Skin aging is not only associated with a compromised physical appearance, but also increased susceptibility of skin diseases and injuries due to loss of integrity and function of the aged skin. The level of aesthetic consciousness increases as society becomes more complex. Therefore, there is an expanding market that focus on treatment strategies to prevent or even reverse aging, due to our society’s increasing demand to look youthful. MSCs and their derivatives have become popular in skin rejuvenation because of their many anti-aging and related effects.

Numerous studies have explored the anti-aging effects of MSCs from different sources and their derivatives. This section discusses the key findings from recent studies using MSC conditioned medium, MSC derivatives such as extracellular vesicles (EVs), exosomes and secretomes, as well as whole cells.

The protective effects of CM of hUC-MSCs, cultured in a bioreactor (BM) and flask (FM) against UVB irradiation in CCD-986SK (human fibroblast) cells were investigated with the aim to determine the effects of culture environment [52]. The study showed that BM treatment protected CCD-986SK cells from UVB-induced cell death, as well as resulted in higher growth factor secretion and higher levels of procollagen in comparison with FM treatment. BM treatment also resulted in increased antioxidant gene promotor activity and downregulation of MM-1 gene in CCD-986SK cells. When SK-MEL-31 cells were stimulated with α-melanocyte-stimulating hormone (α-MSH), both the melanin production and MITF, tyrosinase, TRP-1, and TRP-2 levels decreased with BM treatment. Collectively, the findings suggest that BM from hUC-MSCs display anti-aging, anti-apoptotic and anti-melanogenic effects. Hence, conditioned medium of hUC-MSCs derived from BR may be a potential skin protection agent.

Similarly, in vitro experiments showed that conditioned medium (CM) of human AT-MSCs exhibited protective effects against UVB radiation in human keratinocyte cell line (HaCaTs) and normal human dermal fibroblasts (NHDFs) [53]. The protective effects include (1) modulation of signaling pathways in response to UVB [e.g., pathways involving activator protein 1 (AP-1), mitogen activated protein kinases (MAPKs), and nuclear factor kappa B (NF-κB)], (2) upregulation of antioxidant response element (ARE), (3) stimulation of TGF-β gene expression (which enhances collagen synthesis), (4) suppression of the expression of MMP-1 and (5) suppression of procollagen type I synthesis inhibitors, demonstrating significant potential of CM from AT-MSCs in modulating anti-photoaging effects in vitro.

In another study using CM from fetal dermal MSCs, the CM was shown to exert anti-aging effects in vitro and ameliorate the senescent effects of chemically-induced senescence in adult dermal fibroblasts previously treated with D-galactose. It is worth nothing that the D-galactose-treated fibroblasts had initially showed reduced proliferation, increased reactive oxygen species and increased p16, p21 and p53 mRNA expressions, which had been mitigated by the CM of fetal dermal MSCs in a paracrine manner [54]. In contrast, one study investigated the anti-photo-aging effects of the CM of human BM-MSCs (hBM-MSC-CM) [55]. In a dose-dependent manner, in vitro experiments showed that hBM-MSC-CM markedly decreased MMP-1 expression induced by UVB irradiation and enhanced pro-collagen production. When applied on the skin of hairless mice, hBM-MSC-CM effectively repaired UV-induced dermal damage and promoted wrinkle effacement. The anti-wrinkle effects of hBM-MSC-CM was mediated through increased hydration and collagen synthesis, indicating the potential of hBM-MSC-CM in treating UV-induced skin damage.

There are three sub-populations of EVs released by UC-MSCs in skin aging. These subpopulations include (1) apoptotic bodies (ABs), (2) exosomes (EXs) and (3) microvesicles (MVs). A study showed that EXs from UC-MSCs stimulated by transforming growth factor-β (TGF-β) demonstrated enhanced capacity in promoting fibroblast migration to wounds when compared to EXs from UC-MSCs cultured under normal conditions [56]. Consequently, the study concluded that hUC-MSC-EVs, particularly EVs from TGFβ-primed hUC-MSCs, possess protective effects against skin aging by promoting the release of elastin and total collagen from fibroblasts.

In addition to the protective effects observed in fibroblasts, the skin aging suppressing effects of exosomes derived from UC-MSCs was demonstrated in HaCaT cell line [57]. In vitro experiments revealed enhancement of proliferation and migration, as well as inhibition of damage induced by UVB irradiation in normal HaCaT keratinocytes. The study further showed that UM-MSC-EXs decreased senescence and apoptosis, with increased expression of type I collagen and reduced expression of MMP-1 in aged HaCaT cells, suggesting that UM-MSC-EXs may be a potential therapeutic candidate in skin aging.

