In 2013, Klinger et al. [17] proved that fat particle transplantation can be used to cure HSs. After treatment, the skin regained the softness, elasticity, color, and thickness of normal skin; moreover, histologic analyses identified collagen deposition, blood vessel proliferation, and thickening of the dermis, indicating that scar tissue retains the ability to become normal skin. Also in 2013, Bruno et al. [9] found that fat particle transplantation stimulates the regeneration of elastic fibers under scars, causing disordered collagenous fibers to regain normal alignment and compactness. In recent years, many studies have endeavored to elucidate the underlying mechanism of this repair: because fat tissue is rich in adipocytes, ADSCs, preadipocytes, macrophages, and endotheliocytes, researchers have asserted that these cells not only provide physical support in the injected area, but also secrete cytokines, which are closely connected with regeneration and metabolism. These cytokines may stimulate the regeneration of Fbs and synthesis of collagenous fibers in the recipient area, thicken the dermis, stimulate endotheliocyte proliferation in blood vessels, and hasten the resumption of blood circulation, providing oxygen and nutrition and improving scar texture [1821].

Compared with the large number of fat cells cultivated from unchyled fat, few mature fat cells were cultivated from chyle fat in this study. Mature fat cells account for only one-sixth of all fat cells, but they are in charge of lipid metabolism, the main function of fat cells. It is established that, as terminally differentiated cells, mature fat cells cannot be subcultured. However, after culturing mature fat cells in vitro, Zuk et al. [22] found that they can jettison their lipid and become Fb shaped, which is more tolerant of an anaerobic environment, and under certain conditions can differentiate into fat, cartilage, and bone cells. We believe that the effects of autologous chyle fat transplantation, either during facial rejuvenation or wound repair treatment, are not caused by the fat cells themselves: preadipocytes play a more important role. However, other researchers propose that the anti-scarring effect of fat cells is closely connected with ADSCs [20].

Discovered by Zuk et al. [23] in 2010, ADSCs are a kind of mesenchymal stem cell, but are more abundant and more readily acquired, separated, and cultured. They are now widely used as seed cells in tissue engineering, as well as in wound healing, whitening, antiaging, and antifibrosis studies [2428]. ADSCs have the ability to differentiate into several different fat cells. ADSCs are also able to secrete growth factors, such as growth factors that stimulate the formation of blood vessels, which have antiapoptotic, antioxidant, immunoregulatory, and anti-inflammatory characteristics. They can also affect the metabolism of the ECM through Fbs in the dermis. As stem cells, they can give rise to different cell pedigrees in different environments, such as endothelial cells, which control the vascular bed, thickness of collagen, and formation of granulation tissue [21]. Zhang et al. [28] injected human adipose-derived stem cell-conditioned medium (ADSC-CM) into scars on rabbit ears, and successfully decreased the scar proliferation index, amount of type I collagen, and expression of α-smooth muscle actin. Other researchers have studied the composition of ADSC-CM, and found abundant antifibrotic cell factors [29] such as hepatocyte growth factor and interleukin-10.

Chyle fat transplantation decreases the density of type III collagen in HSs; when collagenous fibers are in good order and their shapes are regular, it has an undoubted beneficial effect on HS tissue. Chyle fat is easier to inject than fat particles, so the treatment efficiency is also improved. Because of these advantages, the clinical applications of the technique are worth promoting. Its mechanism of action involves alteration of the ECM in ADSCs; however, whether this is achieved by perturbogens or protein expression requires further investigation.