Vitamin D enhances mitogenesis mediated by keratinocyte growth factor receptor in keratinocytes

Functional Distinctions of Endometrial Cancer-Associated Mutations in the Fibroblast Growth Factor Receptor 2 Gene

Functional analysis of somatic mutations in tumorigenesis facilitates the development and optimization of personalized therapy for cancer patients. The fibroblast growth factor receptor 2 (FGFR2) gene is frequently mutated in endometrial cancer (EC), but the functional implications of FGFR2 mutations in cancer development remain largely unexplored. In this study, we introduced a reliable and readily deployable screening method to investigate the effects of FGFR2 mutations. We demonstrated that distinct mutations in FGFR2 can lead to differential downstream consequences, specifically affecting a disintegrin- and metalloprotease 17 (ADAM17)-dependent shedding of the epidermal growth factor receptor (EGFR) ligand heparin-binding EGF-like growth factor (HB-EGF) and phosphorylation of mitogen-activated protein kinases (MAPKs). Furthermore, we showed that the distribution of mutations within the FGFR2 gene can influence their oncogenic effects. Together, these findings provide important insights into the complex nature of FGFR2 mutations and their potential implications for EC. By unraveling the distinct effects of different mutations, our study contributes to the identification of personalized treatment strategies for patients with FGFR2-mutated cancers. This knowledge has the potential to guide the development of targeted therapies that specifically address the underlying molecular alterations associated with FGFR2 mutations, ultimately improving patient outcomes in EC and potentially other cancer types characterized by FGFR2 mutations.

Oral fibroblasts rescue osteogenic differentiation of mesenchymal stem cells after exposure to Zoledronic acid in a paracrine effect

Background: Medication-related osteonecrosis of the jaw is a serious complication that develops in oncologic patients treated with Zoledronic acid. Although used for over 30 years, the influence of Zoledronic acid on bone has been thoroughly investigated, mainly on osteoclasts. While decreasing osteoclast differentiation and function, for many years it was thought that Zoledronic acid increased osteoblast differentiation, thus increasing bone volume. Moreover, despite the influence of soft tissue on the bone healing process, the impact of zoledronic acid on the interaction between soft tissue and bone was not investigated. Aim: Our goal was to investigate the influence of Zoledronic Acid and soft tissue cells on osteogenic differentiation of mesenchymal stem cells (MSCs). Materials and methods: Osteogenic differentiation of MSCs was examined after exposure to Zoledronic Acid. To determine the influence of soft tissue cells on MSCs' osteogenic differentiation, conditioned media from keratinocytes and oral fibroblasts were added to osteogenic medium supplemented with Zoledronic Acid. Proteomic composition of keratinocytes' and fibroblasts' conditioned media were analyzed. Results: Zoledronic Acid decreased osteogenic differentiation of MSCs by seven-fold. The osteogenic differentiation of MSCs was restored by the supplementation of fibroblasts' conditioned medium to osteogenic medium, despite Zoledronic acid treatment. Five osteogenic proteins involved in the TGFβ pathway were exclusively identified in fibroblasts' conditioned medium, suggesting their role in the rescue effect. Conclusion: Oral fibroblasts secrete proteins that enable osteogenic differentiation of MSCs in the presence of Zoledronic Acid.

Vitamin D Status in a Bulgarian Population With Type 2 Diabetes and Diabetic Foot Ulcers

The aim of this study was to assess vitamin D status in patients with type 2 diabetes and diabetic foot ulcers (DFU). A total of 242 participants with type 2 diabetes, mean age 59.1 ± 10 years, mean body mass index 31.4 ± 6.3 kg/m², and estimated glomerular filtration rate ≥45 mL/min/1.73m², were divided into 2 groups: 73 with DFU (35 with and 38 without active infection) and 169 without DFU (106 with diabetic peripheral neuropathy, 63 without complications). Neuropathy was assessed by 10 g monofilament, Rydel-Seiffer 128 Hz tuning fork, and temperature discrimination. Serum 25(OH)D (25-hydroxy vitamin D) was assessed by ECLIA (electro-chemiluminescence immunoassay) method. Median 25(OH)D level was 12.6 ng/mL (IQR [interquartile range] 9.3-17.6 ng/mL) in the studied cohort. The DFU group presented with lower 25(OH)D level as compared with diabetic patients without foot ulcers (non-DFU group): 11.6 ng/mL (IQR 8.5-15.8 ng/mL) versus 13.5 ng/mL (IQR 9.6-18.6 ng/mL), P = .001; the diabetic peripheral neuropathy subgroup demonstrated lower 25(OH)D level in comparison with participants without complications: 12.5 ng/mL (IQR 9-17.2 ng/mL) versus 15.9 ng/mL (IQR 10.4-20.8 ng/mL), P = .031. This remained significantly different even after correction for age and duration of diabetes. There was no difference in 25(OH)D level between the subgroups according to the presence of active infection. In conclusion, vitamin D deficiency may play a role in the development of diabetes complications.

