Metabolic and biochemical status of articular cartilage following cryopreservation and transplantation: a rabbit model.

To determine the fate of transplanted cryopreserved articular cartilage, an animal model employing the proximal humerus in the rabbit has been developed. Previous studies have been hindered by problems of postoperative joint instability, secondary injury due to immobilization, and paucity of cartilage for analysis. This experiment demonstrates the survival and function of transplanted cartilage by quantitative assessment of metabolic and biochemical parameters. Forty-five New Zealand white rabbits underwent transplantation of the right proximal humerus. In 29 animals, the proximal half of the humerus was resected and replaced by a cryopreserved osteoarticular allograft. Autograft procedures were carried out in the remaining animals. Following sacrifice at 3, 6, 9, and 12 months postoperatively, articular cartilage was analyzed for gross appearance, collagen synthesis, proteoglycan synthesis, and water, hydroxyproline, hexosamine, and hexuronic acid contents. The results indicate that the cryopreserved osteoarticular allografts retained their metabolic and biochemical integrity and behaved as viable and biologically functional units 1 year postoperatively.     

慢速梯度降温冷冻保存同种异体骨软骨移植治疗膝关节全层软骨缺损(附三例报告)

目的总结冷冻保存同种异体骨软骨移植物治疗3例膝关节全层骨软骨缺损的手术方法及疗效。方法应用梯度降温冷冻保存的6枚同种异体骨软骨移植物治疗3例膝关节全层骨软骨缺损,2例在关节镜下同种异体骨软骨移植,1例行关节切开移植。膝关节股骨髁关节软骨全层缺损平均面积2.16 cm2。所有患者在手术后第1个月、第3个月时进行膝关节MRI检查,了解移植物与周围骨软骨组织的愈合情况。并于门诊复查时进行Brittberg-Peterson膝关节功能评分,了解功能恢复情况。结果随访4～6个月,平均4.7个月。所有患者术后疼痛消失;无排异反应发生。术后3个月时,MRI检查示术后移植物与宿主软骨下骨整合良好,移植软骨组织结构与内部信号良好。Brittberg-Peterson评分术后6个月比手术前明显降低。结论经梯度降温冷冻保存的同种异体骨软骨移植治疗膝关节软骨缺损早期效果满意。     

同种异体软骨移植修复关节软骨缺损实验研究

目的 采用兔膝关节软骨标本经打孔梯度降温冻存后行同种异体移植,研究打孔梯度降温冻存对兔关节软骨的影响及其修复关节软骨缺损的效果.方法 自16只2月龄新西兰白兔膝关节股骨髌面取分别取3块骨软骨移植物,随机分为3组.Ⅰ组为实验组,在软骨上以3 mm×3 mm矩阵打孔,Ⅱ、Ⅲ组为对照组,不打孔.分别将软骨标本置于二甲基亚砜冷冻保护溶液中,并经梯度降温至-80℃(Ⅰ、Ⅱ组)或直接置于-80℃(Ⅲ组)保存1周,复温后移植到成年兔相应膝关节部位.术后分批处死动物,通过对移植物的大体形态学、组织学、免疫组化染色光镜观察,研究各组移植物保存效果的差异.结果 Ⅰ、Ⅱ组光镜观察结果明显优于Ⅲ组;Ⅰ组与Ⅱ组结果差异不明显,但Ⅰ组对中间层软骨组织的保护明显加强.结论 关节软骨的梯度降温冷冻保存效果明显优于快速降温冷冻保存,且关节软骨打孔冷冻保存对深层软骨细胞有一定的保护作用,可提高软骨细胞存活率,延缓移植软骨组织的退变过程.     