In a rat model, the anti-inflammatory and antioxidant effects of subcutaneously injected hUC-MSCs-EXs against apoptosis and DNA damage in photo-aged skin was demonstrated [58]. In vitro studies further revealed the reversal of reduction in sirtuin 1 (SIRT1) expression in HaCaT (skin keratinocytes) induced by UV radiation. It was suggested that SIRT1 activation played a role in oxidative stress inhibition and protected HaCaT cells against cytotoxic damage induced by UV and H2O2, as well as promoted autophagy. The cytoprotective effects of hUC-MSC-EXs was due to modulation of an antioxidant pathway dependent on SIRT1, mediated by 14-3-3ζ protein found inside them.

EXs from human AT-MSCs (ATMSC-EXs) have been shown to exert anti-aging effects on photoaged rat skin subjected to UVB irradiation, with a single injection into photoaged skin showing remarkable reduction in epidermal thickness, reduced proportion of stratum corneum and increased dermal thickness 7 days post treatment [59]. Increased mRNA expressions of type I collagen and decreased expressions of MMP-1, MMP-3 and type III collagen were also observed. Similarly, anti-aging effects of AT-MSCs were also seen in vitro [60]. Co-cultures of HDFs with AT-MSCs and AT-MSC-CM were shown to increase type I procollagen production and suppress expression on MMP-1 in HDFs when exposed to UVB irradiation.

The anti-aging and pro-regenerative effects of hUC-MSCs were also investigated through in vitro and in vivo experiments. Using an in vitro HDF skin aging model, UM-MSCs were shown to promote cell migration, suppress ROS production and restored overexpression of senescent and oxidative markers, which significantly reversed HDF senescence [61]. The paracrine effects of hUC-MSCs were mediated by autophagy inhibition. On the other hand, in vivo experiments revealed that hUM-MSCs improved skin texture, removed wrinkles, enhanced collagen production and dermal thickness of aged skin in a nude mice skin aging model. Up-regulation of Col-1 and VEGF expressions and reversal of (malondialdehyde) MDA and superoxide dismutase (SOD) levels were observed, suggesting that hUM-MSCs exhibit pro-regenerative and anti-oxidative properties against skin aging.

In a photo-aging pigmentation model of guinea pigs, intradermal injections of (AT-MSCs) were shown to improve pigmentation significantly, as evidenced by reduction in visible skin scores and melanin content [62]. Histopathological examination revealed decreased epidermal thickness and increased dermal thickness, accompanied by little inflammation. Further experiments demonstrated that AT-MSCs secreted basic fibroblast growth factor (bFGF) and lowered alpha-melanocyte test hormone (alpha-MSH) and melanocortin 1 receptor (MC1R) levels. The resultant inhibition of melanin synthesis was mediated via blocking of the cAMP signaling pathway.

Another study demonstrated that elderly AT-MSCs showed downregulation of superoxide dismutase 1 and 3 (SOD1 and SOD3), resulting in raised ROS and MEK/ERK pathway downregulation [63]. On the other hand, infant ADMSC-EVs were shown to exert rejuvenation effects in senescent elderly MSCs and improve the functions of the latter via (1) suppression of ROS production and cellular senescence and (2) stimulation of MSC proliferation and functions in mice.

Recent research has highlighted the role of nuclear receptor interacting protein 1 (Nrip1) in regulating the functions of AT-MSCs, where the deletion of Nrip1 delayed skin aging in mice [64]. The effects of Nrip1 deletion in AT-MCS isolated from subcutaneous white adipose tissue (sWAT) include (1) decreased cell proliferation, (2) cell apoptosis prevention, (3) adipogenesis suppression, (4) reduced AT-MSC senescence and (5) increased AT-MSC quiescence. Deletion and suppression of Nrip1 by siNRIP1 resulted in reduced expression of genes associated with (1) senescence, (2) inflammation and (3) growth factors in AD-MCs of the skin of Nrip1 knockout mice. Study findings suggest that Nrip1 play a part in delaying skin aging by maintaining AT-MSC quiescence and reducing AT-MSC senescence.

The anti-aging effects of MSC were also demonstrated in rat models [65]. The rats were divided into three groups: (1) control, (2) skin aging model and (3) treatment group, which received multi-point subcutaneous injections of bone marrow-derived MSCs (BM-MSCs) with the second group showing oxidative stress. The second group also showed histological abnormalities such as disorganized collagen fibers and epidermal cell layers that were loosely arranged. On the other hand, the treatment group revealed improvement in oxidative stress and histological abnormalities, indicating that BM-MSCs may be beneficial in skin rejuvenation by stimulating an antioxidant response in aged skin.

