Biological freezing of human articular chondrocytes

Human Engineered Cartilage and Decellularized Matrix as an Alternative to Animal Osteoarthritis Model

(1) Objective: to obtain a reproducible, robust, well-defined, and cost-affordable in vitro model of human cartilage degeneration, suitable for drug screening; (2) Methods: we proposed 3D models of engineered cartilage, considering two human chondrocyte sources (articular/nasal) and five culture methods (pellet, alginate beads, silk/alginate microcarriers, and decellularized cartilage). Engineered cartilages were treated with pro-inflammatory cytokine IL-1β to promote cartilage degradation; (3) Results: articular chondrocytes have been rejected since they exhibit low cellular doubling with respect to nasal cells, with longer culture time for cell expansion; furthermore, pellet and alginate bead cultures lead to insufficient cartilage matrix production. Decellularized cartilage resulted as good support for degeneration model, but long culture time and high cell amount are required to obtain the adequate scaffold colonization. Here, we proposed, for the first time, the combined use of decellularized cartilage, as aggrecanase substrate, with pellet, alginate beads, or silk/alginate microcarriers, as polymeric scaffolds for chondrocyte cultures. This approach enables the development of suitable models of cartilaginous pathology. The results obtained after cryopreservation also demonstrated that beads and microcarriers are able to preserve chondrocyte functionality and metabolic activity; (4) Conclusions: alginate and silk/alginate-based scaffolds can be easily produced and cryopreserved to obtain a cost-affordable and ready-to-use polymer-based product for the subsequent screening of anti-inflammatory drugs for cartilage diseases.

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.

Platelet rich plasma associated with heterologous fresh and thawed chondrocytes on osteochondral lesions of rabbits

Chondrocytes obtained from stifle joint of New Zealand White rabbits were cultivated. Half of cells were maintained in culture for later implantation and the others frozen during six months to evaluate viability. A circular osteochondral defect was created in the right stifle of other twenty seven rabbits. The control group (CG) received no treatment. The thawed (TH) and fresh (FH) heterologous groups received, respectively, an implant of cultivated thawed or fresh heterologous chondrocytes associated with platelet rich plasma (PRP). The CG group showed greatest pain and lameness compared to the other groups seven days after the implantation. Microscopically, at 45 and 90 days, the TH and FH groups showed filling with cartilaginous tissue containing chondrocytes surrounded by a dense matrix of glycosaminoglycans. In the CG group, healing occurred with vascularized fibrous connective tissue without integration to the subchondral bone. Cryopreserved heterologous chondrocytes were viable for implantation and healing of osteochondral lesions; the association with PRP allows the fixation of cells in the lesion and offers growth factors which accelerates repair with tissue similar to articular hyaline cartilage.

Influence of cryopreservation, cultivation time and patient's age on gene expression in Hyalograft® C cartilage transplants

PURPOSE

Our aim was to evaluate the impact of cryopreservation, cultivation time and patient's age on the expression of specific chondrogenic markers in Hyalograft® C transplants.

METHODS

Gene expression of chondrocyte markers [collagen type I (COL1A1), COL2A1, aggrecan, versican, melanoma inhibitory activity (MIA) and interleukin (IL)-1β] was analysed in cartilage biopsies (n = 17) and Hyalograft® C transplant samples (non-cryopreserved = 78, cryopreserved = 13) by quantitative real-time polymerase chain reaction (PCR). Correlation analyses were performed to evaluate the influence of the above-named parameters on the level of gene expression.

RESULTS

Cryopreservation of cells was found to decrease COL2A1 and MIA significantly (4.6-fold, p < 0.01 and 2-fold, p < 0.045, respectively). The duration of cryopreservation had no further influence on the expression of these factors. No correlation was detected between cultivation time (75 ± 31 days) and the expression level of any gene. Cartilage transplants from older patients (>35 years) exhibited a significantly higher IL-1β expression (3.7-fold, p < 0.039) than transplants from younger patients (≤ 35 years).

