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Lack of growth potential of available grafts represents a bottleneck in the correction of congenital heart defects. Here we used a swine small intestinal submucosa (SIS) graft functionalized with mesenchymal stem cell (MSC)-derived vascular smooth muscle cells (VSMCs), for replacement of the pulmonary artery in piglets. MSCs were expanded from human umbilical cord blood or new-born swine peripheral blood, seeded onto decellularized SIS grafts and conditioned in a bioreactor to differentiate into VSMCs. Results indicate the equivalence of generating grafts engineered with human or swine MSC-derived VSMCs. Next, we conducted a randomized, controlled study in piglets (12-15 kg), which had the left pulmonary artery reconstructed with swine VSMC-engineered or acellular conduit grafts. Piglets recovered well from surgery, with no casualty and similar growth rate in either group. After 6 months, grafted arteries had larger circumference in the cellular group (28.3 ± 2.3 vs 18.3 ± 2.1 mm, P

© 2019 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED. Background:The lack of a standardized system for describing cell therapies acts as a barrier to advancement in clinical and basic research and practice. The aim of this study was to establish an international expert consensus on strategies to improve standardization and transparency when describing cell therapies. The secondary aim was to develop a consensus among experts on the contents of a standardized tool for describing cell therapies.Methods:The need for expert consensus on strategies to improve cell therapy communication was confirmed at the American Academy of Orthopaedic Surgeons/National Institutes of Health Optimizing Clinical Use of Biologics Symposium in 2018. A working group of 6 experts convened an international consensus process involving clinicians and basic scientists using validated Delphi methodology. This iterative process was used to define statements on communication of cell therapies and develop a standardized tool for describing cell therapies.Results:Thirty-four experts completed 3 rounds survey with use of the Delphi process. After 3 rounds, 27 statements relating to existing nomenclature, solutions to improve communication, ideal characteristics of a framework, mandatory elements of a new framework, and future work to facilitate application reached consensus with >80% agreement and

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.

A biodegradable, hyaluronian-based biocompatible scaffold was used for autologous chondrocyte transplantation. This prospective study analyzes a clinical outcome of 70 consecutive patients treated by arthroscopic autologous chondrocyte transplantation at minimum 24 months follow up (47 of these patients achieved minimum 36 months follow-up and 21 patients minimum 48 months follow-up) in order to establish clear indication criteria for this type of treatment. 31 of these patients presented isolated chondral lesions, while 39 patients with associated lesions (23 ACL lesions, 28 meniscal lesions, 1 varus knee) were treated during the same surgical procedure with cartilage harvesting. A statistically significant clinical improvement was shown just at 24 months and the second-look arthroscopy demonstrated a complete coverage of the grafted area with a hyaline cartilage-like tissue in 12 of 15 analyzed patients. A better clinical outcome was observed in young, well-trained patients and in traumatic lesions. Other factors, such as defect size, localization, previous and associated surgery did not influence significantly the results. This matrix autologous chondrocyte transplantation procedure simplifies the surgical procedure and can be performed arthroscopically, thus reducing surgical morbidity and recovery time.

Cartilage repair strategies aim to resurface a lesion with osteochondral tissue resembling native cartilage, but a variety of repair tissues are usually observed. Histology is an important structural outcome that could serve as an interim measure of efficacy in randomized controlled clinical studies. The purpose of this article is to propose guidelines for standardized histoprocessing and unbiased evaluation of animal tissues and human biopsies. Methods were compiled from a literature review, and illustrative data were added. In animal models, treatments are usually administered to acute defects created in healthy tissues, and the entire joint can be analyzed at multiple postoperative time points. In human clinical therapy, treatments are applied to developed lesions, and biopsies are obtained, usually from a subset of patients, at a specific time point. In striving to standardize evaluation of structural endpoints in cartilage repair studies, 5 variables should be controlled: 1) location of biopsy/sample section, 2) timing of biopsy/sample recovery, 3) histoprocessing, 4) staining, and 5) blinded evaluation with a proper control group. Histological scores, quantitative histomorphometry of repair tissue thickness, percentage of tissue staining for collagens and glycosaminoglycan, polarized light microscopy for collagen fibril organization, and subchondral bone integration/structure are all relevant outcome measures that can be collected and used to assess the efficacy of novel therapeutics. Standardized histology methods could improve statistical analyses, help interpret and validate noninvasive imaging outcomes, and permit cross-comparison between studies. Currently, there are no suitable substitutes for histology in evaluating repair tissue quality and cartilaginous character.

