Comparative Study Of The Level Of Vascularization In Tissue Engineering Scaffolds By Different Arteriovenous Bundles

Bone tissue engineering, as one of the important branch of tissue engineering, has been given great concern. With the progress of research, a significant problem that large bone can not be successfully constructed is proposed on the front of researchers.The size of tissue engineering bone constructed in vitro is usually smaller than 5×5×5 mm3. The causes of it may include low level of vascularization, insufficient supply of blood, nutrient deficiency of seed cells, metabolic products accumulation. So, the blood reconstruction has been recently highlighted.Under this circumstance, a professor proposed a new idea that scaffold should be vascularized firstly, and then mixed with osteoblasts to construct tissue engineering bone. And the researcher firstly built the animal mode about vascularizated tissue engineering bone on rats and found that the survival rate of osteocyte enhanced significantly in preliminary experiment. Meanwhile, the scaffold is also the research hot spot. Since the Souyris and Guillemin firstly used coral-transformed hydroxyapatite as implantation material, a great number of researchers have applied the coral as scaffold to bone tissue engineering. The coral from Sanya Hainan province, used by Mao tianqiu etc, is one of the ideal materials.Based on the previous researches, this study is composed with two parts:Experiment 1: feasibility study of treated coral as the scaffold material of vascularized tissue engineering bone.Objective: To test the physical and chemical properties of natural coral and the feasibility as the vascularized bone scaffold material. Methods: The coral, whose apertures are from 100μm to 300μm and porosity arranges from 70% to 90%, was made into oval shape blocks (6×8×10 mm3), and immersed in 5% sodium hypochlorite solution for 2 weeks, and boiled three times with 10 min in each time, and then followed by ultrasonication for five times with 10 min in each time. At last, it was dried in the oven (80℃, 24 h) and sterilized under condition of high temperature and high pressure (1.3 MPa, 131℃, 30 min). Evaluation methods included testing the changes of their general morphology, microstructure and compressive strength during the three stages. Results: There was no great change of compressive strength in different stages (7.07±0.32 MPa, 7.25±0.24 MPa, 7.25±0.13 MPa). After the coral was treated with physical and chemical methods, as well as by sterilization, most of foreign bodies were cleared and the surfaces and interspaces of porites became clean and smooth. Conclusion: The foreign bodies in coral surfaces and interspaces could be cleared by physical and chemical methods. There were no great changes about structure and compressive strength during the treatment. So it is safe to use the treated natural coral as the bone tissues engineering scaffold material. Experiment 2: Histological study of vascularized tissue engineering scaffolds by two arteriovenous bundles.Objective:To investigate the effect of prefabricated vascularized natural corals by flow-through and end-ligated arteriovenous bundles, and provide an experimental foundation for its possible application in vascularized bone tissue engineering through angiogenesis prior to bone formation. Methods:Three months male New Zealand rabbits weighing approximately 2000 g-2500g each were used in this study. In group A, a flow-through vessels between the femoral artery and vein were placed in the side groove of coral(n = 9). In group B, a ligated pedicle arteriovenous bundle at the end of femoral artery and vein was placed around the coral in the same manner (n = 9). The implants were wrapped by an ePTFE membrane. In group C, the coral was implanted under skin, no vessels were inserted (n = 3). Evaluation methods included gross morphological observations, and histological examination. Results:After 2, 4 and 6 weeks, new fibrovascular tissues growed around the surface and deep interspace of corals, majority of vessels distributed around the artery and vein. At 4 week, the coal has been completely encased by new granulation tissue. Histological examination showed new fibrovascular tissue proliferation was evident in group A, and sparse in group C. Conclusion:A vascularized coral could be constructed by inserting arteriovenous bundles, which was expected to be used in bone tissue engineering.