Investigation Of The Tissue-engineered Acellular Vascular Scaffold

Cardiovascular diseases are prevalent and debilitating lesions that affect the quality of life among populations worldwide. Large numbers of patients suffers from diseases of the vascular system, resulting in a clear clinical need for developing functional arterial replacements. As a novel solution, tissue engineering has made significant progress toward the creation of vascular grafts for the repair of damaged or malformed vessels. It aims to address these lesions by integrating engineered, living substitutes with their native counterparts in vivo. For such a purpose, competent vascular scaffolding materials are essential. To date, two major categories of vascular scaffolding materials have been employed: synthetic polymers and natural collagen derivatives. Compared with synthetic polymers, natural acellular vascular scaffolds have the advantages of preserving ECM proteins important for cell attachment and the desired mechanical properties which made it the most intriguing materials used to create scaffolds for tissue engineering vascular applications. Different decellularization methods have been developed to fabricate acellular vascular scaffolds for the purpose of tissue engineering blood vessel, mostly comprising physical methods,detergents and zymatic extraction methods. Recent studies revealed that vascular grafts that had been decellularized using detergents were more resistant to cellular in-growth than those treated with enzymatic extraction. Otherwise, there are also flaws of the enzymatic extraction method; long digestion time may cause a biomechanical damage of the biomaterials and short time treatment results in a residue of the original cells. Then finding an ideal way to produce acellular vascular scaffolds becomes an interesting subject.As with any form of allografts, the risks of disease transmission from either the donor to recipient or from environmental contamination acquired during retrieval and processing of the graft must be considered. Historically, two methods have been commonly applied for the sterilisation of allograft biomaterials; chemical sterilisation utilising ethylene oxide gas and sterilisation with ionising radiation. Whilst both of these techniques have been demonstrated to be effective sterilisation procedures concerns have been raised about their potentially deleterious effects on important properties of the grafts. For these reasons, it is desirable to apply a high-level disinfection or sterilisation procedure to such grafts following retrieval and processing.On the same time, it is also suggested that following acellular treatment, the structure of the acellular scaffold is still compact. How to open up the collagenous matrix and subsequently allow cells to enter and migrate into the scaffold of their own accord without altering the biological or mechanical properties of the scaffold, this will also be the subject for our works. Finally, we want to find out a preservation protocol after fabrication of the acellular vascullar scaffolds to meet the emergency request of the clinical and scientific research.Object:1.This study was to find a new way for tissue engineering vascular scaffold fabrication by investigating the effect of ultrahigh pressure and freezing thawing treatment on natural vessels and to observe the decellularization results of different concentration nuclease solutions after the natural vessels being treated by repeated freeze thawing and ultrahigh pressure.2.To observe the effects that 0.1% Peracetic Acid had on the biological features of the acellular vascular scaffold by analyzing the biocompatibility and biomechanics of the dealed scaffolds treated by 0.1% Peracetic Acid.3.Various intensities of ultrasonication was tested in order to observe the effects that ultrasonication had on the biological features of the acellular vascular scaffold by analyzing the biocompatibility and biomechanics of the dealed scaffolds.4.To investigate the effects of a Freeze-Drying technique preservation protocol on the biocompatibility and biomechanical properties of acellular vascular scaffold.Results and conclusions:1 . The resulting scaffold has been shown to be biocompatible with biochemical and mechanical properties similar to those of natural vessels following ultrahigh pressure and repeated freeze thawing treatment, the vessels were completely cell free when they were treated by nuclease solutions in a fairly low concentration with short treatment time. This tissue processing of decellularization by ultrahigh pressure and repeated freeze thawing treatment can decrease both the treatment time and concentration of nuclease solutions remarkably; it may provide a new idea and method for fabrication of bioscaffolds.2.From the histological and ultrastructural analysis, we can see that treated by 0.1% Peracetic Acid, the main performance indexes of the acellular scaffold changed unremarkably in compared with normal blood vessels. This tissue processing of disinfection by 0.1% Peracetic Acid treatment has not obvious effect on the biocompatibility and biomechanics of the acellular scaffold, and it can be an alternative of disinfector for the acellular bioscaffold preparation.3.Ultrasonication treatment with the intensity of 300W and a pulse time of 1 s for a total of 1 min was found to be the optimal treatment. This process did not have significant effect upon the biochemical constituents, nor did it denature the collagen. Moreover, the acellular sonicated scaffold retained the essential biomechanical characteristics of the native tissue. These findings show us that ultrasonication can provide a novel method to enhance the recellularization of decellularized natural tissues.4.From the vitro investigation we find that treated by Freeze-Drying technique preservation protocol, the main performance indexes of the acellular scaffold changed unremarkably in compared with normal blood vessels. This tissue processing of Freeze-Drying technique preservation protocol has no obvious effects on the biocompatibility and biomechanics of the acellular scaffolds, and it can be a good preservation protocol for the acellular bioscaffold preparation.Summary: In our studies, a novel solution for the fast fbrication, simple sterilization and long preservation of the tissue engineered acelluluar vascular scaffolds is found out. Meanwhile, we also investigate a way to initially solve the problem of opening up the collagenous matrix and subsequently allowing cells to enter and migrate into the scaffold of their own accord without altering the biological or mechanical properties of the acellular vascular scaffold.