The human hyaluronan synthase 2 gene is a primary retinoic acid and epidermal growth factor responding gene

All-trans retinoic acid pretreatment of mesenchymal stem cells enhances the therapeutic effect on acute kidney injury

A promising new therapy option for acute kidney injury (AKI) is mesenchymal stem cells (MSCs). However, there are several limitations to the use of MSCs, such as low rates of survival, limited homing capacity, and unclear differentiation. In search of better therapeutic strategies, we explored all-trans retinoic acid (ATRA) pretreatment of MSCs to observe whether it could improve the therapeutic efficacy of AKI. We established a renal ischemia/reperfusion injury model and treated mice with ATRA-pretreated MSCs via tail vein injection. We found that AKI mice treated with ATRA-MSCs significantly improved renal function compared with DMSO-MSCs treatment. RNA sequencing screened that hyaluronic acid (HA) production from MSCs promoted by ATRA. Further validation by chromatin immunoprecipitation experiments verified that retinoic acid receptor RARα/RXRγ was a potential transcription factor for hyaluronic acid synthase 2. Additionally, an in vitro hypoxia/reoxygenation model was established using human proximal tubular epithelial cells (HK-2). After co-culturing HK-2 cells with ATRA-pretreated MSCs, we observed that HA binds to cluster determinant 44 (CD44) and activates the PI3K/AKT pathway, which enhances the anti-inflammatory, anti-apoptotic, and proliferative repair effects of MSCs in AKI. Inhibition of the HA/CD44 axis effectively reverses the renal repair effect of ATRA-pretreated MSCs. Taken together, our study suggests that ATRA pretreatment promotes HA production by MSCs and activates the PI3K/AKT pathway in renal tubular epithelial cells, thereby enhancing the efficacy of MSCs against AKI.

Hyaluronic Acid as a Modern Approach in Anticancer Therapy-Review

Hyaluronic acid (HA) is a linear polysaccharide and crucial component of the extracellular matrix (ECM), maintaining tissue hydration and tension. Moreover, HA contributes to embryonic development, healing, inflammation, and cancerogenesis. This review summarizes new research on the metabolism and interactions of HA with its binding proteins, known as hyaladherins (CD44, RHAMM), revealing the molecular basis for its distinct biological function in the development of cancer. The presence of HA on the surface of tumor cells is a sign of an adverse prognosis. The involvement of HA in malignancy has been extensively investigated using cancer-free naked mole rats as a model. The HA metabolic components are examined for their potential impact on promoting or inhibiting tumor formation, proliferation, invasion, and metastatic spread. High molecular weight HA is associated with homeostasis and protective action due to its ability to preserve tissue integrity. In contrast, low molecular weight HA indicates a pathological condition in the tissue and plays a role in pro-oncogenic activity. A systematic approach might uncover processes related to cancer growth, establish novel prognostic indicators, and identify potential targets for treatment action.

HAS2-Ezrin-ER axis plays a role in acquired antiestrogen resistance of ER-positive breast cancer

The development of endocrine resistance is a major clinical problem in estrogen receptor-positive (ER+) breast cancer (BrCa) treatment, in which how cancer cells acquire resistance remains obscure. Hyaluronan synthase 2 (HAS2) is the most critical synthase in producing hyaluronan and is well known for its involvement in cancer growth, metabolism and metastasis. Recent evidence has proved that HAS2 is involved in cellular acquired resistance to drug therapy in BrCa. In this work, we first observed that HAS2 expression was decreased in the endocrine-resistant ER+ BrCa cells. Further knocking-out experiments confirmed that the loss of HAS2 in parental ER+ BrCa cells resulted in a following antiestrogen resistance. Next, we found that the HAS2-loss could induce an upregulation of Ezrin, a member of the membrane cytoskeletal protein family who plays key roles in cellular signal transduction. Notably, we identified that the increase of Ezrin induced by HAS2-loss could inhibit the ERα expression and augment antiestrogen resistance, suggesting that a HAS2-Ezrin-ER axis may be associated with the acquirement of endocrine resistance in ER+ BrCa cells. Finally, knockdown or inhibition of Ezrin could restore the sensitivity of endocrine-resistant cells to antiestrogens treatment by activating ERα signaling. Taken together, our findings unraveled a novel HAS2-Ezrin-ER route in regulating the sensitivity of ER+ BrCa cells to antiestrogens, in which Ezrin may be a potential target in endocrine therapy.

The natural antisense transcript HAS2-AS1 regulates breast cancer cells aggressiveness independently from hyaluronan metabolism

Hyaluronan (HA) is a ubiquitous extracellular matrix component playing a crucial role in the regulation of cell behaviors, including cancer. Aggressive breast cancer cells tend to proliferate, migrate and metastatize. Notably, triple-negative breast cancer cells lacking the expression of estrogen receptor (ER) as well as progesterone receptor and HER2 are more aggressive than ER-positive ones. As currently no targeted therapy is available for triple-negative breast cancer, the identification of novel therapeutic targets has a high clinical priority. In ER-negative cells, tumoral behavior can be reduced by inhibiting HA synthesis or silencing the enzymes involved in its metabolism, such as HA synthase 2 (HAS2). HAS2-AS1 is a long non-coding RNA belonging to the natural antisense transcript family which is known to favor HAS2 gene expression and HA synthesis, thus bolstering malignant progression in brain, ovary, and lung tumors. As the role of HAS2-AS1 has not yet been investigated in breast cancer, in this work we report that ER-positive breast cancers had lower HAS2-AS1 expression compared to ER-negative tumors. Moreover, the survival of patients with ER-negative tumors was higher when the expression of HAS2-AS1 was elevated. Experiments with ER-negative cell lines as MDA-MB-231 and Hs 578T revealed that the overexpression of either the full-length HAS2-AS1 or its exon 2 long or short isoforms alone, strongly reduced cell viability, migration, and invasion, whereas HAS2-AS1 silencing increased cell aggressiveness. Unexpectedly, in these ER-negative cell lines, HAS2-AS1 is involved neither in the regulation of HAS2 nor in HA deposition. Finally, transcriptome analysis revealed that HAS2-AS1 modulation affected several pathways, including apoptosis, proliferation, motility, adhesion, epithelial to mesenchymal transition, and signaling, describing this long non-coding RNA as an important regulator of breast cancer cells aggressiveness.

Glycosylated 4-methylumbelliferone as a targeted therapy for hepatocellular carcinoma

BACKGROUND & AIMS

Reaching efficacious drug delivery to target cells/tissues represents a major obstacle in the current treatment of solid malignancies including hepatocellular carcinoma (HCC). In this study, we developed a pipeline to selective add complex-sugars to the aglycone 4-methylumbelliferone (4MU) to help their bioavailability and tumour cell intake.

METHODS

The therapeutic efficacy of sugar-modified rutinosyl-4-methylumbelliferone (4MUR) and 4MU were compared in vitro and in an orthotopic HCC model established in fibrotic livers. The mechanistic bases of its selective target to liver tumour cells were evaluated by the interaction with asialoglycoprotein receptor (ASGPR), the mRNA expression of hyaluronan synthases (HAS2 or HAS3) and hyaluronan deposition.