脂肪颗粒组织在不同低温条件下冻存后活力分析及移植成活率测定

目的探讨脂肪颗粒组织冻存后的活力及移植成活率。方法在-16℃、-80℃及-196℃条件下，经相应的低温保护剂处理，冻存脂肪颗粒组织，分别于2、4、8周复温后研磨，测定其活力与移植成活率，于移植后7周切取移植物，测量其体积，行苏丹3染色。结果-196℃组及-80℃组较好保持了脂肪细胞活力，冻存8周后活力分别达冻存前的70％和60％，各时间点比较差异无统计学意义（P=0．964，P=0．199）；而-16℃组冻存2周后活力已不到50％，各时间点比较差异有统计学意义（P=0．001），随时间延长表现为进行性下降趋势。-196℃组及-80℃组移植成活率与新鲜脂肪移植成活率相比差异无统计学意义，-16℃组移植成活率与新鲜脂肪移植成活率比较差异有统计学意义（P=0．000）；-16℃组移植物以炎性反应为主，几乎无成活脂肪细胞，其余各组均可见大量成活脂肪细胞。结论-196℃及-80℃条件下短期内（8周）冻存脂肪颗粒具有可行性，适用于临床移植需求。-16℃条件下冻存的脂肪颗粒活力明显降低，移植后虽可维持一定体积，但有可能仅起到一种软组织填充物的作用，在此温度下冻存的脂肪颗粒应用于临床注射无可行性。     

Cryopreserved articular chondrocytes grow in culture, maintain cartilage phenotype, and synthesize matrix components

For osteochondral allograft transplantation to be successful, chondrocytes must survive preservation and retain their capacity to produce normal matrix components: proteoglycans and Type II collagen. Clinical success with osteochondral allograft transplantation has created an increased demand for supplies of suitable cartilage-bearing grafts. This demand has stimulated attempts to find successful methods for low temperature storage of cartilage for "banking" and heightened interest in cartilage cryobiology. In order to achieve the maximum viability of cryopreserved articular cartilage, previous comprehensive studies have focused on rates and temperatures of freezing, cryoprotective agents, and methods and influences of thawing. This study presents evidence that cryopreserved articular chondrocytes maintain their ability to grow in tissue culture following thawing and to produce normal matrix components. Chondrocytes isolated from Japanese white rabbits were divided into groups of fresh controls and experimental cryopreserved cells. Cells were incubated in dimethylsulfoxide, frozen at a rate of -1 degrees C/min, stored at -79 degrees C, rapidly thawed, and plated for culture. Growth rates were comparable in all groups. In all groups, typical chondroid characteristics were maintained throughout 14 days of culture. Typical cartilage phenotypic characteristics included maintenance of polygonal and rhomboidal cells, cell aggregation, proteoglycan production, and Type II collagen synthesis. This investigation strongly indicates that articular chondrocyte cryopreservation yields viable, functional cells and although these results cannot be directly extrapolated to intact adult articular cartilage, they do give further support for low temperature banking of cartilage-bearing allografts for transplantation.     

Cryopreservation of intact human articular cartilage.

Damaged articular cartilage (AC) impairs joint function and many treatment techniques are being investigated to determine their long term results. Successful cryopreservation of AC can provide a reliable source of intact matrix with viable chondrocytes to maintain the cartilage over long periods of time. This study investigated the application of an established cryopreservation protocol to determine the recovery of intact chondrocytes from human AC. Ten millimeter diameter osteochondral dowels were harvested from two human donors. The cryopreservation protocol was performed and the samples were rapidly warmed from varying experimental holding temperatures (-10, -20, -30, -40 degrees C), with and without plunging into liquid nitrogen, using 1 M dimethyl sulfoxide as cryoprotectant. The cartilage was stained with membrane integrity dyes and viewed under fluorescence microscopy. The percent of intact chondrocytes was compared to fresh controls. Low recovery of intact chondrocytes was recorded from all temperature levels with and without cryoprotectant. The results of this experiment demonstrated that the cryopreservation procedure used to achieve moderate success with intact sheep AC was not successful with intact human AC and further investigation is required.     

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.     

Clinical application and viability of cryopreserved cadaveric skin allografts in severe burn: A retrospective analysis

Introduction

Cadaveric cutaneous allografts are used in burns surgery both as a temporary bio-dressing and occasionally as definitive management of partial thickness burns. Nonetheless, limitations in the understanding of the biology of these grafts have meant that their role in burns surgery continues to be controversial.

