新鲜和深低温冷冻同种异体骨软骨移植长期转归实验研究

[目的]观察和比较新鲜和深低温冷冻同种异体骨软骨移植后的长期转归情况,为同种异体骨软骨移植治疗关节软骨缺损进一步提供理论基础。[方法]建立兔膝关节软骨缺损模型,行新鲜和深低温冷冻同种异体骨软骨移植。在术后12个月和18个月,骨软骨移植物取材进行关节软骨蛋白多糖、软骨细胞活性检测和软骨细胞超微结构观察。[结果]新鲜和冷冻骨软骨移植物中蛋白多糖阿尔新蓝染色强度和存活软骨细胞比率术后均下降,且在各时间点新鲜移植组的结果优于冷冻移植组,有统计学差异(P0.05)。超微结构显示软骨细胞退行性改变。[结论]新鲜和深低温冷冻同种异体骨软骨在移植术后较长时间均出现严重退变,冷冻骨软骨移植物退变较严重,其作为关节软骨缺损治疗方法目前是不可行的。     

兔同种异体半月板移植后膝胫股关节面生物力学重建的研究

目的探讨兔同种异体半月板移植后膝关节内侧间隙受力面积、压强的变化及其生物力学重建情况。方法 6～7月龄清洁级日本大耳白兔28只,雌雄不限,体重3.0～3.5kg;随机取7只兔右膝关节内侧半月板,制备同种异体半月板。余21只兔随机分为3组,每组7只。A组为空白对照组,单纯打开膝关节后缝合;B组为右膝内侧半月板切除组;C组为右膝内侧半月板切除后行同种异体半月板移植组。术后观察各组实验动物一般情况,于12周处死实验动物取右膝关节行生物力学测试,并取A、C组半月板行组织学及免疫组织化学染色观察。结果术后实验动物均存活至实验完成。术后12周大体观察见C组移植半月板愈合较好,前后角及体部附着良好。术后12周膝关节屈膝0、30、60、90°时,B组膝关节内侧间隙受力面积及压强与A、C组比较,差异均有统计学意义(P<0.05),A、C组间比较差异均无统计学意义(P>0.05);屈膝120°时,任意两组间受力面积及压强比较,差异均有统计学意义(P<0.05)。组织学观察显示C组软骨细胞及胶原纤维数量恢复正常;免疫组织化学染色示C组移植半月板内胶原纤维含有大量Ⅰ型胶原和Ⅱ型胶原。术后12周A、C组Ⅰ型胶原含量分别为0.6125±0.0598和0.5872±0.0639,差异无统计学意义(t=0.765,P=0.465);Ⅱ型胶原含量分别为0.7724±0.0815和0.8143±0.0517,差异无统计学意义(t=—0.136,P=0.894)。结论兔同种异体半月板移植可增加膝关节受力面积,减小压强,有利于保护关节软骨,并可重建生物力学平衡。     

新鲜同种异体骨软骨移植修复软骨缺损

目的联合应用新鲜同种异体骨软骨移植,和局部注射碱性成纤维细胞生长因子(basic fibroblast growthfactor,bFGF),探讨能否促进关节软骨缺损区新生软骨的形成,提高软骨缺损修复的成功率。方法48只青紫兰兔,96个实验关节,随机分为A、B、C、D组。无菌条件下制作骨软骨缺损模型。在A组缺损区单纯植入新鲜的同种异体骨软骨,B组单纯局部注射重组人bFGF,C组局部注射bFGF后同时植入新鲜的同种异体骨软骨,D组用作空白对照。术后第4、8、12周作大体观察、X线摄片、组织学检查及免疫组化检查。结果移植加注射bFGF组促进软骨缺损修复的效果均好于其他组,图像分析仪进行软骨细胞记数有显著差异(P<0.05),有统计学意义。修复软骨型胶原免疫组化染色强阳性。结论采用新鲜的同种异体骨软骨移植及联合应用碱性成纤维细胞生长因子,二者能起交互作用,促进了新生软骨的形成。     

同种异体骨软骨移植修复关节软骨缺损研究现状

关节软骨缺损常因软骨再生能力低而难以自行修复.新鲜的同种异体骨软骨移植修复关节软骨缺损的疗效稳定,成功率逐渐提高.冷冻保存的同种异体骨软骨移植修复关节软骨缺损的成功率可与新鲜的同种异体骨软骨移植媲美,梯度降温法是目前保存软骨细胞存活率最好的冷冻方法.该文就同种异体骨软骨移植的实验和临床研究、免疫排斥问题及其相关研究动态作一综述.     

