Autologous chondrocyte implantation for cartilage repair: monitoring its success by magnetic resonance imaging and histology

Autologous chondrocyte implantation is being used increasingly for the treatment of cartilage defects. In spite of this, there has been a paucity of objective, standardised assessment of the outcome and quality of repair tissue formed. We have investigated patients treated with autologous chondrocyte implantation (ACI), some in conjunction with mosaicplasty, and developed objective, semiquantitative scoring schemes to monitor the repair tissue using MRI and histology. Results indicate repair tissue to be on average 2.5 mm thick. It was of varying morphology ranging from predominantly hyaline in 22% of biopsy specimens, mixed in 48%, through to predominantly fibrocartilage, in 30%, apparently improving with increasing time postgraft. Repair tissue was well integrated with the host tissue in all aspects viewed. MRI scans provide a useful assessment of properties of the whole graft area and adjacent tissue and is a noninvasive technique for long-term follow-up. It correlated with histology (P = 0.02) in patients treated with ACI alone.     

Glycosaminoglycan profiles of repair tissue formed following autologous chondrocyte implantation differ from control cartilage

Currently, autologous chondrocyte implantation (ACI) is the most commonly used cell-based therapy for the treatment of isolated femoral condyle lesions of the knee. A small number of centres performing ACI have reported encouraging long-term clinical results, but there is currently a lack of quantitative and qualitative biochemical data regarding the nature of the repair tissue. Glycosaminoglycan (GAG) structure influences physiological function and is likely to be important in the long-term stability of the repair tissue. The objective of this study was to use fluorophore-assisted carbohydrate electrophoresis (FACE) to both quantitatively and qualitatively analyse the GAG composition of repair tissue biopsies and compare them with age-matched cadaveric controls. We used immunohistochemistry to provide a baseline reference for comparison. Biopsies were taken from eight patients (22 to 52 years old) 1 year after ACI treatment and from four cadavers (20 to 50 years old). FACE quantitatively profiled the GAGs in as little as 5 μg of cartilage. The pattern and intensity of immunostaining were generally comparable with the data obtained with FACE. In the ACI repair tissue, there was a twofold reduction in chondroitin sulphate and keratan sulphate compared with age-matched control cartilage. By contrast, there was an increase in hyaluronan with significantly shorter chondroitin sulphate chains and less chondroitin 6-sulphate in repair tissue than control cartilage. The composition of the repair tissue thus is not identical to mature articular cartilage.     

Treatment of posttraumatic and focal osteoarthritic cartilage defects of the knee with autologous polymer-based three-dimensional chondrocyte grafts: 2-year clinical results

Autologous chondrocyte implantation (ACI) is an effective clinical procedure for the regeneration of articular cartilage defects. BioSeed-C is a second-generation ACI tissue engineering cartilage graft that is based on autologous chondrocytes embedded in a three-dimensional bioresorbable two-component gel-polymer scaffold. In the present prospective study, we evaluated the short-term to mid-term efficacy of BioSeed-C for the arthrotomic and arthroscopic treatment of posttraumatic and degenerative cartilage defects in a group of patients suffering from chronic posttraumatic and/or degenerative cartilage lesions of the knee. Clinical outcome was assessed in 40 patients with a 2-year clinical follow-up before implantation and at 3, 6, 12, and 24 months after implantation by using the modified Cincinnati Knee Rating System, the Lysholm score, the Knee injury and Osteoarthritis Outcome Score, and the current health assessment form (SF-36) of the International Knee Documentation Committee, as well as histological analysis of second-look biopsies. Significant improvement (p < 0.05) in the evaluated scores was observed at 1 and/or 2 years after implantation of BioSeed-C, and histological staining of the biopsies showed good integration of the graft and formation of a cartilaginous repair tissue. The Knee injury and Osteoarthritis Outcome Score showed significant improvement in the subclasses pain, other symptoms, and knee-related quality of life 2 years after implantation of BioSeed-C in focal osteoarthritic defects. The results suggest that implanting BioSeed-C is an effective treatment option for the regeneration of posttraumatic and/or osteoarthritic defects of the knee.     