Background: The synergistic degradation of cartilage by oncostatin M (OSM) in combination with either interleukin 1 (IL1) or tumour necrosis factor α (TNFα) has been previously demonstrated using bovine nasal cartilage (BNC). Objectives: ( a ) To investigate if human nasal cartilage (HNC) responds in the same way as BNC to these cytokine combinations, particularly in collagen degradation. ( b ) To compare the response of human nasal and articular cartilages. Methods: Collagen release was assessed by measuring the hydroxyproline content of culture supernatants and proteoglycan release by the dimethylmethylene blue assay. Matrix metalloproteinase (MMP)-1, MMP-13, and tissue inhibitor of metalloproteinase 1 release were measured by specific enzyme linked immunosorbent assays (ELISAs), and collagenolytic activity was measured by a bioassay using radiolabelled collagen. Results: OSM in combination with either IL1 or TNFα acted synergistically to induce collagenolysis from HNC, with a maximum of 79% collagen release. This degradation strongly correlated with MMP-1 and MMP-13 levels and collagenolytic activity. Conclusion: Collagen release from human cartilage is marked and implicates both MMP-1 and MMP-13 in the synergistic degradation of human cartilage by OSM in combination with either IL1 or TNFα. HNC responds in the same way as BNC, thus validating the bovine cartilage degradation assay as a model relevant to human disease.

OBJECTIVE: To determine if the rheumatoid synovium is a suitable target for hypoxia-regulated gene therapy. METHODS: Sequential sections of wax-embedded synovial membrane samples were obtained from 10 patients with rheumatoid arthritis (RA), 10 with primary osteoarthritis (OA), and from 6 healthy controls. Membrane sections from each patient were immunostained for hypoxia-inducible factor 1alpha (HIF-1alpha) and CD68 (a pan-macrophage marker). RESULTS: HIF-1alpha was expressed abundantly by macrophages in most rheumatoid synovia, predominantly close to the intimal layer but also in the subintimal zone. There was markedly lower expression of HIF-1alpha in OA synovia, and it was absent from all of the healthy synovia. CONCLUSION: These observations indicate that macrophages transduced with a therapeutic gene under the control of a hypoxia-inducible promoter could be administered to RA patients systemically. Migration of these cells to synovial tissue would result in the transgene being switched on in diseased joints but not in healthy tissues

Objective. To determine if degradation of cartilage matrix in primary osteoarthritis (OA) or in OA secondary to rupture of the anterior cruciate ligament (ACL) is a gradual response to excessive loading or an early, initiating event in the disease process. Methods. Biopsy samples were obtained from the low‐weight-bearing articular cartilage of the intercondylar notch, in patients undergoing knee arthroscopy (ACL injury) or arthroplasty (late-stage primary OA) or in controls. In some cases, biopsy samples were also removed from the high‐weight-bearing articular cartilage of the femoral condyles. Biopsy specimens were extracted and assayed for total and denatured type II collagen (CII) by inhibition enzyme-linked immunosorbent assay and for proteoglycan using a colorimetric method. All patients were assessed radiographically for cartilage erosion. In addition, the cartilage of patients with ACL injury was assessed at arthroscopy, and the knee function of patients with primary OA was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Results. Increased CII degradation was detected in the low‐ as well as the high‐weight-bearing cartilage of patients with late-stage OA, and there was a positive correlation between the percentage denatured collagen and the WOMAC score. Most of the patients with ACL injury had no clinical signs of OA or macroscopic cartilage erosion. However, the low‐weight-bearing articular cartilage from these patients showed a significant increase in CII degradation, similar to that observed in late-stage OA. The proteoglycan content of articular cartilage did not change significantly in patients with OA or ACL injury compared with controls. Conclusion. CII degradation is an early event following ACL injury and is unlikely to be a direct result of mechanical loading, since it was observed in cartilage obtained from a low‐weight-bearing site.