自固化磷酸钙复合BMP及同种异体骨修复兔股骨大段骨缺损

[目的] 观察一种新型自固化磷酸钙（CPC）复合BMP与同种异体骨修复兔股骨节段性骨缺损的效果，为临床复合应用大段同种异体骨移植提供参考。[方法] 54只新西兰大白兔随机分成3组，于一侧股骨中上段造成2cm长皮质骨缺损模型，分别进行：A组复合BMP与CPC的新鲜冷冻同种异体骨移植；B组单纯新鲜冷冻同种异体骨移植；C组自体大段骨移植。移植骨均用直径3mm三棱髓内针固定。于术后4、8、12周，进行影像学、组织学检查，对比各组移植骨愈合过程与修复效果。[结果] CPC复合BMP大段同种异体骨移植早期骨修复效果优于单纯异体骨移植（P〈0．01），与自体骨移植修复效果相似，至12周3组均达骨性愈合，以A组及C组骨修复塑形较好。CPC复合BMP组骨痂量较多，分布于移植骨与宿主骨结合部及移植骨周围，形成皮质骨外骨桥，并较早在异体骨外表面形成破骨与成骨，异体骨内哈佛氏管扩大，衬垫细胞、成骨细胞、破骨细胞及血细胞较其它组多。CPC随着新骨的形成及改建塑形逐步缓慢降解。[结论] CPC复合BMP对大段同种异体骨移植的愈合及替代有增强和促进作用。     

骨髓基质细胞移植修复半月板无血运区损伤的实验研究

目的比较自体与同种异体骨髓基质细胞移植对半月板无血运区损伤修复的影响。方法 40只成年新西兰大白兔随机平均分为 A、 B两组。 A组兔的骨髓基质细胞 (MSC)经体外培养后与纤维蛋白凝胶 (FG)混合,自体移植于其一侧的膝关节半月板缺损区,即 FG＋自体 MSC（自体移植组）;另一侧单纯植入 FG(FG植入组 )。于 B组兔的一侧膝关节半月板缺损区移植 FG＋同种异体 MSC(异体移植组 ),另一侧缺损不予修复 (空白对照组 )。分别于术后第 1、 2、 3个月取材,观察半月板损伤部位的组织形态学变化。结果 (1)自体移植组 :术后 1个月缺损区可见纤维组织,内有大量成纤维细胞;术后 2个月见大量软骨细胞并有胶原纤维形成;术后 3个月损伤区呈纤维软骨愈合。 (2)空白对照组 :术后 1～ 3个月缺损区始终未愈合。 (3)单纯 FG植入组 :术后 1～ 3个月缺损区可见纤维组织,内有少量成纤维细胞,没有软骨细胞生长,呈瘢痕样愈合。 (4)同种异体移植组 :与自体移植组所见大致相同,但有 3侧缺损区可见大量淋巴细胞浸润,胶原纤维少。结论骨髓基质细胞移植可促进半月板无血运区损伤的愈合,同种异体骨髓基质细胞移植修复半月板无血运区损伤发生免疫排斥反应的机率较低。     