A second-generation autologous chondrocyte implantation approach to the treatment of focal articular cartilage defects

Autologous chondrocyte implantation (ACI) is the most widely used cell-based surgical procedure for the repair of articular cartilage defects. Challenges to successful ACI outcomes include limitation in defect size and geometry as well as inefficient cell retention. Second-generation ACI procedures have thus focused on developing three-dimensional constructs using native and synthetic biomaterials. Clinically significant and satisfactory results from applying autologous chondrocytes seeded in fibrin within a biodegradable polymeric material were recently reported. In the future, third-generation cell-based articular cartilage repair should focus on the use of chondroprogenitor cells and biofunctionalized biomaterials for more extensive and permanent repair.     

Chondrocyte suspension in fibrin glue

Autologous chondrocyte implantation has been shown to be a promising method for treatment of deep articular cartilage defects. The hyaline cartilage formed by implanted autologous chondrocytes has biomechanical properties similar to those of natural articular cartilage. Between June 2006 and September 2008 we performed Autologous chondrocyte implantation (ACI) in 50 patients and the chondrocytes were supported in fibrin glue. The cartilage biopsy samples were taken from the non-weight bearing area of the patient’s femoral condyle and the samples were transferred to the cell culture laboratory. Chondrocyte were kept in culture about 20 days. Fibrin glue was used as a three dimensional carrier for chondrocyte implantation. A 450 ml of patient’s own blood was collected prior to transplantation to produce autologous fibrinogen. Alternatively the allogenic fibrinogen was prepared from Regional Blood Center voluntary donors. Before surgery the chondrocyte suspension was mixed with fibrin glue and gel—like fibrograft was prepared. The total number of cells and the size of fibrograft depended on the defect size in the knee. Our results suggest that ACI technique with fibrin glue is a promising method for treatment of cartilage defect.     

Serum levels of hyaluronic acid and chondroitin sulfate as a non-invasive method to evaluate healing after cartilage repair procedures

