Topical growth factor preparations for facial skin rejuvenation: A systematic review

Cosmeceutical preparations containing growth factors (GFs) are widely used for facial rejuvenation.


| INTRODUC TI ON
Facial aging is a complex process comprising extrinsic damage (e.g., ultraviolet-mediated photoaging) superimposed on intrinsic (chronological) aging. 1 Both types of aging are characterized by a reduction in collagen and elastin and a loss in hydration leading to the visible consequences of fine lines and wrinkles; loss of volume, firmness, and elasticity; and increased skin roughness. 2,3 In recent years, the use of topical cosmeceutical formulations containing combinations of protective, antioxidant, and cellularmodulating ingredients that improve collagen production and aid in the recovery of aged skin has increased significantly. Popular ingredients including retinoic acid, peptides, and growth factors have been shown to improve fine lines and wrinkles, skin texture, and laxity. 3 Growth factors have emerged as novel anti-aging agents due to their recognized role in dermal wound repair. 4,5 Growth factors are regulatory proteins that mediate signaling pathways between and within cells. 6 In the skin, they are found naturally in fibroblasts and are responsible for the synthesis of collagen and the extracellular matrix. 7 Similarities in the biochemical pathways involved in the aging process and wound healing have resulted in the development of topical products employing growth factor technology. 5 Aging and wound healing both stimulate the release of growth factors, which affect a variety of biochemical pathways critical to repair the dermal matrix. 6 Multiple clinical studies over the last 20 years show that topical application of preparations containing growth factors can stimulate collagen synthesis and thereby decrease the appearance of fine lines and wrinkles. 7 To further clarify the efficacy and safety of topical preparations containing growth factors for the treatment of facial rejuvenation, we performed a systematic review to assess the existing evidence for these preparations. Randomized controlled trials (RCTs) and prospective uncontrolled clinical trials that assess the effects of various topical growth factor preparations were reviewed. Studies were evaluated for methodological strengths and weaknesses, and their data were summarized to estimate the existing evidence.

| MATERIAL S AND ME THODS
A protocol was prospectively developed, detailing the objectives, criteria for study selection, the approach to assessing study quality, and primary and secondary outcomes. The study followed the PRISM (The Preferred Reporting Items for Systemic Reviews and Meta-Analyses) guidelines (Table S1). 8 The study was not registered.

| Study identification
We identified relevant published studies that evaluated the use of topical growth factor preparations for the treatment of facial rejuvenation. Electronic databases (MEDLINE [OVID], EMBASE [OVID], and Scopus) from January 2000 to October 18, 2022 and the Cochrane Library (2022, Issue 10) were searched using the terms growth factor(s) or adipose-derived stem cells or mesenchymal stem cell(s) or stem cell-conditioned media or stem cells or stem cell media or mesenchymal stem cells AND ag(e)ing or photodamage or photoaging or wrinkles or rejuvenation AND skin AND face or facial AND human. A forward search was also conducted in Web of Science as well as a search of the bibliographies of included and excluded journal articles to locate additional studies not identified through the initial search strategy. Relevance was assessed using a hierarchical approach based on the title, abstract, and published manuscript.

| Study selection
Two investigators (DJQ and HH) independently evaluated studies for possible inclusion and any disagreements were resolved by discussion. To be included, studies had to be (1) a randomized or controlled trial, a prospective cohort study, or case series (CS); (2) include ≥10 participants; (3) include participants ≥18 years old; (4) include a minimum of 4 weeks of treatment; and (5) measure the clinical effect (including investigator assessment or via objective methods such as photographic analysis or ultrasound) of preparations containing growth factors for facial rejuvenation. Combination treatments (e.g., with microneedling) were considered for inclusion if the effect of topical growth factor preparations alone were reported separately.
Studies evaluating the use of growth factor preparations as an adjuvant treatment to fractional laser resurfacing were excluded because the therapeutic effect here is mainly related to decreasing the duration and intensity of laser-associated side effects (especially edema and erythema) and improving healing time. 9,10 Studies that used a combination of cosmeceutical treatments besides growth factors and did not identify growth factors as a key component, did not identify the source of the growth factors used or reported incomplete data, did not include topical treatment of the face or evaluated the efficacy of topically applied autologous platelet-derived products (e.g., platelet-rich plasma or platelet-rich fibrin derivatives) for facial rejuvenation (as these are not suitable for prolonged home use), and were not published in a peer-reviewed journal (e.g., conference abstracts, patent applications) were excluded. Retrospective, animal, and in vitro studies were also not included. The rationale for exclusion and article appraisals were recorded at each stage.