Methods

A review of all patients suffering 20% or greater total body surface area (TBSA) burns over an eight year period that received cadaveric allografts were identified. To investigate whether tissue viability plays a role in engraftment success, five samples of cryopreserved cadaveric cutaneous allograft processed at the Donor Tissue Bank of Victoria (DTBV) were submitted to our laboratory for viability analysis using two methods of Trypan Blue Exclusion and tetrazolium salt (MTT) assays.

Results

During the study period, 36 patients received cadaveric allograft at our institution. The average total burn surface area (TBSA) for this group of patients was 40% and all patients received cadaveric skin as a temporizing measure prior to definitive grafting. Cadaveric allograft was used in complicated cases such as wound contamination, where synthetic dressings had failed. Viability tests showed fewer than 30% viability in processed allografts when compared to fresh skin following the thawing process. However, the skin structure in the frozen allografts was histologically well preserved.

Conclusion

Cryopreserved cutaneous cadaveric allograft has a positive and definite role as an adjunct to conventional dressing and grafting where available, particularly in patients with large TBSA burns. The low viability of cryopreserved specimens processed at DTBV suggests that cell viability in cadaveric allograft may not be essential for its clinical function as a wound dressing or even as permanent dermal substitute.     

Mechanical and morphological evaluation of osteochondral implants in dogs

Abstract:  The mechanical behavior of osteochondral defects was evaluated in this study with the intention of developing alternative procedures. Cylindrical pins (5.00 mm in diameter and in height) made of pHEMA hydrogel covered ultra-high molecular weight polyethylene (UHMWPE) or β-tricalcium phosphate (β-TCP) matrix were used. Ostoechondral defects were caused in the knees of adult dogs and the evaluation was carried out after a 9-month follow-up period. The mechanical behavior of the implants was evaluated by means of an indentation creep test that showed that the UHMWPE matrix maintained its viscoelastic behavior even after follow-up time, while the β-TCP matrix osteochondral implants presented significant alterations. It is believed that the β-TCP osteochondral implants were unable to withstand the load applied, causing an increase of complacency when compared to the UHMWPE osteochondral implants. Based on micro and macroscopic analysis, no significant wear was observed in either of the osteochondral implants when compared to the controls. However, morphological alterations, with fragmentation indices in the patella, were observed either due to friction with the hydrogel in the first postoperative months or due to forming of a dense conjunctive tissue. This wear mechanism caused on the counterface of the implant (patella) was observed, notwithstanding the osteochondral implant studied.     

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.     

Time-sequential changes in biomechanical and morphological properties of articular cartilage in cryopreserved osteochondral allografting

This study examined time-sequential changes in the biomechanical and morphological properties of articular cartilage that had received cryopreserved osteochondral allografting. Osteochondral blocks obtained from the femurs of 18 rabbits were cryopreserved with dimethylsulfoxide (DMSO), using a two-step freezing method, and allografted to the femurs of another 18 rabbits. Specimens for biomechanical and morphological examinations were prepared at the second, fourth, and twelfth weeks after allografting (n = 18). In 12 allografted rabbits, biomechanical features were examined with an indentation test apparatus, and histological changes were studied with a light microscope (second week, n = 4; fourth week, n = 4; twelfth week, n = 4). In the other 6 allografted rabbits, cartilage surfaces were studied with a scanning electron microscope (second week, n = 2; fourth week, n = 2; twelfth week, n = 2). For controls, fresh, DMSO-treated, or DMSO-treated + cryopreserved specimens were examined biomechanically and morphologically. In the time-sequential examination of biomechanical features, both the parameter for elasticity (i.e., ratio of instant elastic strain to maximum strain) and the parameter for viscosity (i.e., average retardation time) significantly changed. Light microscopy showed chronological decreases in safranin-O staining intensity in the matrix, and progression of degeneration. On scan-ning electron microscopy, disruption of the cartilage surface was also recognized. Therefore, changes in biomechanical properties due to cryopreservation could cause irreversible changes in the cartilage in cryopreserved osteochondral allografting. Received: August 31, 2000 / Accepted: January 16, 2001     

Transplantation of cryopreserved osteochondral Dowel allografts for repair of focal articular defects in an ovine model.