Magnetic resonance imaging remains the only non-invasive method to assess the quality of cartilage repair procedures, but ideally would be complemented by other modalities, particularly blood tests. Nganvongpanit and colleagues investigated serum levels of hyaluronic acid (HA) and chondroitin sulfate (CS) for their correlation with tissue quality after cartilage repair with autologous chondrocytes versus subchondral drilling in a dog model. They reported better tissue quality in animals treated with chondrocyte implantation. Serum levels correlated with the histological score of biopsy samples: CS showed a negative (r = -0.69) and HA a positive (r = +0.46) correlation. Many questions remain to be answered before serum markers can provide a reliable, non-invasive tool to assess tissue quality, but these data provide an important foundation for additional research.In the previous issue of Arthritis Research & Therapy, Nganvongpanit and colleagues [1], of Chiang Mai University in Thailand, investigated the potential use of serum biomarkers, such as hyaluronic acid (HA) and chondroitin sulfate (CS), to evaluate healing after cartilage repair procedures. They randomly assigned dogs to treatment with autologous chondrocyte implantation (ACI) versus subchondral drilling (SD) and followed the animals for 24 weeks post-operatively with multiple blood draws and a cartilage biopsy at final follow-up.Cartilage defects are a common diagnosis, encountered in over 60% of knee arthroscopies [2]. While the natural history and pathophysiology of cartilage defects remain controversial, a significant number of patients present with symptoms that warrant surgical intervention. These patients undergo various cartilage repair procedures to repair the damaged articular surfaces, including microfracture, osteochondral autografting, and ACI. Progress in the field of cartilage repair has been impeded in part by the relative lack of adequate instruments to evaluate the quality of the reparative tissue. While histological evaluation is desirable, researchers have found it difficult to recruit patients for a second surgical procedure to harvest a tissue biopsy solely for research purposes. Imaging techniques, especially magnetic resonance imaging (MRI), have made significant progress in recent years. Certain cartilage-specific techniques such as delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and T1-rho and T2-mapping have promise to assess tissue quality by indirectly measuring glycosaminoglycan content [3,4]. However, these techniques are associated with substantial cost and potential risk to the patient from contrast exposure; therefore, the development of alternative non-invasive techniques is desirable. In particular, blood tests, which could be repeated multiple times with minimal discomfort to the patient, would present an ideal method to investigate the maturation of repair tissue after cartilage repair. Beyond the scientific benefit of comparing the relative time courses of healing after different repair techniques, once thresholds are established, biomarkers could provide clinical guidance regarding the point when patients might return to full activities.In their article, Nganvongpanit and colleagues investigated the use of monoclonal antibodies and enzyme-linked immunosorbent assay to quantify serum levels of CS and HA, respectively, in a dog model. They followed two groups treated with either SD or autologous chondrocytes (ACs) for 24 weeks, with blood draws at baseline and every 6 weeks thereafter. Other endpoints included the gross visual evaluation of the reparative tissue as well as histologic grading. Animals treated with ACs demonstrated better visual and histological appearance than those treated with drilling. Three of the five AC biopsies were near normal, and the other two showed at least 50% fill and peripheral integration of the repair site. In the SD group, three of five samples demonstrated complete degeneration, and the other two only inconsistent fill and no peripheral integration with the surrounding articular surface. Histologically, both groups demonstrated some fibrocartilage; however, the AC group also showed hyaline cartilage compared with fibrous tissue in the SD group.Interestingly, serum levels of CS and HA demonstrated different trends at final follow-up after 24 weeks: CS had a strong negative correlation with histological scores (r = -0.69), while HA was positively correlated (r = +0.46). In the AC group, CS levels trended downward over time, a finding the authors interpret as a reflection of the normalizing proteoglycan turnover due to a successful repair with maturing tissue. In the SD group, however, levels remained high, possibly reflecting the progressive damage of the surrounding cartilage seen in these samples. Overall, HA levels also decreased from baseline, with relatively higher values in samples with better histological scores, potentially a sign of normalization of joint homeostasis.This study provided two important findings. First, it added to the mounting evidence of improved histological outcomes with cell-based therapy, such as ACI [5], over marrow-stimulation techniques, such as SD or microfracture. Second, the authors describe two potential candidate factors to follow tissue maturation and healing: HA and CS. Many questions remain to be addressed, such as the correlation of marker levels with defect size, number, and location as well as possible differences between chondral and osteochondral defects and patient gender, age, or weight. However, these preliminary results are promising and provide a foundation for future research.In conclusion, while these findings require larger, confirmatory studies (ideally in human patients), they hold promise for non-invasive monitoring after cartilage repair procedures. Reliable, reproducible, and relatively inexpensive methods to evaluate the quality and maturation of reparative tissue will substantially advance the field of cartilage repair. These tests would potentially enable investigators and industry to develop new technologies aimed at repairing articular cartilage, assist surgeons to select the appropriate procedure for any given patient, and post-operatively, allow an individualized determination of when it is safe for the patient to return to higher levels of activity.     

Cartilage tissue engineering: Molecular control of chondrocyte differentiation for proper cartilage matrix reconstruction

Background

Articular cartilage defects are a veritable therapeutic problem because therapeutic options are very scarce. Due to the poor self-regeneration capacity of cartilage, minor cartilage defects often lead to osteoarthritis. Several surgical strategies have been developed to repair damaged cartilage. Autologous chondrocyte implantation (ACI) gives encouraging results, but this cell-based therapy involves a step of chondrocyte expansion in a monolayer, which results in the loss in the differentiated phenotype. Thus, despite improvement in the quality of life for patients, reconstructed cartilage is in fact fibrocartilage. Successful ACI, according to the particular physiology of chondrocytes in vitro, requires active and phenotypically stabilized chondrocytes.

