Cell Therapy - definition of Cell Therapy in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia.

Cell Therapy

Definition

Cell therapy is the transplantation of human or animal cells to replace or repair damaged tissue and/or cells.

Purpose

Cell therapy has been used successfully to rebuild damaged cartilage in joints, repair spinal cord injuries, strengthen a weakened immune system, treat autoimmune diseases such as AIDS, and help patients with neurological disorders such as Alzheimer's disease, Parkinson's disease, and epilepsy. Further uses have shown positive results in the treatment of a wide range of chronic conditions such as arteriosclerosis, congenital defects, and sexual dysfunction. The therapy has also been used to treat cancer patients at a number of clinics in Tijuana, Mexico, although this application has not been well supported with controlled clinical studies.

Description

Origins

The theory behind cell therapy has been in existence for several hundred years. The first recorded discussion of the concept of cell therapy can be traced to Phillippus Aureolus Paracelsus (1493–1541), a German-Swiss physician and alchemist who wrote in his Der grossen Wundartzney ("Great Surgery Book") in 1536 that "the heart heals the heart, lung heals the lung, spleen heals the spleen; like cures like." Paracelsus and many of his contemporaries agreed that the best way to treat an illness was to use living tissue to restore the ailing. In 1667, at a laboratory in the palace of Louis XIV, Jean-Baptiste Denis (1640–1704) attempted to transfuse blood from a calf into a mentally ill patient—and since blood transfusion is, in effect, a form of cell therapy, this could be the first documented case of this procedure. However, the first recorded attempt at non-blood cellular therapy occurred in 1912 when German physicians attempted to treat children with hypothyroidism, or an under-active thyroid, with thyroid cells.

In 1931, Dr. Paul Niehans (1882–1971), a Swiss physician, became known as "the father of cell therapy" quite by chance. After a surgical accident by a colleague, Niehans attempted to transplant a patient's severely damaged parathyroid glands with those of a steer. When the patient began to rapidly deteriorate before the transplant could take place, Niehans decided to dice the steer's parathyroid gland into fine pieces, mix the pieces in a saline solution, and inject them into the dying patient. Immediately, the patient began to improve and, in fact, lived for another 30 years.

Cell therapy is, in effect, a type of organ transplant which has also been referred to as "live cell therapy," "xenotransplant therapy," "cellular suspensions," "glandular therapy," or "fresh cell therapy." The procedure involves the injection of either whole fetal xenogenic (animal) cells (e.g., from sheep, cows, pigs, and sharks) or cell extracts from human tissue. The latter is known as autologous cell therapy if the cells are extracted from and transplanted back into the same patient. Several different types of cells can be administered simultaneously.

Just as Paracelsus's theory of "like cures like," the types of cells that are administered correspond in some way with the organ or tissue in the patient that is failing. No one knows exactly how cell therapy works, but proponents claim that the injected cells travel to the similar organ from which they were taken to revitalize and stimulate that organ's function and regenerate its cellular structure. In other words, the cells are not species specific, but only organ specific. Supporters of cellular treatment believe that embryonic and fetal animal tissue contain active therapeutic agents distinct from vitamins, minerals, hormones, or enzymes.

Swedish researchers have successfully transplanted human fetal stem cells into human recipients, and the procedure is being investigated further as a possible treatment for repairing brain cells in Parkinson's patients. However, because the cells used in these applications must be harvested from aborted human fetuses, there is an ethical debate over their use.

Currently, applications of cell therapy in the United States is still in the research, experimental, and clinical trial stages. The U.S. Food and Drug Administration has approved the use of one cellular therapy technique for repairing damaged knee joints. The procedure involves removing healthy chondrocyte cells, the type of cell that forms cartilage, from the patient, culturing them in a laboratory for three to four weeks, and then transplanting them back into the damaged knee joint of the patient.