| Assessment of study quality and risk of bias
We followed the study-quality criteria outlined by the Oxford Centre for Evidence-Based Medicine ratings of individual studies 11 to evaluate the studies included in our systematic review.
Individual studies were classified as follows: (1a) systematic review of RCTs, (1b) individual RCT, (1c) all or none (e.g., live or die) study, (2a) systematic review of cohort studies, (2b) individual cohort study, (2c) outcomes research, (3a) systematic review of case-control studies, (3b) individual case-control study, (4) CS, and (5) expert opinion. Risk of bias assessment for included RCTs was performed according to the Cochrane Methodology for Systematic Reviews of Interventions 12 in respect of randomization details, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other potential sources of bias. Each category was scored as low, unclear, or high risk of bias and expressed in a summary table. The scoring was performed independently by two reviewers (DJQ and HH), and any disagreement was resolved by consensus.

| Data extraction and outcomes
Two investigators (DJQ and HH) independently extracted data on the study design, study quality, and study outcomes. Clinical-and participant-related outcomes and adverse events were reviewed in detail. We accepted the authors' definitions for clinical outcomes and did not attempt to reclassify them retrospectively. The data abstracted for each trial were confirmed by reviewer consensus. When reported, we extracted data on improvements in individual signs of facial aging such as wrinkles (reported as fine lines and/or coarse wrinkles), skin texture, tactile and visual roughness, pigmentation and dyschromia, skin laxity, and overall facial appearance. Due to a large number of available assessment tools for facial rejuvenation, 13 we concentrated on outcomes most reported in the different studies. When reported, we also extracted data on outcomes reported with objective techniques, including optical profilometry (silicone skin surface impressions of periorbital rhytides), punch biopsies (for microscopic analysis of collagen and epidermal thickness), corneometry (to measure skin hydration), cutometer (to measure skin elasticity), and ultrasound (to measure the epidermal thickness and elastosis). Missing data were requested from the authors or sponsoring companies.

| Data analysis and reporting
The included studies were summarized in descriptive tables to provide the relevant characteristics of the studies. Due to the heterogeneous nature of the outcomes and metrics used in the included studies, a meta-analysis could not be performed.
Where reported, statistically significant differences compared with control (i.e., outcomes reported in RCTs) were simplified to a double plus or double minus. Similarly, statistically significant differences compared with baseline (i.e., outcomes in prospective CS) were simplified to a single plus or minus. To facilitate comparisons, the relative improvement from individual studies was pooled for the key efficacy parameters (wrinkles, skin texture, and overall facial appearance) based on the investigator-and participant-reported outcome measures.

| Search and study selection
The process of study selection for this systematic review is depicted by the PRISMA flow diagram in Figure 1. Our search yielded 1350 nonduplicate citations from the years 2000 to October 2022 across the four electronic databases. An additional nine articles were found using references from the included studies. After scanning their titles and abstracts, 48 potentially eligible studies that met the criteria for inclusion remained. After a review of the full paper, 15 studies were excluded because growth factors were not the main component of the preparation (n = 6); 14-19 the study did not include treatment of the face (n = 2); 20,21 the study involved combination treatment but did not report outcomes for the growth factor preparation alone (n = 5) [22][23][24][25][26] or the growth factor preparation was not applied regularly (n = 2). 27,28 This left 33 studies, involving a combined total of 1180 participants, for inclusion in the systematic review (Table 1). Table 1 summarizes the 33 identified studies and highlights study design, treatments, and methods of evaluation.  There were nine RCTs (7 double-blind and 2 single-blind) 30,[32][33][34]37,42,46,48,56,59 and 24 CS studies. 29,31,35,36,[38][39][40][43][44][45]47,[49][50][51][52][53][54][55]57,58,[60][61][62] RCTs enrolled 331 participants (317 completed) with 811 enrolled in the CS studies (748 completed). Placebo control was used in six of the RCTs, 30,[32][33][34]46,48,56 with an active growth factor preparation control in four trials. 37,42,56,59 One trial had a part that compared treatment with placebo followed by a second part versus and an active control. 56 All trials compared the tested treatment versus baseline, with nine comparing it with a control group (placebo or active control). Twenty-five studies (76%) occurred in the United States and the others in six different countries. Seventeen trials were performed in single centers. One trial was reported in two separate publications. 33,34 Sample sizes ranged from 12 to 120 among the 1180 partic- Two studies did not specify the participants' gender. 51 Twenty-three different topical growth factor preparations were evaluated (Table 1). Further details of the key ingredients in each preparation (including reported growth factors) are shown in Table S2. Eleven of the growth factor preparations were humanderived growth factors; five were from animals, plants, or enzymes; and seven were human-like recombinant derived. When reported, TGF-β1 and EGF were the most common growth factors included in each preparation (12 of the 23 preparations), followed by VEGF (11 of 23), IGF-1 (9 of 23), bFGF (FGF-2), and HGF (9 of 23). The cytokines IL-6 and IL-8 were reported in seven preparations (Table S2).