Those working in the regenerative medicine field currently face numerous regulatory and related challenges. This Perspective captures some of the key ideas of a UK-based working group drawn from academic, clinical and industrial communities and also identifies some key steps that should be taken in the UK and elsewhere to address these challenges.

Content and structure in cartilage Type II collagen is one of the primary structural components of hyaline cartilage, constituting approximately half the dry weight of extracellular matrix. It is composed of a triple helix of three identical a chains organized in fibrils within the extracellular matrix. Whereas these fibrils are ordinarily clearly visible throughout the matrix, close to the cell in the pericellular domain, their identity is often difficult to discern. It is here that there is likely more active turnover of collagen, such as in rheumatoid arthritis (Mansson et al. 1995).

Achieving success in the field of regenerative medicine will depend in part on our learning how best to manipulate cells in vitro in order to elicit therapeutic responses after implantation into patients. The traditional approach to tissue engineering is to combine cells with biomaterial scaffolds in order to create a template for tissue formation. There is a huge body of literature describing the science behind this type of approach but only relatively few clinical trials that shed light on the feasibility and efficacy of turning this interesting science into useful medicine [1]. A number of recent clinical studies have provided important insights into what might be achieved using a range of different techniques. Some examples of these are reviewed here in order to provide an overview of where this young field has got to and some of the challenges that lie ahead.

SUMMARY Rheumatoid arthritis (RA) synovial fluid (SF) stimulated significant loss of glycosaminoglycans (GAG) from normal and pathological human cartilage biopsies over 2 days as compared with normal human serum. By contrast, 15 RA SFs failed to degrade killed normal cartilage, and degraded killed RA cartilage less effectively than living RA cartilage. Four RA SFs were treated with neutralizing anti-cytokine antisera prior to incubation with normal cartilage. The degrading effects of two of the fluids were reversed by anti-interleukin-1α (IL-1α) while degradation by the third and fourth fluids were reversed by anti-intcrleukin-1β (IL-1β) and anti-tumour necrosis factor-alpha (TNF-α). respectively. However, recombinant human IL-1α. 1L-1β. TNFα or a combination of all three cytokines had no degrading effect in this 2-day culture system. It is concluded that RA SF degrades cartilage by a mechanism involving a synergistic interaction between cytokines and some other component of SF.

Summary Background The loss of a normal airway is devastating. Attempts to replace large airways have met with serious problems. Prerequisites for a tissue-engineered replacement are a suitable matrix, cells, ideal mechanical properties, and the absence of antigenicity. We aimed to bioengineer tubular tracheal matrices, using a tissue-engineering protocol, and to assess the application of this technology in a patient with end-stage airway disease. Methods We removed cells and MHC antigens from a human donor trachea, which was then readily colonised by epithelial cells and mesenchymal stem-cell-derived chondrocytes that had been cultured from cells taken from the recipient (a 30-year old woman with end-stage bronchomalacia). This graft was then used to replace the recipient's left main bronchus. Findings The graft immediately provided the recipient with a functional airway, improved her quality of life, and had a normal appearance and mechanical properties at 4 months. The patient had no anti-donor antibodies and was not on immunosuppressive drugs. Interpretation The results show that we can produce a cellular, tissue-engineered airway with mechanical properties that allow normal functioning, and which is free from the risks of rejection. The findings suggest that autologous cells combined with appropriate biomaterials might provide successful treatment for patients with serious clinical disorders. Funding Ministerio de Sanidad y Consumo, Instituto de Salud Carlos III, Fondo de Investigacion Sanitaria, Spain; Charles Courtenay-Cowlin Fund, University of Bristol; UK Arthritis Research Campaign; and the James Tudor Foundation.