骨软骨移植联合rhBMP -2/bFGF修复软骨缺损

[目的]探讨采用冷冻同种异体骨软骨移植,配合骨形态发生蛋白(rhBMP-2)/碱性成纤维细胞生长因子(bFGF)修复软骨缺损的效果,为进一步应用于临床提供理论依据。[方法]48只日本大耳白兔,96个关节,随机分A、B、C、D组。A组采用骨软骨移植联合rhBMP-2/bFGF,B组单纯应用骨软骨移植,C组单纯局部注射rh-BMP-2/bFGF混悬液,D组用作空白对照。无菌条件下制作骨软骨缺损模型。术后第4、8、12周作解剖学观察、磁共振检查、组织学检查及软骨细胞记数、免疫组化检查。[结果]A组软骨缺损修复面光滑,呈瓷白色、半透明,B、C组未完全修复,D组无明显修复。A组修复软骨组织学评分与其他组比较差异有统计学意义(P<0.05),图像分析仪软骨细胞记数与其他组比较差异有统计学意义(P<0.05)。修复软骨Ⅱ型胶原免疫组化染色阳性。[结论]联合应用冷冻同种异体骨软骨移植、rhBMP-2/bFGF,能促进新生软骨的形成,提高软骨缺损修复的质量。     

复合自体骨髓的冷冻异体犬足趾关节移植实验研究

目的探讨经过多重钻孔并复合自体骨髓的冷冻异体犬足趾关节移植的疗效. 方法 24只健康成年杂交犬,制备双侧后肢第2足趾近侧趾间关节1.5 cm缺损模型,共48侧,随机分成A、B、C 3组(n=16).分别采用新鲜自体趾间关节(A组)、经钻孔并复合自体新鲜骨髓的冷冻异体趾间关节(B组)及单纯冷冻异体趾间关节(C组)修复缺损.于术后1、3、6和12个月分别行X线摄片和组织病理学检查,了解移植骨关节的成活情况. 结果根据移植关节术后X线片和组织学改变,犬趾骨关节移植后的病变可分为轻度、中度和重度变性3级.A组移植骨关节3～12个月始终表现为轻度变性;B组移植骨关节1～6个月为轻度变性,骨孔中央软骨内成骨现象明显,12个月部分移植骨关节为中度变性;C组从1个月出现移植骨关节中度变性,3个月移植骨关节重度变性. 结论冷冻异体犬足趾关节内多重钻孔并复合自体新鲜骨髓,能有效延缓异体骨关节的早、中期变性,单纯冷冻异体骨关节移植后早期可能发生严重变性.     

异体气管移植去抗原性的实验研究

目的探讨移植段气管去除上皮细胞和腺体细胞后异体、异位移植排斥反应的强弱。方法25只雄性SD大鼠作为供体,制备新鲜移植段气管、冷冻移植段气管和去上皮细胞移植段气管。取制备的新鲜移植段气管40个平均分为4组,分别用0、0.1、0.3和0.5mg/ml的蛋白酶溶液,4℃浸泡12h,根据镜下移植段气管上皮细胞和腺体细胞脱落情况及软骨细胞破坏程度确定蛋白酶的最佳浓度。另取30只雄性SD大鼠作受体,均分成3组,分别为:新鲜气管移植组(A组)、冷冻气管移植组(B组)及去上皮细胞移植组(C组),n=10。行左上腹旁正中切口,提出大网膜包绕各移植段气管,于21d后取出移植段气管,行组织学观察及淋巴细胞浸润测定。结果0.3mg/ml蛋白酶能去除移植段气管上皮细胞及腺体细胞,而对软骨细胞无明显损坏。异体植入大鼠腹腔的3组气管软骨均成活,血运建立,其中A组管腔内有肉芽组织,出现坏死、实变;B组有少量肉芽组织;C组管腔内无肉芽组织。A、B、C3组淋巴细胞浸润分别为29.16±2.69、15.17±2.19和11.56±0.87个/Hp,A组与B、C组比较及B组与C组比较,差异均有统计学意义(P<0.05),排斥反应强弱为:A组>B组>C组。结论0.3mg/ml蛋白酶,4℃,浸泡12h的移植段气管,能完全脱上皮细胞和腺体,对软骨细胞基本无损伤,与冷冻法比较去抗原作用更好。一期异体大网膜包裹异位移植后,血运重建且移植段气管成活。     