RESULTS

4MUR showed a significant antiproliferative effect on liver tumoural cells as compared to non-tumoural cells in a dose-dependent manner. Further analysis showed that 4MUR is incorporated mostly into HCC cells by interaction with ASGPR, a receptor commonly overexpressed in HCC cells. 4MUR-treatment decreased the levels of HAS2 and HAS3 and the cytoplasmic deposition of hyaluronan. Moreover, 4MUR reduced CFSC-2G activation, hence reducing the fibrosis. In vivo efficacy showed that 4MUR treatment displayed a greater tumour growth inhibition and increased survival in comparison to 4MU. 4MUR administration was associated with a significant reduction of liver fibrosis without any signs of tissue damage. Further, 60% of 4MUR treated mice did not present macroscopically tumour mass post-treatment.

CONCLUSION

Our results provide evidence that 4MUR may be used as an effective HCC therapy, without damaging non-tumoural cells or other organs, most probably due to the specific targeting.

Pre-Clinical Evaluation of Proprietary Lutein, Zeaxanthin, and Rosemary Formulation for Its Dermal Protective Activity in Male Swiss Albino Mice

This study aimed to evaluate the efficacy of the proprietary lutein, zeaxanthin, and rosemary formulation for its dermal protection against ultraviolet (UV) irradiated skin dehydration. A total of 48 male Swiss albino mice of 8∼12 weeks of age were divided into eight groups of 6 mice: mice in group 1 (G1) were considered the normal control, without treatment and without skin shaving; mice in G2 had their skins were shaved, but did not receive treatment; mice in G3 were the pathological control; mice in G4 were treated as standard (hyaluronic acid); mice in G5∼G8 were treated with low and high doses of 2 different test substances, respectively. Mice were anaesthetized and then depilatory was applied on the dorsal skin area (2 cm×2 cm) on alternate days, then UV/blue light irradiation was carried out for 15 min for 6 weeks. Collagen type 1 gene expression was determined via densitometric analysis, skin elasticity was assessed, and stratum corneum water contents were measured using a cutometer and corneometer. Skin hydration was assessed through transepidermal water loss, and several serum biochemical parameters (collagenase, hydroxyproline, hyaluronic acid, and ceramide levels) were determined to assess the skin moisturizing activity of the product. Images for assessing photoaging were considered between different groups on day 42. All these subjective parameters reached statistical significance (P<0.05) in groups treated with the proprietary lutein and rosemary formulation compared with the placebo-treated group. In conclusion, the proprietary lutein, zeaxanthin, and rosemary formulation showed better protection of skin subjected to UV irradiated skin dehydration.

Antiwrinkle efficacy of 1-ethyl-β-N-acetylglucosaminide, an inducer of epidermal hyaluronan production

BACKGROUND

Hyaluronan (HA) has a unique hydration capacity that contributes to firmness and bounciness of the skin. Epidermal HA declines with skin aging, which may lead to clinical signs of aging including skin wrinkles and loss of hydration and elasticity. Recently, we developed a new cosmetic agent 1-ethyl-β-N-acetylglucosaminide (β-NAG2), which enhances HA production in cultured human keratinocytes. The aim of this study was to explore antiaging potential of β-NAG2 in reconstructed human epidermal models and human clinical trial.

MATERIALS AND METHODS

The amount of HA in β-NAG2-treated epidermal models by topical application was analyzed by enzyme-linked immunosorbent assay (ELISA)-like assay. A randomized, double-blind and placebo-controlled study was conducted in Japanese females (n = 33) by topically treating each side of the face with a lotion formulated with β-NAG2 or placebo for 8 weeks.

RESULTS

Topically applied β-NAG2 dose dependently increased HA production in epidermal models. Treatment with β-NAG2-formulated lotion significantly improved skin hydration and elasticity and reduced skin wrinkling in crow's foot areas when compared to the placebo formulation.

CONCLUSION

Topically applied β-NAG2 promoted epidermal HA production in vitro and showed antiwrinkle activity in vivo accompanying the improvement in skin hydration and elasticity. Our study provides a novel strategy for antiwrinkle care through β-NAG2-induced epidermal HA production.

Kahweol Exerts Skin Moisturizing Activities by Upregulating STAT1 Activity

Kahweol is a diterpene present in coffee. Until now, several studies have shown that kahweol has anti-inflammatory and anti-angiogenic functions. Due to the limited research available about skin protection, this study aims to discern the potential abilities of kahweol and the possible regulation targets. First, the cytotoxicity of kahweol was checked by 3-4-5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolium bromide assay, while 2,20-azino-bis (3ethylbenzothiazoline-6-sulphonic acid) diammonium salt and 1-diphenyl-2-picryl-hydrazyl were used to examine the radical scavenging ability. Polymerase chain reaction analysis was performed to explore the proper time points and doses affecting skin hydration and barrier-related genes. Luciferase assay and Western blotting were used to explore the possible transcription factors. Finally, fludarabine (a STAT1 inhibitor) was chosen to discern the relationship between skin-moisturizing factors and STAT1. We found that HaCaT cells experienced no toxicity from kahweol, and kahweol displayed moderate radical scavenging ability. Moreover, kahweol increased the outcome of HAS1, HAS2, occludin, and TGM-1 from six hours in a dose-dependent manner as well as the activation of STAT1 from six hours. Additionally, kahweol recovered the suppression of HAS2, STAT1-mediated luciferase activity, and HA secretion, which was all downregulated by fludarabine. In this study, we demonstrated that kahweol promotes skin-moisturizing activities by upregulating STAT1.

1-Ethyl-β-N-acetylglucosaminide increases hyaluronan production in human keratinocytes by being converted to N-acetylglucosamine via β-N-acetylglucosaminidase-dependent manner

Regulation of hyaluronan (HA) is important for the maintenance of epidermal homeostasis. Here, we examined the mechanism by which 1-ethyl-β-N-acetylglucosaminide (β-NAG2), a newly developed N-acetylglucosamine (NAG) derivative, increases HA production in cultured human epidermal keratinocytes. When keratinocytes were treated with β-NAG2, mRNA expression of HA synthase 3, which is responsible for HA production in human keratinocytes, was not influenced, but the intracellular level of UDP-NAG, a substrate used for HA synthesis, was increased. By using a synthetic substrate for β-N-acetylglucosaminidase (β-NAGase), keratinocytes were found to possess β-NAGase activity, and treatment of o-(2-acetamido-2-deoxy-d-glucopyranosylidene) amino N-phenyl carbamate (PUGNAc), an inhibitor of β-NAGase, abolished the release of NAG from β-NAG2 in keratinocytes. Furthermore, PUGNAc attenuated the β-NAG2-induced intracellular UDP-NAG and HA production in keratinocytes. These results suggest that β-NAG2 is converted to NAG by endogenous β-NAGase in keratinocytes, and the resulting NAG is further metabolized to UDP-NAG and utilized for HA production.