Preparations

There are several processes to prepare cells for use. One form involves extracting cells from the patient they are to be used on and then culturing them in a laboratory setting until they multiply to the level needed for transplant back into the patient. Another procedure uses freshly removed fetal animal tissue, which has been processed and suspended in a saline solution. The preparation of fresh cells then may be either injected immediately into the patient, or preserved by being freeze-dried or deep-frozen in liquid nitrogen before being injected. Cells may be tested for pathogens, such as bacteria, viruses, or parasites, before use.

Precautions

Patients undergoing cell therapy treatments which use cells transplanted from animals or other humans run the risk of cell rejection, in which the body recognizes the cells as a foreign substance and uses the immune system's T-cells to attack and destroy them. Some forms of cell therapy use special coatings on the cells designed to trick the immune system into recognizing the new cells as native to the body.

There is also the chance of the cell solution transmitting bacterial or viral infection or other disease and parasites to the patient. Careful screening and testing of cells for pathogens can reduce this risk.

Many forms of cell therapy in the United States are still largely experimental procedures. Patients should approach these treatments with extreme caution, should inquire about their proven efficacy and legal use in the United States, and should only accept treatment from a licensed physician who should educate the patient completely on the risks and possible side effects involved with cell therapy. These same cautions apply for patients interested in participating in clinical trials of cell therapy treatments.

Side effects

Because cell therapy encompasses such a wide range of treatments and applications, and many of these treatments are still experimental, the full range of possible side effects of the treatments are not yet known. Anaphylactic shock (severe allergic reaction), immune system reactions, and encephalitis (inflammation of the brain) are just a few of the known reported side effects in some patients.

Side effects of the FDA-approved chondrocyte cell therapy used in knee joint repair may include tissue hypertrophy, a condition where too much cartilage grows in the joint where the cells were transplanted to and the knee joint begins to stiffen.

Research and general acceptance

There is a growing debate in the medical community over the efficacy and ethical implications of cell therapy. Much of the ethical debate revolves around the use of human fetal stem cells in treatment, and the fact that these cells must be harvested from aborted fetuses.

While some cell therapy procedures have had proven success in clinical studies, others are still largely unproven, including cell therapy for cancer treatment. Until more large, controlled clinical studies are performed on these procedures to either prove or disprove their efficacy, they will remain fringe treatments.

Resources

Periodicals

Sinha, Gunjan. "On the Road to Recovery: Fetal pig cell therapy has put Parkinson's patient Jim Finn back in the driver's seat." Popular Science 255, no. 4 (Oct 1999): 27.

Organizations

Center for Cell and Gene Therapy. Baylor College of Medicine. 1102 Bates St, Suite 1100, Houston, Texas 77030-2399. (713) 770-4663. http://www.bcm.tmc.edu/genetherapy.

cell

1. the basic structural unit of living organisms.

2. a small more or less enclosed space.

All living cells arise from other cells, either by division of one cell to make two, as in mitosis and meiosis, or by fusion of two cells to make one, as in the union of the sperm and ovum to make the zygote in sexual reproduction.

All cells are bounded by a structure called the cell membrane or plasma membrane, which is a lipid bilayer composed of two layers of phospholipids. Each layer is one molecule thick with the charged, hydrophilic end of the lipid molecules on the surface of the membrane and the uncharged hydrophobic fatty acid tails in the interior of the membrane.

Cells are divided into two classes, eukaryotic cells and prokaryotic cells:

Eukaryotic cells have a true nucleus, which contains the genetic material, composed of the chromosomes, each of which is a long linear deoxyribonucleic acid (DNA) molecule associated with protein. The nucleus is bounded by a nuclear membrane, which is composed of two lipid bilayer membranes.

Prokaryotic cells, the bacteria, have no nucleus, and their genetic material, consisting of a single circular naked DNA molecule, is not separated from the rest of the cell by a nuclear membrane.

Eukaryotic cells are larger and more complex than prokaryotic cells. They also have membrane-bounded structures, such as mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum and lysosomes, that prokaryotic cells lack.

