Repair Of Articular Cartilage Using Injectable Fibrin Glue Combined With Demineralized Bone Matrix

BACKGROUND:Osteoarthritis (OA) is a kind of common osteoarthritis among clinical disease, and it is correlated with age, trauma and force to bear, obesity, genetic and gender. Its pathological changes shows the destroy and repair of cartilage, thickening of joint capsule, adhesions of osteoporosis, synovial phlogistic vascular thickening, focal sparing hemorrhage and bone joints near cystic changes. After the imbalance of the joint mechanical force distribution and excessive load, cartilage wear and cartilage cells metabolism disorders, cartilage cells release lysosome and collagen protease, which cause collagen network fault. Cartilage repair damaged also accompanied by process, but due to the new synthesis of extracellular matrix, the new synthesis of cartilage is abnormal, soon degradation of inflammatory synovitis accelerated destruction of cartilage in factor, so exhausted, cartilage and clinical symptoms appears.The avascularity, low metabolic activity, and catabolic activity of chondrocytes are reasons that may have lead to the 200 year old dogma "Cartilage once destroyed never heals". Current research shows these lesions in cartilage do heal under some biological circumstances, which include untreated cartilage defects. Articular carilage repair and/or regeneration may occur only in the region of defect and only if there are adequate "stimuli" for such activity. This repair progress is initiated when the defect in cartilage reaches subchondral bone and bone marrow and causes bleeding from blood vessels. This leads to formation of hematoma and fibrin clot and encourages accumulation of certain morphogenetic proteins, and glycoproteins, growth factors released by the bone. Progenitor cells like mesenchymal stem cells and fibroblast migrate from the surrounding cartilage, bone, underlying bone marrow, and synovium into the repair site in about two to five days. These play an important role in initiating and maintaining the repair process. After about a week of infiltration of stem cells, the fibrin network from the blood clot serves as a scaffold for growth and differentiation of mesenchymal stem cells.Since 1965, in which Smith successfully cultivated cartilage cells in vitro, cartilage tissue engineering charicterized as cultivating cartilage seed cells in vitro and tranplanting them to the body developped gradually. In 1987, a biological engineering group meeting of the National Science Foundation was held in Washington, a noun called "tissue engineering" was proposed. In 1988, tissue engineering was defined as "the application of principles and methods of engineering and life sciences toward fundamental understanding of structure-function relationships in normal and pathological mammalian tissues and the development of biological substitutes to restore, maintain, or improve tissue function". Especially in recent 10 years, cartilage tissue engineering has made great progress and gradually show the superiority of chondral defect repair.Both of fibrin gel and DBM possess the basic characteristics as a scaffold to culture cartilage seed cells, for their good biocompatibility, biodegradablity etc, and can be a carrier for the growth factors to slow down their release and function continuously. Fibrin gel has a large surface area/volume ratio and porosity, which not only promote the addhesion, proliferation and differentiation of chondrocytes by the big surface area, but also facilitate the transportation of nutrients between the surrounding tissue and cells. By adding tranexamic axid to slow down the degradation speed and synchronize the degradation of materials and cartilage formation. Moreover, cartilage active substances released during the DBM degradation advance the formation of cartilage.Biological engineering scaffolds must have the following properties: biodegradability, biocompatibility, large surface/volume ratio, mechanical strength and permeability to the nerves and blood vessels. Scaffolds for osteochondral tissue engineering should provide mechanical stability, while releasing specific signals for chondral and bone regeneration. Scaffolds should also have a completely interconnected porous network for cell migration, attachment, and proliferation.Currently, collagen and fibrin gels are the most commonly used biological carriers. The superior biocompatibility, weak immunogenicity and molecular structure of these constructs facilitate the combination and adhesion of cells. Both fibrin gel and demineralized bone matrix (DBM) possess the basic characteristics necessary for use as scaffolds to culture cartilage seed cells, due to their good biocompatibility, biodegradablity. These materials can act as carriers for growth factors to continuously inhibit their release and function. OBJECTIVE:The feasibility and efficacy of using compound material made of fibrin glue and demineralized bone matrix as a scaffold for cartilage tissue engineering were investigated. So was the efficacy of the injectable scaffold of FG/DBM to delay OA. METHOD:1. Chondrocytes of rabbit knee joint cartilage were isolated, cultured and passaged in vitro.2. The third passage chondrocytes were seeded in prepared scaffolds after incubation for 4 weeks in vitro.3. Chondrocytes/fibrin glue/demineralized bone matrix constructs were implanted in the trochlear groove of rabbits. The specimens were taken at the 4th,8th and 12th weeks.4. Prepared the OA model of rabbit knee joints.5. Gross morphology.6. Hematoxylin-eosin staining.7. Masson staining.8. Typeâ…¡collagen immunohistochemistry reaction.9. The repairing effect was evaluated with a Wakitani score.10. Injected compound scaffold of FG/DBM/chondrocytes to the rabbit knee without ACL and menicus.11.Made a new score to evaluate OA.RESULT:1. Successful to isolate, culture and passage the chondrocytes.2. Successful to made the OA model of rabbit knee joints.3. The chondrocytes were spherically shaped, and more cells were distributed around the DBM particles.4. Some ivory tissues began to fill the caves 4 weeks following the implantation, and the caves were fully filled with a smooth surface at 12 weeks. Observations under microscopy revealed more typeâ…¡collagen than at 4 weeks and many chondrocytes at 8 weeks. Cartilage lacunas were observed at 12 weeks. 5. Made a new score to evaluate OA according to the Wakitani score and Outerbridge Score.6. Injection of the compound material and chondrocytes can delay the progress of OA.CONCLUSION: The overall results indicated that a combined material made of fibrin glue and demineralized bone matrix can be used as a scaffold for cartilage tissue engineering.