Scope of review

This review describes the unique physiology of cartilage, with the factors involved in its formation, stabilization and degradation. Then, we focus on some of the most recent advances in cell therapy and tissue engineering that open up interesting perspectives for maintaining or obtaining the chondrogenic character of cells in order to treat cartilage lesions.

Major conclusions

Current research involves the use of chondrocytes or progenitor stem cells, associated with “smart” biomaterials and growth factors. Other influential factors, such as cell sources, oxygen pressure and mechanical strain are considered, as are recent developments in gene therapy to control the chondrocyte differentiation/dedifferentiation process.

General significance

This review provides new information on the mechanisms regulating the state of differentiation of chondrocytes and the chondrogenesis of mesenchymal stem cells that will lead to the development of new restorative cell therapy approaches in humans. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.     

The in Vitro Growth of Human Chondrocytes

Autologous chondrocyte implantation (ACI) for the treatment of articular cartilage defects has been described by other workers, however, relatively few details of the in vitro growth of the cells have been published. Here we describe the release of cells from adult human articular cartilage and their growth characteristics in vitro.Cultures were successfully established from 29 of 30 biopsies taken from patients aged 20–72 year. No significant relationship was found between donor age and initial cell yield following cartilage digest, however, the time to primary confluence increased in direct proportion to age. Thereafter the kinetics of cell proliferation was independent of donor age.The proportion of apoptotic or necrotic cells in the cartilage digest was low and increased with time in culture only in those cells which remained non-adherent. Conversely, entry into cell cycle was restricted to those cells which had become adherent.These results illustrate that previously reported techniques for isolating and culturing chondrocytes are reproducible, that adherent chondrocytes have considerable proliferative potential, and that concern about cell growth and viability need not, in itself, limit the clinical application of ACI to younger patients.     

In vitro effect of a synthesized sulfonamido-based gallate on articular chondrocyte metabolism

Autologous chondrocyte implantation (ACI) is a promising strategy for cartilage repair and reconstitution. However, limited cell numbers and the dedifferentiation of chondrocytes present major difficulties to the success of ACI therapy. Therefore, it is important to find effective pro-chondrogenic agents that restore these defects to ensure a successful therapy. In this study, we synthesized a sulfonamido-based gallate, namely N-[4-(4,6-dimethyl-pyrimidin-2-ylsulfamoyl)-phenyl]-3,4,5-trihydroxy-benzamide (EJTC), and investigated its effects on rabbit articular chondrocytes through an examination of its specific effects on cell proliferation, morphology, viability, GAG synthesis, and cartilage-specific gene expression. The results show that EJTC can effectively promote chondrocyte growth and enhance the secretion and synthesis of cartilage ECM by upregulating the expression levels of the aggrecan, collagen II, and Sox9 genes. The expression of the collagen I gene was effectively downregulated, which indicates that EJTC inhibits chondrocytes dedifferentiation. Chondrocyte hypertrophy, which may lead to chondrocyte ossification, was also undetectable in the EJTC-treated groups. The recommended dose of EJTC ranges from 3.125 μg/mL to 7.8125 μg/mL, and the most profound response was observed with 7.8125 μg/mL. This study may provide a basis for the development of a novel agent for the treatment of articular cartilage defects.     

Osteochondral autograft transplantation or autologous chondrocyte implantation for large cartilage defects of the knee: a meta-analysis

Autologous chondrocyte implantation (ACI) and osteochondral autograft transplantation (OAT or mosaicplasty) are two effective surgeries for the treatment of large cartilage defects for more than two decades. But there are always some controversies about which one has the better outcomes for the patients. The purpose of this meta-analysis is to compare the outcomes of these two surgeries and give an advice to the clinical practices. The literature search was performed on multiple electronic databases with specific included criteria. After the assessments, five Randomized controlled trials (level II) were included and two of them were in the same cohort. The continuous data of outcomes were categorized into ranked ones (excellent, good, fair and poor) for comparisons. In the six comparisons of excellent or good results and poor results, the outcomes of ACI were significantly better than OAT in only one comparison (RR 2.57, 95 % CI 1.09–6.07, P = 0.03) while others had no significant differences. We may reach a primary conclusion that there is no significant different outcome between ACI and OAT in a short-term follow-up but it may indicate that the patients with OAT may be more likely to have worse condition than that with ACI for a long-term period.     

