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The Trendy Topicals — Growth Factors, Exosomes, Peptides, NAD, PDRN, and the Rest

Growth Factors, Exosomes, Peptides, NAD, PDRN, and the Rest. What Does the Evidence Actually Say?

A new category of topical ingredient arrives in aesthetic medicine approximately every eighteen months, trailing impressive science and impressive marketing in roughly equal measure. Here is an honest attempt to separate the two.

The question that precedes all others

Before examining any topical ingredient on its own terms, there is a prior that the industry fails to ask loudly enough. Does it penetrate the skin barrier in a biologically active form, in sufficient concentration, to reach the tissue where it is supposed to act?

We in the companion piece that the stratum corneum is a formidably selective membrane. larger than approximately 500 Daltons cannot penetrate it easily under normal conditions.

The optimal characteristics of a topically delivered active ingredient i.e. low molecular weight, moderate and aqueous solubility are met by a small proportion of the ingredients currently being marketed as advanced topical therapies.

For the remainder, the question of penetration is not a minor technical detail. It is the central clinical question, and the one most conspicuously absent from product marketing.

With that question established as the lens through which that follows should be read, here is an honest assessment of the principal trendy topical categories.

Growth factors

Growth factors such as epidermal growth factor (EGF), transforming growth factor beta (TGF-beta), fibroblast growth factor (FGF), and others are endogenous signalling proteins that regulate cell proliferation, differentiation, collagen synthesis, and wound . Their biological relevance to skin ageing is unquestionable. The question is whether they can be delivered effectively through a topical formulation.

studies indicate that topically applied growth factors and cytokines have been clinically shown to promote skin rejuvenation; however, their large molecular size, generally greater than 15,000 Daltons, limits their ability to penetrate the tightly packed stratum corneum. Molecules larger than 500 Daltons generally cannot easily penetrate the corneum to reach the viable keratinocytes in the stratum basale

EGF, at approximately 6,000 Daltons, is considerably smaller than most growth factors and is therefore the most studied and most plausible candidate for topical delivery. The greatest efficiency of EGF was obtained intradermally, with a greater reduction of rhytids, folds, and a longer over time. It may be to improve topical penetration by chemical modification with lipophilic molecules or by facilitating diffusion through compromised skin, for example after microneedling or laser resurfacing

The clinical implication is important: topical growth factor products may have some surface-level effect on keratinocytes in the upper epidermis, and post-procedural application barrier disruption is a more defensible delivery strategy than standard topical application to intact skin.

A systematic review of twenty-three different topical growth factor preparations found of clinical benefit in skin rejuvenation, but noted that study quality was and that the majority of preparations were evaluated in studies of short duration. The is plausible, the evidence is real but modest, and the penetration question remains only partially answered

Peptides

Peptides are short chains of amino acids, smaller and more structurally flexible than intact growth factor proteins, that act as signalling molecules, stimulating fibroblast activity, collagen synthesis, or muscle relaxation depending on their sequence.

Their smaller molecular size makes barrier penetration considerably more achievable than for larger proteins, and the peptide evidence base is correspondingly more developed.

Topical exosome and peptide therapies have shown promise in early trials, but neither is FDA approved. Use of topical products requires unique considerations for of drug due to difficulty penetrating the skin barrier, active ingredients in topical medications can be less than in other methods of drug delivery.

Signal peptides such as palmitoyl pentapeptide (Matrixyl) and its derivatives have a reasonable body of in vitro and clinical evidence supporting their collagen-stimulating effects. Neurotransmitter-inhibiting peptides, which claim to reduce the depth of expression lines by interfering with acetylcholine release at the neuromuscular junction, are mechanistically plausible but clinically considerably less potent than botulinum toxin, which should perhaps be stated more in the marketing. The overall peptide picture is one of real but modest efficacy, significant dependence, and a tendency for the marketing to overstate what the evidence supports

Exosomes

Exosomes are nanoscale extracellular vesicles — typically 30 to 150 nanometres in diameter — secreted by cells and carrying a cargo of proteins, lipids, micro-RNAs, and signalling molecules. Their biology is genuinely fascinating. As mediators of intercellular communication, they play important roles in tissue repair, immune modulation, and cellular regeneration. The injectable exosome evidence, particularly in the context of wound healing and post-procedure recovery, is developing rapidly and with genuine scientific .

The topical story is considerably more complicated. Exosomes are nanoscale and therefore theoretically capable of penetrating the stratum corneum through intercellular routes — but whether they do so in sufficient quantities to exert a meaningful effect on dermal fibroblasts, whether they remain biologically active after the manufacturing and process, and whether the cell source and preparation method produce a standardised and reproducible biological entity, are questions the clinical literature has not yet answered satisfactorily.

The evidence base for topical exosomes remains early-stage and predominantly observational.

It is also worth noting — and we do so with a raised rather than a sledgehammer — that one prominent product in this category proudly carries the prefix "EXO" in its name. On reflection, that designation applies equally to every product ever applied to the surface of the skin. The word is doing marketing work, not scientific work.

