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The Host Response to Grafts and Transplantation Immunology
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Most of the grafts that are transplanted are allografts, or grafts between individuals of the same species. Such individuals are not genetically identical unless they are identical twins. Allografts can come from twins, parents, relatives, or unrelated individuals. Transplantation of grafts between identical siblings, or between mice of the same strain, are termed syngeneic. Not many humans needing grafts are lucky enough to have an identical twin to supply grafts. Such grafts, when available, are not recognized as foreign by the host because they are the same as self, i.e, not foreign. The term autograft means that the grafted tissue is from the same individual, such as skin transplanted from one part of the body to cover a part that has been damaged by a burn. Finally, the term xenograft refers to grafts between individuals of different species. Successful xenografting is a desirable goal since there are not enough human organs to be transplanted into all of the individuals that need an organ graft. Miniature pigs, because they are of a similar size with a similar circulation to that of humans, have been farmed to use as organ donors for humans. Recently, ethical review boards have blocked transplantation of organs between animals and humans because of the possibility of transmission of animal retro viruses to humans. An example of such a transfer is the human immunodeficiency virus that causes AIDS. AIDS is believed to have been transferred from chimpanzees, in whom it does not cause disease, to humans, in whom it does.
Craniofacial Regeneration—Bone
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Laura Guadalupe Hernandez, Lucia Pérez Sánchez, Rafael Hernández González, Janeth Serrano-Bello
Allografted bone is harvested from human donors, mainly cadavers. Its ready availability in various shapes and sizes, avoidance of the need to sacrifice a host structure and no donor-site morbidity are some of the advantages. The disadvantages include infection such as transmission of Human Immunodeficiency Virus (HIV), Hepatitis C Virus (HCV), Human T-Lymphocytic Virus (HTLV), unspecified hepatitis, tuberculosis and other bacteria has been documented for allografts (mainly from those containing viable cells) and immune resistance (Henkel et al. 2013).
Animal Models of Meniscal Repair
Published in Yuehuei H. An, Richard J. Friedman, Animal Models in Orthopaedic Research, 2020
Jan Klompmaker, René P. H. Veth
The meniscus is an important structure of the knee joint and is essential in preventing osteoarthritis. Every effort to preserve this structure should be made. When this is not possible, meniscal replacement is a good alternative. Allografts can provide good results in the short term but have important disadvantages. Synthetic grafts have, at least in theory, fewer disadvantages but until now none has proven to be able to match the results of allografts. Future research will have to improve their qualities in term of biomechanics, induction of fibrocartilage and others. Several animal species can be used for meniscal research but the dog may be the preferable animal.
Cell homing strategy as a promising approach to the vitality of pulp-dentin complexes in endodontic therapy: focus on potential biomaterials
Published in Expert Opinion on Biological Therapy, 2022
Elaheh Dalir Abdolahinia, Zahra Safari, Sayed Soroush Sadat Kachouei, Ramin Zabeti Jahromi, Nastaran Atashkar, Amirreza Karbalaeihasanesfahani, Mahdieh Alipour, Nastaran Hashemzadeh, Simin Sharifi, Solmaz Maleki Dizaj
As previously mentioned, dental pulp tissue engineering regenerates pulp-like tissue with the help of biomaterials to treat inflamed pulp or necrosis. In this strategy, stem cells play a crucial role in tissue regeneration. To date, various studies have been performed on the regeneration of pulp and dentin tissue with the help of dental stem cells transplanted into damaged tooth tissue of large and small animals [2,52]. However, the results of studies have shown that cell-based therapy has many problems in clinical translation and goes through complex steps from cell isolation to pulp tissue preparation. Also, allograft transplantation has the problem of cell survival, high cost, rejection of the cell by the recipient tissue, pathogen transmission, and tumorigenesis. In this case, this technique cannot be an excellent alternative to dental implants and routine dental tissue treatments [53,54]. The cell homing approach solves the problems of cell-to-tooth transplantation. It regenerates dentin or pulp by invoking endogenous host stem cells into damaged tooth tissue with the help of biological signaling molecules [55,56]. This approach is clinically easier than cell transplantation because it does not require isolating and preparing stem cells in vitro [17,57,58]. The cell homing strategy involves bioactive scaffolds with signaling molecules injected into the root canal to recruit endogenous stem cells around the root, including PDLSCs, SCAP, and bone marrow stem cells (BMSCs) into an anatomic compartment of the root canal [6,59].
Comparison of hearing outcomes in patients with congenital aural atresia managed with canaloplasty and bone conduction hearing devices
Published in Acta Oto-Laryngologica, 2022
Sun A Han, Sang-Youp Lee, Moo Kyun Park, Jun Ho Lee, Seung Ha Oh, Myung-Whan Suh
The comparable hearing outcomes in the canaloplasty patients between this study and previous reports are of particular interest because in our patients the TM was reconstructed with a new type of graft material (Megaderm) rather than autologous tissue. A commercialized allograft has several advantages, including reduced invasiveness, as a retro-auricular incision and elevation/retraction of the RCG are avoided. The smaller incision and dissection preserve vascular circulation near the RCG bed, specifically, branches from the posterior auricular and occipital arteries. Moreover, there is no limit to the size and supply of the allograft, whereas the amount of autologous temporalis muscle fascia is limited. The disadvantage of allograft use is the risk for infection if the graft was harvested from a disease-ridden donor, as government regulations for preparing chemical and physical tissue may not be perfect. For instance, prion transmission cannot be fully prevented despite the processing of the graft with proteases, heat, ionizing radiation, and formaldehyde [14]. Allograft rejection is another concern. However, unlike chronic otitis media, in CAA there is no underlying middle ear infection, which would account for the absence of postoperative infection in our allograft-treated patients.
Application of PLGA nano/microparticle delivery systems for immunomodulation and prevention of allotransplant rejection
Published in Expert Opinion on Drug Delivery, 2020
Sanaz Keshavarz Shahbaz, Farshad Foroughi, Ehsan Soltaninezhad, Tannaz Jamialahmadi, Peter E. Penson, Amirhossein Sahebkar
Most common organs and tissues (including transplanted kidneys, liver, heart, corneal and musculoskeletal grafts) have been successfully transplanted. Long-term acceptance of allografts is the main goal of clinical transplantation. The obstacles to successful transplantation are immunologically mediated damage (termed allograft rejection), and adverse effects of immunosuppressant drugs [1]. Improvement in surgical techniques occurred in parallel with developments in the understanding of the immune mechanisms mediating allograft rejection and these developments enabled the first kidney transplant in 1963 [2–5]. The promise of improved immunosuppression and increased survival opened the door to the transplantation of other organs, including the heart, liver, pancreas, lung and small bowel [6–10].