Figure 1
Young skin with active, fast dividing epidermal stem cells (left) in contrast to old skin with aged stem cells (right). Aging of stem cells results in a smaller progeny of differentiated keratinocytes (cells in dark blue). This leads to a thinner epidermis with a lower renewal rate.

Figure 2
PhytoCellTec™ Symphytum improves epidermal thickness and hyaluronic acid content in a 3D epidermis under aging conditions.

Figure 3
Increase in skin renewal (=decrease in skin renewal time) with PhytoCellTec™ Symphytum.

PhytoCellTec™ Symphytum

PhytoCellTec™ Symphytum is an active that is based on stem cells from the roots of comfrey (symphytum). It speeds up skin renewal through the activation of stem cells in the epidermis.

The plant Symphytum officinale (comfrey)
Symphytum officinale has been used as a medicinal plant for many centuries. The name symphytum derives from the Greek word symphyo which means “to grow together” and phyton which means “plant”. In ancient Greece, physicians used symphytum, to treat bone fractures and accelerate wound healing. Nowadays, it is still notably used externally for wound healing and inflammatory and traumatic lesions of muscles and joints.

Epidermal stem cells and their function
Epidermal stem cells that are located at the base of the epidermis continuously divide and differentiate into tissue cells, whereas old cells are shed on the skin surface. This constant renewal is important for the quality of the barrier and ensures that the skin remains smooth and even. However, as we age, this renewal process slows down considerably. This is because epidermal stem cells also age and their capacity to produce new cells decelerates. This leads to a thinner, dry and rough skin that in turn results in a dull complexion (see figure 1).

Aging of skin stem cells can be prevented
Isolated human epidermal stem cells were cultured in a “normal” cell culture medium that was rich in nutritional and growth factors and which imitated the environment in a young skin. These stem cells were able to form a nicely stratified epidermis with high hyaluronic acid (HA) content (see figure 2, left column).

This result was then compared to epidermal stem cells that were cultivated in a specifically designed cell culture medium, which mimicked the environment in an aging skin (“pro-aging medium”). Epidermal stem cells that grew in this medium showed a reduced ability to proliferate (see figure 2). The epidermis grown in the pro-aging medium was much thinner, as well as having a lower HA content and less cell layers (see figure 2, middle column).

However, epidermal stem cells that were cultivated in the pro-aging medium treated with Symphytum stem cell extract were able to form a thicker and more compact epidermis with an increased HA content as compared to the pro-aging control (see figure 2, right column). This result demonstrates that the Symphytum stem cell extract helps the epidermal stem cells in the pro-aging environment to maintain their ability to build new tissues during the aging process.

Increase in both skin smoothness and skin renewal time
In our studies, we also measured the effect of PhytoCellTec™ Symphytum on the renewal time of the epidermis. Twenty women aged between 40 and 60 applied a cream that contained PhytoCellTec™ Symphytum twice daily over a period of 56 days. The results revealed a reduction in skin renewal time by a remarkable 8% as compared to the placebo and this was accompanied by an improvement in skin smoothness of approximately 12% (see figure 3). Thus, PhytoCellTec™ Symphytum rejuvenates the epidermis from the innermost layer and ensures that the skin appears both smooth and even.