EGF Upregulates, Whereas TGF-β Downregulates, the Hyaluronan Synthases Has2 and Has3 in Organotypic Keratinocyte Cultures: Correlations with Epidermal Proliferation and Differentiation

Abstract

Hyaluronan, a major extracellular matrix molecule in the vital cell layers of skin epidermis, has been suggested to support proliferation and migration of keratinocytes, during challenges like wounding and inflammation. An organotypic keratinocyte culture originated from continuous rat epidermal keratinocyte cell line was subjected to the proliferative and antiproliferative growth factors epidermal growth factor and transforming growth factor beta, respectively, to study their influence on hyaluronan synthesis and epidermal morphology. Epidermal growth factor induced a 4-fold increase of epidermal hyaluronan concentration. This was associated with upregulation of the hyaluronan synthases Has2 and Has3, and the hyaluronan receptor CD44. 5-Bromo-2'-deoxyuridine labeling, basal cell height, and the thickness of vital epidermis were increased, reflecting the hyperplastic effects of epidermal growth factor. The expression of keratin 10 and the maturation of filaggrin were inhibited, and epidermal permeability barrier became less efficient, indicating compromised terminal differentiation by epidermal growth factor. In contrast, transforming growth factor beta reduced the content of hyaluronan and the mRNA of Has2 and Has3. At the same time, transforming growth factor beta suppressed keratinocyte proliferation and epidermal thickness, but retained intact differentiation. The results suggest that epidermal hyaluronan synthesis, controlled by epidermal growth factor and transforming growth factor beta through changes in the expression of Has2 and Has3, correlates with epidermal proliferation, thickness, and differentiation.

A Rapid Transient Increase in Hyaluronan Synthase-2 mRNA Initiates Secretion of Hyaluronan by Corneal Keratocytes in Response to Transforming Growth Factor β

“…The particular HAS gene involved, however, appears to be highly cell-and tissue-dependent. In synovial fibroblasts TGF␤ activates mostly HAS1 (15,23,31), whereas HAS3 is up-regulated in chondrocytes and down-regulated in keratinocytes by TGF␤ (15,27,32,33). It is interesting to note that two other cell types reported to respond to TGF␤ with up-regulation of HAS2 are both derived from the anterior segment of the eye: trabecular meshwork cells and corneal endothelial cells (13,25).…”

Hyaluronan-dependent pericellular matrix☆

“…In human skin organ cultures, factors like all-trans-retinoic acid which increase hyaluronan synthesis lead to delayed differentiation [132], like in human skin in vivo. Likewise, organotypic epidermal cultures show that keratinocyte differentiation is stimulated and inhibited by factors that decrease and increase hyaluronan synthesis, respectively [133]. Enhancing turnover of cell surface hyaluronan by hyaluronidase promotes terminal differentiation of keratinocytes [134].…”

Cellular Content of UDP-N-acetylhexosamines Controls Hyaluronan Synthase 2 Expression and Correlates with O-Linked N-Acetylglucosamine Modification of Transcription Factors YY1 and SP1

“…Changes in hyaluronan production have been associated mostly with the expression level of HAS genes (3-6), especially in keratinocytes (7)(8)(9)(10)(11)(12)(13). Of the three genes, particularly HAS2 is subject to regulation by growth factors, cytokines, and hormones (4,14,15).…”

“…Of the three genes, particularly HAS2 is subject to regulation by growth factors, cytokines, and hormones (4,14,15). In keratinocyte cultures, EGF, keratinocyte growth factor, TNF␣, and retinoic acid induce, whereas TGF␤ inhibits, HAS2 expression (8,10,13,16). Accordingly, the HAS2 promoter has been shown to contain functional response elements (REs) 3 for different transcription factors, including retinoid acid receptor, NF-B, CREB1 (cAMP response elementbinding protein 1), and SP1 (specificity protein 1) (7,11,16).…”