Regenerative medicine in the context of "Transplant rejection"

Cell therapy (also called cellular therapy, cell transplantation, or cytotherapy) is a therapy in which viable cells are injected, grafted or implanted into a patient in order to effectuate a medicinal effect, for example, by transplanting T-cells capable of fighting cancer cells via cell-mediated immunity in the course of immunotherapy, or grafting stem cells to regenerate diseased tissues.

Cell therapy originated in the nineteenth century when scientists experimented by injecting animal material in an attempt to prevent and treat illness. Although such attempts produced no positive benefit, further research found in the mid twentieth century that human cells could be used to help prevent the human body rejecting transplanted organs, leading in time to successful bone marrow transplantation as has become common practice in treatment for patients that have compromised bone marrow after disease, infection, radiation or chemotherapy. In recent decades, however, stem cell and cell transplantation has gained significant interest by researchers as a potential new therapeutic strategy for a wide range of diseases, in particular for degenerative and immunogenic pathologies.

Life extension is the concept of extending the human lifespan, either modestly through improvements in medicine or dramatically by increasing the maximum lifespan beyond its generally-settled biological limit of around 125 years. Several researchers in the area, along with "life extensionists", "immortalists", or "longevists" (those who wish to achieve longer lives themselves), postulate that future breakthroughs in tissue rejuvenation, stem cells, regenerative medicine, molecular repair, gene therapy, pharmaceuticals, and organ replacement (such as with artificial organs or xenotransplantations) will eventually enable humans to have indefinite lifespans through complete rejuvenation to a healthy youthful condition (agerasia). The ethical ramifications, if life extension becomes a possibility, are debated by bioethicists.

The sale of purported anti-aging products such as supplements and hormone replacement is a lucrative global industry. For example, the industry that promotes the use of hormones as a treatment for consumers to slow or reverse the aging process in the US market generated about $50 billion of revenue a year in 2009. The use of such hormone products has not been proven to be effective or safe. Similarly, a variety of apps make claims to assist in extending the life of their users, or predicting their lifespans.

Transdifferentiation, also known as lineage reprogramming, is the process in which one mature somatic cell is transformed into another mature somatic cell without undergoing an intermediate pluripotent state or progenitor cell type.(a process where one type of fully developed body cell changes directly into another type of body cell, without the cell turning into a stem cell first) It is a type of metaplasia, which includes all cell fate switches, including the interconversion of stem cells.(it's considered as a form of metaplasia, which refers to any change from one kind of cell to another, including changes involving stem cells.) Current uses of transdifferentiation include disease modeling and drug discovery and in the future may include gene therapy and regenerative medicine.(transdifferentiation is currently used in areas like understanding diseases, testing new drugs, and possibly future treatments such as gene therapy and tissue repair). The term 'transdifferentiation' was originally coined by Selman and Kafatos in 1974 to describe a change in cell properties as cuticle-producing cells became salt-secreting cells in silk moths undergoing metamorphosis.

Life extension is the concept of extending the human lifespan, either through incremental improvements in medicine or through radical increases in maximum lifespan beyond its generally-settled biological limit of around 125 years. This field of study has been explored by numerous researchers and advocates, including "life extensionists", "immortalists", and "longevists" (those who aspire to achieve prolonged lifespans themselves). These researchers and advocates hypothesize that future advancements in tissue rejuvenation, stem cells, regenerative medicine, molecular repair, gene therapy, pharmaceuticals, and organ replacement (such through artificial organs or xenotransplantations) will eventually enable humans to have indefinite lifespans through complete rejuvenation to a state of optimal health and youth (agerasia). The ethical implications of life extension are a subject of discourse among bioethicists.

The sale of purported anti-aging products, such as supplements and hormone replacement therapy, is a lucrative global industry. For example, the industry that promotes the use of hormones as a treatment for consumers to slow or reverse the aging process in the US market generated about $50 billion of revenue a year in 2009. The use of such hormone products has not been proven to be effective or safe. Similarly, a variety of apps make claims to assist in extending the life of their users, or predicting their lifespans.

Strategies for engineered negligible senescence (SENS) is a range of proposed regenerative medical therapies, either planned or currently in development, for the periodic repair of all age-related damage to human tissue. These therapies have the ultimate aim of maintaining a state of negligible senescence in patients and postponing age-associated disease. SENS was first defined by British biogerontologist Aubrey de Grey. While scientists agreed with de Grey that "research into the basic biology of ageing needs and deserves more support", they also viewed de Grey's proposals "to 'engineer' the body to prevent ageing indefinitely" as a fringe theory. De Grey later highlighted similarities and differences of SENS to subsequent categorization systems of the biology of aging, such as the highly influential Hallmarks of Aging published in 2013.

While some biogerontologists support the SENS program, others contend that the ultimate goals of de Grey's programme are too speculative given the current state of technology. The 31-member Research Advisory Board of de Grey's SENS Research Foundation have signed an endorsement of the plausibility of the SENS approach.

In genetics and developmental biology, somatic cell nuclear transfer (SCNT) is a laboratory strategy for creating a viable embryo from a body cell and an egg cell. The technique consists of taking a denucleated oocyte (egg cell) and implanting a donor nucleus from a somatic (body) cell. It is used in both therapeutic and reproductive cloning. In 1996, Dolly the sheep became famous for being the first successful case of the reproductive cloning of a mammal. In January 2018, a team of scientists in Shanghai announced the successful cloning of two female crab-eating macaques (named Zhong Zhong and Hua Hua) from foetal nuclei.

"Therapeutic cloning" refers to the potential use of SCNT in regenerative medicine; this approach has been championed as an answer to the many issues concerning embryonic stem cells (ESCs) and the destruction of viable embryos for medical use, though questions remain on how homologous the two cell types truly are.

Tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. Tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose, but is not limited to applications involving cells and tissue scaffolds. While it was once categorized as a sub-field of biomaterials, having grown in scope and importance, it can be considered as a field of its own.

While most definitions of tissue engineering cover a broad range of applications, in practice, the term is closely associated with applications that repair or replace portions of or whole tissues (i.e. organs, bone, cartilage, blood vessels, bladder, skin, muscle etc.). Often, the tissues involved require certain mechanical and structural properties for proper functioning. The term has also been applied to efforts to perform specific biochemical functions using cells within an artificially created support system (e.g. an artificial pancreas, or a bio artificial liver). The term regenerative medicine is often used synonymously with tissue engineering, although those involved in regenerative medicine place more emphasis on the use of stem cells or progenitor cells to produce tissues.