CONCLUSIONS

Our data demonstrate that cryopreservation has a profound impact on chondrocyte metabolic activity by decreasing the expression of COL2A1 and MIA in Hyalograft® C transplants, independent of the duration of cryopreservation.

Cryopreservation of alginate encapsulated mesenchymal stromal cells

Human mesenchymal stromal cells (MSCs) can differentiate into various cell types, which makes them attractive for regenerative medicine and tissue engineering. Encapsulation of MSCs in alginate microspheres (AMS) is a novel and promising approach of tissue engineering. Application and research of such cell-hydrogel systems require selection of adequate cryopreservation protocols. In this study we investigated the response of MSCs encapsulated in AMS to different cryopreservation protocols. Bone marrow MSCs either encapsulated in AMS and or as cells in suspension, were cryopreserved with 5% and 10% of dimethyl sulfoxide (ME₂SO) using conventional 2-step slow cooling (protocol 1). The viability and metabolism of MSCs in AMS following cryopreservation with 5% Me₂SO were lower than in the group cryopreserved with 10% Me₂SO. MSCs in suspension were more resistant to cryopreservation than cells in AMS when cryopreserved with 5% Me₂SO, although when using a concentration of 10% Me₂SO, no differences were detected. Comparisons of the viability and metabolic activity of MSC cryopreserved either in AMS or as cell suspensions with 10% ME₂SO using protocol 1 (2-step cooling), protocol 2 (3-step slow cooling with induced ice nucleation) or protocol 3 (rapid 1-step freezing), showed that the highest viabilities and metabolic rates were obtained following cryopreservation of MSCs in AMS by protocol 2 (with controlled ice nucleation). Cryopreservation with protocol 3 resulted in critical damage of the encapsulated MSCs. After cryopreservation by protocol 2, AMS encapsulated MSCs were capable of achieving multilineage differentiation directed towards osteogenic, adipogenic and chondrogenic lineages. The data obtained indicate that cryo-banking of AMS encapsulated MSCs is feasible for future regenerative medicine projects.

A method of isolating viable chondrocytes with proliferative capacity from cryopreserved human articular cartilage

This study aimed to optimise methods of cryopreserving human articular cartilage (AC) tissue for the isolation of late chondrocytes. Human AC specimens from osteoarthritis patients who had undergone total knee replacement were used to optimise the chondrocyte isolation process and the choice of cryoprotective agent (CPA). For AC tissue cryopreservation, intact cored cartilage discs (5 mm diameter) and diced cartilage (0.2-1 mm cubes) from the same sized discs were step cooled and stored in liquid nitrogen for up to 48 h before chondrocyte isolation and in vitro assay of cell viability and proliferative potential. The results showed that 10 % dimethyl sulphoxide in 90 % foetal bovine serum was a successful CPA for chondrocyte cryopreservation. Compared with intact cored discs, dicing of AC tissue into 0.2-1 mm cubes significantly increased the viability and proliferative capacity of surviving chondrocytes after cryopreservation. In situ cross-section imaging using focused ion beam microscopy revealed that dicing of cored AC discs into small cubes reduced the cryo-damage to cartilage tissue matrix. In conclusion, modification of appropriate factors, such as the size of the tissue, cryoprotective agent, and isolation protocol, can allow successful isolation of viable chondrocytes with high proliferative capacity from cryopreserved human articular cartilage tissue. Further studies are required to determine whether these cells may retain cartilage differentiation capacity and provide sufficient chondrocytes for use as implants in clinical applications.

Midterm results of the treatment of cartilage defects in the knee using alginate beads containing human mature allogenic chondrocytes

BACKGROUND

The treatment of chondral lesions is still an important challenge for the orthopaedic surgeon. Attempts have been made to restore cartilage lesions by filling the defects with a temporary biocompatible matrix.

