Stem cells: what prospects for cosmetology?

More than 210 people attended the event, held on 3 and 4 February 2011 in Lyon, under the auspices of the Centre européen de dermocosmétologie (European centre of dermocosmetology) and its president Mrs Dominique Bouvier.

Undifferentiated cells

The interest in stem cells (or undifferentiated cells) results in their two main characteristics: they can give specialized cells through cell differentiation and they can renew themselves a very large number of times.

Stem cells are present at the different stages in the development of human beings, thus there are: embryonic stem cells, foetal stem cells and adult stem cells. These cells do not share the same properties.

The very first embryonic stem cells (from the zygote to the eight-cell blastomere, at the fourth day of embryonic development) can give all cell types, and thus an entire organism: they are called totipotent. Then appear pluripotent stem cells, capable of giving rise to all cell types, embryonic annexes excepted. In later stages, there are:

 Multipotent stem cells, which may give different cell types, but specific to a given cell lineage.
 Unipotent stem cells, that can give only one kind of cell. They can, however, like any stem cell, insure self-renewal, it is therefore important to distinguish them from precursors.

Promising prospects

Skin is a considerable reservoir of adult stem cells offering new therapeutic perspectives while giving rise to fewer ethical issues compared the use of stem cells of embryonic origin.

Some of them may be used for therapeutic skin applications, such as the treatment of severe burns. But there are a number of other promising prospects because scientists are now capable of reprogramming them to make so-called multipotent embryonic-type stem cells, which can then reproduce all types of cells. Thus, very recently researchers were able to obtain blood cells and cardiac cells from adult skin stem cells.

The study of skin stem cells is still in its infancy, there are at least seven different reservoirs ("niches") currently identified in human beings at the level of the epidermis, hair follicles, sweat and sebaceous glands, dermis and adipose tissue. Each one has its specificities and its possible uses.

Many unknown factors

Although they are the purpose of much research, stem cells still retain their share of mystery because their identification remains complex due to the lack of specific markers and also to the fact their characteristics will change when they are cultured in vitro which further complicates the study.

Some questions on their biology are also widely debated. In particular, concerning the issue related to their ageing, which seems to be more the consequences of changes in the micro-environment affecting their regenerative capacities, than a reduction in their number. The question remains open.

Some skin applications

Skin applications of stem cells cover very large areas ranging from basic research to regenerative and aesthetic medicine and finally cosmetology.

Researchers are now able to reconstruct in vitro, tissue with melanocytes and hair follicles to deepen the fundamental knowledge on stem cells (evaluating the impact of UV radiation, understanding the phenomena of hair loss or hair bleaching...) or to study some skin diseases (bullous diseases, vitiligo ...). In the medical field, these reconstructed skins can be used for skin grafts for burn victims, for some pigmentation diseases or for the transplantation of hair follicles in the domain of baldness.

In the field of plastic and aesthetic surgery, lipofilling techniques, used for over twenty years, consists in taking from a patient some adipose tissue, with a very rich content in stem cells and to reinject it after centrifugation to help restore contour and volume defects or to facilitate the healing of chronic wounds.

Finally, the cosmetic field is not to be outdone. Skin tissues developed from stem cells allow carrying out pharmaco-toxicology studies. The European project ScreenTox, which has just begun, is also an example of that. It aims to assess the toxicology of drugs, chemicals and cosmetic ingredients through the use of stem cells.

Reconstructed models help achieve a complete skin or some specific tissues such as adipose tissue, which are increasingly used by the industry and the suppliers of cosmetic ingredients to study the effectiveness of active cosmetic ingredients.

A fight against ageing?

In the field of ageing, the stimulation of stem cells or on the contrary, the limitation of their growth to avoid their shortage were discussed repeatedly during the conference. Unknown factors in this area have been widely highlighted and representatives from the R & D departments of major cosmetic brands have presented their research efforts in this area while putting forward their extreme caution as to immediate applications.

The answer of specialist researchers is quite clear: current knowledge on stem cells does not indicate it would be wise to try to change their behaviour. It is nevertheless admitted that a better understanding of how to act on the composition of the niche, its functions and its interactions with stem cells, will enable to act without affecting stem cells themselves. The debate over stem cells in the field of anti-aging cosmetics is not closed either.

Stem Cells and cosmetic ingredients

The second part of the European Dermocosmetology Days was devoted to the presentation of various cosmetic active ingredients, most of them of plant origin. Some of them are called "plant stem cells" and provide the necessary elements to protect skin stem cells. Others allow, thanks to the biotechnology-techniques from which they were produced to protect biodiversity, avoid the problem of pollutants or overcome sourcing problems due to seasonality. And finally, some suppliers have highlighted the interest of skin stem cells to assess the efficacy of their actives.

In short, a very broad area of possibilities, but nonetheless a domain where research efforts to be undertaken and knowledge to be acquired are still considerable.