| Characteristics of included studies
Thirty-two trials mentioned growth factors as the key component of their tested treatment protocol. One comparative trial compared a growth factor preparation that was administered along with a filler-grade hyaluronic acid serum and compared it with a separate growth factor preparation. 59 A further uncontrolled CS reported outcomes with a growth factor preparation combined with a hyaluronic acid serum. 61

| Study quality and risk of bias
Of the 33 included studies, nine were level of evidence Ib and 24 were of evidence level IV (Table S3). Seven of the nine RCTs were double-blind; 30,[32][33][34]42,46,48,56 seven were placebo-controlled. and four trials 37,42,56,59 compared the tested growth factor preparation with an active growth factor control. Dropouts were relatively low F I G U R E 1 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram summarizing the identification, screening, eligibility, and inclusion of studies that investigated the effectiveness of topical growth factors for facial rejuvenation. 8 Records identified through database searching (n=1740) -OVID Medline (n=335) -OVID Embase (n=978) -Scopus (n=318) -Cochrane Library (n=109)   Lipid-free serum containing SCA and antioxidants (hyaluronic acid, epidermal peptides, coffee oil, and olive oil) for normal-oily skin.
g Oil in water cream containing SCA and antioxidants (ectoine, hyaluronic acid, epidermal peptides, coffee oil, and olive oil) for normal-dry skin, and for periocular and eyelid skin (eye area).
h Optional 3 m extension.

TA B L E 1 (Continued)
across the trials and largely unrelated to adverse events from the study treatment. The risk of bias was evaluated in the nine RCTs (Table S4). All trials had a risk that was low on all five subdivided risks. None of the nine studies reported the method or tool used for randomization.

| Efficacy outcome assessment
For evaluating the growth factor product performance, 30 out of the 33 studies used clinical evaluation by the investigator (or blinded expert) as well as photographic documentation. The remaining two studies used 3D imaging to assess wrinkles and dermal characteristics. 43,60 Various numerical scales were used to assess each of the above outcomes, including predominantly individual scales (Table S5).
Self-assessment questionnaires were used in 28 of the 33 studies (Table 1). These were based either on the same scales used in the investigator assessment or using separate questionnaires developed and was greater than 99% in each. Table 2 summarizes the key outcomes in the individual trials for the investigator-and participant-reported clinical outcomes (wrinkles, skin texture, and overall appearance), objective outcomes, and adverse events using the symbols described above. Full details of the outcomes reported in each trial are provided in Table S2. The key findings are summarized below.

| Fine lines/wrinkles
Investigator assessment of fine lines/wrinkles was evaluated in 1068 participants from 30 studies (9 RCTs and 21 CS) ( Table 2). A numerical improvement in wrinkles at the end of each trial with the growth factor preparation versus baseline or versus placebo was reported in all these trials.
Two of the nine RCTs reported an improvement (numerical or statistical) with the growth factor preparation from baseline but showed no statistically significant difference in fine lines/wrinkles compared with each of their placebo controls. 34,46 Of the remaining 7 RCTs, 6 reported a statistically significant improvement in fine lines or coarse wrinkles from baseline or their placebo control. 30,32,37,48,56,59 The remaining trial showed mean improvements of 34% and 41% in wrinkles after 3 months of treatment with the two growth factor preparations but did not report any statistical analysis for the observed changes from baseline. 42 Three RCTs comparing a growth factor preparation with an active growth factor control showed no statistically significant difference in fine lines/wrinkles between treatments, 37,42,56 with a fourth comparative trial showing a treatment difference in favor of growth factor preparation combined with a hyaluronic acid serum compared with a separate growth factor preparation. 59 Where reported, the median improvement in wrinkles scores from baseline was 34.0% (range 6.9%-41.5%) and 19.0% in a single trial 32 versus placebo control (Figure 2A). in wrinkles scores by participants in the RCTs was 38.0% (range 18.8%-46.0%).
Among the 17 CS studies, in which participants assessed fine lines/wrinkles, all reported a numerical or statistically significant improvement versus baseline or placebo. Where reported, median improvement in wrinkles scores was 49.6% (range 26.0%-65.3%).