Molecular Mechanisms Underlying Remodeling of Ductus Arteriosus: Looking beyond the Prostaglandin Pathway

The ductus arteriosus (DA) is a physiologic vessel crucial for fetal circulation. As a major regulating factor, the prostaglandin pathway has long been the target for DA patency maintenance or closure. However, the adverse effect of prostaglandins and their inhibitors has been a major unsolved clinical problem. Furthermore, a significant portion of patients with patent DA fail to respond to cyclooxygenase inhibitors that target the prostaglandin pathway. These unresponsive medical patients ultimately require surgical intervention and highlight the importance of exploring pathways independent from this well-recognized prostaglandin pathway. The clinical limitations of prostaglandin-targeting therapeutics prompted us to investigate molecules beyond the prostaglandin pathway. Thus, this article introduces molecules independent from the prostaglandin pathway based on their correlating mechanisms contributing to vascular remodeling. These molecules may serve as potential targets for future DA patency clinical management.

The Attenuated Secretion of Hyaluronan by UVA-Exposed Human Fibroblasts Is Associated with Up- and Downregulation of HYBID and HAS2 Expression via Activated and Inactivated Signaling of the p38/ATF2 and JAK2/STAT3 Cascades

Little is known about the effects on hyaluronan (HA) metabolism of UVA radiation. This study demonstrates that the secretion of HA by human dermal fibroblasts (HDFs) is downregulated by UVA, accompanied by the down- and upregulation of mRNA and protein levels of the HA-synthesizing enzyme (HAS2) and the HA-degrading protein, HYaluronan Binding protein Involved in HA Depolymerization(HYBID), respectively. Signaling analysis revealed that the exposure distinctly elicits activation of the p38/MSK1/CREB/c-Fos/AP-1 axis, the JNK/c-Jun axis, and the p38/ATF-2 axis, but downregulates the phosphorylation of NF-kB and JAK/STAT3. A signal inhibition study demonstrated that the inhibition of p38 significantly abrogates the UVA-accentuated mRNA level of HYBID. Furthermore, the inhibition of STAT3 significantly downregulates the level of HAS2 mRNA in non-UVA exposed HDFs. Analysis using siRNAs demonstrated that transfection of ATF-2 siRNA but not c-Fos siRNA abrogates the increased protein level of HYBID in UVA-exposed HDFs. An inhibitor of protein tyrosine phosphatase but not of protein serine/threonine phosphatase restored the diminished phosphorylation level of STAT3 at Tyr 705, accompanied by a significant abolishing effect on the decreased mRNA expression level of HAS2. Silencing with a protein tyrosine phosphatase PTP-Meg2 siRNA revealed that it abrogates the decreased phosphorylation of STAT3 at Tyr 705 in UVA-exposed HDFs. These findings suggest that the UVA-induced decrease in HA secretion by HDFs is attributable to the down- and upregulation of HAS2 and HYBID expression, respectively, changes that are mainly ascribed to the inactivated signaling of the STAT3 axis due to the activated tyrosine protein phosphatase PTP-Meg2 and the activated signaling of the p38/ATF2 axis, respectively.

The vitamin A ester retinyl propionate has a unique metabolic profile and higher retinoid-related bioactivity over retinol and retinyl palmitate in human skin models

Human skin is exposed daily to environmental stressors, which cause acute damage and inflammation. Over time, this leads to morphological and visual appearance changes associated with premature ageing. Topical vitamin A derivatives such as retinol (ROL), retinyl palmitate (RPalm) and retinyl propionate (RP) have been used to reverse these changes and improve the appearance of skin. This study investigated a stoichiometric comparison of these retinoids using in vitro and ex vivo skin models. Skin biopsies were treated topically to compare skin penetration and metabolism. Treated keratinocytes were evaluated for transcriptomics profiling and hyaluronic acid (HA) synthesis and treated 3D epidermal skin equivalents were stained for epidermal thickness, Ki67 and filaggrin. A retinoic acid receptor-alpha (RARα) reporter cell line was used to compare retinoid activation levels. Results from ex vivo skin found that RP and ROL have higher penetration levels compared with RPalm. RP is metabolized primarily into ROL in the viable epidermis and dermis whereas ROL is esterified into RPalm and metabolized into the inactive retinoid 14-hydroxy-4,14-retro-retinol (14-HRR). RP treatment yielded higher RARα activation and HA synthesis levels than ROL whereas RPalm had a null effect. In keratinocytes, RP and ROL stimulated similar gene expression patterns and pathway theme profiles. In conclusion, RP and ROL show a similar response directionality whereas RPalm response was inconsistent. Additionally, RP has a consistently higher magnitude of response compared with ROL or RPalm.

Mycosporine-like amino acids stimulate hyaluronan secretion by up-regulating hyaluronan synthase 2 via activation of the p38/MSK1/CREB/c-Fos/AP-1 axis

Hyaluronan (HA) is an extracellular matrix glycosaminoglycan that critically supports the physicochemical and mechanical properties of the skin. Here, we demonstrate that mycosporine-like amino acids (MAAs), which typically function as UV-absorbing compounds, can stimulate HA secretion from normal human fibroblasts. MAA-stimulated HA secretion was associated with significantly increased and decreased levels of mRNAs encoding HA synthase 2 (HAS2) and the HA-binding protein involved in HA depolymerization (designated HYBID), respectively. Using immunoblotting, we found that MAAs at 10 and at 25 μg/ml stimulate the phosphorylation of the mitogen-activated protein kinase (MAPK) p38, extracellular signal-regulated kinase (ERK)/c-Jun, and mitogen- and stress-activated protein kinase 1 (MSK1) (at Thr-581, Ser-360, and Ser-376, respectively) and activation of cAMP-responsive element-binding protein (CREB) and activating transcription factor 2 (ATF2), but not phosphorylation of JUN N-terminal kinase (JNK) or NF-κB (at Ser-276 or Ser-536, respectively), and increased c-Fos protein levels. Moreover, a p38-specific inhibitor, but not inhibitors of MAPK/ERK kinase (MEK), JNK, or NF-κB, significantly abrogated the increased expression of HAS2 mRNA, accompanied by significantly decreased MAA-stimulated HA secretion. These results suggested that the p38-MSK1-CREB-c-Fos-transcription factor AP-1 (AP-1) or the p38-ATF2 signaling cascade is responsible for the MAA-induced stimulation of HAS2 gene expression. Of note, siRNA-mediated ATF2 silencing failed to abrogate MAA-stimulated HAS2 expression, and c-Fos silencing abolished the increased expression of HAS2 mRNA. Our findings suggest that MAAs stimulate HA secretion by up-regulating HAS2 mRNA levels through activation of an intracellular signaling cascade consisting of p38, MSK1, CREB, c-Fos, and AP-1.

Scalable Generation of Mesenchymal Stem Cells and Adipocytes from Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) can provide unlimited supply for mesenchymal stem cells (MSCs) and adipocytes that can be used for therapeutic applications. Here we developed a simple and highly efficient all-trans-retinoic acid (RA)-based method for generating an off-the-shelf and scalable number of human pluripotent stem cell (hPSC)-derived MSCs with enhanced adipogenic potential. We showed that short exposure of multiple hPSC lines (hESCs/hiPSCs) to 10 μM RA dramatically enhances embryoid body (EB) formation through regulation of genes activating signaling pathways associated with cell proliferation, survival and adhesion, among others. Disruption of cell adhesion induced the subsequent differentiation of the highly expanded RA-derived EB-forming cells into a pure population of multipotent MSCs (up to 1542-fold increase in comparison to RA-untreated counterparts). Interestingly, the RA-derived MSCs displayed enhanced differentiation potential into adipocytes. Thus, these findings present a novel RA-based approach for providing an unlimited source of MSCs and adipocytes that can be used for regenerative medicine, drug screening and disease modeling applications.

