Induction Of Axial Vascularization In An Bovine Cancellous Bone Matrix Using An Arteriovenous Loop

Bone defects represent a medical and socioeconomic challenge. Among so much established treatment of bone defects, autologous bone grafts are still considered as the gold standard for reconstruction of extended bone defects.However, the clinical use of autologous osseous transplants is limited by a considerable donor site morbidity that increases with the amount of harvested bone. The generation of bioartificial bone tissues may help to overcome the problems related to donor site morbidity and size limitations. Different types of biomaterials are applied for reconstru-ctive indications and receive rising interest. While reconstruction of small to moderate sized bone defects using engineered bone tissues is technically feasible, and some of the currently developed concepts may represent alternatives to autologous bone grafts for certain clinical conditions, the reconstruction of large volume defects remains challenging.Adequate vascularization is a prerequisite for formation of high quality bone. When in vitro engineered cellular constructs are transferred in vivo they have to rely on processes like interstitial fluid diffusion, Which often limits the survival of cells in the center of large cell-containing constructs. Cell labeling experiments disclosed a considerable loss of osteoblasts within the first week following transplantation in porous cancellous bone matrices. Which represent a relevant limitation of many tissue-engineering approaches, particularly when larger volumes of tissues are generated. Therefore the induction of vascularization in biomaterials prior to cell transplantation will help to increase the initial survival and engraftment of transplanted cells. This strategy is so called the prevascularization of scaffolds.One of an other major challenges in tissue engineering today is the generation of large vascularised three-dimensional structures.This involves the creation of both a microvascular network and a macroscopic circulation with internal diameters greater than 1mm , to permit reliable microsurgical transplantation.Here we present a novel approach for induction of axial vasculari-zation in preformed mechanically stabile matrices suitable for engineering of bone tissues, including a porous processed bovine cancellous bone matrix and an AV loop as vascular carrier. The axial type of vascularization is the opposite of the random pattern type of vascularization, which means that one vascular axis provides blood supply to a given volume of tissue. Therefore, after the completion of revascularization, the engineered tissue may be transferred and anastomosed to a blood supply and venous drainage at the defect site by microsurgical technique, at the same time it is associated with minimal donor site morbidity. In this study, dissecting of the vessels in the groin of rats under an operative microscope and then interposing the vessels between the proximal stumpts of the other side femoral artery and vein.An arteriovenous loop was created.The other rats without vascular implantation were served as control group. After 2,4 and 8 weeks of operation , capillary vessel ink infusion,histological examination and micrangium density were conducted to observe angiogenesis .Cancellous bone matrixes in experimental group gained better effect in the volume of new capillary vessels , especially in 8 weeks . At this point, the new formed vessels tend to be mature and integrate into network. capillaries sprouted from arteriovenous loop were also significant .This study shows that the experimental pattern is a feasible and effective approach to induce vascularization in bovine cancellous bone by using an arteriovenous loop . As a new strategy of pre-vascular, it perhaps eventually be able to create functional bioartificial bone tissues .