Mir-455-3p-1 represses FGF7 expression to inhibit pulmonary arterial hypertension through inhibiting the RAS/ERK signaling pathway

OBJECTIVE

To analyze the effects of miR-455-3p-1 and its possible mechanisms in pulmonary arterial hypertension (PAH).

METHODS

A microarray assay was used to examine the expressed genes between normal and PAH. The expressed genes in PAH was assessed by qRT-PCR. The targeted interaction between miRNAs and FGF7 was confirmed using a dual luciferase reporter assay. A CCK-8 assay and cell count were used to analyze the pulmonary artery smooth muscle cells (PASMCs) activity and proliferation level, respectively. Apoptotic PASMCs were detected by flow cytometry. In addition, the mRNA and protein expression levels of RAS/ERK signaling pathway were determined by qRT-PCR and a Western blot assay, respectively. A PAH rat model was used to identify the effects of miR-455-3p-1 in vivo.

RESULTS

FGF7 was upregulated in PAH. MiR-455-3p-1 was downregulated in PAH. MiR-455-3p-1 targeted FGF7. MiR-455-3p-1 decreased the expression of FGF7. Moreover, the effect of FGF7 on PASMCs was suppressed by miR-455-3p-1. MiR-455-3p-1 upregulation was associated with reduced mRNA and protein levels of core RAS/ERK signal genes, suggesting the inhibition of the RAS/ERK pathway. Furthermore, miR-455-3p-1 upregulation improved the RVSP, mPAP, ratio of RV/LV + S, CO and RV function of PAH rat model in vivo.

CONCLUSION

Our findings illustrate a role for miR-455-3p-1 in modulating FGF7-RAS/ERK signaling and suggest that an agomir of miR-455-3p-1 could inhibit the proliferation of PASMCs and mitigate PAH in vivo.

Vitamin D Increases Glucose Stimulated Insulin Secretion from Insulin Producing Beta Cells (INS1E)

BACKGROUND

Vitamin D affects the pancreatic beta cell function and in vitro studies have shown that vitamin D may influence insulin secretion, apoptosis, and gene regulation. However, the outcomes have differed and there has been uncertainty regarding the effect of different vitamin D metabolites on insulin secretion.

OBJECTIVES

We hypothesized that vitamin D could increase insulin secretion in insulin producing beta cells and investigated the effect of 25(OH) vitamin D and 1,25(OH)₂ vitamin D on insulin secretion.

METHODS

The study was conducted in INS1E cells, an established insulinoma cell line from rat. The cells were divided into three groups; a control group, a group with 1,25(OH)₂ vitamin D enriched medium (10 nM), and a group with 25(OH) vitamin D (10 nM) supplemented medium. After 72 hours of treatment, the cells underwent glucose stimulation at different concentrations (0, 5, 11, and 22 mM) for 60 minutes.

RESULTS

INS1E cells treated with 1,25(OH)₂ vitamin D showed a trend towards increased insulin secretion at all glucose concentrations compared to control cells and at 22 mM glucose, the difference was significant (18.40 +/- 1.97 vs 12.90 +/- 2.22 nmol/L, P < 0.05). However, pretreatment with 25(OH) vitamin D did not show any significant increase in insulin secretion compared to cells without vitamin D treatment. There was no difference in insulin secretion in cells not stimulated with glucose.

CONCLUSIONS

Treatment with 1,25(OH)₂ vitamin D combined with high levels of glucose increased insulin secretion in INS1E cells, whereas 25(OH) vitamin D had no effect. This suggests that glucose stimulated insulin secretion in INS1E beta cells appears to be related to the type of vitamin D metabolite treatment.

Clinical Trial of Vitamin D2 vs D3 Supplementation in Critically Ill Pediatric Burn Patients

BACKGROUND

Hypovitaminosis D exists postburn. However, evidence-based guidelines for vitamin D repletion are unknown. This investigation examined differences between D₂ and D₃ supplementation on outcome in children with burn injuries.