3,6-Anhydro-L-galactose increases hyaluronic acid production via the EGFR and AMPKα signaling pathway in HaCaT keratinocytes

BACKGROUND

Hyaluronic acid (HA) is an important factor in skin hydration maintenance. In mammalian keratinocytes, hyaluronan synthase 2 (HAS2) is a critical enzyme in HA production. Therefore, the promotion of HAS2 expression in keratinocytes may be a strategy for maintaining skin moisture.

OBJECTIVE

The aim was to determine the skin hydration effect and regulatory mechanisms of 3,6-anhydro-L-galactose (L-AHG), a main component of red macroalgal carbohydrates in human keratinocytes.

METHODS

L-AHG was applied to an immortalized human epidermal keratinocyte cell line (HaCaT cells). HA production, HAS2 protein and mRNA levels, and the activation of the signaling pathways involved in HAS2 expression were measured. HA levels were also evaluated for three dimensional (3D) reconstructed human skin.

RESULTS

Our results suggest that L-AHG upregulates HA production and may enhance HAS2 expression by activating EGFR-mediated ERK, PI3K/Akt, and STAT3 signaling pathways. We confirmed that L-AHG activated the AMPKα signaling pathway which in turn could regulate HAS2 expression in HaCaT cells. The effects of L-AHG on HA production were observed in the 3D reconstructed human skin model.

CONCLUSION

Our results suggest that L-AHG may enhance skin moisture retention by increasing HA synthesis in human epidermal keratinocytes.

In vitro study of RRS® Silisorg CE Class III medical device composed of silanol: effect on human skin fibroblasts and its clinical use

Introduction

Silanol (organic silicon) has been used for decades in the treatment of skin photoaging as it stabilizes and maintains skin structures through hydrogen bonding electrostatic interaction with extracellular matrix (ECM) proteins or glycosaminoglycans. Organic silicon-based products are often presented as silanol derivatives which are currently associated to other structural molecules such as orthohydroxybenzoate, carboxymethyl theophylline alginate, ascorbate, acetyltyrosine, sodium lactate or mannuronate. Consequently, organic silicon formulations may differ substantially between the medical devices available on the market, which may result in additional effect on the skin. Therefore, there is a real need for a better characterization of the products in terms of their action on human skin and in vitro skin model.

Materials and methods

In this in vitro study, the effect of RRS® Silisorg was analyzed. RRS® Silisorg is a dermal implant (CE Class III medical device) containing monomethylsilanol mannuronate associated to an antioxidant resveratrol. Skin fibroblast viability and capacity to induce the production of key ECM genes were evaluated in the presence of different concentrations of RRS® Silisorg. The key ECM genes selected were collagen type I, elastin and hyaluronan synthase type 2 (HAS2), which is the cellular enzyme responsible for high-molecular weight hyaluronic acid (HA) production. Viability was evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and expression was quantified by quantitative polymerase chain reaction.

Results

RRS® Silisorg increased fibroblast gene expression of HAS2 in the first 24 hours, 25 times in the presence of 1 mg/mL of solution, followed by a collagen type I gene expression (4.7 times) and elastin expression (2.5 times) increase after 48 hours.

Conclusion

These results demonstrate that the silanol-based medical device RRS® Silisorg sustains HA, collagen and elastin production in human skin fibroblasts in vitro.

Regulation of hyaluronan biosynthesis and clinical impact of excessive hyaluronan production

The tightly regulated biosynthesis and catabolism of the glycosaminoglycan hyaluronan, as well as its role in organizing tissues and cell signaling, is crucial for the homeostasis of tissues. Overexpression of hyaluronan plays pivotal roles in inflammation and cancer, and markedly high serum and tissue levels of hyaluronan are noted under such pathological conditions. This review focuses on the complexity of the regulation at transcriptional and posttranslational level of hyaluronan synthetic enzymes, and the outcome of their aberrant expression and accumulation of hyaluronan in clinical conditions, such as systemic B-cell cancers, aggressive breast carcinomas, metabolic diseases and virus infection.

Cactus cladodes (Opuntia humifusa) extract minimizes the effects of UV irradiation on keratinocytes and hairless mice

CONTEXT

Cactus cladodes [Opuntia humifusa (Raf.) Raf. (Cactaceae)] is one of the cactus genera, which has long been used as a folk medicine for skin disorders.

OBJECTIVE

This study investigated the skincare potential of cactus cladodes extract (OHE), including its ability to regulate ultraviolet B (UVB)-induced hyaluronic acid (HA) production.

MATERIALS AND METHODS

Gene expression levels of hyaluronic acid synthases (HASs) and hyaluronidase (HYAL) were measured in UVB-irradiated HaCaT cells with OHE treatment (10, 25, 50, 100 μg/mL) by real-time polymerase chain reaction (PCR). The HA content was analyzed in hairless mice (SKH-1, male, 6 weeks old) treated with OHE for 10 weeks by using enzyme-linked immunosorbent assay (ELISA). Haematoxylin and eosin (H&E) and immunohistological staining were performed to examine epidermal thickness and levels of CD44 and hyaluronic acid-binding protein (HABP).

RESULTS

HA synthases (HAS,1 HAS2, HAS3) mRNA levels were increased by 1.9-, 2.2- and 1.6-fold, respectively, with OHE treatment (100 μg/mL), while UVB-induced increase of hyaluronidase mRNA significantly decreased by 35%. HA content in animal was decreased from 42.9 to 27.1 ng/mL by OHE treatment. HAS mRNA levels were decreased by 39%, but HYAL mRNA was increased by 50% in OHE group. CD44 and HABP levels, which were greatly increased by UVB-irradiation, were reduced by 64 and 60%, respectively. Epidermal thickness, transepidermal water loss (TEWL), and erythema formation was also decreased by 45 (45.7 to 24.2 μm), 48 (48.8 to 25 g/h/m²) and 33%, respectively.

CONCLUSION

OHE protects skin from UVB-induced skin degeneration in HaCaT cells and hairless mice.

Effect of MT3 on Retinal and Choroidal TGF-β2 and HAS2 Expressions in Form Deprivation Myopia of Guinea Pig

Purpose

To confirm its dose-dependent effect on form deprivation myopia and evaluate the effect of MT3 at different tissue concentrations on changes in mRNA and protein expression for TGF-β2 and HAS2.

Methods

MT3 was intravitreally injected into deprived eyes at two-day intervals. Refraction was measured by streak retinoscopy after cycloplegia. The axial dimensions were measured by A-scan ultrasound. The quantitative RT-PCR and Western blot were used to detect the changes of TGF-β2 and HAS2 expressions in the retina and choroid of guinea pigs.

