Cell Specification
The epithelial layer of the skin provides an essential function as a protective barrier against insult from the outside environment. The major cell type in this layer is keratinocytes which consists around 85% of living epidermal cells. Kertinocytes are the cells of stratified squamous epithelia. It is so named because its most abundant protein is keratin. Keratinocyte divide and are thus generated in the basal layer of the epidermis; this division is followed by a programmed death as they produce keratin and move up to the surface of the epidermis. Keratinocyte proliferation, differentiation, and apoptosis are a complex and carefully choreographed process [1]. Keratinocytes have been demonstrated to produce a wide range of cytokines and growth factors, including IL- 1, IL-3, IL-6, IL-8, colony-stimulating factors, TNF-alpha, TGF-alpha and beta, fibroblast growth factor, amphiregulin and PDGF [2, 3]. Besides the protective function, keratinocyte also plays a central role in tissue homeostasis, wound healing, cancers, and skin-based gene-therapy. Human keratinocytes express adhesion molecules and cytokines indicating their participation in skin innate immunity and homeostasis in vivo [4, 5].

HEK from ScienCell Research Laboratories are isolated from human epidermis. HEK are cryopreserved on primary culture and delivered frozen. Each vial contains >5 x 10⁵ cells in 1 ml volume. HEK are characterized by immunofluorescent method with antibodies to cytokeratine-8, -18 and -19. HEK are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HEK are guaranteed to further expand for 15 population doublings in the conditions provided by ScienCell Research Laboratories.

Recommended Medium
It is recommended to use Keratinocyte Medium (KM, Cat. No. 2101) for the culturing of HEK in vitro.

Product Use
HEK are for research use only. It is not approved for human or animal use, or for application in in vitro diagnostic procedures.

Storage
Directly and immediately transfer cells from dry ice to liquid nitrogen upon receiving and keep the cells in liquid nitrogen until cell culture needed for experiments.

Shipping
Dry ice.

Reference
[1] Eckert, R. L., Efimova, T., Dashti, S. R., Balasubramanian, S., Deucher, A., Crish, J. F., Sturniolo, M. and Bone, F. (2004) Keratinocyte survival, differentiation, and death: many roads lead to mitogen-activated protein kinase. J Investig Dermatol Symp Proc 7(1):36-40.
[2] Luger, T. A. (1992) Epidermal cytokines and growth factors. Marcel Dekker, Inc., New York , pp. 147-162.
[3] John C. Ansel, Jay P. Tiesman, John E. Olerud, James G. Krueger, Jeffrey F. Krane,t David C. Tara, Gary D. Shipley, Debra Gilbertson, Marcia L. Usui,I and Charles E. Hart (1993) Human Keratinocytes Are a Major Source of Cutaneous Platelet-derived Growth Factor. J. Clin. Invest. 92:671-678.
[4] Song, P. I., Park, Y. M., Abraham, T., Harten, B., Zivony, A., Neparidze, N., Armstrong, C. A. and Ansel, J. C. (2004) Human keratinocytes express functional CD14 and toll-like receptor 4. J Invest Dermatol 119(2):424-32.
[5] de Panfilis, G., Semenza, D., Lavazza, A., Mulder, A. A., Mommaas, A. M. and Pasolini, G. (2004) Keratinocytes constitutively express the CD95 ligand molecule on the plasma membrane: an in situ immunoelectron microscopy study on ultracryosections of normal human skin. Br J Dermatol. 147(1):7-12.