The purpose of this study was to test whether successful cryopreservation of osteochondral tissue is possible and whether, with the appropriate surgical procedure, it can be used for the successful repair of focal articular defects within joints. Fresh (nonfrozen) and snap-frozen (plunged in liquid nitrogen and thawed in a water bath at 37 degrees C, repeated three times) autografts were used as positive and negative controls, respectively. Snap-frozen, frozen (fresh tissue placed in a freezer at -80 degrees C), and cryopreserved (immersed in 10% dimethyl sulfoxide for 30 minutes and then frozen at 1 degrees C/min to -80 degrees C) allografts were transplanted into the knees of adult sheep. Outcomes were evaluated 3, 6, and 12 months after transplantation. The morphological, histological, biochemical, and biomechanical behaviors and characteristics of the graft cartilage, the host cartilage adjacent to the grafts, and the opposing tibial cartilage were assessed. Freezing protocols that yielded poor chondrocyte recovery after thawing (frozen and snap-frozen) resulted in poor overall graft outcome. The cryopreservation protocol, however, resulted in intermediate recovery (50%) of chondrocytes and in intermediate overall graft outcome compared with fresh autografts. The membrane integrity of the allograft chondrocytes immediately following cryopreservation was identified as the most reliable predictor of long-term outcome of the graft. Further improvements in cryopreservation technique may lead to an effective method of banking osteochondral tissue for successful transplantation for the repair of focal defects and larger joint reconstructions.     

Evaluation of fluorescein diacetate for flow cytometric determination of cell viability in orthopaedic research

Accurate estimation of cellular viability is important both in research and in aspects of orthopaedic clinical practice. We have been interested in the potential for flow cytometric application of fluorescein diacetate (FDA) in evaluating chondrocyte survival following cryopreservation of osteochondral allografts as well as in the assessment of sarcoma necrosis following preoperative chemotherapy. In order to evaluate the suitability of this method for cell viability assays, this study compared FDA with more traditional methodology (trypan blue, clonigenic assay, metabolic activity analysis, measurement of DNA synthesis, and histological assessment of necrosis). Both chondrocytes and sarcoma cells were exposed to various experimental injuries prior to viability analysis. Although it is evident from these experiments that FDA accurately reflects cell survival after physical injury, it underestimates the effect of chemotherapy on cell reproductive potential in vitro. However, FDA is highly correlated with histological assessment of tumor viability after chemotherapy in vivo. It is apparent that the methodology chosen for determination of viability should be appropriate for the type of experimental injury and should analyze the cell function (i.e., metabolic activity or reproductive capacity) that is appropriate for the experimental model.     

不同复温方法对液氮保存人同种瓣活性影响的实验研究

寻找一种能最大程度保持液氮贮存人同种主动脉瓣活性的复温方法。方法同种主动脉瓣（ｎ＝３６）随机分为６组，Ⅰ组为新鲜同种主动脉瓣，Ⅱ～Ⅵ组经液氮保存３月后，分别采用①４２℃水浴复温（Ⅱ组），②（１．０±０．２）℃／ｍｉｎ（Ⅲ组），③（４．０±０．５）℃／ｍｉｎ（Ⅳ组），④（１０．０±２．０）℃／ｍｉｎ（Ⅴ组）；⑤（３０．０±４．５）℃／ｍｉｎ（Ⅵ组）。将同种主动脉瓣复温至４℃，对所有同种主动脉瓣进行台盼蓝染色活细胞计数、２４小时葡萄糖代谢率测定，氰化胸腺嘧啶脱氧核甙（３Ｈ－ＴｄＲ）参入、瓣膜组织培养。结果上述指标Ⅰ组显著优于其余各组（Ｐ＜０．０５），Ⅳ组优于Ⅱ、Ⅲ、Ⅴ、Ⅵ组（Ｐ＜０．０５）。组织培养Ⅰ组细胞生长优于其余各组，且早于各组３～４天。结论不同复温方法对同种主动脉瓣活性影响不同，以４℃／ｍｉｎ匀速复温法对同种主动脉瓣活性影响最轻。     