Results

MT3 treatment produced a significant dose-dependent reduction in relative myopia compared to FD group (both p < 0.001). There were statistically significant increases in retinal and choroidal mRNA levels for both TGF-β2 and HAS2 after injections of 10 μM of MT3, when compared to the FD group. There were no significant differences in retinal and choroidal TGF-β2 protein expression levels between the MT3 treatment groups and FD group (all p > 0.05). The injections of 10 μM of MT3 caused a marked decrease in retinal HAS2 protein expression level, when compared to the FD group (p = 0.001).

Conclusion

MT3 can inhibit form deprivation myopia, and MT3 treatment can result in changes of retinal and choroidal TGF-β2 and HAS2 mRNA and protein expressions.

A Trickster in Disguise: Hyaluronan's Ambivalent Roles in the Matrix

Hyaluronan (HA) is a simple but diverse glycosaminoglycan. It plays a major role in aging, cellular senescence, cancer, and tissue homeostasis. In which way HA affects the surrounding tissues greatly depends on the molecular weight of HA. Whereas high molecular weight HA is associated with homeostasis and protective effects, HA fragments tend to be linked to the pathologic state. Furthermore, the interaction of HA with its binding partners, the hyaladherins, such as CD44, is essential for sustaining tissue integrity and is likewise related to cancer. The naked mole rat, a rodent species, possesses a special form of very high molecular weight (vHMW) HA, which is associated with the extraordinary cancer resistance and longevity of those animals. This review addresses HA and its diverse facets: from HA synthesis to degradation, from oligomeric HA to vHMW-HA and from its beneficial properties to the involvement in pathologies. We further discuss the functions of HA in the naked mole rat and compare them to human conditions. Though intensively researched, this simple polymer bears some secrets that may hold the key for a better understanding of cellular processes and the development of diseases, such as cancer.

Human Keratinocytes Respond to Extracellular UTP by Induction of Hyaluronan Synthase 2 Expression and Increased Hyaluronan Synthesis

The release of nucleotides into extracellular space is triggered by insults like wounding and ultraviolet radiation, resulting in stimulatory or inhibitory signals via plasma membrane nucleotide receptors. As similar insults are known to activate hyaluronan synthesis we explored the possibility that extracellular UTP or its breakdown products UDP and UMP act as mediators for hyaluronan synthase (HAS) activation in human epidermal keratinocytes. UTP increased hyaluronan both in the pericellular matrix and in the culture medium of HaCaT cells. 10-100 μm UTP strongly up-regulated HAS2 expression, although the other hyaluronan synthases (HAS1, HAS3) and hyaluronidases (HYAL1, HYAL2) were not affected. The HAS2 response was rapid and transient, with the maximum stimulation at 1.5 h. UDP exerted a similar effect, but higher concentrations were required for the response, and UMP showed no stimulation at all. Specific siRNAs against the UTP receptor P2Y₂, and inhibitors of UDP receptors P2Y₆ and P2Y₁₄, indicated that the response to UTP was mediated mainly through P2Y₂ and to a lesser extent via UDP receptors. UTP increased the phosphorylation of p38, ERK, CREB, and Ser-727 of STAT3 and induced nuclear translocation of pCaMKII. Inhibitors of PKC, p38, ERK, CaMKII, STAT3, and CREB partially blocked the activation of HAS2 expression, confirming the involvement of these pathways in the UTP-induced HAS2 response. The present data reveal a selective up-regulation of HAS2 expression by extracellular UTP, which is likely to contribute to the previously reported rapid activation of hyaluronan metabolism in response to tissue trauma or ultraviolet radiation.

Ability of sodium copper chlorophyllin complex to repair photoaged skin by stimulation of biomarkers in human extracellular matrix

PURPOSE

To examine the effect of sodium copper chlorophyllin complex on the expression of biomarkers of photoaged dermal extracellular matrix indicative of skin repair.

PATIENTS AND METHODS

Following a previously published 12-day clinical assessment model, skin biopsy samples from the forearms of four healthy females with signs of photoaged skin were obtained and samples were analyzed by immunohistochemistry for key biomarkers of aging skin after each subject was treated with a test material consisting of a gel containing a liposomal dispersion of sodium copper chlorophyllin complex 0.05%, a positive control of tretinoin cream 0.025%, and an untreated negative control.

RESULTS

There was a statistically significantly greater amount of fibrillin/amyloid P and epidermal mucins found for skin treated with the test material containing 0.05% sodium copper chlorophyllin complex and the reference control tretinoin 0.025% cream compared to the negative control (untreated site). Expression of procollagen 1 and dermal mucin also showed a greater presence in the samples treated with the test material and the reference control compared to the negative control, though the differences were not statistically significant. No adverse events were observed or reported by the subjects during the course of the study.

CONCLUSION

The results of this human biopsy study suggest that both retinoids and sodium copper chlorophyllin complex have beneficial effects on biomarkers of photoaged skin. Products containing both sodium copper chlorophyllin complex and retinols may provide a dual approach to reversing age-related decreases in hyaluronic acid (HA) in the skin: inhibition of the breakdown of HA via sodium copper chlorophyllin complex by inhibition of hyaluronidase, and stimulation of HA synthases by retinol.

An Fgf-Shh signaling hierarchy regulates early specification of the zebrafish skull

The neurocranium generates most of the craniofacial skeleton and consists of prechordal and postchordal regions. Although development of the prechordal is well studied, little is known of the postchordal region. Here we characterize a signaling hierarchy necessary for postchordal neurocranial development involving Fibroblast growth factor (Fgf) signaling for early specification of mesodermally-derived progenitor cells. The expression of hyaluron synthetase 2 (has2) in the cephalic mesoderm requires Fgf signaling and Has2 function, in turn, is required for postchordal neurocranial development. While Hedgehog (Hh)-deficient embryos also lack a postchordal neurocranium, this appears primarily due to a later defect in chondrocyte differentiation. Inhibitor studies demonstrate that postchordal neurocranial development requires early Fgf and later Hh signaling. Collectively, our results provide a mechanistic understanding of early postchordal neurocranial development and demonstrate a hierarchy of signaling between Fgf and Hh in the development of this structure.

Roles of Proteoglycans and Glycosaminoglycans in Wound Healing and Fibrosis

A wound is a type of injury that damages living tissues. In this review, we will be referring mainly to healing responses in the organs including skin and the lungs. Fibrosis is a process of dysregulated extracellular matrix (ECM) production that leads to a dense and functionally abnormal connective tissue compartment (dermis). In tissues such as the skin, the repair of the dermis after wounding requires not only the fibroblasts that produce the ECM molecules, but also the overlying epithelial layer (keratinocytes), the endothelial cells, and smooth muscle cells of the blood vessel and white blood cells such as neutrophils and macrophages, which together orchestrate the cytokine-mediated signaling and paracrine interactions that are required to regulate the proper extent and timing of the repair process. This review will focus on the importance of extracellular molecules in the microenvironment, primarily the proteoglycans and glycosaminoglycan hyaluronan, and their roles in wound healing. First, we will briefly summarize the physiological, cellular, and biochemical elements of wound healing, including the importance of cytokine cross-talk between cell types. Second, we will discuss the role of proteoglycans and hyaluronan in regulating these processes. Finally, approaches that utilize these concepts as potential therapies for fibrosis are discussed.

