in the control and BMP-7 groups demonstrated fibrocartilagenous repair tissue.

CONCLUSION

Statistically significant improvements in gross repair, mechanical properties and histological score were found over empty defects when Chondromimetic was combined with rhFGF18. These results suggest that rhFGF18 may play a significant role in articular cartilage repair applications.

Intra-articular injection of rhFGF-18 improves the healing in microfracture treated chondral defects in an ovine model

Microfracture is a common cartilage repair procedure. Strategies to improve healing post-microfracture include the use of growth factors to enhance hyaline cartilage production. This study investigates the effect of intra-articular recombinant human fibroblastic growth factor 18 (rhFHF18) on the healing of a chondral defect treated with microfracture in an ovine model. Chondral defects (8 mm diameter) were created in the medial femoral condyle of 80 sheep (n = 16/treatment group). Defects were treated with microfracture alone or microfracture + intra-articular rhFGF-18 (administered either as one or two cycles of 3× weekly injections). Outcome measures included mechanical testing, macroscopic International Cartilage Repair Society repair score, modified O'Driscoll histology score, qualitative histology, and immunohistochemistry for types I, II, and VI collagen. In treated animals, there was a statistically significant improvement in ICRS tissue repair score and tissue infill score, in the modified O'Driscoll score between control and 1 cycle of rhFGF-18 at 6 m, and in the cartilage repair score and structural characteristic score between the control and both rhFGF-18 groups at 6 m. There was no evidence of degeneration of adjacent cartilage in the rhFGF-18 treated cartilage. The increase in hyaline cartilage-like tissue formed in the microfracture + rhFGF-18 treated groups indicates that rhFGF-18 potentiates the formation of hyaline cartilage repair following microfracture.

Evaluation of sedation for standing clinical procedures in horses using detomidine combined with buprenorphine

OBJECTIVES

To examine the effect of including buprenorphine with detomidine for sedation of horses undergoing clinical procedures.

STUDY DESIGN

Partially blinded, randomised, prospective clinical field trial.

ANIMALS

Eighty four client-owned horses scheduled for minor surgery or diagnostic investigation under standing sedation.

METHODS

The effects of buprenorphine (5 μg kg(-1) ) (Group B, n = 46) or placebo (5% glucose solution) (Group C, n = 38) in combination with detomidine (10 μg kg(-1) ) were compared in standing horses undergoing minor clinical procedures. The primary outcome measure was successful completion of the procedure. The degree of sedation and ataxia were scored using simple descriptive scales. Heart and respiratory rates were recorded at 15-30 minute intervals. Parametric data from each group were compared using anova or t-test and non parametric data using the Mann-Whitney U test.

RESULTS

The procedure was carried out successfully in 91% of Group B and 63% of Group C (p < 0.01). Repeat dosing was required in 24% of Group B and 32% of Group C (p < 0.05). Sedation was more profound and lasted longer (60 versus 45 minutes) in Group B (p < 0.01). Ataxia occurred after detomidine, increased after buprenorphine but not glucose administration, was more profound in group B and lasted longer (60 versus 30 minutes) p < 0.001). Heart and respiratory rates remained within normal limits in both groups and there were no serious adverse events.

CONCLUSIONS AND CLINICAL RELEVANCE

Buprenorphine 5 and 10 μg kg(-1) enhanced the sedation produced by detomidine 10 and 20 μg kg(-1) with minor side effects similar to other alpha2 agonist/opioid combinations. Detomidine-buprenorphine sedation is suitable for standing procedures in horses.

The Augmentation of a Collagen/Glycosaminoglycan Biphasic Osteochondral Scaffold with Platelet-Rich Plasma and Concentrated Bone Marrow Aspirate for Osteochondral Defect Repair in Sheep: A Pilot Study

OBJECTIVE

This study investigates the combination of platelet-rich plasma (PRP) or concentrated bone marrow aspirate (CBMA) with a biphasic collagen/glycosaminoglycan (GAG) osteochondral scaffold for the treatment of osteochondral defects in sheep.