Hyalograft C is an innovative tissue-engineering approach for the treatment of knee cartilage defects involving the implantation of laboratory expanded autologous chondrocytes grown on a three-dimensional hyaluronan-based scaffold. This technique has recently been introduced into clinical practice, with more than 600 patients treated so far. Because no periosteal coverage is required to keep the graft in place, surgical time and morbidity are reduced, and handling of the graft is much simpler than currently available autologous chondrocyte implantation techniques. The safety profile of the treatment appears positive, with a limited number of adverse events reported. Here we discuss the clinical, arthroscopic and histological results from a cohort of 67 patients treated with Hyalograft C (mean follow-up time from implantation of 17.5 months). Results are reported based on four endpoints: patients' subjective evaluation of knee conditions (97% of patients improved) and quality of life (94% improved), surgeons' knee functional test (87% of patients with the best scores), arthroscopic evaluation of cartilage repair (96.7% biologically acceptable) and histological assessment of the grafted site (majority of specimens hyaline-like). The positive clinical results obtained indicate that Hyalograft C may be a viable therapeutic option for the treatment of acute cartilage lesions.

Outcome measures for cartilage repair techniques include clinical assessment of functional status, magnetic resonance imaging, mechanical indentation in situ and second-look biopsies, which are used for detailed ex vivo histological and immunohistochemical assessment. Biopsy analysis is considered an important outcome measure, despite being highly invasive, since it provides a visual record of the spatial organization of matrix proteins and cells. We propose that the value of second-look biopsies would be significantly enhanced if accurate quantification of cartilage matrix molecules could also be obtained. The goal of our work has been to develop a combined method for histological and biochemical analysis of a single biopsy. We have developed a method of cutting frozen sections of cartilage and recovering the uncut tissue for subsequent biochemical analysis. We have also developed a range of miniaturized assays that can be performed after cartilage digestion with trypsin. In this way we are now able to analyse biopsies with a wet weight as low as 5 mg using both histological and biochemical methods, so obtaining the maximum amount of information from the minimum volume of tissue. This new approach will allow a more accurate assessment of the quality of cartilage repair tissue than histological analysis alone.

The dimethylmethylene blue assay showed higher concentrations of glycosaminoglycans in many synovial fluids from patients with rheumatoid arthritis (RA) than in autologous sera or sera or synovial fluids from normal subjects. These results were taken to suggest that the glycosaminoglycans in RA synovial fluid were abnormally raised and derived from cartilage. To discover what stimulated such glycosaminoglycan release in RA joints relations were sought between synovial fluid concentrations of glycosaminoglycans and immunological and inflammatory mediators. It was shown that RA synovial fluid glycosaminoglycan concentrations correlated with synovial fluid C3d concentrations but not with synovial fluid rheumatoid factor concentrations, polymorphonuclear leucocyte numbers, myeloperoxidase concentrations, or the ability of the synovial fluids to release free radicals from normal polymorphonuclear leucocytes. A correlation was found between synovial fluid C3d and interleukin 1 concentrations as judged by both lymphocyte activating factor activity and immunoassay, but no significant correlation was detected between interleukin 1 and glycosaminoglycan concentrations. It is suggested that in the rheumatoid joint locally produced cytokines, in addition to interleukin 1, together stimulate glycosaminoglycan release from cartilage and render it vulnerable to attack by other processes.