Identification and analysis of the promoter region of the human HAS3 gene

Hyaluronan (HA) is a key component of the vertebrate extracellular matrix that is synthesized at the plasma membrane by the hyaluronan synthases including HAS1, HAS2 and HAS3. The expression and regulation of HAS1-3 are implicated in numerous physiological and pathological processes. The promoters of human HAS1 and HAS2 genes have been identified previously whereas HAS3 promoter remains unclear. In the present study, we have for the first time identified and characterized the human HAS3 gene promoter region. 5' RACE assay revealed two novel transcriptional variants of HAS3 gene with distinct transcription start sites. Progressive deletion analysis of the 5'-flanking region of HAS3 gene demonstrated that HAS3 proximal promoter is mainly restricted to a 450-bp region (i.e. -761 to -305 bp upstream of the major HAS3 transcription start site), whereas its core promoter is located to a minimal 129-bp region (i.e. -433 to -305 bp upstream of the major HAS3 transcription start site). Transcriptional factor binding analysis indicated that HAS3 gene promoter lacks of canonical TATA box, but contains classical GC box as well as other putative binding sites for transcriptional factors such as C/EBP and NFκB. In addition, site-directed mutagenesis assay demonstrated that the proximal Sp1 binding site is essential for the robust proximal promoter activity of HAS3 gene whereas the core MTE (core promoter motif ten elements) motif is required for the basic core promoter activity of HAS3 gene. Our present study should facilitate further studies on the mechanism regulating the expression of this important gene.

20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol, a metabolite of ginsenoside Rb1, enhances the production of hyaluronic acid through the activation of ERK and Akt mediated by Src tyrosin kinase in human keratinocytes

The aim of the present study was to determine the mechanisms through which 20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol (20GPPD) promotes the production of hyaluronic acid (HA) in human keratinocytes. 20GPPD is the primary bioactive metabolite of Rb1, a major ginsenoside found in ginseng (Panax ginseng). We sought to elucidate the underlying mechanisms behind the 20GPPD-induced production of HA. We found that 20GPPD induced an increase in HA production by elevating hyaluronan synthase 2 (HAS2) expression in human keratinocytes. The phosphorylation of extracellular signal-regulated kinase (ERK) and Akt was also enhanced by 20GPPD in a dose-dependent manner. The pharmacological inhibition of ERK (using U0126) or Akt (using LY294002) suppressed the 20GPPD-induced expression of HAS2, whereas treatment with an epidermal growth factor receptor (EGFR) inhibitor (AG1478) or an intracellular Ca2+ chelator (BAPTA/AM) did not exert any observable effects. The increased Src phosphorylation was also confirmed following treatment with 20GPPD in the human keratinocytes. Following pre-treatment with the Src inhibitor, PP2, both HA production and HAS2 expression were attenuated. Furthermore, the 20GPPD-enhanced ERK and Akt signaling decreased following treatment with PP2. Taken together, our results suggest that Src kinase plays a critical role in the 20GPPD-induced production of HA by acting as an upstream modulator of ERK and Akt activity in human keratinocytes.

More than just a filler - the role of hyaluronan for skin homeostasis

In recent years, hyaluronan (HA) has become an increasingly attractive substance as a non-immunogenic filler and scaffolding material in cosmetic dermatology. Despite its wide use for skin augmentation and rejuvenation, relatively little is known about the molecular structures and interacting proteins of HA in normal and diseased skin. However, a comprehensive understanding of cutaneous HA homeostasis is required for future the development of HA-based applications for skin regeneration. This review provides an update on HA-based structures, expression, metabolism and its regulation, function and pharmacological targeting of HA in skin.

Construction of collagen gel scaffolds for mechanical stress analysis

We designed a cyclic compression system using readily available six-well culture plates to investigate the influence of mechanical stress on skin-like structures. The effects of cyclic mechanical stress on protein expression by cells were easily examined, and hence, this system should be useful for further analysis of skin responses to mechanical stress.

Extracellular UDP-glucose activates P2Y14 Receptor and Induces Signal Transducer and Activator of Transcription 3 (STAT3) Tyr705 phosphorylation and binding to hyaluronan synthase 2 (HAS2) promoter, stimulating hyaluronan synthesis of keratinocytes

Hyaluronan, a major matrix molecule in epidermis, is often increased by stimuli that enhance keratinocyte proliferation and migration. We found that small amounts of UDP-sugars were released from keratinocytes and that UDP-glucose (UDP-Glc) added into keratinocyte cultures induced a specific, rapid induction of hyaluronan synthase 2 (HAS2), and an increase of hyaluronan synthesis. The up-regulation of HAS2 was associated with JAK2 and ERK1/2 activation, and specific Tyr(705) phosphorylation of transcription factor STAT3. Inhibition of JAK2, STAT3, or Gi-coupled receptors blocked the induction of HAS2 expression by UDP-Glc, the latter inhibitor suggesting that the signaling was triggered by the UDP-sugar receptor P2Y14. Chromatin immunoprecipitations demonstrated increased promoter binding of Tyr(P)(705)-STAT3 at the time of HAS2 induction. Interestingly, at the same time Ser(P)(727)-STAT3 binding to its response element regions in the HAS2 promoter was unchanged or decreased. UDP-Glc also stimulated keratinocyte migration, proliferation, and IL-8 expression, supporting a notion that UDP-Glc signals for epidermal inflammation, enhanced hyaluronan synthesis as an integral part of it.

Hyaluronan metabolism in human keratinocytes and atopic dermatitis skin is driven by a balance of hyaluronan synthases 1 and 3

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.

A novel mutation of Hyaluronan synthase 2 gene in Chinese children with ventricular septal defect

As a major product of extracellular matrix (ECM), Hyaluronic acid (HA) is involved in early cardiac development and mainly synthesized by Hyaluronan synthase 2 (HAS2) during embryogenesis. Targeted deletion of HAS2 gene in mice led to obvious cardiac and vascular defects. To clarify the potential association of the mutation in HAS2 with the development of congenital heart disease (CHD), in this study, we sequenced the coding region of HAS2 and identified a novel non-synonymous variant c.A1496T (p.Glu499Val) in one of 100 non-syndromic Ventricular Septal Defect (VSD) patients. The variant was not observed in 250 controls. In addition, to determine the contribution of HAS2 variant in VSD, we compared HA content in supernatant using HA quantitative analysis and found that the mutation obviously affected the HA synthetic activity of HAS2. To our knowledge, this is the first time that the mutation in HAS2 was found in Chinese VSD patients, which suggested that HAS2 may be involved in the etiology of non-syndromic VSD and have the vital function in the development of heart septum.

