MicroRNAs in the Functional Defects of Skin Aging

Humankind has always been intrigued by death, as illustrated by the eternal quest for the fountain of youth. Aging is a relentless biological process slowly progressing as life cycle proceeds. Indeed, aging traduces an accumulation of physiological changes over time that render organisms more likely to die. Thus, despite our mastery of advanced technologies and robust medical knowledge, defining the molecular basis of aging to control lifespan is still currently one of the greatest challenges in biology. In mammals, the skin is the ultimate multitasker vital organ, protecting organisms from the world they live in. As a preferential interface with the environment, the skin is reflecting the internal physiological balances. The maintenance of these balances, called homeostasis, depends on the concurrent assimilation of diversified signals at the cellular level. MicroRNAs (miRNAs) are noncoding RNAs that regulate gene expression by mRNAs degradation or translational repression. Their relatively recent discovery in 2000 provided new insights into the understanding of the gene regulatory networks. In this chapter, we focused on the role of three miRNA families, namely miR-30, miR-200, and miR-181, playing a key role in the progression of the skin aging process, with particular input in mechanistic considerations related to autophagy, oxidative stress, and mitochondrial homeostasis

Connexin30 mutations responsible for hidrotic ectodermal dysplasia cause abnormal hemichannel activity

Clouston syndrome or hidrotic ectodermal dysplasia (HED) is a rare dominant genodermatosis characterized by palmoplantar hyperkeratosis, generalized alopecia and nail defects. The disease is caused by mutations in the human GJB6 gene which encodes the gap junction protein connexin30 (Cx30). To gain insight into the molecular mechanisms underlying HED, we have analyzed the consequences of two of these mutations (G11R Cx30 and A88V Cx30) on the functional properties of the connexons they form. Here, we show that the distribution of Cx30 is similar in affected palmoplantar skin and in normal epidermis. We further demonstrate that the presence of the wild-type protein (wt Cx30) improves the trafficking of mutated Cx30 to the plasma membrane where both G11R and A88V Cx30 co-localize with wt Cx30 and form functional intercellular channels. The electrophysiological properties of channels made of G11R and A88V Cx30 differ slightly from those of wt Cx30 but allow for dye transfer between transfected HeLa cells. Finally, we document a gain of function of G11R and A88V Cx30, which form functional hemichannels at the cell surface and, when expressed in HeLa cells, generate a leakage of ATP into the extracellular medium. Such increased ATP levels might act as a paracrine messenger that, by altering the epidermal factors which control the proliferation and differentiation of keratinocytes, may play an important role in the pathophysiological processes leading to the HED phenotyp

Impact of Human Dermal Microvascular Endothelial Cells on Primary Dermal Fibroblasts in Response to Inflammatory Stress

The aim of the present study was to evaluate the impact of the microenvironment produced by dermal microvascular endothelial cells, secondary to a pro-inflammatory challenge, on 2D culture models using dermal fibroblasts and in 3D reconstructed skin model using dermal fibroblasts and keratinocytes from healthy donors. We hypothesized that specific microvascular endothelial low grade inflammation could change fibroblasts phenotype and be involved in extracellular matrix (ECM) modification and skin alteration. Following IFNγ, TNFα, IL-1β pro-inflammatory stress on Human Dermal Endothelial Cells (HDMEC) we observed the increased release of Chemokine ligand 2 (CCL2), IL-6 and IL-8 but not VEGF-A in the conditioned medium (CM). The subsequent addition of this endothelial pro-inflammatory CM in dermal fibroblasts revealed an upregulation of IL6, IL8 and CCL2 but no NF-κB gene expression. The resulting ECM formation was impaired with a reduction of the collagen 1 network and a decrease in COL1A1 gene expression in 2D and 3D models. Collagen 1 and pro-LOX protein expression were significantly reduced confirming an impairment of the collagen network related to endothelial inflammation secretion. To conclude, this work showed that, without any immune cells, the endothelial secretion in response to a pro-inflammatory stress is able to activate the fibroblasts that will maintain the pro-inflammatory environment and exacerbate ECM degradation

Severe PATCHED1 deficiency in cancer-prone Gorlin patient cells results in intrinsic radiosensitivity

