Remodeling of the dermal extracellular matrix occurs during photoaging. Here, the effect of repetitive UVB irradiation on dermal hyaluronic acid (HA) was examined. C57/BL6 mice were chronically (182 days) irradiated with UVB, and consecutive skin biopsies were collected during the irradiation period and afterward (300 and 400 days of age). UVB caused marked loss of HA from the papillary dermis and down-regulation of HA synthase 1 (HAS1), HAS2, and HAS3 mRNA expression. In contrast, hyaluronidases (HYAL) 1, HYAL2, and HA receptor CD44 were unchanged. Furthermore, transforming growth factor ␤-1 (TGF-␤1) and TGF-␤1-receptor II expression were decreased in UVB-irradiated biopsies, and TGF-␤1 strongly induced HAS1 and HAS2 expression in cultured dermal fibroblasts. Therefore, TGF-␤1 might be one factor involved in UVB-induced down-regulation of HAS enzymes. In addition, total cell number and the percentage of proliferating fibroblasts in the papillary dermis of UVB-irradiated mice were decreased. Down-regulation of HAS2 by lentiviral overexpression of short hairpin RNA in vitro caused inhibition of HA synthesis, DNA synthesis, and migration of dermal fibroblasts. In conclusion, chronic UVB irradiation induces loss of HA from the dermis, thereby contributing to the quiescent phenotype of dermal fibroblasts. 1 Photoaging is the most common form of skin damage caused by chronic, repetitive sun exposure.2 The long-term exposure to solar UV irradiation induces damage to the dermal connective tissue and the extracellular matrix (ECM), which in turn leads to the aged appearance of photodamaged skin. Hallmark of this UV-induced ECM remodeling is the degradation of collagen and elastin through the UVB-induced activation of matrix metalloproteinases and decreased de novo synthesis of collagen. The mechanisms of UVB-induced matrix metalloproteinase activation 3 and inhibition of collagen synthesis have been studied in detail.2 In contrast the effect of UVB on hyaluronic acid (HA), another key component of the dermal ECM, is much less understood, and the underlying mechanisms are primarily unknown. HA is a linear polymer composed of repeating disaccharides (D-glucuronic acid-␤-1,3-N-acetylglucosamine-␤-1,4-) and assembled from the respective activated nucleotide sugars (UDPglucuronic acid, UDP-N-acetylglucosamine) at the inner plasma membrane by HA synthases (HAS). Three different HAS isoforms are known that reside in the plasma membrane and extrude the growing HA polymer into the extracellular space.4 HAS1 and HAS2 produce high molecular mass HA (2 to 4 ϫ 10 6 Da), whereas HAS3 synthesizes smaller HA (0.4 to 2.5 ϫ 10 5 Da). 5 The variation of the MW is the only modification of HA because O-or N-sulfations do not occur. HA is an agonist of CD44 and RHAMM (receptor of HA-mediated motility), which enables HA to initiate specific signaling events.6 This receptor signaling and the formation of pericellular HA coats supports proliferation and migration of a variety of cell types including skin fibroblasts. 7 In addition, antiapoptoti...

BackgroundOesophageal cancer is a highly aggressive tumour entity with at present poor prognosis. Therefore, novel treatment options are urgently needed. Hyaluronan (HA) is a polysaccharide present in the matrix of human oesophageal squamous cell carcinoma (ESCC). Importantly, in vitro ESCC cells critically depend on HA synthesis to maintain the proliferative phenotype. The aim of the present study is (1) to study HA-synthase (HAS) expression and regulation in human ESCC, and (2) to translate the in vitro results into a mouse xenograft model of human ESCC to study the effects of systemic versus tumour targeted HAS inhibition on proliferation and distribution of tumour-bound and stromal hyaluronan.MethodsmRNA expression was investigated in human ESCC biopsies by semiquantitative real-time RT PCR. Furthermore, human ESCC were xenografted into NMRI nu/nu mice. The effects on tumour progression and morphology of 4-methylumbelliferone (4-MU), an inhibitor of HA-synthesis, and of lentiviral knock down of HA-synthase 3 (HAS3), the main HAS isoform in the human ESCC tissues and the human ESCC cell line used in this study, were determined. Tumour progression was monitored by calliper measurements and by flat-panel detector volume computed tomography (fpVCT). HA content, cellular composition and proliferation (Ki67) were determined histologically.ResultsmRNA of HAS isoform 3 (HAS3) was upregulated in human ESCC biopsies and HAS3 mRNA was positively correlated to expression of the epidermal growth factor (EGF) receptor. EGF was also proven to be a strong inductor of HAS3 mRNA expression in vitro. During the course of seven weeks, 4-MU inhibited progression of xenograft tumours. Interestingly, remodelling of the tumour into a more differentiated phenotype and inhibition of cell proliferation were observed. Lentiviral knockdown of HAS3 in human ESCC cells prior to xenografting mimicked all effects of 4-MU treatment suggesting that hyaluronan produced by ESCC is accountable for major changes in tumour environment in vivo.ConclusionsSystemic inhibition of HA-synthesis and knockdown of tumour cell HAS3 cause decreased ESCC progression accompanied by tumour stroma remodelling and may therefore be used in novel approaches to ESCC therapy.

Myocardial infarction (MI) is followed by extracellular matrix (ECM) remodeling, which is on the one hand required for the healing response and the formation of stable scar tissue. However, on the other hand, ECM remodeling can lead to fibrosis and decreased ventricular compliance. The small leucine-rich proteoglycan (SLRP), biglycan (bgn), has been shown to be critically involved in these processes. During post-infarct remodeling cardiac fibroblasts differentiate into myofibroblasts which are the main cell type mediating ECM remodeling. The aim of the present study was to characterize the role of bgn in modulating the phenotype of cardiac fibroblasts. Cardiac fibroblasts were isolated from hearts of wild-type (WT) versus bgn ؊/0 mice. Phenotypic characterization of the bgn