The regeneration of damaged organs requires that engineered tissues mature when implanted at sites of injury or disease. We have used new analytic techniques to determine the extent of tissue regeneration after treatment of knee injury patients with a novel cartilage tissue engineering therapy and the effect of pre-existing osteoarthritis on the regeneration process. We treated 23 patients, with a mean age of 35.6 years, presenting with knee articular cartilage defects 1.5 cm2 to 11.25 cm2 (mean, 5.0 cm2) in area. Nine of the patients had X-ray evidence of osteoarthritis. Chondrocytes were isolated from healthy cartilage removed at arthroscopy. The cells were cultured for 14 days, seeded onto esterified hyaluronic acid scaffolds (Hyalograft C), and grown for a further 14 days before implantation. A second-look biopsy was taken from each patient after 6 to 30 months (mean, 16 months). After standard histological analysis, uncut tissue was further analyzed using a newly developed biochemical protocol involving digestion with trypsin and specific, quantitative assays for type II collagen, type I collagen, and proteoglycan, as well as mature and immature collagen crosslinks. Cartilage regeneration was observed as early as 11 months after implantation and in 10 out of 23 patients. Tissue regeneration was found even when implants were placed in joints that had already progressed to osteoarthrosis. Cartilage injuries can be effectively repaired using tissue engineering, and osteoarthritis does not inhibit the regeneration process.

Objective To assess the associations between pain, loss of function, and radiographic changes in knee osteoarthritis (OA), taking into account both the patellofemoral and tibiofemoral compartments. Methods Both knees of 167 community-based patients with OA in at least 1 of their knees were assessed. Pain was measured by visual analog scale, and function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index. Anteroposterior standing radiographs with the knee in extension and lateral 30° flexion were obtained and assessed for the Kellgren/Lawrence score and for individual features (osteophytes, joint space narrowing, and subchondral bone sclerosis) in each compartment. Results Knees with structural changes in both compartments were more likely to be painful and to be associated with loss of function than were knees in which only 1 compartment was affected. The individual feature most strongly associated with pain was subchondral bone sclerosis. Conclusion Studies exploring the associations between structural and symptomatic knee OA need to include an assessment of the patellofemoral compartment, and individual radiographic features rather than a global severity score should be considered in these studies.

Reliable and reproducible outcome measures are essential to assess the efficacy of competing and novel tissue-engineering techniques. The aim of this study was to compare traditional histological analyses with newly developed quantitative biochemical outcome measures for the repair of articular cartilage. The production of a new anti-peptide antibody and the development and validation of a novel method for the extraction and immunoassay of type I collagen are described. The assay was used, in conjunction with existing assays for type II collagen and proteoglycans, to measure levels of the matrix components in repair tissue biopsies obtained from patients treated with the new tissue-engineering therapy Hyalograft C. Frozen sections cut from the same biopsies were stained for proteoglycans, using safranin O, and immunohistochemical analysis was used to assess type I and II collagen staining. Although there was general agreement between the extent of staining and the amounts of the three matrix components, there was a large degree of overlap in biochemical content between biopsies classified histologically on the basis of low, moderate, or abundant staining. The results demonstrate that histological grading of matrix protein abundance to classify repair cartilage as hyaline or fibrocartilagenous is often misleading. In addition, we demonstrate for the first time the ability to measure collagen cross-links in repair tissue biopsies and show that it can be used as a surrogate marker for tissue maturity. Our new range of biochemical techniques provides a standardized method to assess the quality of both engineered cartilage produced in vitro and repair tissue biopsies obtained after in vivo implantation.