Clinical outcome and histologic findings of costal osteochondral grafts for cartilage defects in finger joints

PURPOSE: For the purpose of achieving anatomical reduction as precisely as possible, we performed osteochondral grafting from the costo-osteochondral junction in 16 patients (17 joints) with posttraumatic articular cartilage injury or avascular necrosis in finger joints. The purpose of this study was to review our series of costal osteochondral grafts in order to determine the practicality, effectiveness, and functionality of this grafting technique in a clinical setting. METHODS: Patients were followed for at least 18 months postoperatively (18-57 months; average, 28 months). The injured joints included 3 metacarpophalangeal, 9 proximal interphalangeal, 3 distal interphalangeal, and 2 thumb interphalangeal joints. The defect accounted for 50% to 100% of the articular surface (average, 63%). RESULTS: The average time until bone union of the graft was 58 days. The mean arc of motion was 13 degrees before surgery versus 58 degrees after surgery, with a mean increase of 45 degrees . In 7 patients (8 joints), an extremely small portion (approximately 1 x 1 mm in size and thinner than 0.1 mm) of the implanted cartilage was obtained via biopsy using a scalpel with the consent of the patient at the time of screw removal and was used to prepare histologic specimens, which revealed scattered chondrocytes within the matrix without differences from normal hyaline cartilage in any. The chondrocytes in the grafts appeared viable, and the reconstruction of the joint surface could be confirmed histologically. CONCLUSIONS: Osteochondral grafting from the costo-osteochondral junction achieves excellent reconstruction of the injured joint without affecting other joints. This technique is particularly beneficial in cases where it is difficult to obtain allograft donors, as is often the case in Japan. Despite these encouraging findings in this small series, we believe that it is necessary to conduct further studies of this method over a longer period.     

Repair of articular cartilage lesions in aged chickens by allogeneic transplantation of fresh embryonic epiphyses

Introduction The potential of fresh whole chick epiphyses of embryonic origin to serve as implant material for cartilage defects of aged chicken was tested. Materials and methods Fresh epiphyses of 11-day-old embryos were collected from 24 animals and transplanted into defects created in the weight-bearing areas of tibiotarsal joint cartilage of 2-year-old chicks. Upon sacrifice, samples were examined macroscopically and microsections were prepared for histology. Results Macroscopically, control defects remained empty at all the time intervals. Defects of the experimental group were, on the other hand, filled with cartilaginous tissue as early as 2 weeks posttransplantation, although individual epiphyses could still be noted in the implant tissue. At 4 weeks and later, defects were filled with cartilaginous material indistinguishable from hyaline cartilage. Histologically, all grafts remained within the defect’s pits, showing mitotic and metabolic activity typical to proliferating hyaline cartilage. The engrafted epiphyses showed a partial incorporation and integration with the surrounding host tissues already at 2 weeks. At 4 weeks and later, the integration was complete. Conclusions It is concluded that a chick embryonic epiphyseal cartilage is suitable as a graft source for articular cartilage transplantation. The embryonic epiphyses provide immediate inherent stability to the graft and supply a good mix of mesenchymal progenitor cells responsible for the high rate of cell proliferation and adhesion to the differentiated committed chondrocytes of the host that create the typical favorable chondrogenic milieu. Based on the present findings, it is postulated that human embryonic epiphyses may, in the future, represent an alternative source to the commonly used techniques of hyaline cartilage repair. We declare that the experiments comply with the current laws of the state of Israel     

Factors influencing changes in articular cartilage following hemiarthroplasty in sheep.