METHODS

Fifty patients with total body surface area burn of 55.7% ± 2.6% and full-thickness injury of 40.8% ± 3.8% were enrolled, ranging in age from 0.7-18.4 years. All participants received multivitamin supplementation per standardized clinical protocol. In addition, 100 IU/kg D₂, D₃, or placebo was administered daily during hospitalization using a randomized, double-blinded study design. Assay of total 25-hydroxyvitamin D (D25), 1,25-dihydroxyvitamin D (D1,25), 25-hydroxyvitamin D₂ (25-OH-D₂), 25-hydroxyvitamin D₃ (25-OH-D₃), and parathyroid hormone (PTH) was performed at 4 preplanned time intervals (baseline, midpoint, discharge, and 1 year postburn). Differences in vitamin D status were compared over time and at each specific study interval.

RESULTS

There were no significant differences in serum vitamin D levels between groups, but >10% of patients had low D25 at discharge, and percent deficiency worsened by the 1-year follow up for the placebo (75%), D₂ (56%), and D₃ (25%) groups. There were no statistical differences in PTH or clinical outcomes between treatment groups, although vitamin D supplementation demonstrated nonsignificant but clinically relevant decreases in exogenous insulin requirements, sepsis, and scar formation.

CONCLUSIONS

The high incidence of low serum D25 levels 1 year following serious thermal injury indicates prolonged compromise. Continued treatment with vitamin D₃ beyond the acute phase postburn is recommended to counteract the trajectory of abnormal serum levels and associated morbidity.

Vitamins and cutaneous wound healing

BACKGROUND

Vitamins have long been thought to modulate the various stages of wound healing through a variety of proposed mechanisms. Our goal was to investigate relevant studies examining the role of different vitamins in wound healing.

METHODS

MEDLINE, Cochrane Database of Systematic Reviews, and Google Scholar were searched for basic science and clinical studies examining the role of vitamins as adjuncts in wound healing.

RESULTS

Mechanisms of action for each of the vitamins are reviewed. It was suggested by many of the studies that the major vitamins A, C, E, D, K, and B have demonstrated utility as adjuncts in wound care in basic science and clinical trials.

CONCLUSION

There is a vast amount of literature on the effect of vitamins on wound healing at the basic science level. Further understanding and controlled trials will help better understand how to utilize vitamins in wound care.

DECLARATION OF INTEREST

None.

Migration of growth factor-stimulated epithelial and endothelial cells depends on EGFR transactivation by ADAM17

The fibroblast growth factor receptor 2-IIIb (FGFR2b) and the vascular endothelial growth factor receptor 2 (VEGFR2) are tyrosine kinases that can promote cell migration and proliferation and have important roles in embryonic development and cancer. Here we show that FGF7/FGFR2b-dependent activation of epidermal growth factor receptor (EGFR)/ERK1/2 signalling and cell migration in epithelial cells require stimulation of the membrane-anchored metalloproteinase ADAM17 and release of heparin-binding epidermal growth factor (HB-EGF). Moreover, VEGF-A/VEGFR2-induced migration of human umbilical vein endothelial cells also depends on EGFR/ERK1/2 signalling and shedding of the ADAM17 substrate HB-EGF. The pathway used by the FGF7/FGFR2b signalling axis to stimulate shedding of substrates of ADAM17, including ligands of the EGFR, involves Src, p38 mitogen-activated protein-kinase and PI3K, but does not require the cytoplasmic domain of ADAM17. Based on these findings, ADAM17 emerges as a central component in a triple membrane-spanning pathway between FGFR2b or VEGFR2 and EGFR/ERK1/2 that is required for cell migration in keratinocytes and presumably also in endothelial cells.

Procathepsin D secreted by HaCaT keratinocyte cells - A novel regulator of keratinocyte growth

Procathepsin D (pCD), the precursor form of lysosomal aspartic protease, is overexpressed and secreted by various carcinomas. The fact that secreted pCD plays an essential role in progression of cancer has been established. In this study, we describe substantial secretion of pCD by the human keratinocyte cell line HaCaT, under serum-free conditions. Moreover, exogenous addition of purified pCD enhanced the proliferation of HaCaT cells. The proliferative effect of pCD was inhibited by a monoclonal antibody against the activation peptide (AP) of pCD. Treatment of HaCaT cells with pCD or AP led to the secretion of a set of cytokines that might promote the growth of cells in a paracrine manner. The role of secreted pCD and its mechanism of action were studied in a scratch wound model and the presence of pCD and AP enhanced regeneration, while this effect was reversed by the addition of anti-AP antibody. Expression and secretion of pCD was upregulated in HaCaT cells exposed to various stress conditions. Taken together, our results strongly suggest that the secretion of pCD is not only linked to cancer cells but also plays a role in normal physiological conditions like wound healing and tissue remodeling.

