Decellularization of tissues and organs

192 CMJ Review June 2020, Volume: 42, Number: 2 Cumhuriyet Medical Journal 192-197 http://dx.doi.org/10.7197/cmj.vi.609592 Decellularization of tissues and organs Dokuların ve organların hücresizleştirilmesi Nevra Pelin Cesur, Volkan Yalman, Nelisa Türkoğlu Laçin Yıldız Technical University, Molecular Biology and Genetics Department, Istanbul, Turkey Corresponding author: Nelisa Türkoğlu Laçin, MD., Yıldız Technical University, Molecular Biology and Genetics Department, Istanbul, Turkey E-mail: Received/Accepted: August 22, 2019 / July 06, 2020 Conflict of interest: There is not a conflict of interest. SUMMARY Decellularized tissues and organs have been successfully used in various tissue engineering and regenerative medicine applications. A biological scaffold obtained from the extracellular matrix can be produced by a variety of decellularization methods that effectively remove cells from the tissue to be treated. Decellularization methods is changed according to the target structure of tissues and organs. These methods can be summarized with chemically, physically, enzymatically and using Supercritical Fluid Extraction (SFE) ways. Each of these methods affects the biochemical composition in the structure of the remaining extracellular matrix (ECM), the structure of the tissue (ultrastructure), and the mechanical behavior. In this article, the most commonly used decellulization methods are introduced and their effects on biological tissue scaffold materials are discussed. Keywords: Extracellular matrix, decellularization, supercritical fluid extraction (SFE) Nevra Pelin Cesur Volkan Yalman Nelisa Türkoğlu Laçin ORCID IDs of the authors: N.P.C. 0000-0003-3979-6053 V.Y. 0000-0001-8267-9712 N.T.L. 0000-0003-3176-0902 ÖZET Hücresizleştirilmiş dokular ve organlar çeşitli doku mühendisliği ve rejeneratif tıp uygulamalarında başarıyla kullanılmıştır. Hücre dışı matristen elde edilen biyolojik bir iskele, tedavi edilecek dokuya ait hücreleri etkili bir şekilde uzaklaştıran çeşitli hücresizleştirme yöntemleri ile elde edilebilir. Hücresizleştirme yöntemleri, doku ve organların hedef yapısına göre değiştirilir. Bu yöntemler kimyasal, fiziksel, enzimatik ve süper kritik akışkan ekstraksiyonu (SFE) yöntemleri ile özetlenebilir. Bu yöntemlerin her biri, elde edilen hücre dışı matrisin (ESM) yapısındaki biyokimyasal bileşimini, dokunun yapısını (altyapı) ve mekanik davranışını etkiler. Bu makalede, en sık kullanılan hücresizleştirme yöntemleri üzerinde durulmuş ve bu yöntemler ile elde edilen biyolojik doku iskeleleri üzerindeki etkileri tartışılmıştır. Anahtar sözcükler: Hücre dışı matris, desellulizasyon, süperkrik akışkan ekstraksiyonu (SFE) INTRODUCTION In recent years; insufficiency of organs and tissues is one of the most critical health problems for humanity. Even many patients are waiting for donors, and the donor waiting list continues for a long time. Generally, the workflow begins with the transplantation of organs from donors. However, this procedure is not as easy as it seems. Because the compatibility of the tissues should be ensured, and acute rejection of the implanted graft should be prevented 1. Therefore, one of the ways to solve this problem is the development of artificial tissues and organs by the help of tissue engineering (TE). Tissue engineering is composed of three main factors; signal molecules, cells, and scaffolds complemented with each other. The piers are two types, synthetic and natural. Additionally; TE scaffolds, whether natural or synthetic, must be 193 mechanically stable, biocompatible, sterile, porous, and of adequate strength 2. However, maintaining the complexity of the cell microenvironment causes many difficulties in the use of synthetic scaffolds. Therefore, studies on the extracellular matrix (ECM) are increasing dramatically in all areas of the world 3. The extracellular matrix is the main part of the tissue without the cells on it with a highly organized structure. Collagen, elastin, fibronectin, laminin, glycoprotein, proteoglycan and glycosaminoglycan are the main macromolecular components of the ECM structure. The composition of ECM determines the mechanical and biochemical behavior of the tissue or organ. The mechanical behavior of a decellularized tissue/organ is critical for the re-celling procedures. It affects the proliferation efficiency of the cells on it. Thus, the combination and amount of the macromolecular components for each tissue is unique and critical for the determination of the cell fate. In addition, ECM mediates many functions such as cell growth, migration, differentiation, survival. It also plays protective and supportive role for tissue formation and rearrangement of dynamic cellular behavior 4. On the other hand; natural tissue scaffolds can be obtained by decellularization technology. The use of decellularized tissue matrices instead of tissue scaffolds prepared with synthetic materials is critical due to the ability to mimic the 3D natural structures of tissues while maintaining the biomechanical, structural and biochemical properties of the ECM 3. The primary purpose of the decellularization process is to ensure the removal of cells and cell contents (genetic materials such as DNA or RNA) from the ECM 5. In addition, the resulting ECM will prevent the formation of an immunological and thrombogenic reaction when combined with the recipient's own stem cells. In short, using decellularized ECM, it would be possible to produce personalized tissues. Moreover, decellularization can be applied to the entire organ and various tissue fragments. Especially in the literature, there are many successful studies on heart, blood vessels, cartilage bone, adipose tissue, small intestine, umbilical cord and liver6,7. Figure 1 summarizes almost all types of processes in decellularization and 4 recellularization techniques . Figure 1: Decellularization and recellularization processes Decellularization is performed using a wide range of techniques which are mainly consisting of physically, chemically and enzymatically treatment methods 8,9. Each of these methods affects the biochemical composition, the ultrastructure of the tissue, and the mechanical behavior of the remaining extracellular matrix (ECM) structure. Additionally, obtained ECM by decellularization has also been formed an antiinflammatory, immune response which can be associated with a reduced risk of rejection 10,11. Although there is no universally accepted standard for the decellularization processes, if no cell nuclei was determined by using various staining methods after the decellularization processes, and amount of double-stranded DNA is less than 50 ng for per mg of extracellular matrix, and the length of doublestranded DNA is less than 200 bp, this tissue can be evaluated as decellularized 8. Deccellularization strategies Physical methods Physical methods used to facilitate decellularization mainly include freezing, direct pressure, sonica (...truncated)