PURPOSE

The authors present their midterm experience with the implantation of alginate beads containing human mature allogenic chondrocytes for the treatment of cartilage lesions in the knee.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A biodegradable, alginate-based biocompatible scaffold containing human mature allogenic chondrocytes was used for the treatment of cartilage lesions in the knee. Twenty-one patients were clinically prospectively evaluated with use of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and a visual analog scale (VAS). The mean follow-up time was 6.3 years (range, 5-8 years). Magnetic resonance imaging (MRI) data were analyzed based on the MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) system, allowing morphologic assessment of the repair tissue. Magnetic resonance images were taken at 1 year of follow-up and at a mean follow-up of 6.1 years (range, 5-7 years).

RESULTS

During the follow-up period, the WOMAC and VAS scores improved significantly. No signs of clinical deterioration or adverse reactions to the alginate beads/allogenic chondrocyte implantation were observed. Four failures occurred during the follow-up period in this study (19.05%). The MOCART scores were moderate and remained stable in time.

CONCLUSION

This investigation provided useful information on the efficacy of the implantation of alginate beads containing human mature allogenic chondrocytes for the treatment of cartilage lesions in the knee. The midterm clinical outcome of the presented technique was satisfactory. However, these results were not confirmed by the MRI findings.

Effect of freezing on rabbit cultured chondrocytes

This work evaluated the effect of freezing on chondrocytes maintained in culture, aiming the establishment of a cell bank for future application as heterologous implant. Chondrocytes extracted from joint cartilage of nine healthy New Zealand White rabbits were cultivated and frozen with the cryoprotector 5% dimethylsulfoxide for six months. Phenotypic and scanning electron microscopy analyses were carried out to identify morphological and functional differences between fresh and thawed cells. After enzymatic digestion, a total of 4.8x10(5)cells per rabbit were obtained. Fresh chondrocytes showed a high mitotic rate and abundant matrix was present up to 60 days of culture. Loss of phenotypic stability was notable in the thawed chondrocytes, with a low labeling of proteoglycans and weak immunostaining of type II collagen. The present study showed important loss of chondrocyte viability under the freezing conditions. For future in vivo studies of heterologous implant, these results suggests that a high number of cells should be implanted in the host site in order to achieve an adequate number of viable cells. Furthermore, the chondrocytes should be implanted after two weeks of culture, when the highest viability rate is found

Advances in Tissue Engineering Techniques for Articular Cartilage Repair

The limited repair potential of human articular cartilage contributes to development of debilitating osteoarthritis and remains a great clinical challenge. This has led to evolution of cartilage treatment strategies from palliative to either reconstructive or reparative methods in an attempt to delay or "bridge the gap" to joint replacement. Further development of tissue engineering-based cartilage repair methods have been pursued to provide a more functional biological tissue. Currently, tissue engineering of articular cartilage has three cornerstones; a cell population capable of proliferation and differentiation into mature chondrocytes, a scaffold that can host these cells, provide a suitable environment for cellular functioning and serve as a sustained-release delivery vehicle of chondrogenic growth factors and thirdly, signaling molecules and growth factors that stimulate the cellular response and the production of a hyaline extracellular matrix (ECM). The aim of this review is to summarize advances in each of these three fields of tissue engineering with specific relevance to surgical techniques and technical notes.

Assessment of strategies to increase chondrocyte viability in cryopreserved human osteochondral allografts: evaluation of the glycosylated hydroquinone, arbutin

OBJECTIVE

Allogeneic cartilage is used to repair damaged areas of articular cartilage, requiring the presence of living chondrocytes. So far, no preservation method can effectively meet that purpose. Identification of more effective cryoprotective agents (CPAs) can contribute to this goal. The aim of this study was to determine whether the glycosylated hydroquinone, arbutin, alone or in combination with low concentrations of other CPAs, has cryoprotective properties towards human articular cartilage.

MATERIAL AND METHODS

Human tibial plateaus were procured from multi-organ donors, with the approval of the Ethics Committee of the University Hospital of Coimbra. The tibial plateaus were treated with or without arbutin (50 or 100mM), alone or in combination with various concentrations of dimethyl sulfoxide (DMSO) and glycerol, for 0.5-1.5h/37 degrees C, then frozen at -20 degrees C and 24h later transferred to a biofreezer at -80 degrees C. Two to 3 months later, thawing was achieved by immersion in cell culture medium at 37 degrees C/1h. Chondrocyte viability was assessed before and after freeze-thawing using a colorimetric assay based on the cell's metabolic activity and fluorescent dyes to evaluate cell membrane integrity.

