An Experimental Study Of Rabbit Knee Full-thickness Cartilage Defects Repaired By Tissue Engineered Osteochondral

Articular cartilage lesion is a common clinical problem, and most timecombined with subchondral bone lesion. Even till now, there still have notideal measurement. Tissue engineering technique is a most promisingmethod. However, there is currently cartilage tissue engineering can not berepaired subchondral bone at the same time, engineered cartilage withsurrounding cartilage and subchondral bone around the junction integratednot well, engineering cartilage fixed not strong, instant mechanicaldefects,long-term degeneration and other issues.Therefore, building theintegration of osteochondral tissue engineering to repair subchondral boneand bone, fixed firmly and immediate stability and good mechanicalproperties is the research direction and focus of cartilage tissueengineering.So we have designed a layered decalcification cancellous bonescaffold, the upper of the scaffold is decalcified completely as the cartilagetissue engineering scaffold, the lower not decalcified as the bone tissueengineering scaffold. Using the feature of bone repaired faster thancartilage to achieve engineered bone cartilage firmly fixed and interfaceintegration, at the same time, the upper of the scaffold use Alginate gel asthe second scaffold to distribute cells to build tissue engineeringOsteochondral in order to repair cartilage or Osteochondral pathologicallesions or defects.In this study, bovine cancellous bone is used as scaffold materials,through defatting, cell removing and layered decalcifying preparation stepsto make such an integration scaffold for osteochondral tissue engineering.New Zealand white rabbits were used as the experimental animals. Alginate gel suspended the rabbit chondrocytes, and was loaded to the top of thescaffold subsequently to build a “seed cell-scaffold composites”, and wastransplanted into the full-thickness articular cartilage defects in rabbitmodels after in vitro culture. Observed the repair of the defects in differentperiods, and investigated the feasibility of osteochondral tissue engineeringto repair the full-thickness articular cartilage defects.The fresh bovine distal femur metaphyseal cancellous bone with1:1formaldehyde/chloroform skimmed,100g·L-1NaCl with1%TritonX-100to removed cells, and the cancellous bone was partially embedded withbone wax to layered decalcification in order to make the integrationscaffold for osteochondral tissue engineering. The scaffold was observedwith HE staining and SEM, detected scaffold porosity, cell adhesion rate,degradation rate and other characteristics.The48knees of24New Zealand rabbits were divided into threegroups: control group, simple scaffold group and experimental group(autologous chondrocyte-scaffold composites), each knee joint as a unit,and both knee joints of a rabbit were divided into different groups.Each rabbit femoral condyle surface was made a full-thicknessarticular cartilage defect model about4.0mm diameter, and depth to thebone marrow cavity. Control group: without any treatment. Simple scaffoldgroup: implanted the4.0mm diameter scaffold. Experimental group:implanted alginate entrapped autologous chondrocyte-layereddemineralized cancellous bone scaffold composites. Results of articularcartilage defect repaired were assessed with histological examination,pathology scoring and other testings after3months or6months.The layered demineralized cancellous bone integration scaffold porediametar made from bovine cancellous is (358.53±79.67) μm, porosity is(85.55±4.66)%, ratio is (67.68±8.83)%, completely degraded after10~12weeks.Histopathological analysis of rabbits experiments showed that the full-thickness articular cartilage defect of control group has not beenrepaired significantly after3months, gross observation score is (0±0),Wakitani pathology score is (11.75±1.39) points. The full-thicknessarticular cartilage defect of simple scaffold group has a certain degree offibrous tissue repair, some areas repaired incompletely, gross observationscore is (2.00±1.41) points and Wakitani pathology score is (7.50±0.53)points. The full-thickness articular cartilage defect of experimental grouphas a better repair, the surface was nearly flat, and cartilage-like tissuerepaired the defect area, but some defects had poor integration, grossobservation score is (3.25±1.39) points and Wakitani pathology score is(3.87±1.55) points. Compared with control group and simple group, therepair of articular cartilage defect was better in experimental group. Therewere significant difference between them (P <0.01).The full-thickness articular cartilage defect has been mild repaired incontrol group after6months, but part defect still be seen, gross observationscore is (1.00±0) points and Wakitani pathology score is (10.75±1.39)points. The full-thickness articular cartilage defect of simple scaffold grouphas a certain degree of fibrous tissue repair, a few areas repairedincompletely, and significantly improved than3months ago, grossobservation score is (3.75±1.91) points and Wakitani pathology score is(6.25±1.39) points. The full-thickness cartilage defect of experimentalgroup has a better repair, the surface was nearly flat, and cartilage-liketissue repaired the defect area, the defect edge integrated well, articularcartilage thickness increased, gross observation score is (6.13±2.53) pointsand Wakitani pathology score is (2.25±0.71) points. Compared withcontrol group and simple group, the repair of articular cartilage defect wasbetter in experimental group. There were also significant differencebetween them（P <0.01).The layered demineralized cancellous bone integration scaffold madefrom bovine cancellous bone met the need of osteochondral tissue engineering. Using alginate gel embedded autologous chondrocytecomposited layered demineralized cancellous bone integration scaffold tobuild “seed cell-scaffold” composites, which can repair the full-thicknesscartilage defects very well in rabbit knee joints. It also provided a newchoice to cure the full-thickness articular cartilage defects.