Moreover, the anti-aging effects of EVs released by gingiva-derived MSCs (GMSC-EVs) was investigated on human umbilical vein endothelial cells (hUVECs) and skin fibroblasts (SKs) [66]. The cellular senescence induced by oxidative stress in hUVECs and SKs was inhibited by GMSC-EVs, as evidenced by the suppression of senescence-related gene expressions. GMSC-EVs also restored proliferation impairment induced by oxidative stress in hUVECs. Additionally, following systemic administration of GMSC-EVs, the heart and skin of aged mice showed reduced expression of interleukin 6, p21, mTOR/pS6, and tumor necrosis factor α (TNF-α). Taken together, these findings suggest that the potential of GMSC-EVs as cell-free treatment of skin aging and age-related vascular dysfunctions due to its ability to inhibit oxidative stress-induced cellular senescence.

Numerous clinical studies have highlighted the promising anti-aging effects of MSCs and their derivatives, with their ability to rejuvenate, repair and improve skin across various patient populations.

To illustrate, following a single intradermal injection of autologous adipose-derived stem cells (AD-SCs), eight patients showed diminished wrinkles (including crow’s feet, glabella, eyelids and forehead grooves) within months after the injection and the effects persisted over a year [67]. Furthermore, these patients experienced a significant reduction of facial pores and more defined double eyelids. These skin revitalization effects are attributed to the activation of myoblasts when cultured with AD-SC-derived exosomes, highlighting the involvement of muscle in skin rejuvenation.

Beyond facial rejuvenation, another area of clinical studies involving MSCs focuses on striae distensae, commonly known as stretch marks. Findings from a recent randomized clinical trial revealed that the treatment combination of microneedling (MN) and UC-MSC-derived CM had better patient and physician satisfaction [68]. While no significant difference was observed in the improvement in dermal and complete thickness, and skin density between the control group (receiving MN only) and the combination treatment group, the combination therapy of MN and MSC may offer enhanced perceived benefits and improve the overall treatment experience for individuals with stretch marks.

In contrast, clinical trial patients with facial skin aging, who underwent 5 bi-weekly sessions of combination treatment of CM from hUC-MSC and MN showed significant improvements in skin brightness (reduction in UV spots, brown spots and melanin index) and skin texture (increase in skin elasticity and reduction of wrinkles and pores) [69]. Compared to those who only received MN treatment, these patients also had better self-satisfaction scores. Likewise, the combined CM of amniotic fluid-derived MSCs (AF-MSC-CM) with MN treatment showed improvement based on morphometrical assessment (p < 0.01), with dermal structural remodeling [70]. The study was carried out by treating both sides of the face of ten volunteers with facial aging with skin microneedling. After skin microneedling treatment, AF-MSC-CM was topically applied to the right side of the face only. In terms of histometric skin analysis, both sides of the face showed significant epidermal thickness, suggesting that microneedling and AF-MSC-CM treatment is more efficient in facial aging treatment when compared with microneedling alone. Nevertheless, more research is needed to ascertain the efficacy of the combined MN treatment with MSCs.

As for skin aging, MSC-EVs were shown to promote skin cell proliferation and migration, reduce inflammation, and protect against oxidative stress through cell signaling pathways that influence skin aging [71]. Nonetheless, further research is needed to fully understand their mechanisms of action and address potential limitations before they can be widely applied in clinical settings.

To potentiate the anti-senescence effect of MSCs, the combined anti-aging effects of hydrolyzed collagen oligopeptides (HCOPs) and exosomes derived from human UC-MSC-EXs were investigated on human skin fibroblasts [72]. Researchers found that the combination of HCOPs and UC-MSC-EXs enhanced cell proliferation, migration, and collagen production while reducing oxidative stress, inflammation, and senescence markers. These findings suggest that combining HCOPs with UC-MSC-EXs could be a promising approach for developing novel anti-aging skin treatments.

In terms of delivery of AT-MSCs secretome, both MN and fractional CO2 laser (FL) demonstrated significant improvement in total dermoscopy photo-aging scale (DPAS) and wrinkles in 30 Indonesian women aged 35 to 59 years with signs of facial senescence [73]. However, in most parameters, there were no significant intergroup differences in the treatment outcome. Nevertheless, the FL method showed a higher satisfaction and preference scores with lower comfort levels. Some observed adverse effects include burning sensation, itch, pain and temporary skin redness post-FL, which were relieved with moisturizer. The study concluded that MN and FL demonstrated comparable efficacy, but showed differences in preferences, comfort and adverse events in skin anti-aging treatment.

