Xeno-Free (XF) or Animal Component Free Media (ACF) – Media made without animal derived components. Depending on the supplier, these products may or may-not contain products of human origin. For media free of all animal and human-derived components, growth factors are of either plant or microbial origin.


Defined Media – Media in which all components are added as highly purified compounds. Defined media therefore do not contain elements such as serum, BPE, or conditioned media.


Serum Free Media (SFM) – Media which do not contain serum. They may contain BPE or other non-defined additives.


Bovine Pituitary Extract (BPE) – Extract from bovine pituitary gland used as a non-defined source of growth factors in cell culture.


Fetal Bovine Serum (FBS) or Fetal Calf Serum (FCS) – Serum obtained from fetal bovine / calf by blood clotting and subsequent sterile filtrations. Used as a non-defined source of growth factors and proliferation supporting factors in cell culture media.


Progenitor Cell Targeted (PCT) – PCT factors are included in the Prime media to more accurately mimic the progenitor cell environment found in vivo. PCT factors improve retention of cells in a proliferative progenitor cell phenotype, and improve cell isolation and growth of cells.


Passage Number – The number of times confluent cells have been detached from their culture vessel and then seeded into new vessels at a lower density to allow continued proliferation. Passage zero cultures are formed by seeding cells directly taken from a tissue. Following one detachment and seeding (or subcultivation), such cultures reach Passage 1 (P1). Also a freezing and thawing step of cells is a passage.


Primary Cell Culture – Term used by researchers denoting a recently isolated cell culture. Strictly speaking, only cells immediately following isolation (e.g. up to passage 1) are primary cells, but the term is commonly used to describe cell cultures in their first passages. Primary cells typically provide the most accurate modeling of cell behavior in vivo, and are also able to differentiate, dependent on the cells type. Primary cell cultures generally have a finite lifespan, i.e. they stop proliferating and enter senescence after a certain period in vitro.


Confluency – The amount of surface area of the tissue culture plate that is covered with cells expressed as a percent (e.g. 100% means that the whole culture vessel surface is covered with cells).


Dermis – Layer of the skin, located below the epidermis. Comprised primarily of fibroblasts in an extracellular matrix which consists mainly of collagen. Also contains nerve endings, sweat and sebaceous glands and blood and lymph vessels.


Epidermis – Multilayered epithelium forming the uppermost layer of the skin. Comprised primarily of keratinocytes. Key role is to provide the barrier function essential for protecting the body. The barrier is formed by fully differentiated, highly cohesive keratinocytes (corneocytes) embedded in lipid layers.


Epithelium – Tissue composed of one or more cell layers which form the covering of internal and external surfaces of the body and its organs. Epithelial layers are separated from the underlying connective tissue by a membrane, and are typically polarized.


Keratinocyte – An epithelial cell that produces keratins. Most commonly located in the epidermis, although also present in other epithelia (e.g. cornea, oral mucosa).


Embryonic Stem Cells (ESC) – Pluripotent cells, able to differentiate into all tissue types of the body. Mainly isolated from the inner cell mass of the blastocyst that forms during early embryonic development.


Adult Stem Cells (ASC) – Unspecialized, multipotent cells with a high differentiation potential found in virtually all tissues of the body. Their capacity for asymmetrical division allows them to both maintain the pool of stem cells in the tissue, whilst providing the supply of new proliferative cells essential for tissue homeostasis and stem cell self-renewal.


Progenitor Cells – Partially commited cells found in all tissues that are still able to proliferate, and have not yet commited to terminal differentiation down one (unipotent) or more (multipotent) lineages.


Stem Cell Niche – The location within a tissue where adult stem cells reside. It is characterized by a very specific environment, which controls both the maintenance of the stem cell pool, as well as the release of cells from the niche to supply the needs of tissue maintenance and regeneration (homeostasis).