Science Focus ( Issue 21)

Have you ever woken up one day, looked in the mirror, and seen several new pimples on your face? If yes, then these pimples could be acne (or acne vulgaris). Acne arises from inflammation occurring on the skin. To be exact, it occurs on the pi losebaceous units. These are skin pores responsible for hair growth and sebum production. Acne can be found most commonly on faces, forehead, neck, upper chest, and shoulders, where pilosebaceous units are abundant [1]. There are three common observations associated with acne formation: overproduction of sebum, infection by skin bacteria, and abnormal follicular keratinization [2]. Overproduction of Sebum As mentioned earlier, the pores produce sebum. Sebum is an oi ly l iquid that protects our skin from harmful bacter ia and dryness. However, too much sebum can clog the pores, causing acne to form. The production of sebum is controlled by many different factors, but one of the well-studied factors is androgens [2, 3]. Androgens are sex hormones responsible for bodily changes during puberty. Since androgen levels increase dramatically during puberty, the hormone can also cause the overproduction of sebum [3, 4]. This is why acne outbreaks are common during teenage years. Infection by Skin Bacteria Certain species of bacteria live on our skin. One of them, known as Cutibacter ium acnes (former ly Propionibacter ium acnes [5]), may involve in acne formation. C. acnes feeds on sebum, and when there is excess sebum, the bacterial population can grow and multiply. The pores clogged with excess sebum can become infected with C. acnes , which may aggravate inflammation around the area and result in acne [2, 6]. By compar ing the st rains of C. acnes in the pilosebaceous units on the noses of acne patients and healthy individuals, researchers reported that certain strains were strongly associated with acne but some were linked to healthy skin [7]. Revealed by genomic analysis, each of these strains contains unique genetic elements that could potential ly contr ibute to the formation of acne or maintain skin health [7]. Further investigation on the functions of these strains could help shed l ight on the pathogenesis of acne and may ultimately lead to the development of targeted therapeutics [7]. Abnormal Follicular Keratinization Keratinization is the process where a type of skin cells, keratinocyte, hardens itself with keratin proteins [8]. The hardened cells are pushed towards skin surface to form a protective layer, such as stratum corneum, which provides protection against infection, desiccation and mechan ical s t res s [8]. However, fo l l icu lar hyperkeratinization is observed in acne patient, from which a thickened layer of stratum corneum forms due to the deposition of excess keratin [6, 9]. Such a keratinous plug blocks the fol l icle and provides an anaerobic environment for the proliferation of C. acnes [10, 11], while the bacteria is also known to influence keratinization by secreting propionic acid (IUPAC name: propanoic acid), leading to skin cel ls with altered shapes [2]. These altogether result in the formation of comedo. Below are some common misconceptions people may have about acne. By Paolo Miguel Magallanes Mallorca