Tissue engineering of functional articular cartilage: the current status

Osteoarthritis is a degenerative joint disease characterized by pain and disability. It involves all ages and 70% of people aged >65 have some degree of osteoarthritis. Natural cartilage repair is limited because chondrocyte density and metabolism are low and cartilage has no blood supply. The results of joint-preserving treatment protocols such as debridement, mosaicplasty, perichondrium transplantation and autologous chondrocyte implantation vary largely and the average long-term result is unsatisfactory. One reason for limited clinical success is that most treatments require new cartilage to be formed at the site of a defect. However, the mechanical conditions at such sites are unfavorable for repair of the original damaged cartilage. Therefore, it is unlikely that healthy cartilage would form at these locations. The most promising method to circumvent this problem is to engineer mechanically stable cartilage ex vivo and to implant that into the damaged tissue area. This review outlines the issues related to the composition and functionality of tissue-engineered cartilage. In particular, the focus will be on the parameters cell source, signaling molecules, scaffolds and mechanical stimulation. In addition, the current status of tissue engineering of cartilage will be discussed, with the focus on extracellular matrix content, structure and its functionality.     

Functional properties of cartilaginous tissues engineered from infrapatellar fat pad-derived mesenchymal stem cells

Articular cartilage has a poor intrinsic capacity for self-repair. The advent of autologous chondrocyte implantation has provided a feasible method to treat cartilage defects. However, the associated drawbacks with the isolation and expansion of chondrocytes from autologous tissue has prompted research into alternative cell sources such as mesenchymal stem cells (MSCs) which have been found to exist in the bone marrow as well as other joint tissues such as the infrapatellar fat pad (IFP), synovium and within the synovial fluid itself. In this work we assessed the chondrogenic potential of IFP-derived porcine cells over a 6 week period in agarose hydrogel culture in terms of mechanical properties, biochemical content and histology. It was found that IFP cells underwent robust chondrogenesis as assessed by glycosaminoglycan (1.47±0.22% w/w) and collagen (1.44±0.22% w/w) accumulation after 42 days of culture. The 1 Hz dynamic modulus of the engineered tissue at this time point was 272.8 kPa (±46.8). The removal of TGF-β3 from culture after 21 days was shown to have a significant effect on both the mechanical properties and biochemical content of IFP constructs after 42 days, with minimal increases occurring from day 21 to day 42 without continued supplementation of TGF-β3. These findings further strengthen the case that the IFP may be a promising cell source for putative cartilage repair strategies.     

Human polymer-based cartilage grafts for the regeneration of articular cartilage defects

The use of autologous chondrocyte implantation (ACI) and its further development combining autologous chondrocytes with bioresorbable matrices may represent a promising new technology for cartilage regeneration in orthopaedic research. Aim of our study was to evaluate the applicability of a resorbable three-dimensional polymer of pure polyglycolic acid (PGA) for the use in human cartilage tissue engineering under autologous conditions. Adult human chondrocytes were expanded in vitro using human serum and were rearranged three-dimensionally in human fibrin and PGA. The capacity of dedifferentiated chondrocytes to re-differentiate was evaluated after two weeks of tissue culture in vitro and after subcutaneous transplantation into nude mice by propidium iodide/fluorescein diacetate (PI/FDA) staining, scanning electron microscopy (SEM), gene expression analysis of typical chondrocyte marker genes and histological staining of proteoglycans and type II collagen. PI/FDA staining and SEM documented that vital human chondrocytes are evenly distributed within the polymer-based cartilage tissue engineering graft. The induction of the typical chondrocyte marker genes including cartilage oligomeric matrix protein (COMP) and cartilage link protein after two weeks of tissue culture indicates the initiation of chondrocyte re-differentiation by three-dimensional assembly in fibrin and PGA. Histological analysis of human cartilage tissue engineering grafts after 6 weeks of subcutaneous transplantation demonstrates the development of the graft towards hyaline cartilage with formation of a cartilaginous matrix comprising type II collagen and proteoglycan. These results suggest that human polymer-based cartilage tissue engineering grafts made of human chondrocytes, human fibrin and PGA are clinically suited for the regeneration of articular cartilage defects.     