This study examined the relationship between acetabular cartilage properties after hemiarthroplasty surgery and surgical variables including femoral head size and position. Nineteen sheep received unilateral hip arthroplasties and were euthanized one year post-operatively to harvest the femora and acetabula. Cartilage histology, biochemistry and material properties were determined from samples located in the superior load-bearing region. Femoral head size mismatch, leg length difference, anterior-posterior and medial lateral offset and anteversion were measured. In the acetabulum. substantial cartilage degradation occurred with widespread librillation and significant changes in the biochemical and material properties compared to the intact contralateral joint. Regression analyses on the surgical variables explained 75-80% of the changes in tissue biochemistry but did not explain the material changes. Head size mismatch and leg length difference were the most significant contributors of the five variables examined and therefore may be critical to successful outcome in hemiarthroplasty.     

How to improve donor skin availability: Pragmatic procedures to minimize the discard rate of cryopreserved allografts in skin banking

BackgroundMicrobial contamination of human skin allografts is a frequent cause of allograft discard. Our purpose was to evaluate the discard rate of skin bank contaminated allografts and specific procedures used to reduce allograft contamination without affecting safety.MethodsWe conducted at the Lille Tissue Bank a retrospective study of all deceased donors (n = 104) harvested from January 2018 to December 2018. Skin procurement was split into 3 zones: the back of the body and the two legs that were processed separately. It represented 433 cryopreserved skin allograft pouches of approximatively 500 cm² each. Donors were almost equally split between brain-dead (53%, 55/104) and cadaveric (47%, 49/104) donors.ResultsOut of all donors, 42 (40.5%) had at least one sampling zone with a positive microbiological test resulting in 106 (24%) contaminated skin pouches. The contamination rate did not vary according to the harvested zone or type of donor. Traumatic deaths showed significantly less contamination rates than other death types (p < 0.05). Contamination rate decreased with time spent in the antibiotic solution. The risk of having contaminated allografts was five-fold higher when the skin spent less than 96 h in the antibiotic cocktail (p < 0.05). According to our validation protocol, most donors (32/42, 76%) had skin allografts contaminated with bacteria (mainly Staphylococcus spp) compatible with clinical use. No recipient infection was recorded as a result of skin graft contaminated with saprophytic or non-pathogenic germs. By harvesting 3 separate zones per donor, the total surface area for clinical use increased by 53% for contaminated donors. Overall, the proportion of contamination-related discarded allografts was 3.2% (14/433 of pouches).ConclusionFew simple pragmatic measures (including skin incubation in the antibiotic bath for at least 96 h at 4 °C, splitting the skin harvesting areas to minimize the risk of cross-infection and clinical use of allografts contaminated with saprophytic and non-pathogenic germs) can reduce the discard rate of contaminated allografts without affecting clinical safety.     

Tensile mechanical properties of bovine articular cartilage: variations with growth and relationships to collagen network components.

One approach to repairing articular defects is to regenerate cartilage by recapitulating the changes that occur during fetal and postnatal growth into adulthood, and to thereby restore functional biomechanical properties, especially those of the normally strong superficial region. The objectives of this study were (1) to characterize and compare tensile biomechanical properties of the superficial region of articular cartilage of the patellofemoral groove (PFG) and femoral condyle (FC) from bovine animals over a range of growth stages (third-trimester fetal, 1-3 week-old calf, and adult), and (2) to determine if these properties were correlated with collagen network components. With growth from the fetus to the adult, the equilibrium and dynamic tensile moduli and strength of cartilage samples increased by an average of 391-1060%, while the strain at the failure decreased by 43%. The collagen concentration (per wet weight) increased by 98%, and the pyridinoline cross-link concentration increased by 730%, while the glycosaminoglycan concentration remained unchanged or decreased slightly. Some growth-associated changes were location-specific, with tensile moduli and strength attaining higher values in the PFG than the FC. The growth-associated variation in tensile moduli and strength were associated strongly with variation in the contents of collagen and pyridinoline cross-link, but not sulfated glycosaminoglycan. The marked changes in the tensile properties and collagen network components of articular cartilage with growth suggest that such parameters may be used to evaluate the degrees to which regenerated cartilage recapitulates normal development and growth.