PURPOSE: Gorlin syndrome (or basal-cell nevus syndrome) is a cancer-prone genetic disease in which hypersusceptibility to secondary cancer and tissue reaction after radiation therapy is debated, as is increased radiosensitivity at cellular level. Gorlin syndrome results from heterozygous mutations in the PTCH1 gene for 60% of patients, and we therefore aimed to highlight correlations between intrinsic radiosensitivity and PTCH1 gene expression in fibroblasts from adult patients with Gorlin syndrome. METHODS AND MATERIALS: The radiosensitivity of fibroblasts from 6 patients with Gorlin syndrome was determined by cell-survival assay after high (0.5-3.5 Gy) and low (50-250 mGy) γ-ray doses. PTCH1 and DNA damage response gene expression was characterized by real-time polymerase chain reaction and Western blotting. DNA damage and repair were investigated by γH2AX and 53BP1 foci assay. PTCH1 knockdown was performed in cells from healthy donors by using stable RNA interference. Gorlin cells were genotyped by 2 complementary sequencing methods. RESULTS: Only cells from patients with Gorlin syndrome who presented severe deficiency in PATCHED1 protein exhibited a significant increase in cellular radiosensitivity, affecting cell responses to both high and low radiation doses. For 2 of the radiosensitive cell strains, heterozygous mutations in the 5' end of PTCH1 gene explain PATCHED1 protein deficiency. In all sensitive cells, DNA damage response pathways (ATM, CHK2, and P53 levels and activation by phosphorylation) were deregulated after irradiation, whereas DSB repair recognition was unimpaired. Furthermore, normal cells with RNA interference-mediated PTCH1 deficiency showed reduced survival after irradiation, directly linking this gene to high- and low-dose radiosensitivity. CONCLUSIONS: In the present study, we show an inverse correlation between PTCH1 expression level and cellular radiosensitivity, suggesting an explanation for the conflicting results previously reported for Gorlin syndrome and possibly providing a basis for prognostic screens for radiosensitive patients with Gorlin syndrome and PTCH1 mutations

Concordance for curve type in idiopathic scoliosis among family members

OBJECTIVE: To evaluate the concordance for the curve pattern, side and levels of the superior apical vertebrae, apex and inferior apical vertebrae of curves in patients and their relatives with idiopathic scoliosis. METHODS: Concordance according to the Lenke classification for curve pattern, side and levels of the superior apical vertebrae, apex and inferior apical vertebrae were evaluated comparative and prospectively in 243 pairs of patients and respective relatives with idiopathic scoliosis. RESULTS: The family concordance for the curve pattern and side was 51.4% (125 pairs). Among these pairs, the concordance of the levels of the vertebrae was 91.2% (114 pairs). The concordance rate for the curve pattern and side between parents/children was 51.6% and between siblings was 50.0% (p-value= 0.411). The concordance rates of the levels of vertebrae were 86.8% and 95.1%, respectively (p-value = 0.219). CONCLUSION: Curve shape in idiopathic scoliosis is related to family and degree of kinship, since the data showed a high concordance for the curve pattern, side and levels of the apical vertebrae and apex between patients and relatives with this deformity. The concordance was higher in those with a closer degree of kinship. Level of Evidence II, Lesser Quality Prospective Study

L’hypersensibilité aux radiations ionisantes: Modélisation d’un syndrome d’hypersensibilité aux radiations ionisantes pour l’estimation du risque de cancers et l’identification de biomarqueurs d’exposition aux faibles doses

La population générale est soumise de manière chronique à de faibles doses de radiations ionisantes. La dose annuelle moyenne reçue par un Français était en 2010 de l’ordre de 3,7 millisievert. Cette exposition chronique a plusieurs origines : radioactivité naturelle (ex. radon), examens et traitements médicaux (ex. radiographie)... Les doses reçues par la population, se situent dans le domaine des faibles doses. On peut les définir comme celles pour lesquelles l’induction d’effets négatifs déterministes sur la santé n’est pas démontrée. Il y a un fort intérêt à mieux comprendre l’effet des faibles doses mais, du fait de leur caractère non déterministe, l’impact sur la santé est difficile à évaluer. Une solution pour mieux comprendre ces effets consiste à développer des modèles humains d’hypersensibilité pour amplifier les réponses cellulaires

Vieillissement et intégrité de la peau

La peau est un organe sentinelle, soumis au vieillissement chronologique et environnemental qui fragilise sa structure et ses fonctions. La fonction barrière de la peau, ses propriétés élastiques et de résistance, ainsi que sa réactivité vasculaire sont atteintes par le vieillissement dans les compartiments épidermiques, dermiques et vasculaires. Les progrès de la recherche ont permis de révéler des processus biologiques sous-jacents, qui peuvent être ciblés par des approches médicamenteuses topiques ou globales à base notamment d’anti-oxydants ou de sénolytiques. Ces stratégies anti-âge pourront contribuer à restaurer, au moins en partie, l’intégrité fonctionnelle de la peau âgée