Tissue engineering in the rheumatic diseases

Diseases such as degenerative or rheumatoid arthritis are accompanied by joint destruction. Clinically applied tissue engineering technologies like autologous chondrocyte implantation, matrix-assisted chondrocyte implantation, or in situ recruitment of bone marrow mesenchymal stem cells target the treatment of traumatic defects or of early osteoarthritis. Inflammatory conditions in the joint hamper the application of tissue engineering during chronic joint diseases. Here, most likely, cartilage formation is impaired and engineered neocartilage will be degraded. Based on the observations that mesenchymal stem cells (a) develop into joint tissues and (b) in vitro and in vivo show immunosuppressive and anti-inflammatory qualities indicating a transplant-protecting activity, these cells are prominent candidates for future tissue engineering approaches for the treatment of rheumatic diseases. Tissue engineering also provides highly organized three-dimensional in vitro culture models of human cells and their extracellular matrix for arthritis research.     

Treatment of focal degenerative cartilage defects with polymer-based autologous chondrocyte grafts: four-year clinical results

Introduction

Second-generation autologous chondrocyte implantation with scaffolds stabilizing the grafts is a clinically effective procedure for cartilage repair. In this ongoing prospective observational case report study, we evaluated the effectiveness of BioSeed^®-C, a cell-based cartilage graft based on autologous chondrocytes embedded in fibrin and a stable resorbable polymer scaffold, for the treatment of clinical symptomatic focal degenerative defects of the knee.

Methods

Clinical outcome after 4-year clinical follow-up was assessed in 19 patients with preoperatively radiologically confirmed osteoarthritis and a Kellgren-Lawrence score of 2 or more. Clinical scoring was performed before implantation of the graft and 6, 12, and 48 months after implantation using the Lysholm score, the Knee injury and Osteoarthritis Outcome Score (KOOS), the International Knee Documentation Committee (IKDC) score, and the International Cartilage Repair Society (ICRS) score. Cartilage regeneration and articular resurfacing were assessed by magnetic resonance imaging (MRI) 4 years after implantation of the autologous cartilage graft.

Results

Significant improvement (P < 0.05) of the Lysholm and ICRS scores was observed as early as 6 months after implantation of BioSeed^®-C and remained stable during follow-up. The IKDC score showed significant improvement compared with the preoperative situation at 12 and 48 months (P < 0.05). The KOOS showed significant improvement in the subclasses pain, activities of daily living, and knee-related quality of life 6 months as well as 1 and 4 years after implantation of BioSeed^®-C in osteoarthritic defects (P < 0.05). MRI analysis showed moderate to complete defect filling with a normal to incidentally hyperintense signal in 16 out of 19 patients treated with BioSeed^®-C. Two patients without improvement in the clinical and MRI scores received a total knee endoprosthesis after 4 years.

Conclusions

The results show that the good clinical outcome achieved 1 year after implantation of BioSeed^®-C remains stable over the course of a period of 4 years and suggest that implanting BioSeed^®-C is a promising treatment option for the repair of focal degenerative defects of the knee.     

