| Background: Articular cartilage lesions that caused by trauma, osteoarthritis and osteochondritis diseases are commonly encountered medical problem. Because of the avascular nature of the articular cartilage and the fact that differentiated chondrocytes are trapped within matrix, mobilization of regenerative cells to areas of injury is insufficient, the capacity of cartilage to heal after sustaining damage is very limited, even fail to heal spontaneously. It is a well known phenomenon that a defect which is confined to the substance of articular cartilage tissue itself (partial thickness or chondral lesion), they lead to irreversible damage and fail to heal spontaneously. However, if the defect penetrates the underlying layer of subchondral bone (full thickness defects or osteochondral lesion), a limited spontaneous repair reaction occurs, with cells originating from the bone marrow and synovial membrance, but this generally leads to the formation of less durable fibrocartilage rather than hyaline cartilage. Numerous strategies currently in clinical treatment are lavage and debridement, microfracture techniques, subcondral drilling, transplantation of chondrocytes, periosteal or perichondrial grafts, transplantation of osteochondral autografts or allografts. So many methods that mean no effective clinical treatment that can restore a damaged cartilage surface and prevent the outcome of degenerative joint disease except joint replacement. Cartilage tissue engineering by means of cell amplification, which can be obtained and isolated from small biopsy specimens, and seeded onto biodegradable polymers scaffold as cell-polymer constructs to reconstruct the function of damaged tissue. But the application of autogenous chondrocytes is limited by donor-site morbidity and the availability of tissue. The research of stem cells (i.e., bone marrow-derived steml cells MSC)have given rise to the new field of tissue engineering. Depending on the characteristic of self-proliferation and multidifferentiation, it was possible that fabrication osteochondral composite using scaffolds of different materials and MSCs. With the above as an experimental base, we use small composite grafts fabricated by special kind of synthetic biodegradble polymers, (i.e., double-layer PLGA) as scaffold onto which seeded MSCs that were culture-expanded either in the presence of TGF-pl, bFGF and dexamethasone or transfected adHGF gene for chondrogenic defferentiation, and then implanted into the rabbit model to repair aryicular cartilage damage.Methods: Bone marrow-derived stem cells of a five-month-old New Zealand White rabbit were isolated with a density gradient and culture-expanded in DMEM supplemented with 15% FBS at 37 , 5%CO2 atmosphere incubator. The nonadherent cells were removed along with the change of culture medium. The 5th passage MSCs were treated according the groups: (1) common mediea (DMEM with 15%FBS). (2) DMEM with 15%FBS containing TGF-pl at 10ng/ml, bFGF at 25ng/ml and dexamethasone at 10-7M, as induced MSC. (3) Adenovirus carrying hypotocyte growth factor cDNA(adHGF) transduced MSC, as gene modified MSC. (4) adHGF transduced MSC which was induced with cytokines. Rabbit chondrocytes served as the control. The morphological change in five kinds of cells was observed with phase chontrast mocroscope. Cell proliferation capacity was tested by MTT; quantitative secreation of GAG was tested by alcin blue; collagen I, II were tested by immunohistochemical and RT-PCR; FCM for the transduction efficency after adGFP modified MSCs; and ELISA for HGF expression of adHGF transfected MSCs. The morphology of double-layer PLGA scaffold and MSCs was obsrevied with SEM. MSCs exposed to different treatments were loaded into PLGA double-layer scaffold(diameter 3.5mm, thickness 3 to 4 mm)to form composite osteochondral grafts, which were incubated for 24 hours at 37 , 5%CO2 incubator, and then implanted respectively into subcutaneous pockets on the backs of 5 five-weeks-old female athymic mice. The composites were harvested...
|
PDF Full Text Request