Creative Touch Permanent Makeup and Aesthetics

E-cadherin (encoded by CDH1) is a type I classical cadherin expressed on keratinocyte lateral membranes from the stratum basale through the stratum spinosum. Its extracellular domain contains five cadherin repeat units, each of which requires Ca²⁺ binding to maintain the rigid, rod-like conformation that enables homophilic adhesion between adjacent cells. When the epidermal calcium gradient is disrupted and extracellular calcium falls below the threshold required for ectodomain rigidity, the cadherin repeat units lose their rod-like conformation and the adhesion interface collapses.

In the spinous layer, E-cadherin forms the adherens junction component of the apical junctional complex – providing lateral keratinocyte cohesion independently of but alongside corneodesmosomal adhesion. Where corneodesmosomes anchor cells structurally against shear and tensile forces, E-cadherin junctions couple the intracellular actin cytoskeletons of adjacent cells, co-ordinating the collective mechanical behaviour of the spinous layer as a tissue rather than an assembly of individual cells. E-cadherin–β-catenin signalling downstream of junction formation also feeds into the Wnt pathway, connecting adherens junction status to keratinocyte proliferation and differentiation decisions at the transcriptional level.

The calcium dependency gives E-cadherin a direct connection to the epidermal calcium gradient disruption that hard water and alkaline pH shift produce. Under normal conditions the calcium paradox operates primarily at the SC and upper SG levels – below the spinous layer where E-cadherin junctions are established. Sustained barrier disruption, alkaline pH shift, and chronic calcium gradient redistribution in aged skin each progressively reduce the calcium availability in the upper spinous layers where new E-cadherin junctions are assembled as differentiating cells migrate upward, impairing the junction formation that should accompany early differentiation. This is a mechanistically plausible link rather than a directly confirmed endpoint in hard water research, and should be understood as such.

In the polynucleotides clinical literature, E-cadherin upregulation has been confirmed as a barrier recovery marker following PDRN treatment – reflecting restored adherens junction formation alongside the broader differentiation programme recovery that polynucleotides produce through A2A receptor activation and NF-κB suppression. Its upregulation is one of several confirmed molecular markers of barrier recovery in that context, and gives the Polynucleotides entity a specific, named molecular outcome to reference rather than a general “barrier improvement” descriptor.