Inhibition of JNK promotes differentiation of epidermal keratinocytes

In inflamed tissue, normal signal transduction pathways are altered by extracellular signals. For example, the JNK pathway is activated in psoriatic skin, which makes it an attractive target for treatment. To define comprehensively the JNK-regulated genes in human epidermal keratinocytes, we compared the transcriptional profiles of control and JNK inhibitor-treated keratinocytes, using DNA microarrays. We identified the differentially expressed genes 1, 4, 24, and 48 h after the treatment with SP600125. Surprisingly, the inhibition of JNK in keratinocyte cultures in vitro induces virtually all aspects of epidermal differentiation in vivo: transcription of cornification markers, inhibition of motility, withdrawal from the cell cycle, stratification, and even production of cornified envelopes. The inhibition of JNK also induces the production of enzymes of lipid and steroid metabolism, proteins of the diacylglycerol and inositol phosphate pathways, mitochondrial proteins, histones, and DNA repair enzymes, which have not been associated with differentiation previously. Simultaneously, basal cell markers, including integrins, hemidesmosome and extracellular matrix components, are suppressed. Promoter analysis of regulated genes finds that the binding sites for the forkhead family of transcription factors are over-represented in the SP600125-induced genes and c-Fos sites in the suppressed genes. The JNK-induced proliferation appears to be secondary to inhibition of differentiation. The results indicate that the inhibition of JNK in epidermal keratinocytes is sufficient to initiate their differentiation program and suggest that augmenting JNK activity could be used to delay cornification and enhance wound healing, whereas attenuating it could be a differentiation therapy-based approach for treating psoriasis.

Generation and Differentiation of Human Embryonic Stem Cell-Derived Keratinocyte Precursors

Human embryonic stem cells (hESC) hold tremendous potential in the future of tissue engineering, offering promise as a source of virtually unlimited quantities of desired cell and tissue types. We have identified soluble chemical and extracellular matrix factors that permit isolation of keratinocyte precursors from hESCs. Culturing embryoid bodies (EB) formed from hESCs in a defined serum-free keratinocyte growth medium on a gelatin matrix generated keratin 14 (K14) expressing cells with an epithelial morphology. These K14 expressing cells could be subcultured in medium supplemented with hydrocortisone and induced to stratify and terminally differentiate by addition of calcium. Optimum times for obtaining K14 expressing cells were found for EB formation and for differentiation and growth of cultures after EB plating. EB formation was not necessary to generate keratinocyte precursors; direct transfer of hESC colonies to keratinocyte growth medium permitted differentiation into the keratinocyte lineage. With further studies to optimize generation and purification of hESC-derived keratinocyte precursors, these cells could provide a source of epidermal cells for skin tissue engineering applications in vitro or in vivo.

Programmed cell death of stressed keratinocytes and its inhibition by vitamin D: The role of death and survival signaling pathways

The epidermis is confronted with multiple environmental and pathophysiological stresses. This study shows that TNFalpha, oxidative stress, hyperosmotic and heat shock induced both caspase-dependent and independent cell death in human HaCaT keratinocytes. The hormonal form of vitamin D, 1,25(OH)2D3, which is an autocrine hormone in the epidermis, protected the cells from all the examined stresses and pathways leading to cell death. We aimed to define the signaling pathways that determine the life-death balance of stressed keratinocytes and participate in their protection by 1,25(OH)2D3. As assessed by employing specific inhibitors, the survival pathways mediated by the EGF receptor, ERK, PI-3K or Src kinase, or basal transcriptional activity are important for unstressed cell survival. However, only the EGF receptor, PI-3K and the Src kinase pathways mediate the survival of stressed cells in a stimulus-specific manner. Inhibition of the p38 and/or the JNK death pathways reduced caspase activation induced by oxidative stress, hyperosmotic shock and TNFalpha. The protective effect of 1,25(OH)2D3 was not mediated by the examined survival pathways. 1,25(OH)2D3 inhibited the stress-induced activation of p38 and JNK. Since mimicking this effect by pharmacological inhibition resulted in the attenuation of caspase activation, we infer that these pathways are involved in keratinocyte protection by 1,25(OH)2D3.

