Creative Touch Permanent Makeup and Aesthetics

PGA’s clinical relevance in skin biology operates through four converging mechanisms. As a humectant, it binds up to 5,000 times its weight in water under optimal conditions – substantially exceeding hyaluronic acid’s water retention capacity – while remaining on the skin surface as a breathable hydrating film rather than penetrating the stratum corneum. Its anionic structure inhibits hyaluronidase – the enzyme family that degrades dermal hyaluronic acid – protecting both endogenous HA and injected HA from enzymatic breakdown. patents.google.com At the barrier level, topical γ-PGA dose-dependently upregulates mRNA expression of filaggrin, loricrin, involucrin, serine palmitoyl transferase, fatty acid synthase, and HMG- CoA reductase in keratinocytes – simultaneously upregulating HAS-1, HAS-2, and HAS-3 for endogenous HA synthesis and aquaporin-3 for hydration regulation. ^[1] PGA additionally inhibits tyrosinase activity, connecting it to the melanogenesis pathway and giving it relevance beyond hydration and barrier biology. www.sciencedirect.com

Water Binding and Surface Film Formation

PGA’s molecular architecture – a densely branched, crosslinked polypeptide chain carrying multiple carboxylate groups – gives it an extraordinary capacity to capture and retain water molecules through electrostatic interaction. At up to 5,000 times its weight in water under optimal conditions, it substantially exceeds the ~1,000 times figure commonly cited for hyaluronic acid.

The high molecular weight of topically applied PGA – typically 100–4,000 kDa – means it does not penetrate the stratum corneum but instead forms a continuous hydrating film on the skin surface. This film behaviour has two consequences that differ fundamentally from how HA operates topically: PGA primarily retains existing moisture within the SC rather than drawing moisture from the deeper epidermis, making it more effective in low-humidity environments where HA can paradoxically draw water from the skin when atmospheric humidity is insufficient to compensate. At the same time, the surface film reduces TEWL during the overnight permeability peak described in the Circadian Rhythm of Skin Barrier entity – functioning as a partial occlusive that does not fully block barrier gas exchange.

The combination of PGA and lower-molecular-weight actives is mechanistically rational: PGA’s surface film reduces evaporation of the hydrated environment in which smaller molecules – peptides, vitamins, ceramide precursors – are diffusing, extending their contact time with the SC surface without itself requiring penetration.

Hyaluronidase Inhibition

The most clinically distinctive property of PGA in the context of skin treatment is its inhibition of hyaluronidase – the family of glycosidase enzymes that hydrolyse hyaluronic acid in the dermis, contributing to ground substance depletion as part of the ageing process described in the Skin Ageing entity. PGA’s polyanionic structure competitively interferes with hyaluronidase substrate binding, and this inhibitory activity has been demonstrated across a wide range of molecular weights (50–4,000 kDa), indicating the mechanism is structural rather than size-dependent. patents.google.com

The evidence base for this mechanism is primarily patent-origin and in vitro – the Korean patent (US8916141B2) represents the primary documented source – and clinical trial data on the magnitude of in vivo hyaluronidase inhibition by topical PGA in human subjects remains limited. The mechanism is chemically coherent and the in vitro inhibition is well-documented; the translation to meaningful in vivo dermal HA protection from topical application is plausible but requires appropriately scaled expectations rather than treatment-as-established-clinical-fact framing.

Where the hyaluronidase inhibition claim has more direct clinical grounding is in the context of injected hyaluronic acid. Hyaluronidase activity is upregulated in inflammatory tissue environments – the same inflammatory tissue responses that post-injection recovery involves – and the potential for topical PGA applied over an HA-treated area to extend HA longevity by reducing enzymatic degradation at the tissue surface is mechanistically coherent, even if the clinical magnitude of this effect has not been formally measured in RCT conditions.

Barrier Protein and Endogenous HA Upregulation

The most comprehensively evidenced skin barrier mechanism for PGA comes from a 2025 study examining γ-PGA derived from a novel Bacillus subtilis strain in both keratinocyte cell culture and reconstructed human skin models. ^[1] Topical γ-PGA treatment produced dose-dependent upregulation of:

• Barrier structural proteins: filaggrin, loricrin, involucrin – the three primary terminal differentiation markers whose suppression by IL-4/ IL-13 defines atopic barrier dysfunction
• Lipid synthesis enzymes: serine palmitoyl transferase (the rate-limiting step in ceramide de novo synthesis), fatty acid synthase, and HMG-CoA reductase (the rate-limiting step in cholesterol synthesis)
• Endogenous HA production: HAS-1, HAS-2, and HAS-3 – all three hyaluronic acid synthase isoforms – indicating PGA drives HA synthesis from within rather than merely delivering HA externally
• Aquaporin-3: the water channel protein that regulates keratinocyte hydration and participates in glycerol transport through the epidermal layers

This profile is unusually broad for a single topical ingredient. The simultaneous upregulation of filaggrin, ceramide precursor synthesis enzymes, cholesterol synthesis, and endogenous HA production means PGA addresses multiple nodes of the barrier biology simultaneously – the SC lipid bilayer components (ceramides, cholesterol), the NMF pathway (filaggrin), and the ground substance hydration environment (HA) – rather than targeting one mechanism in isolation.

The filaggrin upregulation is particularly significant in the context of the IL-4/IL-13 suppression pathway: where Th2 cytokines suppress filaggrin, loricrin, and claudin-1 through JAK-STAT6, PGA’s upregulation of the same proteins through a distinct pathway offers a compensatory mechanism that does not require the cytokine environment to resolve first.

Tyrosinase Inhibition

PGA inhibits tyrosinase activity independently of its humectant and barrier-regulatory functions. www.sciencedirect.com Tyrosinase is the rate-limiting enzyme of the melanogenesis pathway described in the Hyperpigmentation entity – its inhibition reduces melanin synthesis upstream of pigment transfer and deposition. The mechanism by which PGA inhibits tyrosinase is not fully characterised in published literature but is consistent with the copper-chelating or competitive inhibition patterns seen with other anionic polypeptide structures.

This tyrosinase inhibitory property extends PGA’s clinical relevance beyond purely hydration-focused applications to brightening and hyperpigmentation management protocols, particularly where a hydrating carrier that simultaneously reduces melanogenesis is desirable – such as post-procedure brightening care or as a base layer in combination depigmentation routines.