Activation of the FGFR-STAT3 pathway in breast cancer cells induces a hyaluronan-rich microenvironment that licenses tumor formation

Aberrant activation of fibroblast growth factor receptors (FGFR) contributes to breast cancer growth, progression, and therapeutic resistance. Because of the complex nature of the FGF/FGFR axis, and the numerous effects of FGFR activation on tumor cells and the surrounding microenvironment, the specific mechanisms through which aberrant FGFR activity contributes to breast cancer are not completely understood. We show here that FGFR activation induces accumulation of hyaluronan within the extracellular matrix and that blocking hyaluronan synthesis decreases proliferation, migration, and therapeutic resistance. Furthermore, FGFR-mediated hyaluronan accumulation requires activation of the STAT3 pathway, which regulates expression of hyaluronan synthase 2 (HAS2) and subsequent hyaluronan synthesis. Using a novel in vivo model of FGFR-dependent tumor growth, we demonstrate that STAT3 inhibition decreases both FGFR-driven tumor growth and hyaluronan levels within the tumor. Finally, our results suggest that combinatorial therapies inhibiting both FGFR activity and hyaluronan synthesis is more effective than targeting either pathway alone and may be a relevant therapeutic approach for breast cancers associated with high levels of FGFR activity. In conclusion, these studies indicate a novel targetable mechanism through which FGFR activation in breast cancer cells induces a protumorigenic microenvironment.

Retinoic acid improves morphology of cultured peritoneal mesothelial cells from patients undergoing dialysis

Patients undergoing continuous ambulatory peritoneal dialysis are classified according to their peritoneal permeability as low transporter (low solute permeability) or High transporter (high solute permeability). Factors that determine the differences in permeability between them have not been fully disclosed. We investigated morphological features of cultured human peritoneal mesothelial cells from low or high transporter patients and its response to All trans retinoic Acid (ATRA, vitamin A active metabolite), as compared to non-uremic human peritoneal mesothelial cells. Control cells were isolated from human omentum. High or low transporter cells were obtained from dialysis effluents. Cells were cultured in media containing ATRA (0, 50, 100 or 200 nM). We studied length and distribution of microvilli and cilia (scanning electron microscopy), epithelial (cytokeratin, claudin-1, ZO-1 and occludin) and mesenchymal (vimentin and α-smooth muscle actin) transition markers by immunofluorescence and Western blot, and transforming growth factor β1 expression by Western blot. Low and high transporter exhibited hypertrophic cells, reduction in claudin-1, occludin and ZO-1 expression, cytokeratin and vimentin disorganization and positive α-smooth muscle actin label. Vimentin, α-smooth muscle actin and transforming growth factor-β1 were overexpressed in low transporter. Ciliated cells were diminished in low and high transporters. Microvilli number and length were severely reduced in high transporter. ATRA reduced hypertrophic cells number in low transporter. It also improved cytokeratin and vimentin organization, decreased vimentin and α-smooth muscle actin expression, and increased claudin 1, occludin and ZO-1 expression, in low and high transporter. In low transporter, ATRA reduced transforming growth factor-β1 expression. ATRA augmented percentage of ciliated cells in low and high transporter. It also augmented cilia length in high transporter. Alterations in structure, epithelial mesenchymal markers and transforming growth factor-β1 expression were differential between low and high transporter. Beneficial effects of ATRA were improved human peritoneal mesothelial cells morphology tending to normalize structures.

Low dose ultraviolet B irradiation increases hyaluronan synthesis in epidermal keratinocytes via sequential induction of hyaluronan synthases Has1-3 mediated by p38 and Ca2+/calmodulin-dependent protein kinase II (CaMKII) signaling

Hyaluronan, a major epidermal extracellular matrix component, responds strongly to different kinds of injuries. This also occurs by UV radiation, but the mechanisms involved are poorly understood. The effects of a single ultraviolet B (UVB) exposure on hyaluronan content and molecular mass, and expression of genes involved in hyaluronan metabolism were defined in monolayer and differentiated, organotypic three-dimensional cultures of rat epidermal keratinocytes. The signals regulating the response were characterized using specific inhibitors and Western blotting. In monolayer cultures, UVB increased hyaluronan synthase Has1 mRNA already 4 h postexposure, with a return to control level by 24 h. In contrast, Has2 and Has3 were persistently elevated from 8 h onward. Silencing of Has2 and especially Has3 decreased the UVB-induced accumulation of hyaluronan. p38 and Ca(2+)/calmodulin-dependent protein kinase II pathways were found to be involved in the UVB-induced up-regulation of Has2 and Has3 expression, respectively, and their inhibition reduced hyaluronan deposition. However, the expressions of the hyaluronan-degrading enzymes Hyal1 and Hyal2 and the hyaluronan receptor Cd44 were also up-regulated by UVB. In organotypic cultures, UVB treatment also resulted in increased expression of both Has and Hyal genes and shifted hyaluronan toward a smaller size range. Histochemical stainings indicated localized losses of hyaluronan in the epidermis. The data show that exposure of keratinocytes to acute, low dose UVB increases hyaluronan synthesis via up-regulation of Has2 and Has3. The simultaneously enhanced catabolism of hyaluronan demonstrates the complexity of the UVB-induced changes. Nevertheless, enhanced hyaluronan metabolism is an important part of the adaptation of keratinocytes to radiation injury.

Soybean extract showed modulation of retinoic acid-related gene expression of skin and photo-protective effects in keratinocytes

Soy extracts are well known as medicinal and nutritional ingredients, and exhibit benefits towards human skin including depigmenting or anti-ageing effects. Despite the wrinkle decreasing effects of retinoids on skin as an anti-ageing ingredient, retinoid application can causes photo-sensitive responses such as skin irritation. Thus, their daytime usage is not recommended. The aim of this study is the investigation into the activities of soybean extract as an anti-ageing ingredient and their comparison to retinoids in this respect. Soybean extract decreased the relative ratio of MMP-1/TIMP-1 mRNA to the same degree as retinoic acid in normal human fibroblasts. It also affected mRNA levels of HAS2 and CRABP2 in normal human keratinocytes. Furthermore, we investigated its effect on mRNA expression of histidase, an enzyme that converts histidine into urocanic acid, the main UV light absorption factor of the stratum corneum. Unlike the complete inhibition of histidase exhibited by the mRNA expression of retinoic acid, the effect of soybean extract on histidase gene expression was weaker in normal human keratinocytes. Also, soybean extract pretreatment inhibited UVB-induced cyclobutane pyrimidine dimer formation dose-dependently in normal human keratinocytes. In this study, we found that soybean extract modulated retinoic acid-related genes and showed photo-protective effects. Our findings suggest that soybean extract could be an anti-ageing ingredient that can be safely used under the sunlight.

Does the cranial mesenchyme contribute to neural fold elevation during neurulation?