The contents of a cell are referred to collectively as the protoplasm. In eukaryotic cells the contents of the nucleus are referred to as nucleoplasm and the rest of the protoplasm as the cytoplasm.

The lipid bilayer of eukaryotic cells is impermeable to many substances, such as ions, sugars and amino acids; however, membrane proteins selectively move specific substances through the cell membrane by active or passive transport. Water, gases such as oxygen and carbon dioxide, and nonpolar compounds pass through the cell membrane by diffusion. Materials can also be engulfed and taken into the cell enclosed in a portion of the cell membrane. This is called phagocytosis when solids are ingested and pinocytosis when liquids are ingested. The reverse process is called exocytosis. All of these processes permit the cell to maintain an internal environment different from its exterior. See also body fluids.

The cells of the body differentiate during development into many specialized types with specific tasks to perform. Cells are organized into tissues and tissues into organs. Embedded in the cell membrane are a wide range of molecules that vary with the cell type and are typically composed of proteins or glycoproteins that have a cytoplasmic transmembrane and external domains. These molecules serve as cell receptors and are involved in signal transduction for a wide range of ligands, including hormones, cytokines and incidentally serve as receptors for viruses and drugs.

Structure of the cell as seen by light microscopy. By permission from Guyton R, Hall JE, Textbook of Medical Physiology, Saunders, 2000

accessory c's

macrophages involved in the processing and presentation of antigens making them immunogenic.

acinar cell, acinous cell

any of the cells lining an acinus, especially applied to the zymogen-secreting cells of the pancreatic acini.

adherent cell

one that adheres to the glass or plastic container in cell cultures, to form the monolayer. See also cell culture.

alpha c's

1. cells in the islets of Langerhans that secrete glucagon.

2. acidophilic cells of the anterior pituitary.

APUD c's

see apud cells.

argentaffin c's

enterochromaffin cells containing cytoplasmic granules capable of reducing silver compounds, located throughout the gastrointestinal tract, chiefly in the basilar portions of the gastric glands and the crypts of Lieberkühn. They secrete serotonin.

band cell

an immature neutrophil in which the nucleus is not lobulated but is in the form of a continuous band, horseshoe shaped, twisted or coiled. Called also band-form granulocyte and stab cell.

basal cell

an early keratinocyte, present in the basal layer of the epidermis.

basket c's

cells in the cerebellar cortex whose axons carry basket-like groups of fibrils which enclose the cell body of each Purkinje cell.

beta c's

1. basophilic cells in the pancreas that secrete insulin and make up most of the bulk of the islets of Langerhans; they contain granules that are soluble in alcohol.

2. basophilic cells of the anterior pituitary.

blood cell

one of the formed elements of the blood. See also blood.

cell body

the nucleus of the cell and the adjacent cytoplasm in cells which have processes, e g. neurons which consist of a cell body, an axon and dendrites.

bone cell

a nucleated cell in the lacunae of bone. Called also osteocyte.

cartilage cell

chondrocyte.

chromaffin c's

cells whose cytoplasm shows fine brown granules when stained with potassium bichromate, occurring in the adrenal medulla and in scattered groups in various organs and throughout the body.

cleavage cell

any of the cells derived from the fertilized ovum by mitosis; a blastomere.

cell count

see erythrocyte, leukocyte, milk cell counts.

cell culture

see cell culture.

cell cycle

see cell cycle.

daughter cell

a cell formed by division of a mother cell.

cell dehydration

fluid loss from cells due to elevation of the osmotic pressure of blood and tissue fluid; a potent stimulus to thirst.

dendritic cell

macrophage-like cells with long, filamentous processes located in the cortex of lymph nodes and the skin. Important in antigen trapping, processing and presentation. See also langerhans' cell.

cell differentiation

the process whereby cells become specialized usually with concurrent loss of reproductive capacity.

embryonic stem cell

a stem cell of fetal origin. See stem cell (below).

epithelioid cell

enlarged macrophages with enlarged lysosomes and much endoplasmic reticulum. May fuse to form multinucleated giant cell (below).

