Age and the Epidermis
The skin forms a barrier that protects humans against dehydration and external threats. This barrier function is provided mainly by the epidermis. The epidermis is constantly renewed; cells that are shed from the stratum corneum are replaced by newly formed cells from the inner layer of the epidermis. This constant renewal is important for the quality of the barrier and keeps the skin smooth and even. The epidermal turnover time is about one month. But between the ages of 30 and 80, the turnover rate reduces by 30-50%, leading to a much longer turnover time. The consequence of the slowdown of the renewal in elderly people is a dry, rough, uneven and dull skin.
Epidermal stem cells that are dispersed in the inner layer of the epidermis are responsible for constant renewal. Only these cells have the potential to generate new cells for tissue renewal. But the rate of propagation of these cells is known to be reduced in elderly people. This is the principal reason for the reduced turnover rate and a slower epidermal renewal with advancing age.
Stimulating Epidermal Stem Cells
As human's age, skin renewal slows, leading to an uneven surface and the formation of scales. This has a negative influence on skin complexion and makes the skin look dull and grey. Instead of using irritating peeling procedures, Mibelle Biochemistry Group proposes an extract of comfrey stems cells, PhytoCellTec Symphytum, to address the root of the trouble.
PhytoCellTec Symphytum (INCI: Symphytum Officinale Root Cell Extract (and) Isomalt (and) Lecithin (and) Sodium Benzoate (and) Water (aqua)) activates the propagation rate of human epidermal stem cells. Therefore, it restores the renewal potential of aged skin.
PhytoCellTec Symphytum is an extract of comfrey stem cells. Comfrey is a perennial shrub with purple or pink flowers that grows in damp, grassy areas in Europe. It is used as herbal medicine, mainly for skin treatments. Comfrey ointments are applied for wound-healing and the treatment of bone fractures.
In Vitro and Clinical Testing
The positive effect of the comfrey cell extract on the propagation rate of epidermal stem cells was discovered in a novel cell culture assay. To mimic the tissue environment of aged skin, a cell culture medium was developed that contained the essential elements but was devoid of protecting and stimulating compounds. The proliferation of isolated epidermal stem cells cultured in this aging medium was clearly reduced compared to a normal medium. But epidermal stem cells cultured in the aging medium supplemented with low amounts of the comfrey cell extract proliferated much more than in the control culture without comfrey cell extract. The comfrey cell extract was also found to improve morphology and hyaluronic acid content in epidermis models formed in the aging medium.
Next, the comfrey cell extract was formulated into a vehicle cream and was tested in a clinical trial with 20 women, ages 40-60. After four weeks application, a significant increase in the skin renewal rate was found. Concomitant, skin smoothness analysis by PRIMOS showed a 12% improvement.