同种异体软骨细胞与自体骨髓基质干细胞混合共培养构建软骨皮下移植的可行性研究

背景：软骨组织工程的种子细胞问题是目前研究的热点和难点,如何找到一种既能够避免对自体软骨进行取材又能够达到稳定软骨构建目的的方法呢？本研究尝试利用少量同种异体羊软骨细胞作为软骨诱导微环境提供者,与扩增后的羊自体BMSC混合共培养并植入皮下环境,探讨利用同种异体软骨细胞共培养构建软骨皮下移植的可行性。方法：本实验对山羊软骨细胞和BMSC分别进行取材和分离培养扩增,并将以上细胞分为以下四组进行混合并接种在PGA支架材料上：A组：100%自体软骨细胞;B组：30%自体软骨细胞＋70%自体BMSCs;C组：30%同种异体软骨细胞＋70%自体BMSCs;D组：100%同种异体软骨细胞。经过体外构建6周后植入羊皮下进行体内构建12周,对所形成的组织块进行大体观察和组织学染色等评价。结果：自体软骨细胞组和自体软骨细胞混合自体BMSC组皮下移植后可见成熟软骨组织形成,但同种异体软骨细胞参与的两组（包括同种异体软骨细胞混合自体BMSC的实验组和单纯异体软骨细胞组）在皮下环境中都因为较强的免疫反应未能形成软骨组织。结论：同种异体软骨细胞以及PGA支架材料的存在对于组织工程软骨在羊皮下环境的构建有负面影响。     

Comparison of meniscal allograft transplantation techniques using a preclinical canine model

Meniscal allograft transplantation (MAT) can be a safe, effective treatment for meniscal deficiency resulting in knee dysfunction, leading to osteoarthritis (OA) without proper treatment with 5‐year functional success rates (75%‐90%). While different grafts and techniques have generally proven safe and effective, complications include shrinkage, extrusion, progression of joint pathology, and failure. The objective of this study was to assess the functional outcomes after MAT using three different clinically‐relevant methods in a preclinical canine model. The study was designed to test the hypothesis that fresh meniscal‐osteochondral allograft transplantation would be associated with significantly better function and joint health compared with fresh‐viable or fresh‐frozen meniscus‐only allograft transplantations. Three months after meniscal release to induce meniscus‐deficient medial compartment disease, research hounds (n = 12) underwent MAT using meniscus allografts harvested from matched dogs. Three MAT conditions (n = 4 each) were compared: frozen meniscus–fresh‐frozen meniscal allograft with menisco‐capsular suture repair; fresh meniscus–fresh viable meniscal allograft (Missouri Osteochondral Preservation System (MOPS)‐preservation for 30 days) with menisco‐tibial ligament repair; fresh menisco‐tibial–fresh, viable meniscal‐tibial‐osteochondral allografts (MOPS‐preservation for 30 days) with menisco‐tibial ligament preservation and autogenous bone marrow aspirate concentrate on OCA bone. Assessment was performed up to 6 months after MAT. Pain, comfortable range of motion, imaging, and arthroscopic scores as well histological and cell viability findings were superior (P < .05) for the fresh menisco‐tibial group compared with the two other groups. Novel meniscal preservation and implantation techniques with fresh, MOPS‐preserved, viable meniscal‐osteochondral allografts with menisco‐tibial ligament preservation appears to be safe and effective for restoring knee function and joint health in this preclinical model. This has the potential to significantly improve outcomes after MAT.     

Architectural remodeling in deep frozen meniscal allografts after total meniscectomy

This study assesses the biological characteristics of cell repopulation and matrix remodeling in deep frozen meniscal allografts after total meniscectomy and allograft transplantation. Thirty-two mature New Zealand White rabbits were operated on, and the allografts were assessed at 12 and 26 weeks postsurgery. Before transplantation, fresh medial menisci were placed into liquid nitrogen to kill all intrinsic cells. Frozen meniscal allografts showed collagen remodeling coincident with revascularization and cellular repopulation. Biochemical characterization showed active collagen remodeling of the allografts at 12 and 26 weeks. In situ hybridization showed that expression of types I and III procollagen mRNAs were increased at 12 weeks, especially near the region of the synovial capsule. At 26 weeks after transplantation, the pattern of collagen-type expression progressed toward normal; that is, type I procollagen mRNA expression was prominent, whereas only a small amount of type III procollagen mRNA was observed. These data indicate the adaptation of the repopulating cells from the host to the frozen allograft at 26 weeks after transplantation.Arthroscopy 1998 Apr;14(3):250-7     