Informing future cartilage repair strategies: a comparative study of three different human cell types for cartilage tissue engineering

A major clinical need exists for cartilage repair and regeneration. Despite many different strategies having been pursued, the identification of an optimised cell type and of pre-treatment conditions remains a challenge. This study compares the cartilage-like tissue generated by human bone marrow stromal cells (HBMSCs) and human neonatal and adult chondrocytes cultured on three-dimensional (3D) scaffolds under various conditions in vitro and in vivo with the aim of informing future cartilage repair strategies based upon tissue-engineering approaches. After 3 weeks in vitro culture, all three cell types showed cartilage-like tissue formation on 3D poly (lactide-co-glycolide) acid scaffolds only when cultured in chondrogenic medium. After 6 weeks of chondro-induction, neonatal chondrocyte constructs revealed the most cartilage-like tissue formation with a prominent superficial zone-like layer, a middle zone-like structure and the thinnest fibrous capsule. HBMSC constructs had the thickest fibrous capsule formation. Under basal culture conditions, neonatal articular chondrocytes failed to form any tissue, whereas HBMSCs and adult chondrocytes showed thick fibrous capsule formation at 6 weeks. After in vivo implantation, all groups generated more compact tissues compared with in vitro constructs. Pre-culturing in chondrogenic media for 1 week before implantation reduced fibrous tissue formation in all cell constructs at week 3. After 6 weeks, only the adult chondrocyte group pre-cultured in chondrogenic media was able to maintain a more chondrogenic/less fibrocartilaginous phenotype. Thus, pre-culture under chondrogenic conditions is required to maintain a long-term chondrogenic phenotype, with adult chondrocytes being a more promising cell source than HBMSCs for articular cartilage tissue engineering.     

Quantification of Intermuscular Adipose Tissue in the Erector Spinae Muscle by MRI: Agreement With Histological Evaluation

Deposition of fat between skeletal muscle bundles and beneath the muscle fascia, recently called intermuscular adipose tissue (IMAT), is gaining attention as potential contributor to insulin resistance, metabolic syndrome, muscle function impairment, and disability. The aim of this study was to compare IMAT as measured at the erector spinae level by magnetic resonance imaging (MRI), a well‐recognized gold standard method to evaluate fat content inside muscles, and histology estimates. In 18 healthy elderly men and women with a wide range of BMI (25.05–35.58 kg/m²), undergoing elective vertebral surgery, IMAT within the erector spinae muscle was evaluated by MRI, by body composition using dual‐energy X‐ray absorptiometry and histological evaluation of intraoperative biopsy sample. The concordance between IMAT/total area (TA) ratio evaluated by MRI and histological examination was analyzed employing Lin's concordance correlation coefficient and the procedure proposed by Bland and Altman. Two thresholds to distinguish between muscle and IMAT calculated, respectively, by 20 and 10% reduction of the gray‐level intensity evaluated by MRI from surrounding subcutaneous adipose tissue (SAT) were used. With a 20% reduction, calculated IMAT/TA as evaluated by MRI on average exceeds histological evaluation by 21.79%, whereas by reducing the threshold by 10% agreement between MRI and histology improved with a 12.42% difference. Our data show a good degree of concordance between IMAT assessment by MRI and histology and seems to show that agreement between the two methods could be improved by using a more restrictive threshold between muscle and fat.     

Clinical experience in cell-based therapeutics: disc chondrocyte transplantation A treatment for degenerated or damaged intervertebral disc