RESULTS

Before freezing, chondrocyte metabolic activity was identical in all the conditions tested. After freeze-thawing, the highest activity, corresponding to 34.2+/-2.1% of that in the Fresh Control, was achieved in tibial plateaus incubated in 50mM arbutin for 1h whereas in those left untreated it was 11.1+/-4.7. Addition of DMSO and glycerol to arbutin did not increase chondrocyte viability any further. Fluorescence microscopy confirmed these results and showed that living chondrocytes were mainly restricted to the superficial cartilage layers.

CONCLUSION

Arbutin seems to be an effective cryoprotective agent for osteochondral allografts with potential benefits over DMSO and glycerol.

Treatment of cartilage defects in the knee using alginate beads containing human mature allogenic chondrocytes

BACKGROUND

The repair of osteochondral lesions is imperfect and transient; chondral lesions do not heal in mature cartilage. Attempts have been made to restore cartilage lesions by filling the defects with a temporary artificial biocompatible matrix.

PURPOSE

To determine whether the implantation of alginate beads containing human mature allogenic chondrocytes is feasible and safe for the treatment of symptomatic cartilage defects in the knee.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A biodegradable, alginate-based, biocompatible scaffold containing human mature allogenic chondrocytes was used for the treatment of chondral and osteochondral lesions in the knee. Twenty-one patients were clinically and prospectively evaluated with use of the Western Ontario and McMaster Universities Osteoarthritis Index and a visual analog scale for pain preoperatively and at 3, 6, 9, 12, 18, and 24 months of follow-up. Of the 21 patients, 13 consented to having a biopsy sample taken for investigative purposes from the area of implantation at 12 months of follow-up, allowing histologic assessment of the repair tissue.

RESULTS

A statistically significant clinical improvement became apparent after 6 months, and patients improved during the 24 months of follow-up. Adverse reactions to the alginate/fibrin matrix seeded with the allogenic cartilage cells were not observed. Histologic analysis of the biopsy specimens rated the repair tissue as hyaline-like in 15.3% of the samples, as mixed tissue in 46.2%, as fibrocartilage in 30.8%, and as fibrous in 7.7%.

CONCLUSION

The results of this short-term pilot study show that the alginate-based scaffold containing human mature allogenic chondrocytes is feasible and safe for the treatment of symptomatic cartilage defects of the knee. The described technique provides clinical and histologic outcomes that are equal but not superior to those of other cartilage repair techniques.

Cartilage repair: third-generation cell-based technologies--basic science, surgical techniques, clinical outcomes

The goal of all cartilage replacement techniques is the reformation of mature organized hyaline cartilage. However, currently cartilage repair techniques lead principally to production of fibrocartilage, which has material properties that are inferior to hyaline cartilage. Cell-based therapies such as autologous chondrocyte implantation hold promise for cartilage regeneration; however, these techniques still do not predictably result in hyaline cartilage formation. The newest, "third-generation techniques" have been developed to address the limitations of earlier techniques. These new procedures use 3 novel approaches: chondro-inductive or chondro-conductive matrix; use of allogeneic cells, both of which may allow a single-stage surgical approach; and techniques to mechanically condition the developing tissue before surgical application to improve the material properties and maturation of the implant. However, at this time there is very limited clinical data available on the nature and outcomes of these procedures.