Structural analysis of meniscal allografts after immediate and delayed transplantation in rabbits

Purpose: To compare long-term performance of meniscal allografts transplanted immediately after meniscectomy and allografts transplanted 6 weeks after meniscectomy. Type of Study: Experimental study. Methods: Twenty-one rabbits were subjected to meniscectomy and divided into 3 groups of 7 animals. Immediate meniscal transplantation was performed in group A (6-week follow-up) and group B (1-year follow-up). Group C underwent delayed transplantation 6 weeks after meniscectomy. One animal in group B developed infective arthritis and was not included. Six nonoperated knees served as controls. Four other knees were subjected to a sham procedure. Menisci were examined macroscopically and histologically at 6 weeks (group A and 2 sham- operated animals) and 1 year (group B, C, controls, and 2 sham-operated animals). Results: Capsular ingrowth was observed in all allografts. At 1 year, osteoarthritic changes in the delayed transplant group were more pronounced than in the immediate transplant group. Menisci in nonoperated controls and sham-operated knees appeared normal. No differences in shrinkage of allografts were observed between groups A and B. Group C showed significantly more shrinkage than allografts in both group A (P = .004) and group B (P = .005). Two allografts in group C were completely degenerated. Differences in architecture of the allografts were not found between groups A, B, and C. In both the peripheral and central areas of transplanted menisci, the number of cells was frequently increased because of repopulation even at 6-week follow-up. Conclusions: Delayed meniscal allograft transplantation causes distinct structural damage to menisci in comparison with immediate transplantation.     

Transplantation of osteochondral allografts after cold storage

BACKGROUND: Transplantation of fresh osteochondral allografts stored at hypothermia into knee cartilage defects is a common procedure; however, the length of time that allografts can be stored prior to transplantation is controversial and has been determined, in part, by the results of vital stain uptake by chondrocytes. This study was performed to further define the limits of allograft storage. METHODS: Articular cartilage from six cadavers was stored for up to fifty-one days in tissue-culture media, and histologic sections were evaluated histomorphometrically to quantify the loss of chondrocytes. Samples of the cartilage were also placed into tissue culture to assess cell growth. Animal studies were performed in parallel on sixteen adult baboons with osteochondral allografts transplanted into the medial femoral condyle. Prior to transplantation, all allografts were stored in RPMI-1640 with 10% fetal calf serum at 4 degrees to 6 degrees C for up to eighty-five days. The transplants were graded on their gross and histological appearance, as well as their histochemical properties. RESULTS: Many of the human samples stored at hypothermia in culture media for up to forty days retained some recognizable chondrocytes, but morphometry showed a gradual, significant decrease in the number of chondrocytes after nine days (p = 0.001). In addition, the cell outgrowth occurred from all specimens stored for up to fifteen days but not in samples stored for longer than thirty-four days. In animal studies, transplanted allograft cartilage that had been stored for less than eighteen days looked smooth and glistening, but grafts stored for over twenty-one days were pale, pitted, fragmented, or yellow, and chondrocytes were absent. CONCLUSIONS: Time-dependent loss of chondrocytes in articular cartilage stored at hypothermia, especially in specimens stored for longer than fifteen to twenty days, was observed in this study. Cartilage allografts transplanted into nonhuman primates after twenty-one days of storage underwent more severe degenerative changes than allografts that had been stored for less than twenty-one days. These findings suggest caution when transplanting cartilage stored at hypothermia for over twenty days.     