DESIGN

Acute osteochondral defects were created in the medial femoral condyle (MFC) and the lateral trochlea sulcus (LTS) of 24 sheep (n = 6). Defects were left empty or filled with a 6 × 6-mm scaffold, either on its own or in combination with PRP or CBMA. Outcome measures at 6 months included mechanical testing, International Cartilage Repair Society (ICRS) repair score, modified O'Driscoll histology score, qualitative histology, and immunohistochemistry for type I, II, and VI collagen.

RESULTS

No differences in mechanical properties, ICRS repair score, or modified O'Driscoll score were detected between the 4 groups. However, qualitative assessments of the histological architecture, Safranin O content, and collagen immunohistochemistry indicated that in the PRP/scaffold groups, there was a more hyaline cartilage-like tissue repair. In addition, the addition of CBMA and PRP to the scaffold reduced cyst formation in the subchondral bone of healed lesions.

CONCLUSION

There was more hyaline cartilage-like tissue formed in the PRP/scaffold group and less subchondral cystic lesion formation in the CBMA and PRP/scaffold groups, although there were no quantitative differences in the repair tissue formed.

Platelet-rich plasma activation in combination with biphasic osteochondral scaffolds-conditions for maximal growth factor production

PURPOSE

The combination of scaffolds and biological factors may enhance articular cartilage repair. Little is known regarding the activation and subsequent growth factor release of platelet-rich plasma (PRP) in contact with biosynthetic scaffolds. The purpose of this study was i) to identify whether the addition of thrombin was required to activate PRP in the presence of a collagen osteochondral scaffold and ii) to compare the activity of PRP when applied to both collagen- and polylactide-based osteochondral scaffolds.

METHODS

Equal combined volumes of test substances were used (n = 3): 500 μl PRP alone or on scaffolds; 375 μl PRP + 125 μl autologous thrombin on scaffolds; 455 μl PRP + 45 μl bovine thrombin on scaffolds. Scaffolds and/or PRP were cultured in vitro in DMEM/F12 medium for 10 days. TGF-β1, PDGF-AB and bFGF were measured using ELISA.

RESULTS

A similar cumulative release profile in all growth factors was found over the 10-day period i.e. a burst release and further physiological prolonged release. A significantly higher release of PDGF-AB was seen in the PRP + collagen scaffold groups at all time points, compared to scaffold + PRP + thrombins (P < 0.001). A significantly increased cumulative volume of PDGF-AB was released from the collagen scaffold compared to the polylactide scaffold (P < 0.001).

CONCLUSION

This study shows that polylactide and particularly collagen osteochondral scaffolds activate PRP in vitro. If PRP is combined with these scaffolds clinically, no exogenous activation with thrombin is required to achieve growth factor release, which may be of benefit for articular cartilage repair applications.

The use of scaffolds in musculoskeletal tissue engineering

The use of bioengineering scaffolds remains an integral part of the tissue engineering concept. A significant amount of basic science and clinical research has been focused on the regeneration of musculoskeletal tissues including bone, articular cartilage, meniscus, ligament and tendon. This review aims to provide the reader with a summary of the principals of using material scaffolds in musculoskeletal tissue engineering applications and how these materials may eventually come to be incorporated in clinical practice.

Extruded collagen fibres for tissue engineering applications: effect of crosslinking method on mechanical and biological properties

Reconstituted collagen fibres are promising candidates for tendon and ligament tissue regeneration. The crosslinking procedure determines the fibres' mechanical properties, degradation rate, and cell-fibre interactions. We aimed to compare mechanical and biological properties of collagen fibres resulting from two different types of crosslinking chemistry based on 1-ethyl-3-(3-dimethyllaminopropyl)carbodiimide (EDC). Fibres were crosslinked with either EDC or with EDC and ethylene-glycol-diglycidyl-ether (EDC/EGDE). Single fibres were mechanically tested to failure and bundles of fibres were seeded with tendon fibroblasts (TFs) and cell attachment and proliferation were determined over 14 days in culture. Collagen type I and tenascin-C production were assessed by immunohistochemistry and dot-blotting. EDC chemistry resulted in fibres with average mechanical properties but the highest cell proliferation rate and matrix protein production. EDC/EGDE chemistry resulted in fibres with improved mechanical properties but with a lower biocompatibility profile. Both chemistries may provide useful structures for scaffolding regeneration of tendon and ligament tissue and will be evaluated for in vivo tendon regeneration in future experiments.