| Skin texture
Investigator assessment of the effect of topical growth factor preparations on skin texture was evaluated in 850 participants from 23 studies (7 RCTs and 16 CS) ( Table 2). A statistically significant improvement versus baseline or placebo was seen in 17 of these stud-  Table 2). The median improvement versus baseline was 28.0% (range 13.3%-89.0%) ( Figure 2B) with 4 trials reporting improvement within 2-4 weeks of initial administration.
Among the 7 RCTs reporting this outcome versus baseline or versus placebo, a statistically significant improvement was observed in 3 of the trials. 32,42,46 Where reported, the median improvement in skin texture scores by participants was 49.0% (range 8.0%-54.0%).
Among the 17 CS studies that reported participant skin texture, all reported a numerical (nine studies) or statistically significant (eight studies) improvement versus baseline or placebo. Where reported, the median improvement in skin texture scores was 37.9% (range 21.0%-86.0%).

| Overall facial skin appearance or photodamage
Investigator assessment of overall facial skin appearance or photodamage was evaluated in 612 participants from 17 studies (5 RCTs and 12 CS) ( Table 2). A statistically significant improvement versus baseline or placebo was reported in 12 studies (2 RCT and 10 CS) with a numerical improvement in a further two CS studies. 39,45 Where reported, the median improvement in overall facial skin appearance in the CS studies was 16.5% (range 14.2%-27.3%).
Participant's assessment of overall facial skin appearance was evaluated in 720 participants from 22 studies (5 RCTs and 17 CS). A statistically significant improvement versus baseline or placebo was reported in 12 studies (2 RCT, 10 CS) with a numerical improvement in an additional 7 CS studies. Where reported, the median improvement in overall facial skin appearance in the CS studies was 32.0% (range 21.0%-42.4%).

| Other objective analyses
Optical profilometry using silicone impressions was used in 4 studies (2 RCT and 2 CS) ( Table 2). All studies showed a statistically significant improvement in one or more of the measured parameters, including shadows due to fine lines/wrinkles, 30 periocular rhytides and coarse crow's feet lines, 48 texture irregularities and wrinkle depth, 29 skin dryness/roughness, and wrinkle depth. 47 Significant improvements in skin elasticity, as measured by a cutometer, was reported in 5 of the 6 studies that evaluated this outcome (1 RCT and 4 CS).
Increased skin hydration was also reported in 4 studies (1 RCT and 3 CS) that evaluated this outcome.

| Safety outcomes
Adverse events were assessed in 28 studies (1051 participants) ( Table 2). Three trials reported mild treatment-related adverse events. 37,39,50 In one trial, where the preparation was applied to infraorbital and lateral canthal skin, 39 there was one case of mild canthal erythema, and one case of mild eye irritation that resolved spontaneously. In the other trial applying topical kinetin 0.1% lotion, 50

| Limitations
Limitations of the trials included in this review are recognized. These Consistent with many studies in aesthetic medicine, the included studies had relatively small sample sizes (mean of 35 participants) meaning that it was more difficult to establish statistically significant differences between the experimental group and the placebo group.
The study outcomes quantifying the degree of skin rejuvenation in most trials were largely based on pre-and posttreatment clinical or photographic comparisons using a variety of assessment scales instead of being analyzed by a blinded, objective, independent third observer or using an objective, validated, computer analysis.

| Future directions
Future studies may help to determine which aging-specific features (e.g., texture versus fine lines/wrinkles) are most responsive to treatment with topical growth factor preparations and which patient characteristics (e.g., age, gender, ethnicity, the severity of photoaging) best predict a favorable response to treatment. 74 The optimal duration of topical treatment and the duration of clinical benefit after stopping treatment also remains to be eluci-

| CON CLUS IONS
Based on the current evidence, topical application of growth factor products designed to directly influence collagen metabolism are suitable as one of the preventive measures and early aesthetic interventions to improve wrinkles, skin surface texture, and overall facial appearance. The overall improvements in fine lines and wrinkles and skin texture are relatively modest (<50%) but consistent in the investigator and participant assessments. Improvements were seen with several parameters as early as 2-4 weeks with a low number of reported adverse events.

AUTH O R CO NTR I B UTI O N S
DJQ conceived and designed the study, collected data, analyzed the data, and wrote the first draft of the article. HH provided input on the study design and inclusion of studies and contributed to revisions of the article. All authors approved the final version of the submitted article.