epsilon cell

one of the groups of acidophilic cells in the adenohypophysis. Contains granules that stain with azocarmine dye.

foam cell

a cell with a vacuolated appearance due to the presence of complex lipoids; seen in xanthoma.

cell fusion

see syncytial giant cell.

ganglion cell

a large nerve cell, especially one of those of the spinal ganglia.

germ cell

see germ cell.

giant cell

a very large, multinucleate cell; applied to megakaryocytes of bone marrow, to giant cells formed by coalescence and fusion of macrophages occurring in infectious granulomas and about foreign bodies, and to certain cancer cells.

glial c's

neuroglial cells.

goblet cell

a unicellular mucous gland found in the epithelium of various mucous membranes, especially that of the respiratory passages and intestines.

granular cell

one containing granules, such as a keratinocyte in the stratum granulosum of the epidermis, when it contains a dense collection of darkly staining granules.

gustatory cell

see taste bud.

heart failure c's, heart lesion c's

iron-containing, rust-colored macrophages found in the pulmonary alveoli in congestive heart failure.

helmet cell

schistocyte.

helper cell

a subset of T lymphocytes which cooperate with B and other T lymphocytes for the synthesis of antibodies to many antigens; they play an integral role in immunoregulation.

hybrid cell

a mononucleate cell produced from a binucleate heterokaryon after the latter undergoes mitosis. Such cells are initially unstable, tending to lose randomly some of the double complement of chromosomes. Used for mapping genes to particular chromosomes. See also heterokaryon, hybridoma.

immunologically competent cell

see immunocyte.

interstitial c's

the cells of the connective tissue of the ovary or of the testis (Leydig's cells) which furnish the internal secretion of those structures, i.e. testosterone.

islet c's

cells composing the islets of Langerhans in the pancreas. See alpha cells, beta cells (above).

juxtaglomerular c's

specialized cells, containing secretory granules, located in the tunica media of the afferent glomerular arterioles. They cause aldosterone production by secreting the enzyme renin and play a role in the regulation of blood pressure and fluid balance.

K c's, killer c's

T lymphocytes or null lymphocytes that have cytotoxic activity against target cells coated with specific IgG antibody.

lacis cell

accumulation of cells between the arterioles at the glomerular hilus. Called also granular cell.

lacunar cell

precursor of the malignant interdigitating reticular cell in Hodgkin-like lymphoma in humans.

LE cell

a mature neutrophilic polymorphonuclear leukocyte characteristic of lupus erythematosus. See also lupus erythematosus (le) cell.

Leydig's c's

interstitial cells of the testis, which secrete testosterone.

cell line

see cell culture.

lutein c's

the plump, pale-staining, polyhedral cells of the corpus luteum.

lymph cell

lymphocyte.

lymphoid c's

lymphocytes and plasma cells.

mast cell

a connective tissue cell that has basophilic, metachromatic cytoplasmic granules that contain histamine, heparin, hyaluronic acid, slow-reacting substance of anaphylaxis (SRS-A), and, in some species, serotonin. Have Fc receptors specific for IgE in the cell membrane.

cell-mediated immune reaction

see cellular immunity.

cell migration

movement of cells from their place of origin to other tissues; one of the fundamental processes of development.

microglial cell

see microglia. See also neuroglia cells (below).

milk cell count

see milk cell counts.

mother cell

a cell that divides to form new, or daughter, cells.

Mott cell

a plasma cell with large, clear cytoplasmic pockets.

natural killer c's, NK c's

cells capable of mediating cytotoxic reactions without themselves being specifically sensitized against the target.

nerve cell

any cell of the nervous system; a neuron.

cell nests

see isogenous groups.

neuroglia c's, neuroglial c's

see neuroglia.

null c's

lymphocyte-like cells that lack specific antigen receptors and other surface markers characteristic of B and T lymphocytes; they include K and NK cells; their numbers are elevated in active systemic lupus erythematosus and other disease states.

olfactory c's

a set of specialized cells of the mucous membrane of the nose; the receptors for smell.

parafollicular c's

see c cell.