Reduced chondrocyte viability is associated with the use of surgical marker pen ink

BACKGROUND

Sterile surgical marker pens are commonly used in cartilage repair surgery to aid in the placement of periosteal patches or collagen membranes in autologous chondrocyte implantation.

PURPOSE

To investigate the effects that methylene blue and crystal violet marker pen ink have on human chondrocytes when cultured on collagen membranes in vitro.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human chondrocytes were applied to Chondro-Gide collagen membranes at a volume of 12 million cells. In the first experiment, 2 sterile marker pens, one containing methylene blue and the other crystal violet inks, were used to mark membranes immediately before the addition of cells. In the second experiment, the same marker pens marked the membranes after 7 days of cell culture. In each experiment, 3 groups of membrane were tested for each pen. Group A consisted of no ink mark, group B had only the uppermost "smooth" layer marked, and group C had the lower "porous" layer marked. All membranes were then cultured in standard growth media for 24 hours. Cell viability was assessed at 24 hours on all membranes using a live/dead-cell viability assay. Cell viability was quantified with florescent microscopy with mean percentage of live cells in each marker pen group compared with control membranes using the Student t test (P < .05).

RESULTS

Control membranes (group A) with no ink showed cell viability approaching 100%. A statistically significant reduction in cell viability with both methylene blue (23.1%; P < .0001) and crystal violet (18.9%; P < .0001) was found adjacent to the ink mark on the smooth side (group B) and on the porous side remote from the ink (group C) in both experiments (<30%; P < .0001). A reduction in cell viability was noted on the smooth side remote from the ink mark but did not reach statistical significance. Marked cell death was seen with both dyes (<15%; P < .0001) adjacent to the ink on the porous side.

CONCLUSION

Chondrocyte viability is significantly reduced when cells are cultured in vitro on collagen membranes marked with methylene blue and crystal violet pen ink.

CLINICAL RELEVANCE

Surgeons should be aware of the potential negative effect of marker pens in cell-based therapies.

Dynamic compressive strain inhibits nitric oxide synthesis by equine chondrocytes isolated from different areas of the cartilage surface

REASONS FOR PERFORMING STUDY

Chondrocytes within articular cartilage respond to the mechanical stresses associated with normal joint loading via a series of signalling pathways. Specific biomolecules, such as nitric oxide (NO), have been implicated in these mechanotransduction processes. It has been shown that the synthesis of NO can be inhibited by dynamic compressive strain of chondrocytes in vitro which, in turn, leads to an up-regulation of specific metabolic parameters.

HYPOTHESIS

Chondrocytes isolated from different joint locations and seeded in agarose constructs respond in a distinct manner to the application of dynamic compression.

METHODS

Chondrocytes were isolated separately from the equine patella groove and the femoral condyle, representing high loaded areas (HLA) and low loaded areas (LLA), respectively, of 6 specimens of different ages. The cells were seeded in agarose constructs and cultured either in an unstrained state or strained under dynamic loading at 1 Hz for 48 h. The synthesis of nitric oxide (NO), proteoglycan synthesis and chondrocyte proliferation were assessed.

RESULTS

Equine chondrocytes were found to synthesise significant basal levels of NO, regardless of topographical origin or age of tissue. Marked differences in both proteoglycan synthesis and cell proliferation were, however, revealed between the 2 chondrocyte subpopulations. Dynamic compression inhibited NO synthesis but significant alterations in proteoglycan synthesis and cell proliferation were apparent in a minority of cases.

CONCLUSIONS AND POTENTIAL RELEVANCE

The differential response of the subpopulations of chondrocytes derived from the HLA and LLA provides a potential mechanism which enables the biomechanical demands of differing joint regions to be maintained.

The China diary. AMRA delegation's visit to China. Part I

In May, 22 AMRA representatives toured the People's Republic of China at the invitation of the Chinese government. Designated delegates kept a diary of the informational exchange between the AMRA delegates and their hosts, as well as a commentary on places seen during their travels. Their diary entries have been compiled into a two-part article. The first part appears in this issue, and the second part will appear in the September issue.