The central nervous system is derived from the neural plate, which undergoes a series of complex morphogenetic events resulting in formation of the neural tube in a process known as neurulation. The cellular behaviors driving neurulation in the cranial region involve forces generated by the neural tissue itself as well as the surrounding epithelium and mesenchyme. Of interest, the cranial mesenchyme underlying the neural plate undergoes stereotypical rearrangements hypothesized to drive elevation of the neural folds. As the neural folds rise, the hyaluronate-rich extracellular matrix greatly expands resulting in increased space between individual cranial mesenchyme cells. Based on inhibitor studies, expansion of the extracellular matrix has been implicated in driving neural fold elevation; however, because the surrounding neural and epidermal ectoderm were also affected by inhibitor exposure, these studies are inconclusive. Similarly, treatment of neurulating embryos with teratogenic doses of retinoic acid results in altered organization of the cranial mesenchyme, but alterations in surrounding tissues are also observed. The strongest evidence for a critical role for the cranial mesenchyme in neural fold elevation comes from studies of genes expressed exclusively in the cranial mesenchyme that when mutated result in exencephaly associated with abnormal organization of the cranial mesenchyme. Twist is the best studied of these and is expressed in both the paraxial mesoderm and neural crest derived cranial mesenchyme. In this article, we review the evidence implicating the cranial mesenchyme in providing a driving force for neural fold elevation to evaluate whether there are sufficient data to support this hypothesis.

Increased hyaluronan content and stromal cell CD44 associate with HER2 positivity and poor prognosis in human breast cancer

Previous in vitro studies have suggested interactions between hyaluronan (HA), CD44 and HER2. We have studied the expression of HA and CD44 in a material of 278 breast cancer cases, half of which were HER2-positive. Intense stromal HA staining was associated with HER2 positivity, large tumor size, lymph node positivity, hormone receptor negativity, poor differentiation, a high body mass index, increased relapse rate and shortened overall survival. Among the 139 HER2-positive cases, the relapse rate was associated with the intensity of stromal HA staining as most of the relapses occurred in the cases with intense stromal HA staining. The presence of HA in the carcinoma cells was related to the frequency of relapses as none of the patients without HA in carcinoma cells experienced a relapse, whereas 33.3% of those with a high percentage of HA-positive carcinoma cells suffered a relapse. CD44 positivity in carcinoma cells was related to poor differentiation, postmenopausal status and triple negative breast carcinoma. CD44 positivity in stromal cells was associated with HER2 positivity, large tumor size, hormone receptor negativity, poor differentiation, increased relapse rate and shortened overall survival. The association between HER2 positivity and intense stromal HA staining indicates that HA could be one of the factors involved in the unfavorable outcome of HER2-positive patients. This study also suggests that HA in breast carcinoma cells and CD44 in stromal cells may have clinical significance.

[Role of the extracellular matrix in extrinsic skin aging]

Photoaged skin is clinically characterized by wrinkling, laxity and a leather-like appearance. These symptoms of actinic aging are causally connected to histological and ultrastructural changes of the connective tissue of the dermis. Changes include both enzymatic degradation and reduced de novo synthesis of collagen which cause premature wrinkling of the skin. Changes in the hyaluronan and proteoglycan matrix lead to reduced water content and thereby increased laxity of the skin. Furthermore, the UV-induced remodeling of the extracellular matrix strongly affects the cellular phenotypes such as the regenerative capacity of dermal fibroblasts. In recent years considerable progress has been made towards the understanding of molecular and cellular mechanisms underlying the UV-induced changes of the extracellular matrix. Current findings in this field reveal interesting insights in the dermal aging and provide new targets and strategies for the treatment of photoaging.

Chronic UVR causes increased immunostaining of CD44 and accumulation of hyaluronan in mouse epidermis

Chronic intense UV radiation is the main cause of epidermal tumors. Because hyaluronan (HA), a large extracellular polysaccharide, is known to promote malignant growth, hyaluronan expression was studied in a model in which long-term UV radiation (UVR) induces epidermal tumors. Mouse back skin was exposed three times a week for 10.5 months to UVR corresponding to one minimal erythema dose, processed for histology, and stained for hyaluronan and the hyaluronan receptor CD44. This exposure protocol caused epidermal hyperplasia in most of the animals; tumors, mainly squamous cell carcinomas (SCCs), were found in ~20% of the animals. Specimens exposed to UVR showed increased hyaluronan and CD44 staining throughout the epidermal tissue. In hyperplastic areas, hyaluronan and CD44 stainings correlated positively with the degree of hyperplasia. Well-differentiated SCCs showed increased hyaluronan and CD44 staining intensities, whereas poorly differentiated tumors and dysplastic epidermis showed areas where HA and CD44 were locally reduced. The findings indicate that HA and CD44 increase in epidermal keratinocytes in the premalignant hyperplasia induced by UV irradiation and stay elevated in dysplasia and SCC, suggesting that the accumulation of hyaluronan and CD44 is an early marker for malignant transformation and may be a prerequisite for tumor formation.

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

Hyaluronan, a high molecular mass polysaccharide on the vertebrate cell surface and extracellular matrix, is produced at the plasma membrane by hyaluronan synthases using UDP-GlcNAc and UDP-GlcUA as substrates. The availability of these UDP-sugar substrates can limit the synthesis rate of hyaluronan. In this study, we show that the cellular level of UDP-HexNAc also controls hyaluronan synthesis by modulating the expression of HAS2 (hyaluronan synthase 2). Increasing UDP-HexNAc in HaCaT keratinocytes by adding glucosamine down-regulated HAS2 gene expression, whereas a decrease in UDP-HexNAc, realized by mannose treatment or siRNA for GFAT1 (glutamine:fructose-6-phosphate amidotransferase 1), enhanced expression of the gene. Tracing the UDP-HexNAc-initiated signal to the HAS2 promoter revealed no change in the binding of STAT3, NF-κB, and cAMP response element-binding protein, shown previously to mediate growth factor and cytokine signals on HAS2 expression. Instead, altered binding of SP1 and YY1 to the promoter correlated with cellular UDP-HexNAc content and inhibition of HAS2 expression. siRNA silencing of YY1 and SP1 confirmed their inhibitory effects on HAS2 expression. Reduced and increased levels of O-GlcNAc-modified SP1 and YY1 proteins were associated with stimulation or inhibition of HAS2 expression, respectively. Our data are consistent with the hypothesis that, by regulating the level of protein O-GlcNAc modifications, cellular UDP-HexNAc content controls HAS2 transcription and decreases the effects on hyaluronan synthesis that would result from cellular fluctuations of this substrate.

RNA content in the nucleolus alters p53 acetylation via MYBBP1A

A number of external and internal insults disrupt nucleolar structure, and the resulting nucleolar stress stabilizes and activates p53. We show here that nucleolar disruption induces acetylation and accumulation of p53 without phosphorylation. We identified three nucleolar proteins, MYBBP1A, RPL5, and RPL11, involved in p53 acetylation and accumulation. MYBBP1A was tethered to the nucleolus through nucleolar RNA. When rRNA transcription was suppressed by nucleolar stress, MYBBP1A translocated to the nucleoplasm and facilitated p53-p300 interaction to enhance p53 acetylation. We also found that RPL5 and RPL11 were required for rRNA export from the nucleolus. Depletion of RPL5 or RPL11 blocked rRNA export and counteracted reduction of nucleolar RNA levels caused by inhibition of rRNA transcription. As a result, RPL5 or RPL11 depletion inhibited MYBBP1A translocation and p53 activation. Our observations indicated that a dynamic equilibrium between RNA generation and export regulated nucleolar RNA content. Perturbation of this balance by nucleolar stress altered the nucleolar RNA content and modulated p53 activity.