Human iPSC-derived sebocytes | Ref. PCi-SEB
 
Sebocytes are epithelial cells specialized in sebum production. They are located in the sebaceous gland, in association with a hair follicle, building the pilo-sebaceous unit. These glands are found all over the body, with 400 to 900 glands/cm², except on the palms of the hands and soles of the feet. A young sebocyte is a tiny cell, the older they get the biggest they are, as they produce and accumulate lipids until their membrane breaks down and release the sebum. This process is called holocrine secretion. Sebaceous glands continuously release sebum, a mixture of lipids and cell debris, via a channel along the hair. A lot of different functions are attributed to sebum : antimicrobial, antioxidant, transport of pheromones, thermoregulation, hydration, and suppleness of the skin. Sebocyte functions are still a topic of intense research.
 
Sebum composition is :
Fatty acids / Diglycerides / Triglycerides : 60 %
Wax esters : 25 %
Squalene : 13%
Cholesterol : 2%
 
The secretion of sebum can be extremely different from one person to another. Not enough sebum (hyposeborrhea) can lead to skin dryness and to breakable hair ;  too much sebum (or hyper-seborrhoea) leads to oily skin and hair. Oily skin may lead to the most common skin disease: acne vulgaris.
 
The process of acne vulgaris takes place in three steps:
Excessive sebum production by sebaceous glands, often owing to hormone dysregulation.
Colonization of the pilo-sebaceous unit by Propionibacterium acnes, which feeds itself with sebum.
Release of inflammatory mediators, leading to inflammation and the formation of pimple.
 
Sebocytes behavior is under the regulation of a range of agents such as androgens, estrogens, retinoids, LXR, PPAR, IGF and growth hormone, as well as melanocortins. Obtaining primary sebocytes from a human donor is time-consuming and low-yield. Over the past decades, immortalized (cancer-like) cell lines have been developed as in vitro models, such as SEB-1 and SZ95 lines. While they express some of the characteristics of primary sebocytes, they do not display the same range of functions and response to stimulating agents as primary sebocytes. More faithful alternatives have been developed recently based on the iPSC technology. PCi-SEB are a unique in vitro tool for hyper- and hyposeborrhea, inflammation and aging research and for the development of innovative therapies.