Disc herniation treated by discectomy results in a significant loss of nucleus material and disc height. Biological restoration through the use of autologous disc chondrocyte transplantation offers a potential to achieve functional integration of disc metabolism and mechanics. Chondrocytes that have been removed from damaged cartilaginous tissues maintain a capacity to proliferate, produce and secrete matrix components and respond to physical stimuli such as dynamic loading. Nucleus regeneration using autologous cultured disc-derived chondrocytes (ADCT) has been demonstrated in a canine model and in clinical pilot studies. In 2002 a prospective, controlled, randomised, multi-center study, EuroDISC, comparing safety and efficacy of autologous disc chondrocyte transplant, chondrotransplant DISC, plus discectomy (ADCT), with discectomy alone was initiated. A dog model was used to investigate the hypothesis that autologous disc chondrocytes can be used to repair damaged intervertebral disc. Disc chondrocytes were harvested and expanded in culture under controlled and defined conditions, returned to the same animals from which they had been sampled (autologous transplantation) via percutaneous delivery. The animals were analyzed at specific times after transplantation by several methods to examine whether disc chondrocytes integrated with the surrounding tissue, produced the appropriate intervertebral disc extracellular matrix, and might provide a formative solution to disc repair. The clinical goals of the EuroDISC study, were to provide long-term pain relief, maintain disc height and prevent adjacent segment disease. Interim analysis was performed after 2 years; Oswestry (low back pain/disability), Quebec Back-Pain Disability Scale, as well as Prolo and VAS score were used for the evaluation. Disc height was assessed by MRI. In the context of degenerative changes in an injury model: () autologous disc chondrocytes were expended in culture and returned to the disc by a minimally invasive procedure after 12 weeks; () disc chondrocytes remained viable after transplantation as shown by bromodeoxyuridine incorporation and maintained a capacity for proliferation after transplantation as depicted by histology; () transplanted disc chondrocytes produced an extracellular matrix that displayed composition similar to normal intervertebral disc tissue. Positive evidence of Proteoglycan content was supported by accepted histochemical staining techniques such as Safranin O-Fast Green; () both Type II and Type I collagens were demonstrated in the regenerated intervertebral disc matrix by immunohistochemistry after chondrocyte transplantation; and () when the disc heights were analyzed for variance according to treatment a statistically significant-correlation between transplanting cells and retention of disc height was achieved. A clinically significant reduction of low back pain in the ADCT-treated group was shown by all three pain score systems. The median total Oswestry score was 2 in the ADCT-treated group compared with 6 in the control group. Decreases in the disability index and VAS score in ADCT-treated patients correlated strongly with the reduction of low back pain. Decreases in disc height over time were only found in the control group, and of potential significance, intervertebral discs in adjacent segments appeared to retain hydration when compared to those adjacent to levels that had undergone discectomy without cell intervention. Autologous chondrocyte transplantation is technically feasible and biologically relevant to repairing disc damage and retarding disc degeneration.     

Ex vivo and in vivo characterization of cold preserved cartilage for cell transplantation

Due to the inconvenient and invasive nature of chondrocyte transplantation, preserved cartilage has been recognized as an alternative source of chondrocytes for implantation. However, there are major concerns, in particular, the viability and quality of the chondrocytes. This study investigated the biochemistry and molecular characterization of chondrocytes isolated from preserved cartilage for purposes of transplantation. Ex vivo characterization was accomplished by storing human cartilage at either 4 or ?80 °C in a preservation medium. Microscopic evaluation of the preserved cartilage was conducted after 1, 2, 3 and 6 weeks. The chondrocytes were isolated from the preserved cartilage and investigated for proliferation capacity and chondrogenic phenotype. Transplantation of chondrocytes from preserved cartilage into rabbit knees was performed for purposes of in vivo evaluation. The serum cartilage degradation biomarker (WF6 epitopes) was evaluated during the transplantation procedure. Human cartilage preserved for 1 week in a 10 % DMSO chondrogenic medium at 4 °C gave the highest chondrocyte viability. The isolated chondrocytes showed a high proliferative capacity and retained chondrogenic gene expression. Microscopic assessment of the implanted rabbit knees showed tissue regeneration and integration with the host cartilage. A decreased level of the serum biomarker after transplantation was evidence of in vivo repair by the implanted chondrocytes. These results suggest that cartilage preservation for 1 week in a 10 % DMSO chondrogenic medium at 4 °C can maintain proliferation capacity and the chondrogenic phenotype of human chondrocytes. These results can potentially be applied to in vivo allogeneic chondrocyte transplantation. Allogeneic chondrocytes from preserved cartilage would be expected to maintain their chondrogenic phenotype and to result in a high rate of success in transplanted grafts.