Pick's c's

round, oval or polyhedral cells with foamy, lipid-containing cytoplasm found in the bone marrow and spleen in Niemann-Pick disease.

plasma cell

a spherical or ellipsoidal cell with a single, eccentrically placed nucleus containing dense masses of chromatin in a wheel-spoke arrangement, an area of perinuclear clearing which contains the Golgi apparatus, and generally abundant cytoplasm. Plasma cells are produced by cell division of B lymphocytes following antigen stimulation and are involved in the synthesis and release of antibody. Called also plasmacyte and plasmocyte.

prickle cell

a dividing keratinocyte of the prickle-cell layer of the epidermis, with delicate radiating process connecting with other similar cells.

prokaryotic cell

see prokaryote.

Purkinje's c's

large branching cells of the middle layer of the cerebellar cortex.

red cell, red blood cell

erythrocyte.

Reed-Sternberg c's

giant histiocytic cells, typically multinucleate, which are the common histological characteristic of Hodgkin's disease in humans.

reticular c's

the cells forming the reticular fibers of connective tissue; those forming the framework of lymph nodes, bone marrow and spleen. They are weakly phagocytic, stromal in origin and are distinct from the monocyte-macrophage system.

reticuloendothelial cell

a cell of the reticuloendothelial system.

Schwann cell

any of the large nucleated cells whose cell membrane spirally enwraps the axons of myelinated peripheral neurons supplying the myelin sheath between two nodes of Ranvier.

Sertoli c's

elongated cells in the tubules of the testes to which the spermatids become attached; they provide support, protection and, apparently, nutrition until the spermatids are transformed into mature spermatozoa.

sickle cell

a crescentic or sickle-shaped erythrocyte seen in some humans and deer. The abnormal shape caused by the presence of varying proportions of hemoglobin S.

signet-ring cell

a cell in which the nucleus has been pressed to one side by an accumulation of intracytoplasmic mucin.

somatic c's

the cells of the body other than the germ cells.

cell sorting

see fluorescence-activated cell sorter.

cell specialization

conversion of a simple cell type into a specialized cell type capable of a special function, e.g. a secretory cell; a major part of the growth of an embryo and the differentiation of basic mesenchymal tissue into specialized organs.

spindle cell

spindle shaped cells of the dermis or subcutis; principal component of spindle cell tumors.

spur cell

spiculed mature erythrocyte.

squamous c's

flat, scalelike epithelial cells.

stab cell

see band cell (above).

stellate cell

any star-shaped cell, as a Kupffer cell or astrocyte, having many filaments extending in all directions.

stem cell

1. any precursor cell.

2. a primitive hematopoietic cell that is capable of self-replicating or differentiating into precursor cells of erythrocytes or any of the leukocytes.

stipple cell

an erythrocyte containing granules that take a basic or bluish stain with Wright's stain.

suppressor c's

a not well defined subset of T lymphocytes that are reported to inhibit antibody and cell-mediated immune responses. They may play a role in immunoregulation, and are believed to be abnormal in various autoimmune and other immunological disease states. See also T lymphocytes.

target cell

1. an abnormally thin erythrocyte showing, when stained, a dark center and a peripheral ring of hemoglobin, separated by a pale, unstained zone containing less hemoglobin; seen in various anemias and other disorders. Called also codocyte.

2. any cell selectively affected by a particular agent, such as a hormone or drug.

3. cell containing nonself antigens in its cell membranes that is a target for nonimmune and immune cytolysis, e.g. virus-infected or tumor cell.

taste c's

cells in the taste buds associated with the nerves of taste.

cell therapy

see glandular therapy.

totipotential cell

an embryonic cell that is capable of developing into any type of body cell.

Türk's cell

a lymphocyte with increased basophilia.

visual c's

the neuroepithelial elements of the retina.

white cell, white blood cell

leukocyte.