Precision medicine in oncology: An overview
Debmalya Barh in Precision Medicine in Cancers and Non-Communicable Diseases, 2018
A xenograft is the transplant of one tissue to another species. Patient-derived xenograft (PDX) is transplanting cancer tissue of one individual to another species and aims to investigate the molecular characteristics, drug response, and the aggressiveness of the tumor formation. The most common application of PDX is transplanting the cancer tissue from a patient to a nude mouse with a suppressed immune system and obtaining information about histology, genomic structure, cellular heterogeneity, and drug responsiveness of the tumor. A treatment approach can be tested on this mouse model and the potential outcome of the treatment can be anticipated. It is an important development regarding personalized medicine for being an in vivo study at the single-patient level (Cho et al., 2016).
Medicolegal aspects of death
Jason Payne-James, Richard Jones in Simpson's Forensic Medicine, 2019
Xenotransplantation is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenografts or xenotransplants. Advances in xenotransplantation have the potential to resolve the issue of organ shortages. Organs or tissue such as heart valves, corneas, hearts and kidneys have been explored for potential as xenografts. However, such procedures may meet with a degree of concern from the public. Grafting of animal tissue into humans has always seemed tempting and clinical trials have been performed with some success. But there is, for example, considerable difficulty with cross-matching the tissues and considerable concern about the possibility of transfer of animal viruses to an immunocompromised human host. Strains of donor animals, usually pigs, are being bred in clinically clean conditions to prevent viral contamination, but there is still no guarantee of a close or ideal tissue match. There has also been an increasing interest in the development of patient-derived xenograft (PDX) models where human tumours are xenotransplanted into immunocompromised mice and such models act as translational tools in preclinical studies of cancer treatments. It is essential that clear protocols are in place for the study of the many aspects of xenotransplantation and for the introduction of such xenografts into the clinical setting. Such protocols must take into account the variable religious and cultural sensitivities which will influence individuals’ perception of such practices.
Basic implantology – An American perspective
John Dudley Langdon, Mohan Francis Patel, Robert Andrew Ord, Peter Brennan in Operative Oral and Maxillofacial Surgery, 2017
Autografts are the preferred source of bone material due to the lack of antigenicity of the graft material. In addition, we can use Allografts that are obtained from a human cadaver. The clinical success of these grafts is well proven. The advantage of allografts is that there is not an additional surgical procedure to obtain the bone. Xenografts are grafts from one species to another, e.g. bovine bone; they are useful when mixed with the patient’s blood. Alloplastic grafts are synthetic bone substitute that may act as a framework for bone formation. Bone morphogenic protein (BMP) has recently been approved by the U.S. Food and Drug Administration for use in bone grafting. These molecules act to signal stem cells that migrate to the site of the graft and differentiate into osteoblasts which lay down new bone.
Advances in surgical strategies for prolapse
Published in Climacteric, 2019
A. Giannini, M. Caretto, E. Russo, P. Mannella, T. Simoncini
Reconstruction of a failed pelvic floor can be obtained through re-creation of an anatomical support that resembles as much as possible the original. However, there is no indication for repairing an asymptomatic POP as an isolated procedure where surgical correction is of uncertain benefit and adds perioperative and postoperative risks. The surgical repair techniques are classified as ‘native tissue repair’ when only pelvic organ support tissues are used and as ‘augmented repair’ when some other material (prosthesis or graft) is used to reinforce the defective support system. Prostheses are classified as meshes, implants, and tapes (slings). Grafts are classified as autologous grafts, allografts, and xenografts. Today, synthetic polypropylene mesh is the most commonly used reconstructive material in surgical augmented repair of POP17.
Patient and family expectations of beta-cell replacement therapies in type 1 diabetes
Published in Islets, 2018
Akitsu Kawabe, Shinichi Matsumoto, Masayuki Shimoda
XIT is islet transplantation from other animals, commonly pigs, to humans. XIT would resolve many of the difficulties associated with AIT, including immediate availability and unlimited supply of islets. However, xenografts are associated with immunological rejection and potential risk of the transmission of viral infections. Accordingly, research and clinical applications using islets derived from designated pathogen-free pigs with an immunoisolating membrane or hydrogel have proceeded to minimize the infection risk and prevent immunological rejection. Some clinical trials have already been conducted to assess the effect and safety of clinical pig XIT.19,20 These trials indicated a certain effect, such as the reduction of unaware hypoglycemia events in unstable T1DM patients; in addition, no transmission of retroviruses and microorganisms was reported. Conversely, because the current encapsulation technology may deteriorate islet function, the main endpoint of achieving insulin-free status has not yet been reached. In this survey, XIT was well accepted and was the second choice option after IPS. Patients reportedly prefer to receive a new organ from a donor of the same species, especially under circumstances in which a human organ was supposed to be unavailable.21,22 Accurate information about xenotransplantation could help patients to accept these treatments. In our present survey, the advantages of XIT, such as its greater availability, might have appealed to the respondents.
An improved surface for enhanced stem cell proliferation and osteogenic differentiation using electrospun composite PLLA/P123 scaffold
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Gebremariam Birhanu, Hamid Akbari Javar, Ehsan Seyedjafari, Ali Zandi-Karimi, Mehdi Dusti Telgerd
Currently autologous bone grafting is commonly used as a gold standard for the treatment of critical-sized bone defects [5]. But autograft have drawbacks like infection, scarring, blood loss [3], donor site morbidity and secondary damage to the patient, plus the source is limited [6]. Similarly, use of allograft or xenograft is associated with high risks of infectious diseases and rejection by the host immune system [7]. The need for alternative approaches to develop reliable bone grafts reducing the risks and expenses of using autografts and allografts [8] is increasing. Bone tissue engineering is an emerging technology which brings a solution for this problem [7]. It uses the knowledge of life sciences and engineering to support the function of injured bone tissue via a triad of artificial extracellular matrix (ECM) scaffold, stem cells that can become osteoblasts and osteogenic agents [9,10]. Hence, scaffold, cells and growth factors are the three main components of bone tissue engineering [11]. Development of a tissue engineering scaffold as an artificial bone matrix is crucial for regenerating bone tissue [12]. It provides a three- dimensional environment for cell attachment and proliferation as well as filling bone defects while providing mechanical competence during bone regeneration [13]. Hence, tissue engineering process begins with the fabrication of a biologically compatible scaffold that will support living cells to attach (adhere), proliferate and differentiate, and thus promote tissue regeneration both in vitro and in vivo[12].
Related Knowledge Centers
- Allotransplantation
- Autotransplantation
- Chimera
- Syngenic
- Tissue
- Organ Transplantation
- Cell
- Species
- Human–Animal Hybrid
- Patient Derived Xenograft