Stem cells (SCs) are defined as their ability to renew themselves and differentiate into other cell types. In view of these unique regenerative characteristics, they have aroused interest in many medical fields. Stem cells were originally used to treat chronic degenerative diseases, but recently, they are being used in medical aesthetics as a promising minimally invasive therapy.

Mechanism of action.

Mechanism of action. Stem cells are used because of their ability to regenerate. Some inducing factors promote these pluripotent stem cells to differentiate into different cell lineages. In an appropriate environment, stem cells can change their microenvironment by directly differentiating into cells of interest. Autologous and allogeneic stem cells can also stimulate and recruit endogenous stem cells. These effects are mediated by a series of secretory factors!

Androgenic alopecia. 

Preclinical studies on the use of various SCs preparations for hair repair in androgenic alopecia (AGA) are promising. Recently, these findings have been translated into clinical studies with similarly favorable results. The efficacy of a commercial adipose-derived stem cell conditioned medium (ASC-CM), a freeze-dried powder of protein secreted from ASC, has been reported. Because the growth factors expressed by ADSC affect the paracrine regulation of follicular stem cells, ADSC has been tried to be used in the study of alopecia areata. 

Some small clinical studies have shown that ADSC conditioned medium is effective in the treatment of hair loss when it is applied to the scalp or when its cell isolates are injected into the scalp. In addition to the above effects, ADSC can also be used in the repair of bone defects and nerve defects with scaffolds, which have been recorded in detail in many literatures and will not be discussed here.

Skin regeneration. 

Given the encouraging preclinical data, stem cells have been used for skin regeneration. Subcutaneous injection of ASCs into mice with UVB (ultraviolet B)-induced wrinkles proved that wrinkles were clinically improved with the increase of dermal thickness and collagen. These results are thought to be partly mediated by apoptosis and decreased secretion of human skin fibroblasts induced by UVB (ultraviolet B type). Many animal experiments have shown that subcutaneous injection of ADSC can promote collagen synthesis and angiogenesis in mice. In the basic experiment, the conditioned medium of ADSC promoted the migration of fibroblasts and reversed the induction of fibroblast apoptosis when incubating dermal fibroblasts. A clinical trial proved the therapeutic effect of this method. 

ADSC has also been found to inhibit melanogenesis in B16 melanoma cells, suggesting that ADSC may play a role in preventing sun-induced melanoma. ADSC has also been shown to protect skin fibroblasts from oxidative stress. The use of PRP,ADSC will promote the angiogenesis of facial skin during subcutaneous injection, regardless of whether it is added or not.

Cosmetics. 

The role of stem cells in makeup has not been fully determined. Hydrophilic molecules with a molecular weight greater than 500 Dalton cannot penetrate the intact stratum corneum. Although the local preparation of stem cells has this limitation, there are theories that macromolecular stem cells and their growth factors can affect the epidermis and dermis through hair follicles and sebaceous glands or through the damaged stratum corneum of aging skin. Therefore, fat exocrine has become one of the commercial components and is registered in the International Cosmetic Raw material Dictionary (ICID) as a cosmetic ingredient.

Conclusion. 

Because of their regenerative and paracrine effects, the use of stem cells is gaining momentum in a variety of medical fields, including cosmetic dermatology. 

Although there are many promising preclinical and clinical studies, the real role of SCs in aesthetics is still in its infancy. There is still a lack of a large number of high-quality clinical trials, and standardized products and technologies seem to be far from established, but published evidence has paved the way for these urgent clinical needs.