Transplantation of viable meniscal allograft. Survivorship analysis and clinical outcome of one hundred cases

BACKGROUND: Few medium-term or long-term reports on meniscal allograft transplantations are available. In this study, we present the results of a survival analysis of the clinical outcomes of our first 100 procedures involving transplantation of viable medial and lateral meniscal allografts performed in ninety-six patients. METHODS: Thirty-nine medial and sixty-one lateral meniscal allografts were evaluated after a mean of 7.2 years. Survival analysis was based on specific clinical end points, with failure of the allograft defined as moderate occasional or persistent pain or as poor function. An additional survival analysis was performed to assess the results of the sixty-nine procedures that involved isolated use of a viable allograft (twenty of the thirty-nine medial allograft procedures and forty-nine of the sixty-one lateral allograft procedures) and of the thirteen viable medial meniscal allografts that were implanted in combination with a high tibial osteotomy in patients with initial varus malalignment of the lower limb. RESULTS: Overall, eleven (28%) of the thirty-nine medial allografts and ten (16%) of the sixty-one lateral allografts failed. The mean cumulative survival time (11.6 years) was identical for the medial and lateral allografts. The cumulative survival rates for the medial and lateral allografts at ten years were 74.2% and 69.8%, respectively. The mean cumulative survival time and the cumulative survival rate for the medial allografts used in combination with a high tibial osteotomy were 13.0 years and 83.3% at ten years, respectively. CONCLUSIONS: Transplantation of a viable meniscal allograft can significantly relieve pain and improve function of the knee joint. Survival analysis showed that this beneficial effect remained in approximately 70% of the patients at ten years. This study identified the need for a prospective study comparing patients with similar symptoms and clinical findings treated with and without a meniscal allograft and followed for a longer period with use of clinical evaluation as well as more objective documentation tools regarding the actual fate of the allograft itself and the articular cartilage.     

去细胞处理对化学去细胞异体神经免疫原性的影响

目的研究化学去细胞异体神经的免疫学和制备方法,以期进一步降低同种异体神经移植的免疫反应。方法取SD大鼠的坐骨神经,经4．0％Triton X-100和3．0％脱氧胆酸钠消化进行去细胞处理。将化学去细胞和新鲜的SD大鼠坐骨神经植入Wistar大鼠皮下,通过免疫组化方法观察移植物及周围组织中的CD3、CIM和CD8阳性T细胞浸润程度,评价免疫反应强度。将犬的尺神经按上述方法进行去细胞处理,按去细胞处理次数分为3个组,分别从去细胞程度、髓鞘染色程度、GAG免疫组化染色和神经基底板层结构完整性方面进行组织学观察。结果与新鲜异体神经移植比较,化学去细胞异体神经植入后可明显降低大鼠的免疫原性,但仍有轻度细胞介导的免疫反应存在。经化学去细胞处理的神经,其残余神经轴突髓鞘的染色强度不随去细胞处理次数增加而明显减弱,GAG染色强度也无改变,但神经基底板层结构的破坏程度随去细胞处理次数的增加而增强。结论移植经化学去细胞处理的异体神经后,可有轻微的免疫反应,诱发免疫反应的物质可能与糖蛋白成分有关,残余的髓鞘组分不随去细胞处理次数增加而明显减少。     

Cryopreservation of osteochondral allografts: dimethyl sulfoxide promotes angiogenesis and immune tolerance in mice