The viability and proliferation of human chondrocytes following cryopreservation

Human articular cartilage samples were retrieved from the resected material of patients undergoing total knee replacement. Samples underwent automated controlled freezing at various stages of preparation: as intact articular cartilage discs, as minced articular cartilage, and as chondrocytes immediately after enzymatic isolation from fresh articular cartilage. Cell viability was examined using a LIVE/DEAD assay which provided fluorescent staining. Isolated chondrocytes were then cultured and Alamar blue assay was used for estimation of cell proliferation at days zero, four, seven, 14, 21 and 28 after seeding. The mean percentage viabilities of chondrocytes isolated from group A (fresh, intact articular cartilage disc samples), group B (following cryopreservation and then thawing, after initial isolation from articular cartilage), group C (from minced cryopreserved articular cartilage samples), and group D (from cryopreserved intact articular cartilage disc samples) were 74.7% (95% confidence interval (CI) 73.1 to 76.3), 47.0% (95% CI 43 to 51), 32.0% (95% CI 30.3 to 33.7) and 23.3% (95% CI 22.1 to 24.5), respectively. Isolated chondrocytes from all groups were expanded by the following mean proportions after 28 days of culturing: group A ten times, group B 18 times, group C 106 times, and group D 154 times. This experiment demonstrated that it is possible to isolate viable chondrocytes from cryopreserved intact human articular cartilage which can then be successfully cultured.

Chondrocyte viability in fresh and frozen large human osteochondral allografts: effect of cryoprotective agents

Chondrocyte survival is a major goal for the effective storage and clinical performance of human osteochondral allografts. The majority of animal and human cryopreservation studies conducted so far have been performed in small osteochondral cylinders. Using human tibial plateaus as a model for large osteochondral pieces, this work sought to evaluate the cryoprotective efficiency of glycerol and dimethylsulfoxide (DMSO), and to identify cryopreservation conditions suitable for use in tissue banks. Human tibial plateaus harvested from 7 cadaveric tissue donors were incubated in the presence or absence of cryoprotective agents (CPA): 10% or 15% glycerol and 10% DMSO in a Ham F-12 nutrient mixture. Chondrocyte viability was assessed immediately after thawing, using the MTT reduction assay and a fluorescence microscopic method. The tibial plateaus frozen in the absence of CPA showed a significant decrease in chondrocyte viability. The use of CPA significantly increased chondrocyte viability compared with cartilage frozen without CPA (nearly 50% versus 80% living chondrocytes with 10% glycerol versus 10% DMSO, respectively) relative to that in fresh cartilage. In this regard, 10% DMSO was slightly more effective than either 10% or 15% glycerol, eliciting the recovery of approximately 15% relative to the living chondrocyte content in fresh cartilage. In all conditions, fluorescence microscopic studies showed that surviving chondrocytes were restricted to the superficial cartilage layer. Human tibial plateaus seemed to be a good experimental model to establish cryopreservation methods applicable to large human osteochondral pieces in tissue banks.

Cell viability and protein composition in cryopreserved cartilage

Chondrocyte survival in frozen-stored osteochondral allografts is low. We analyzed different storage conditions to determine the best for maintenance or storage for preserving cartilage. We hypothesized cell viability and extracellular protein content could be improved with better cryopreservation. Articular cartilage from nine sheep femoral condyles were stored at 4 degrees C, -80 degrees C, and -196 degrees C with and without cryopreservative agents for 1 month. We determined cell viability and performed Western blot analysis for TGF-beta, IGF-1, and MMP-2, 9, and 13. We observed decreases in viability in cartilage stored at 4 degrees C: 36.2% viability when stored without solution, 40.4% in phosphate-buffered saline, and 48.1% in culture medium. TGF-beta and IGF-1 decreased in the first week in all groups. The groups stored at -80 degrees C and -196 degrees C contained less protease in the last 2 weeks. In the groups stored at 4 degrees C in phosphate-buffered saline, we detected no increase in the levels of MMPs. Our data discourage the use of frozen cartilage because of the decrease of cell viability and elevation in MMPs. However, modifying the freezing conditions might moderate these changes and improve the state of preserved cartilage.

