Tissue obtained from a donor source unrelated to the patient. Tissue that is genetically different and not compatible when transplanted (in contrast to autologous).
Tissue obtained from an individual and returned to the same person (in contrast to allogenic).
The basic building block of all living organisms. A single cell contains a nucleus, that has the genetic material of the organism, organelles, such as mitochondria (used in energy production), and a surrounding membrane. (plants have a cell wall).
The study of the physiology, composition, environmental interaction, and life cycle of cells at the microscopic or molecular level. Cytology (derived from Greek kytos, “container”) is an academic discipline that studies cells.
The in vitro replication of genetically identical whole organisms from a single cell of that organism.
A fibrous protein found in connective tissue (i.e.: skin, bone and cartilage). It is made by fibroblasts and is the most common protein in mammals.
An artificial substance in which cells can growth outside the body.
Dermal Papillae (DP)
Dermal cells, called fibroblasts that protrude into the base of the hair follicle and interact with the epidermal cells of the follicle to regulate the hair cycle and hair growth.
Dermal Sheath (DS)
Fibroblasts surrounding the lower part of the hair follicle. The dermal sheath appears to modulate hair growth and development.
Layer of skin made up mostly of collagen, containing blood vessels, nerves and the mid-part of the hair follicles. It lies below the epidermis and above the subcutaneous fat.
In a double-blind experiment, neither the subjects nor the researchers know who belongs to the control group and the experimental group. The purpose is to eliminate bias on the part of both the subjects and the observers.
The thin, outermost layer of the skin. The surface if the epidermis is composed of dead, flattened cells made of the protein keratin that forms a protective layer and helps to hold in water.
Thin layer of tightly packed cells on the inner or outer surfaces of the body. There is an epithelial lining to the lungs, stomach and intestines. The epithelium of the skin is called the epidermis.
An insoluble protein, produced in the liver that is instrumental in the clotting of blood. When activated, the protein forms a complex network that forms a plug or clot to control bleeding.
The primary type of cell found in the dermis of skin, they are responsible for wound healing and the secretion of proteins that form collagen. These are the easiest of cells to be cultured in a Petri dish.
The new growth of living hair follicles.
A basic unit of heredity that transmits the characteristics of one generation to the next generation. Genes represent a segment of the DNA on a chromosome that determines a specific trait.
The modification of genetic material by technological means. Scientific applications may include the treatment of disease, enhancement of agriculture and manufacture of biological products. (Syn: genetic modification, gene splicing)
The manipulation of an individual’s genetic makeup to prevent or treat a disease. A form of therapy that attempts to fix the defective gene causing the disease.
The process by which cells from a hair follicle are multiplied outside the body and then implanted in the scalp to generate new hair follicles. It is not true cloning, since cloning generally refers to the replication of an entire organism or creating an identical copy of something. With the current models of hair cloning, the cells (multiplied in tissue culture) would be used to stimulate new hair to form. This would involve some interaction with the scalp tissue and thus not produce a product identical to the original hair. More accurate terms would be hair induction or hair multiplication. These technologies are currently not available.
The process by which existing hairs are plucked from a hairy area of the scalp or body and then multiplied and implanted into the bald part of the scalp. These hairs may be separated from the shafts and cultivated in vitro (outside the body). The idea is that some germinative cells at the base of the hair follicle will be pulled out along with the hair and grow. This technology has not yet proven to be successful.
A cell that can cause another cell to perform a specific function. Fibroblasts found in the outer root sheath of the hair follicle that can stimulate the skin to produce new hair.
Inner Root Sheath (IRS)
The layer most closely apposed to the hair shaft that coats and supports the hair shaft up to the level of the isthmus, at which it breaks down. It consists of three concentric cell layers; Henle layer, Huxley layer and the cuticle. The cells of the innermost layer (IRS cuticle) point downward and inward and interconnect with the cells of the cuticle of the hair shaft, holding the hair in place.
Something found or introduced into the dermal (middle) layer of the skin.
The technique of performing an experiment in a controlled environment outside the body of a living organism, such as within a test tube.
Literally “within the living.” This refers to the technique of performing an experiment within the living tissue of a whole, living organism.
A fibrous insoluble protein that comprises the outermost layers of the epidermis. It is the main structural element in hair and nails.
The primary cell type found in the epidermis that forms the outer protective keratin layer. They make up approximately 90% of the epidermal cell. Other epidermal cell types include melanocytes (that produce pigment) and Langerhan cells (involved in the immune system).
The introduction of small quantities of liquid into individual cells using fine gauge needles.
The examination of the physical make up and interaction of cells of plants and animals at a molecular level, particularly the relationships between DNA, RNA and protein synthesis, and how these interactions are regulated.
Outer Root Sheath (ORS)
The tissue that surrounds the hair follicle in the dermis and blends into the epidermis on the surface of the skin forming what is commonly called the pore.
Phase 0 Pre-Clinical Study
Studies on animals, or in vitro, used to determine preliminary information about a drugs effects and dose.
Phase I Clinical Study
The first phase of testing in humans. Usually a small group of normal volunteers are used (20-80). This phase includes trials designed to assess the safety, tolerability, and pharmacologic action of a therapy, as well as to refine the dosing. These trials are usually conducted in a hospital setting, where the subjects can be observed around the clock.
Phase II Clinical Study
After the drug has shown to be safe in Phase I trials, Phase II trials are performed on larger groups (20-300) and are designed to assess the beneficial effects of the treatment; as well as to continue Phase I safety assessments in a larger group of volunteers.
- Phase IIA is specifically designed to assess dosing requirements (by balancing the effects and side effects of a drug)
- Phase IIB is specifically designed to study efficacy (“clinical proof of concept”)
Phase III Clinical Study
Randomized controlled trials on large groups of patients (300–3,000 or more) whose results must meet a high degree of statistical significance showing that the treatment is effective for a particular population in a particular formulation and dose. Phase III trials are the most expensive and time-consuming of the trials. The regulatory authorities decide whether to approve a treatment based on the results of these trials.
- Phase IIIB studies are used to show additional efficacy for uses beyond the original use for which the drug was designed, to obtain additional safety data, or to support specific marketing claims
Phase IV Clinical Study
Phase IV trials involve the post-launch safety surveillance to detect any rare or long-term adverse effects over a much larger patient population and timescale than was possible during the initial clinical trials.
The observable characteristics of an individual organism which are be determined by an individual’s genes and/or environmental factors.
An inert drug with no active ingredients. It is used in clinical studies to compare the performance of an actual drug (experimental group) with a control group of test subjects (the placebo group).
A medical effect based solely on the power of suggestion, since the drug had no active ingredients.
The ability to regrow or recreate lost or damaged limbs, tissues or organs.
A type of tissue engineering that focuses on the use of stem cells to produce new tissue rather than by improving the function of existing tissue.
Tissue not accepted by the body due to an immunologic response of the host.
An undifferentiated cell from which specialized cells develop. These cells retain the ability to renew themselves through cell division, but lack the characteristics of specialized tissue.
A collection of related cells that perform a similar function in the body. Four basic tissue types include nerve, muscle, epidermal and connective.
The use of suitable biochemical and physio-chemical factors to improve or replace the biological functions of cells. The term is commonly used for applications that repair or replace portions of or whole tissues, i.e., bone, cartilage, blood vessels.
Cells which are living and are able to reproduce or develop normally.
By: Dr. Robert M. Bernstein
Updated: 2015-05-22 | Published: 2009-07-30