Processing of Resorbable Poly-a-Hydroxy Acids for Use as Tissue-Engineering Scaffolds Minna Kellomaki and Pertti Tormala Fibrin Microbeads (FMB) As Biodegradable Carriers for Culturing Cells and for Accelerating Wound Healing Raphael Gorodetsky, Akiva Vexler, Lilia Levdansky, and Gerard Marx Synthesis and Characterization of Hyaluronan-Based Polymers for Tissue Engineering Carlo Soranzo, Davide Renier, and Alessandra Pavesio Synthesis and Characterization of Chitosan Scaffolds for Cartilage-Tissue Engineering Steven H. Elder, Dana L. Nettles, and Joel D. Bumgardner Characterization of a Calcium Phosphate-Based Matrix for rhBMP-2 Hyun D. Kim, John M. Wozney, and Rebecca H. Li Methodologies for Processing Biodegradable and Natural Origin Scaffolds for Bone and Cartilage Tissue-Engineering Applications Manuela E. Gomes, Patricia B. Malafaya, and Rui L. Reis Alginates in Tissue Engineering Marcy Wong Production and Surface Modification of Polylactide-Based Polymeric Scaffolds for Soft-Tissue Engineering Yang Cao, Tristan I. Croll, Justin J. Cooper-White, Andrea J. O'Connor, and Geoffrey W. Stevens Modification of Materials With Bioactive Peptides Jennifer L. West Isolation and Osteogenic Differentiation of Bone-Marrow Progenitor Cells for Application in Tissue Engineering Antonio J. Salgado, Manuela E. Gomes, Olga P. Coutinho, and Rui L. Reis Cell Seeding of Polymer Scaffolds Gordana Vunjak-Novakovic and Milica Radisic Chondrocyte Isolation, Expansion, and Culture on Polymer Scaffolds Aileen Crawford and Sally C. Dickinson Bioreactor Culture Techniques for Cartilage-Tissue Engineering David A. Lee and Ivan Martin Microscopic Methods for the Analysis of Engineered Tissues Sally Roberts and Janis Menage Transmission Electron Microscopy ofTissue-Polymer Constructs Paul V. Hatton Application of Microscopic Methods for the Detection of Cell Attachment to Polymers John Hunt and Deborah Heggarty Biochemical Methods for the Analysis of Tissue-Engineered Cartilage Wa'el Kafienah and Trevor J. Sims Real-Time Quantitative RT-PCR Assays Ivan Martin and Oliver Frank Mechanical Testing of Cell-Material Constructs: A Review John Kisiday, Alex Kerin, and Alan Grodzinsky Index

Physical injury frequently causes tissue damage, including laceration. Repair of the damage usually results in the formation of a scar; complete anatomic healing and true regeneration are rare. Connective tissues tend to heal naturally and successfully only if the injury is minor. If the damage is more severe, then a good functional result can be achieved only if Nature is assisted by surgical intervention. The efficacy of such measures has been established in the cases of bone and tendon injuries but not in the case of cartilage damage 1. In the latter situation, we are still prejudiced by Hippocrates' opinion that "ulcerated cartilage is universally allowed to be a troublesome disease." 2 In addition, our view is necessarily colored by the scarcity of successful therapeutic modalities 3. Articular cartilage is a narrow layer of specialized connective tissue that permits smooth, frictionless movement of diarthrodial joints. It is comprised of a relatively small number of cells (chondrocytes) embedded in an abundant extracellular matrix 4. The latter consists predominantly of type-II collagen, proteoglycans, and water, along with smaller amounts of other collagen types and noncollagenous proteins. Histologically, articular cartilage is divided into three zones, which are distinguished by the shape of the chondrocytes and the arrangement of type-II collagen fibers. The superficial zone is characterized by flattened disc-like chondrocytes, a low proteoglycan content, and densely-packed, horizontally-arranged collagen fibrils of uniform diameter. This layer has been described as a tension-resisting diaphragm 5 by virtue of its tendency to curl when the articular cartilage is released from the subchondral bone 6. In the middle zone, chondrocytes attain a more rounded profile, proteoglycan content increases, and the collagen fibers decussate to provide an oblique transitional network between the superficial tangential zone and the deep radial zone. The deep radial zone is …

“In June 2008, a young woman with end-stage bronchial disease received a decellularized donor tracheal graft that had been repopulated with autologous cells, many of which ... were derived from mesenchymal stem cells; 6 months later, she is well and actively caring for her two young children.” Anthony Hollander Department of Cellular & Molecular Medicine, University of Bristol, School of Medical Sciences, University Walk, Clifton, Bristol BS8 1TD, UK Paolo Macchiarini Department of General Thoracic Surgery, Hospital Clinic, c Villaroel 170, E-08036 Barcelona, Spain Bert Gordijn Ethics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland

Synovial fluid (SF) from rheumatoid arthritis (RA) patients were tested for their ability to inhibit the proliferative responses of normal peripheral blood mononuclear cells (PBM) to mitogens and interleukin-2 (IL-2). SF significantly inhibited the responses to concanavalin A (CON A) and phytohaemagglutinin (PHA), but significantly enhanced the responses to IL-2. Similarly, SF mononuclear cells (SFM) were hyporesponsive to CON A and PHA compared with autologous PBM, but hyper-responsive to IL-2. It is concluded that an IL-2 inhibitor in RA SF is unlikely to be the cause of SFM hyporesponsiveness to mitogens.