Cryopreservation and in vitro expansion of chondroprogenitor cells isolated from the superficial zone of articular cartilage

Understanding the proliferation mechanisms of chondroprogenitor cells and their influence on cell differentiation is crucial in order to develop large-scale expansion processes for tissue engineering applications. Proliferation control mechanisms were mainly attributed to substrate limitation and cell-cell contact inhibition. The limiting substrates were found to be components of the FCS, with an optimal proliferation rate achieved in the presence of 40% FCS. In addition, the medium supply rate was found to be essential in reducing substrate limitation. In terms of FCS, 10 microL FCS cm(-2) h(-1) was the threshold feed rate required to prevent substrate limitation. Above this rate, maximum cell densities of 5.3 x 10(5) cells/cm2 were achieved, representing a 53-fold expansion. To reduce the need for high supply rates, the effect of specific growth factors was also investigated. Cell densities of 3.3 x 10(5) cells/cm2 were achieved in batch cultures using 40% FCS and 1 ng/mL TGF-beta1. Chondroprogenitor cells were expanded in this medium up to three passages without compromising their ability to differentiate and produce cartilage-like matrix in pellet cultures. In addition to substrate limitation, cell-cell contact, even at very sparse subconfluent densities, appeared capable of exerting some degree of growth inhibition. The cells exhibited deceleratory growth kinetics, characterized by a decrease of specific growth rates over time.

Cryoprotectant permeation through human articular cartilage

OBJECTIVE

The cryopreservation of intact articular cartilage is constrained by minimal chondrocyte survival. It was the aim of the present study to gain an insight into the permeation kinetics of cryoprotectants through cartilage. This knowledge is essential for achieving adequate tissue permeation prior to cooling.

DESIGN

The diffusion coefficients and penetration rates through human articular cartilage of dimethyl sulfoxide (Me(2)SO) and glycerol at different temperatures (4 degrees C, 17 degrees C, 27 degrees C and 37 degrees C) and at two concentrations [10% (v/v) and absolute state] were measured using diffusion nuclear magnetic imaging. Deuterated water (D(2)O) was used as a control substance.

RESULTS

Glycerol penetrated faster than Me(2)SO at all temperatures and at rates that were comparable to those for D(2)O. The penetration rate of each agent increased with increasing temperature. The diffusion coefficients for glycerol and Me(2)SO increased with increasing temperature and decreased at the higher concentration, but the differences between each agent were not significant.

CONCLUSIONS

The classical cryopreservation protocols expose cartilage samples to Me(2)SO at a too low temperature and/or for an insufficient time period for optimal cell survival. When considering the penetration rate, glycerol appears to be a more efficient cryoprotective agent than Me(2)SO. The present study demonstrates the power of nuclear magnetic resonance technology to elucidate key physiological factors in cryobiology.

Intramatrix events during cryopreservation of porcine articular cartilage using rapid cooling

Cryopreservation of articular cartilage may improve long-term transplantation results if cell and matrix integrity can be maintained. This study examined intramatrix events in intact porcine articular cartilage that occurred during a rapid-cooling technique with various concentrations of dimethyl sulfoxide (DMSO) (1, 3, 5, 6 and 7 M). Thermocouples were inserted into the solution and in the cartilage matrix to record the temperature during rapid cooling. In addition, scanning electron microscopy of freeze-substituted samples was performed and quantitatively evaluated for the areas representing ice in the matrix. The results of this study showed that low concentrations of DMSO resulted in the largest temperature gradient between the matrix and the surrounding solution, which occurred near the freezing point of the cryoprotectant solution. At higher concentrations of DMSO, the peak temperature gradient occurred near the glass transition temperature. The temperature measurements suggested that a significant amount of ice formed within the matrix at lower DMSO concentrations. At higher DMSO concentrations that resulted in vitrification of the external solution, there was evidence of some ice in the matrix. The scanning electron micrographs demonstrated significantly more matrix disruption (likely due to ice formation) (P<0.02) in the lower DMSO concentrations (1 and 5 M) while the 6 M DMSO concentration demonstrated minimal matrix disruption. Cryopreservation of articular cartilage with a rapid-cooling technique and high concentrations of DMSO resulted in partial vitrification of the matrix and significantly less matrix disruption. It appears that successful cryopreservation of viability and function in articular cartilage will require high concentrations of cryoprotectants and rapid cooling.