Targeting perlecan in human keratinocytes reveals novel roles for perlecan in epidermal formation

Heparin-binding growth factors are crucial for the formation of human epidermis, but little is known about the role of heparan sulfate proteoglycans in this process. Here we investigated the role of the heparan sulfate proteoglycan, perlecan, in the formation of human epidermis, by utilizing in vitro engineered human skin. By disrupting perlecan expression either in the dermis or the epidermis, we found that epidermally derived perlecan is essential for epidermal formation. Perlecan-deficient keratinocytes formed a strikingly thin and poorly organized epidermis because of premature apoptosis and failure to complete their stratification program. Exogenous perlecan fully restored epidermal formation. Perlecan deposition in the basement membrane zone correlated with formation of multilayered epidermis. Perlecan deficiency, however, had no effect on the lining and deposition of major basement membrane components as was evident by a continuous linear staining of laminin and collagen IV. Similarly, perlecan deficiency did not affect the distribution of beta1 integrin. Addition of the perlecan ligand, fibroblast growth factor 7, protected perlecan-deficient keratinocytes from cell death and improved the thickness of the epidermis. Taken together, our results revealed novel roles for perlecan in epidermal formation. Perlecan regulates both the survival and terminal differentiation steps of keratinocytes. Our results suggested a model whereby perlecan regulates these processes via controlling the bioavailability of perlecan-binding soluble factors involved in epidermal morphogenesis.

Modulation of tyrosine phosphorylation signalling pathways by 1alpha,25(OH)2-vitamin D3

Hormonally active vitamin D(3), 1alpha,25(OH)(2)D(3), interacts with the classic vitamin D nuclear receptor that regulates gene transcription and with a putative cell membrane receptor that mediates rapid biological responses. 1alpha,25(OH)(2)D(3) actions on target tissues regulate: mineral metabolism and intracellular Ca(2+); protein kinase cascades leading to cell proliferation, differentiation and apoptosis; muscle growth and contractility; and the immune system. There is evidence for underlying 1alpha,25(OH)(2)D(3)-mediated protein tyrosine phosphorylation signalling in bone, intestine, muscle, epidermal and cancer cells. Extracellular-signal-regulated kinases-1/2, p38 and/or c-jun N-terminal kinase pathways play important roles in mediating 1alpha,25(OH)(2)D(3) actions. Studies to elucidate key regulatory metabolic steps and crosstalk sites in these pathways would enhance our understanding of the significance of tyrosine phosphorylation cascades in normal 1alpha,25(OH)(2)D(3) physiology, pathophysiology and pharmacology.

An autocrine/paracrine loop linking keratin 14 aggregates to tumor necrosis factor alpha-mediated cytotoxicity in a keratinocyte model of epidermolysis bullosa simplex

Epidermolysis bullosa simplex (EBS) is a blistering cutaneous disease featuring protein aggregates. Here we investigate the molecular mechanisms linking protein aggregates to cell death in a cellular model of EBS in which HaCaT keratinocytes are transfected with plasmids expressing various mutant forms of keratin 14 (K14). In HaCaT cells, mutant K14 was found to form ubiquitinated protein aggregates that suppressed 20 S proteasome function instead of being degraded by 20 S proteasome. Keratinocytes with mutant K14-induced phosphorylation of the stress-activated kinase c-Jun, as well as up-regulation of unfolding protein Bip, indicates induction of endoplasmic reticulum stress. HaCaT cells were susceptible to apoptosis by activation of caspases-3, and -8, but not caspase-9 or -12. Tumor necrosis factor-alpha (TNFalpha) in the culture medium was increased in keratinocytes with mutant K14 compared with wild K14, and the addition of neutralizing anti-TNFalpha antibody to the culture medium rescued keratinocytes from cell death. Thus, TNFalpha release and the subsequent activation of the TNFalpha receptor by an autocrine/paracrine pathway links protein aggregates to cell death in this keratinocyte EBS cellular model. Furthermore, mutation in K14 reduced its affinity to TNFalpha receptor-associated death domain (TRADD), suggesting that the susceptibility of keratinocytes to caspase-8-mediated apoptosis is increased in mutated K14 because of impairment of the cytoprotective mechanism mediated by K14-TRADD interaction.