Synovial fluids from patients with rheumatoid arthritis and from patients with osteoarthritis degraded the matrix of living, but not killed, normal human cartilage as judged by loss of glycosaminoglycans. Normal human serum did not degrade living cartilage and neither, unexpectedly, did recombinant human cytokines.

This study was designed to determine if the maturation stage of engineered cartilage implanted in a goat model of cartilage injury influences the repair outcome. Goat engineered cartilage was generated from autologous chondrocytes cultured in hyaluronic acid scaffolds using 2 d, 2 weeks or 6 weeks of pre-culture and implanted above hydroxyapatite/hyaluronic acid sponges into osteochondral defects. Control defects were left untreated or treated with cell-free scaffolds. The quality of repair tissues was assessed 8 weeks or 8 months post implantation by histological staining, modified O’Driscoll scoring and biochemical analyses. Increasing pre-culture time resulted in progressive maturation of the grafts in vitro. After 8 weeks in vivo, the quality of the repair was not improved by any treatment. After 8 months, O’Driscoll histology scores indicated poor cartilage architecture for untreated (29.7 ± 1.6) and cell-free treated groups (24.3 ± 5.8). The histology score was improved when cellular grafts were implanted, with best scores observed for grafts pre-cultured for 2 weeks (16.3 ± 5.8). As compared to shorter pre-culture times, grafts cultured for 6 weeks (histology score: 22.3 ± 6.4) displayed highest type II/I collagen ratios but also inferior architecture of the surface and within the defect, as well as lower integration with native cartilage. Thus, pre-culture of engineered cartilage for 2 weeks achieved a suitable compromise between tissue maturity and structural/integrative properties of the repair tissue. The data demonstrate that the stage of development of engineered cartilage is an important parameter to be considered in designing cartilage repair strategies.

Introduction The present study established characteristics of tissue regrowth in patients suffering knee lesions treated with grafts of autologous chondrocytes grown on three-dimensional hyaluronic acid biomaterials. Methods This multicentred study involved a second-look arthroscopy/biopsy, 5 to 33 months post implant (n = 63). Seven patients allowed a third-look biopsy, three of which were performed 18 months post implant. Characteristics of tissues were histologically and histochemically evaluated. The remaining bone stubs were evaluated for cartilage/bone integration. For data analysis, biopsies were further divided into those obtained from postoperative symptomatic patients (n = 41) or from asymptomatic patients (n = 22). Results The percentage of hyaline regenerated tissues was significantly greater in biopsies obtained after, versus within, 18 months of implantation. Differences were also observed between symptomatic and asymptomatic patients: reparative tissues taken from symptomatic patients 18 months after grafting were mainly fibrocartilage or mixed (hyaline–fibrocartilage) tissue, while tissues taken from asymptomatic patients were hyaline cartilage in 83% of biopsies. In a small group of asymptomatic patients (n = 3), second-look and third-look biopsies taken 18 months after surgery confirmed maturation of the newly formed tissue over time. Cartilage maturation occurred from the inner regions of the graft, in contact with subchondral bone, towards the periphery of the implant. Conclusions The study indicates that, in asymptomatic patients after chondrocyte implantation, regenerated tissue undergoes a process of maturation that in the majority of cases takes longer than 18 months for completion and leads to hyaline tissue and not fibrous cartilage. Persistence of symptoms might reflect the presence of a nonhyaline cartilage repair tissue.