text: Researchers are able to take the tissue from a donor or cadaver, lyse and kill the cells within the tissue without damaging the extracellular components, and finish with a product that is the natural ECM scaffold that has the same physical and biochemical functions of the natural tissue.  After acquiring the ECM scaffold, scientists can recellularize the tissue with potent stem or progenitor cells that will differentiate into the original type of tissue.  By removing the cells from a donor tissue, the immunogenic antibodies from the donor will be removed.  The progenitor cells can be taken from the host, therefore they will not have an adverse response to the tissue.  This process of decellularizing tissues and organs is still being developed, but the exact process of taking a tissue from a donor and removing all the cellular components is considered to be the decellularization process. The steps to go from a decellularized ECM scaffold to a functional organ is under the umbrella of recellularization.  Because of the diverse applications of tissue in the human body, decellularization techniques have to be tailored to the specific tissue being exercised on. The researched methods of decellularization include physical, chemical, and enzymatic treatments.  Though some methods are more commonly used, the exact combination of treatments is variable based on the tissue’s origin and what it is needed for.
  As far as introducing the different liquidized chemicals and enzymes to an organ or tissue, perfusion and immersion decellularization techniques have been used. Perfusion decellularization is applicable when an extensive vasculature system is present in the organ or tissue. It is crucial for the ECM scaffold to be decellularized at all levels, and evenly throughout the structure.  Because of this requirement, vascularized tissues can have chemicals and enzymes perfused through the present arteries, veins, and capillaries. Under this mechanism and proper physiological conditions, treatments can diffuse equally to all of the cells within the organ. The treatments can be removed through the veins at the end of the process. Cardiac and pulmonary decellularization often uses this process of decellularization to introduce the treatments because of their heavily vascularized networks. Immersion decellularization is accomplished through the submersion of a tissue in chemical and enzymatic treatments. This process is more easily accomplished than perfusion, but is limited to thin tissues with a limited vascular system.