BACKGROUND: Although transplantation of cryopreserved bone allografts has become a routine procedure in orthopaedic surgery, biological and immunological impairment remains an unsolved problem that causes clinical failures. Experimental and clinical evidence has indicated that bone grafts that are revascularized early remain viable and contribute to union at the recipient site. Unprotected cryopreservation, used in most bone banks to reduce graft antigenicity, is associated with complete loss of graft viability, potentially contributing to graft failure. The differences in the survival of various cell types during cryopreservation with use of dimethyl sulfoxide, particularly the increased sensitivity of leukocytes to fast freezing, has resulted in a new approach to modulate immunogenicity. On the basis of this concept, it was proposed that a reduction in the immune response and enhanced revascularization of osteochondral allografts could be achieved by rapid cryopreservation with dimethyl sulfoxide. To test this hypothesis, angiogenesis and immune tolerance were quantified in a murine model with use of intravital microscopy. METHODS: Fresh osteochondral tissue and osteochondral tissue that had been cryopreserved with and without dimethyl sulfoxide was transplanted into dorsal skinfold chambers as isografts and as allografts in presensitized and nonsensitized recipient mice. To quantify angiogenesis, the onset of hemorrhages in the vicinity of the grafts and the revascularization of the grafts were determined by means of intravital fluorescence microscopy. To determine the recipient's intravascular immune response to the grafts, the leukocyte-endothelium interaction was assessed on the twelfth day after transplantation. RESULTS: Nine of nine fresh isografts were revascularized at a mean (and standard deviation) of 57 +/- 33 hours, eight of nine isografts that had been cryopreserved with dimethyl sulfoxide were revascularized at 98 +/- 50 hours, and zero of nine isografts that had been cryopreserved without dimethyl sulfoxide were revascularized. Seven of seven fresh allografts were revascularized at 53 +/- 6 hours, and ten of ten allografts that had been cryopreserved with dimethyl sulfoxide were revascularized at 82 +/- 29 hours. However, signs of revascularization faded in four of the seven fresh allografts whereas reperfusion was maintained in the majority (seven) of the ten grafts frozen in the presence of dimethyl sulfoxide. Similar to the findings associated with unprotected frozen isografts, zero of ten unprotected frozen allografts were revascularized. None of the allografts that had been transplanted into presensitized recipients were revascularized, regardless of whether they had been implanted fresh (nine grafts) or had been implanted after protected (eight grafts) or unprotected (nine grafts) freezing. Quantification of the leukocyte-endothelium interaction revealed a reduction in the intravascular immune response to frozen allografts (both protected and unprotected) compared with fresh allografts. CONCLUSION: Osteochondral allografts that had been pretreated by cryopreservation with dimethyl sulfoxide demonstrated improved angiogenesis induction and enhanced immune tolerance compared with unprotected frozen grafts. A selective reduction in donor passenger leukocytes is the proposed mechanism underlying this phenomenon. Clinical Relevance: In the absence of presensitization, cryopreservation with dimethyl sulfoxide appears to reduce the immune response to allografts and to enhance their revascularization; in the presence of presensitization, alternatives to allograft transplantation should be considered since the allografts will be exposed to a deleterious immune response.     

Glutaraldehyde-cross-linked meniscal allografts: clinical, gross, and histological results

Osteoarthritic changes in the knee are often a late result of total meniscectomy. In cases of total resection, availability of a prosthetic meniscus might limit development of these changes. The objective of this research was to evaluate a glutaraldehyde-cross-linked medial meniscus as a morphologically and biologically compatible prosthesis in a canine model. Medial and lateral menisci were harvested from donor dogs, frozen in saline, and cross-linked with glutaraldehyde. Five host animals were selected and matched with donors. Glutaraldehyde-cross-linked medial menisci were implanted bilaterally in the stifle joints and one glutaraldehyde cross-linked lateral meniscus was implanted subcutaneously. Clinical results showed asymptomatic limb and joint usage during the 12 postoperative weeks. Gross and histological evaluations indicated acceptable biocompatibility. The subcutaneous implants were encapsulated with a thin fibrous tissue capsule that was only mildly inflamed. Within the joints, the anterior attachment and periphery were maintained in position by their sutures; however, there was dehiscence of the posterior suture in all cases. The articulating surfaces of the implants were intact. There was an initial loss in the quantity of proteoglycans following glutaraldehyde treatment, with significant recovery after implantation into the joints. There were significant degenerative changes (loss of proteoglycans and fibrillation) in the articular cartilage on the femoral condyle and tibial plateau most likely a result of the posterior attachment failure. It was concluded that glutaraldehyde-cross-linked meniscal allografts showed an acceptable degree of histocompatibility. However, failure of the posterior attachment interfered with testing the efficacy of the prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)