Hyaluronan Metabolism in Human Keratinocytes and Atopic Dermatitis Skin Is Driven by a Balance of Hyaluronan Synthases 1 and 3

Abstract

Hyaluronan (HA) is a glycosaminoglycan synthesized directly into the extracellular matrix by three hyaluronan synthases (HAS1, HAS2, and HAS3). HA is abundantly synthesized by keratinocytes but its epidermal functions remain unclear. We used culture models to grow human keratinocytes as autocrine monolayers or as reconstructed human epidermis (RHE) to assess HA synthesis and HAS expression levels during the course of keratinocyte differentiation. In both the models, epidermal differentiation downregulates HAS3 mRNA expression while increasing HAS1 without significant changes in hyaluronidase expression. HA production correlates with HAS1 mRNA expression level during normal differentiation. To investigate the regulation of HAS gene expression during inflammatory conditions linked to perturbed differentiation, lesional and non-lesional skin biopsies of atopic dermatitis (AD) patients were analyzed. HAS3 mRNA expression level increases in AD lesions compared with healthy and non-lesional skin. Simultaneously, HAS1 expression decreases. Heparin-binding EGF-like growth factor (HB-EGF) is upregulated in AD epidermis. An AD-like HAS expression pattern is observed in RHE incubated with HB-EGF. These results indicate that HAS1 is the main enzyme responsible for HA production by normal keratinocytes and thus, must be considered as an actor of normal keratinocyte differentiation. In contrast, HAS3 can be induced by HB-EGF and seems mainly involved in AD epidermis.

Methyl‐β‐cyclodextrin concurs with interleukin (IL)‐4, IL‐13 and IL‐25 to induce alterations reminiscent of atopic dermatitis in reconstructed human epidermis

“…2a), in agreement with the upregulation observed in AD. 4,8 Though, no significant changes were found with respect to HAS1 expression levels (data not shown), unlike data collected from AD lesions. S4a).…”

Hyaluronan Does Not Regulate Human Epidermal Keratinocyte Proliferation and Differentiation

“…Hyaluronidase Treatment Decreases HA Production without Affecting Cell Proliferation-Previously, we demonstrated that hyaluronidase treatment does not affect the differentiation of keratinocyte monolayer models (16). Here, we investigated the effect of HA degradation on proliferation in the same model.…”

“…In those studies, we suppressed HA from keratinocyte monolayer cultures using either 4MU or hyaluronidase. Surprisingly, HA depletion had no influence on the differentiation process (16). In light of those conflicting data, the present study was designed to unravel the role of HA in proliferation and differentiation of human keratinocytes grown in a monolayer model and in an in vitro model that is as close as possible to native human epidermal growth, i.e.…”

“…We have recently demonstrated that HAS1 is the main synthase involved in extracellular HA production by normal human keratinocytes, whereas HAS2 and HAS3 are instead implicated during the early steps of keratinocyte culture as well as in atopic dermatitis conditions (16). In those studies, we suppressed HA from keratinocyte monolayer cultures using either 4MU or hyaluronidase.…”

Hyaluronidase-1 Is Mainly Functional in the Upper Granular Layer, Close to the Epidermal Barrier

“…During spontaneous differentiation of keratinocytes HA of high molecular mass accumulates simultaneously with increased HAS1 and decreased HAS2/3 expressions. (Malaisse et al, 2014). Under physiological conditions HA catabolism is mainly due to hyaluronidases (HYAL).…”