Chemistry: molecular biology and microbiology – Apparatus – Bioreactor
Reexamination Certificate
2000-11-17
2002-07-09
Beisner, William H. (Department: 1744)
Chemistry: molecular biology and microbiology
Apparatus
Bioreactor
C435S297200, C435S284100, C623S916000, C623S921000
Reexamination Certificate
active
06416995
ABSTRACT:
FIELD OF THE INVENTION
A variety of vascular grafts are commercially available and include mechanical, bioprosthetic, and cryopreserved and decellularized human and animal heart valves. In addition, non-valved vascular grafts made of expanded polytetrafluoroethylene (ePTFE), decellularized veins and arteries, and cryopreserved veins and arteries are available. Vascular grafts constructed from naturally occurring molecules, for example collagens, elastins, hyaluronins, etc. can be manufactured using tissue engineering techniques. Such vascular grafts, whether valved or non-valved can be used in clinical applications in an essentially cellularized on decellularized state. The current invention is directed at providing a device and process for recellularizing essentially acellular, i.e. avital, vascular grafts derived from human or animal sources or as constructed using any number of tissue engineering methodologies.
BACKGROUND OF THE INVENTION
Vascular grafts include a wide variety of natural and synthetic tubular structures that may or may not contain valves. Valves in these tubular structures are usually intended to direct the flow of blood (or other nutrient materials) in one direction by preventing the backward flow of this (these) liquid solution(s). Examples of valved tubular structures include aortic, pulmonary, and mitral valves present in the hearts of most vertebrate animals and veins used to return blood flow from the periphery of the body to the heart for recirculation. Vascular grafts constructed of synthetic materials include devices constructed from man-made polymers, notably Dacron and Teflon in both knitted and woven configurations such as those marketed by W. L. Gore, Inc. and Impra, Inc. where various forms of polytetrafluoroethylene (PTFE) are molded into a wide array of tubule structures (see for example U.S. Pat. Nos. 4,313,231; 4,927,676; and 4,655,769). The present invention does not involve vascular grafts derived from synthetic means and thus these types of vascular grafts will not be further discussed. Natural vascular grafts, taken in the context of this present invention, include valved and non-valved tubular structures obtained by methodologies broadly classified under the term “tissue engineering”. Notably, tissue engineered blood vessels such as described in U.S. Pat. Nos. 4,539,716, 4,546,500, 4,835,102, and blood vessels derived from animal or human donors such as described in U.S. Pat. Nos. 4,776,853, 5,558,875, 5,855,617, 5,843,181, and 5,843,180, and a pending patent application entitled “A Production Technology for Commercial Scale Decellularization Processing of Soft-Tissue Engineered Medical Implants” (patent application Ser. No. 09/528,371 incorporated herein in its entirety) are known. The present invention involves vascular grafts derived using a specific process associated with tissue engineering as well as a bioreactor device to be used in this process.
Tissue engineered natural vascular grafts, hereinafter vascular grafts, can be manufactured by processing of natural vascular grafts (veins, arteries, heart valves, etc.) with the objective of removing the cellular elements without damaging the matrix structure of that tissue-a “reductionist” approach. This approach is generally referred to as decellularization and is the subject of several patents, of which U.S. Pat. No. 4,801,299 by Brendel and Duhamel is considered as one of the earliest such patents, and pending patent applications as described above. Decellularization of tissues such as vascular grafts can be readily accomplished by incubating tissues in the presence of detergents, both anionic and nonionic, with and without digestion of nucleic acids using DNase and RNase enzymes, or more recently a commercially available recombinant endonuclease called Benzonase™. The decellularized tissues typically retain the structurally important molecules such as collagens, elastins, proteoglycans, and associated polysaccharides such as the hyaluronins, (see U.S. Pat. No. 5,855,620 as an example). Specifically, the Brendel & Duhamel patent (U.S. Pat. No. 4,801,299) defines decellularization as “A method of treating body tissue to remove cellular membranes, nucleic acids, lipids, and cytoplasmic components and form extracellular matrix having as one major component collagens and making said body tissue suitable for use as a body implant . . . ” The Klement, Wilson, and Yeger patent (U.S. Pat. No 4,776,853) defines decellularization as “A process for preparing biological material for implant in a mammal's cardiovascular system, respiratory system or soft tissue by removing cellular membranes, nucleic acids, lipids, and cytoplasmic components and forming an extracellular matrix having as major components collagens and elastins . . . ” A devitalization process/method (i.e. producing an avital tissue) would be defined for purposes of the present invention as a process or method of treating body tissue to remove cellular membranes, nucleic acids, lipids, and small molecular weight cytoplasmic components forming an extracellular matrix having as one major component collagens, elastins, and high molecular weight polysaccharides. By leaving the high molecular weight cytoplasmic molecules, for example actins, complete decellularization would not be obtained and the tissue would be considered to be devitalized. In specific instances, patented technologies have suggested that such decellularized vascular grafts can function for extended periods of time following clinical implantation without the need for recellularization. Indeed some such technologies have treated tissues with high concentrations of the anionic detergent sodium docecylsulfate (SDS) to attempt to prevent recellularization of implanted vascular grafts (U.S. Pat. Nos 4,776,853 and 5,558,875).
Tissue engineered natural vascular grafts have also been constructed using a “constructionist” approach. This approach involves the extraction of natural cellular and matrix components to obtain purified (or partially purified) fractions and then using these fractions to reconstruct a vascular graft from individual components. Alternatively, specific components of a vascular graft, for example collagen(s), can be obtained using recombinant DNA technologies and such highly purified and homogeneous materials used in the construction of natural vascular grafts via tissue engineering. Methods and materials for 3-dimensional cultures of mammalian cells are known in the art. See, e.g., U.S. Pat. No. 5,266,480. Typically, a scaffold is used in a bioreactor growth chamber to support a 3-dimensional culture, see for example U.S. Pat. No. 6,008,049. The scaffold can be made of any porous, tissue culture compatable material(s) into which cultured mammalian cells can enter and attach.
Both the reductionist and constructionist approaches are designed to provide an acellular matrix (unless the constructionist approach also intends to incorporated living cells in the matrix during the construction of the tissue engineered vascular graft) that can be used directly as an acellular graft. Alternatively the acellular matrix can be reseeded with specific cell populations to provide a recellularized graft (see for example, U.S. Pat. Nos. 5,792,603; 5,613,982; 5,855,617; 5,843,180; 5,843,181; and 5,843,182). One U.S. Pat. No. 5,855,617 describes the use of fibroblast growth factor to attract fibroblast cells to migrate into a substantially non-immunogenic vascular graft.
Vascular tissues such as an aortic heart valve contain a limited number of cell types. For aortic valves, these cell types include endothelial cells that line the luminal surface of the valve providing for a smooth, non-thrombogenic, surface for efficient blood flow. These cells are known for their role in nitric oxide (a vasodilating agent), expression of vasoconstricting endothelins, and smooth muscle proliferative mitogens and cytokine (Interleukin-1, tumor necrosis factor, Interleukin 6, Interleukin 8, Monocyte Chemoattractant protein-1, granulocyte monocyte-CSF, and Monocyte chemoattractant an
Beisner William H.
Bio Science Consultants, L.L.C.
Matney, Jr. W. Jackson
Milbank Tweed Hadley & McCloy LLP
LandOfFree
Bioreactor mediated recellularization of natural and tissue... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bioreactor mediated recellularization of natural and tissue..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bioreactor mediated recellularization of natural and tissue... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2910857