Glossary of terms

Production under conditions designed to exclude micro-organisms at every step, used where a finished product cannot be sterilised without being destroyed. It requires validated facilities, environmental monitoring and process controls rather than a single terminal step.

A document recording the tests performed on a specific batch of a product, the methods used and the results obtained. Where a specification exists, it also records the acceptance limits and whether the batch met them.

A demonstration that product made after a change, or in a different run, performs equivalently to product made before, assessed against defined quality attributes and where necessary biological readouts. It is a formal exercise, not an assertion of similarity.

The culture liquid collected after cells have been grown in it, containing whatever those cells released during that period, along with the residual components of the original medium.

A range of values around an estimate, indicating the uncertainty in that estimate. A wide interval means the data are compatible with many different true values, including, often, no effect at all.

A situation in which a secondary interest, such as financial gain or professional advancement, could influence judgement about a primary interest such as the validity of a result. Its presence does not establish that judgement was influenced.

The process by which a cell takes material into itself by wrapping a region of its own membrane around that material and pinching it off into an internal compartment. Material internalised this way is inside a membrane-bound compartment, not free in the cytoplasm.

A small extracellular vesicle formed by inward budding within a multivesicular body and released when that compartment fuses with the plasma membrane. The term describes a route of formation, not simply a size.

The generic term for any particle bounded by a lipid bilayer that is released from a cell and cannot replicate. It covers exosomes, particles that bud directly from the plasma membrane, and apoptotic fragments, and it makes no claim about biogenesis.

The sequence of events by which tissue responds to an implanted material it recognises as foreign, typically involving immune cell recruitment, encapsulation of the material and deposition of surrounding matrix. It is a normal and expected tissue behaviour, not a complication in itself.

A protein that binds a specific cell surface receptor and alters the behaviour of the target cell, for example by promoting division, migration or matrix production. Growth factors act in tightly regulated concentration ranges and in sequences during tissue repair.

A polysaccharide found naturally in skin and connective tissue that binds large amounts of water. In injectable products it is chemically modified to vary how long it persists in tissue before being broken down.

Literally in glass. An experiment performed on cells, tissue fragments or molecules outside a living organism, under conditions set by the experimenter.

The licence required before a medicinal product may be placed on the UK market, granted after assessment of quality, safety and efficacy for a defined indication. Absence of an authorisation does not mean a product has been assessed and rejected; it usually means it has not been assessed.

A product that qualifies as a medicine because of how it is presented, meaning it is put before the public as having properties for treating or preventing disease, regardless of whether it has any such properties.

A cell type isolated from tissues including bone marrow and adipose tissue, expandable in culture, and widely used in regenerative medicine research. The extent to which such preparations meet a strict stem cell definition has been debated within the field.

A procedure in which fine needles create a regular array of micro-channels through the epidermis into the upper dermis, both providing a temporary route for topical substances and provoking a wound healing response.

A short non-coding RNA molecule that regulates gene expression by pairing with messenger RNA and reducing how much protein is produced from it. Detecting microRNA in a vesicle preparation shows it is present, not that it is delivered to a recipient cell in a functional quantity.

A late endosomal compartment containing small vesicles formed by inward budding of its own limiting membrane. If it fuses with the plasma membrane rather than with a lysosome, those internal vesicles are released as exosomes.

A method that estimates the size and concentration of particles in a liquid by tracking their random motion under illumination. It counts light-scattering objects within a size range and does not identify what those objects are.

Cell to cell communication in which a released molecule acts on neighbouring cells over a short distance, without travelling through the bloodstream to distant tissue. It is the standard mechanism of local tissue coordination.

The number of particles measured per unit of total protein in a preparation, used as an indicator of purity. A higher ratio suggests less non-vesicular protein accompanying the particles.

The number of times a cell culture has been subcultured, that is, harvested and reseeded into new vessels. Cells change with passage, including in what they secrete, so passage number is part of the specification of a cell-derived product.

Assessment of a manuscript by other researchers in the field before publication, addressing whether methods support conclusions and whether reporting is adequate. It does not usually involve verification of raw data or repetition of experiments.

A fraction of blood prepared by centrifugation so that platelets are concentrated in a volume of plasma. The name specifies the intent of the preparation and not its composition, which depends on the protocol used.

A polymer made of many nucleotide units linked in a chain. DNA and RNA are polynucleotides. In aesthetic products the term refers to purified, fragmented nucleic acid formulated as an injectable gel.

A requirement that a product be assessed and licensed by a regulator before it may be placed on the market. Frameworks that instead rely on notification and post-market surveillance allow products to be sold without prior assessment.

Restoration of tissue to its original architecture and function, rather than closure of a defect with tissue of different structure. In most adult human tissues, true regeneration is limited, and repair with altered architecture is the usual outcome.

A commercial category covering treatments intended to prompt the skin's own repair processes rather than to add volume or relax muscle. The biological accuracy of the word regenerative is examined separately on this site.

The path by which a substance is brought into contact with the body, for example topical, oral, intradermal or intravenous. Regulatory frameworks treat routes differently because they differ in what reaches tissue and in the risks that follow.

The outermost layer of the epidermis, composed of flattened dead cells within a lipid matrix. It is the principal barrier to substances entering the skin from outside and the reason most large molecules cannot be delivered topically in useful quantities.

Documentary evidence held by an advertiser before an objective claim is made, sufficient to support that claim. The requirement sits on the advertiser, and the standard rises with the strength of the claim and the potential for harm.

A measurement used in place of a clinical outcome because it is easier or faster to obtain, on the assumption that it tracks the outcome of interest. The assumption can fail, and a treatment can move a surrogate without changing what the patient experiences.

A filtration method in which fluid flows parallel to a membrane rather than directly through it, so that retained material is swept along the surface instead of accumulating on it. Widely used because it scales to production volumes.

The ability to identify and follow material from the donor through every stage of processing to the recipient, and back again. It exists so that if a safety problem emerges, everyone affected can be identified.

The process of moving a finding from laboratory research towards clinical use. Attrition at each stage is high across all of medicine, and most candidates do not complete the journey.

A comparison arm receiving the formulation without the active component, delivered by identical technique. It isolates the contribution of the active ingredient from the effects of the formulation and the procedure.