A case study in honest complexity — Medik8 EXO-PDRN Prismatic+

Medik8 are a company we have considerable respect for. Their team is serious, their formulation standards are generally above industry average, and their willingness to engage with the clinical literature distinguishes them from most of the market. The recent acquisition by L'Oreal is a separate and somewhat melancholy observation.

Their EXO-PDRN Prismatic+ product, designed for post-microneedling application is worth examining in some detail precisely because it represents the category at its most scientifically credible.

The product contains several active ingredients, each of which merits assessment

A "Prismatic PDRN" described as a vegan, stable tetrahedral structure addresses the traditional sourcing concern around salmon-derived PDRN and claims structural optimisation for penetration. The tetrahedral DNA concept has genuine scientific in drug delivery research; this specific formulation meaningful dermal penetration through post-microneedling channels, before those channels close, typically within thirty to sixty minutes, is a question the marketing does not answer and the literature for this specific product does not yet address.

The "GF MiniProtein" and "Expression Line MiniProtein" are proprietary peptide complexes, the former likely a collagen-stimulating signal peptide, the latter suggesting something in the acetyl family. The smaller molecular size of purpose-designed peptides makes penetration more achievable, and the post-microneedling delivery context is the most defensible application window for these ingredients.

The "Triple Exosome Complex, up to 50 billion exosomes per tube" raises the penetration and standardisation questions discussed above. The number is impressive; its clinical significance depends on factors the product information does not specify. The ATP precursor, almost certainly a NAD or NMN precursor addresses cellular energy metabolism; the topical evidence for this application remains thin.

The overall picture is of a thoughtfully formulated product with a scientifically plausible rationale, delivered in a context, post-microneedling, that represents the most defensible window for enhanced penetration of larger molecules. The gap between that plausibility and the clinical evidence for this specific combination in this specific delivery context is real, but it is a smaller gap than for most products in this category. Medik8 are operating at the credible end of a market that has a great deal of occupying the other end.

PDRN as a topical

We have written elsewhere about PDRN and as injectable biostimulators, where the evidence base is considerably more developed. As a topical ingredient, the picture is more speculative. PDRN molecules, typically in the range of 50 to 1,500 kilodaltons, are considerably larger than the 500 Dalton threshold for comfortable stratum corneum penetration. Post-procedural application following barrier disruption represents the most scientifically defensible route of topical delivery, which is precisely the context in which the Medik8 product is positioned.

NAD and its precursors

Nicotinamide adenine dinucleotide (NAD) and its precursors, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), have attracted considerable attention in the longevity and anti-ageing space based on their role in cellular energy metabolism and DNA repair. The systemic evidence for NAD precursor supplementation in skin and overall ageing is genuinely interesting. The topical evidence is considerably thinner. Whether topically applied NAD precursors reach in viable keratinocytes in clinically meaningful concentrations, given the barrier and the metabolic complexity of the conversion pathway, is not established to the standard the marketing implies. It is an area to watch with interest rather than one to invest heavily in on current evidence.

Bakuchiol — the "natural retinol alternative"

is a plant-derived meroterpene extracted from the seeds of Psoralea corylifolia, marketed as a gentler, natural alternative to retinol and occasionally as ‘equivalent’ to it in efficacy. The evidence is more than either the enthusiasts or the sceptics tend to acknowledge.

A systematic review of fifteen human clinical trials using topical bakuchiol found that twelve trials were unblinded, open-label trials without a control group, and ten trials used bakuchiol in combination therapy rather than as a standalone ingredient.

That is a significant methodological limitation that should temper the confidence with which bakuchiol is described as a proven retinol equivalent. What the evidence does is that bakuchiol has genuine antioxidant and anti-inflammatory properties, some collagen-stimulating activity in vitro, and a better tolerability profile than retinoids.

Bakuchiol is a retinol alternative with anti-ageing, antibacterial, and anti-inflammatory properties, though additional are warranted to better understand its applications in dermatology. 

The honest clinical positioning is: a useful, well-tolerated ingredient with real but modest anti-ageing activity, appropriate for who cannot tolerate retinoids rather than as a replacement for patients who can. Describing it as equivalent to retinol in efficacy is not currently supported by the evidence, and doing so does a disservice to patients who might otherwise work through the retinoid adaptation period and access a considerably more powerful active ingredient.

Stem cell extracts

A brief word on stem cell extracts — plant or human — which appear in an increasing number of premium products. Plant stem cells are biologically irrelevant to human skin biology. Human stem cell extracts raise questions about standardisation, stability, and whether any active material survives the formulation process in a form that can penetrate the barrier and reach target cells. We are aware of no peer-reviewed evidence that stem cell extracts in topical skincare produce clinically meaningful results through the mechanisms claimed. This is perhaps the category where marketing has most comprehensively outpaced science.

The framework for evaluation

Having examined the principal trendy topical categories, the following framework emerges