In another study, the injection of AT-MSCs (derived from lipoaspirates and expanded in vitro) in the facial skin of healthy subjects (n = 20, 45–65 years) restored skin elastin matrix in photo-aged skin [74]. Before AT-MSC treatment, skin biopsy showed histological features of solar elastosis, including (1) elastin matrix degeneration with loss of subepidermal elaunin fibers and oxytalan, (2) flattening of the dermal-epidermal junction with partial or complete loss of dermal papillae and (3) deposition of degenerated elastic fibers and scattered elastotic materials. ADMSC-treated skin, on the other hand, showed (1) formation of new elaunin fibers and oxytalan in the subepidermis, (2) restoration of dermal-epidermal junction papillary structure and (3) substitution of elastotic deposits with normal networks of elastic fibers, accompanied by cathepsin K and MMP-12 activation and M2 macrophage infiltration. These findings show that AT-MSCs may be a potential therapeutic agent for skin regeneration in photo-aged skin.

Using topical AT-MSC-CM combined with niacinamide, the anti-aging effects in post laser treatment skin showed significant improvement in global aesthetic improvement scale (GAIS), melanin index, wrinkle index and patient satisfaction score [75]. In this study, 25 subjects with aging skin were treated with moisturizer either with or without AT-MSC-CM plus 2% niacinamide after ablative fractional laser therapy. In vitro experiments demonstrated reduced proinflammatory cytokine levels in human keratinocytes cultures with AT-MSC-CM with niacinamide. Increased type 1 collagen expression and reduced MMP-1 and MMP-2 expressions were also observed.

Likewise, the application of human USC-CM on the skin of 24 females resulted in increased dermal density and had anti-wrinkle effects [76]. In vitro experiments showed that when HDFs were cultured using USC-CM, the overexpression of growth differentiation factor-11 (GDF-11) stimulated HDF growth, migration and ECM production. However, such effects were not observed using CM from other origins.

Besides using the CM directly from MSCs for aging treatment, the potential of CM of epidermal progenitor cells (EPC-CM) derived from MSCs has been examined [77]. Clinical topical application of 5% EPC-CM containing formulation (n = 25, aged 29–69 years) improved wrinkle, skin depression and skin texture within four weeks. The instruments used for assessment include the crow’s feet scale, wrinkle index by ANTERA 3D® and physician global assessment scale. The clinical improvements were backed by in vitro evidence. When human dermal fibroblasts were exposed to hydrogen peroxide (HP) in vitro, increased intracellular reactive oxygen species (ROS) levels were observed, with inhibition of fibroblast proliferation. On the other hand, pre-treatment with EPC-CM revealed increased expressions of anti-oxidative enzymes (e.g. catalase, superoxide dismutase and glutathione peroxidase) when fibroblasts were exposed to HP. In addition, EPC-CM also protected against HP-induced reduction in type I collagen production and enhanced MAPK signaling protein phosphorylation.

The effects of injection of fat obtained from liposuction with (1) stromal vascular fraction (SVF) or (2) expanded AT-MSCs in the preauricular areas (n = 6, aged 45–65 years) has also been investigated to determine the best fat graft for aging treatment [78]. The researchers removed fragments of skin before treatment and three months after treatment and observed similar post-treatment histologic and ultrastructural findings for both groups of subjects. Such findings include: (1) reduction in elastosis, (2) new oxytalan elastic fiber formation in papillary dermis, (3) modified reticular dermis, and (4) increased microvascular beds, suggesting that fat graft with either SVC or ADMSCs exert rejuvenation effects in skin by modifying the architecture of the dermis.

Another type of MSC is nanofat-derived stem cells (NDSCs), which was found to have positive effects on skin rejuvenation and facial contour remodeling [79]. Compared to traditional autologous fat transplantation (TAFT), patients who received nanofat transplantation (n = 62) showed greater improvements in signs and symptoms of skin aging or facial soft tissue depression and a higher overall satisfaction rate (> 90%) when compared with the patients who received TAFT (n = 77). Findings of the study also demonstrated that NFSCs had similar functions as MSCs and shared similar biological characteristics of traditional adipose-derived stem cells, indicating that nanofat transplantation with PRF may be beneficial in skin rejuvenation and facial contour remodeling.

The protein extracts from AT-MSC medium have also been studied to counteract aging [80]. The protein extracts (test) and ultrapure water (control) were randomly applied to either the left or the right side of the face of 30 Asian volunteers in a double blind, randomized control study through MN. Findings of the study showed significant improvements on the side that received the protein extracts when compared with the side that received ultrapure water, as measured by (1) melanin index, (2) skin color, (3) skin radiance, (4) skin surface topography, (5) skin elasticity and (6) quantitative analysis of periorbital skin relief (p < 0.05). As for self-evaluation, > 70% of subjects described strong improvements in the side of the face tested with the protein extracts. There were no reported adverse events throughout the 12-week study.