Striae reconstructed, a full thickness skin model that recapitulates the pathology behind stretch marks.

OBJECTIVE: Stretch marks are disfiguring skin lesions that often cause problems of self-esteem, but little effort has been put to studying this pathology. We therefore analysed cell cultures of dermal fibroblasts isolated from a striae albae, to thereafter reconstruct a full thickness skin model. METHODS: Human Dermal Fibroblasts (HDF) were isolated from a striae distensae (SD) lesion and from the adjacent non-lesioned skin. The dermis of two full thickness skin models was reconstructed with either striae- or normal-HDF, while the epidermis was in both reconstructed with Normal Human Epidermal Keratinocytes. RESULTS: Main observations and pertinent data: Gene expression analysis of cell cultures revealed a generalized decomposition of the Extra Cellular Matrix (ECM), since collagens type I and III, lysyl oxidase (LOX), biglycan, lumican and fibronectin were downregulated, while MMP3 was increased together with a decrease of its natural inhibitors (TIMP1, TIMP2 and PAI-1). These findings were statistically corroborated for key ECM elements at the protein level (COL1, MMP1 and TGFB1). Interestingly, striae albae fibroblasts retained a pro-inflammatory phenotype, as suggested by increased gene expression of CXCL8, HAS1 and TNFA. We next reconstructed a full thickness skin model (Striae Reconstructed) with dermal fibroblasts from striae albae. Gene expression analysis showed that the Striae Reconstructed elicited not only ECM decomposition, but also skin ageing, as indicated by the upregulation of P16, PTGS2 and SOD2. Discussion points: Although the epidermis was constructed with normal human epidermal keratinocytes, the Striae Reconstructed presented epidermal atrophy and a dramatic increase of ß1-integrin at the epidermal-dermal junction providing, for the first time to our knowledge, a rationale showing that the key cell player behind stretch marks are dermal fibroblasts rather than epidermal keratinocytes. CONCLUSION: New knowledge: Taken together, our findings shed new light into the aetiology of stretch marks and indicate that the Striae Reconstructed, a new model for in vitro testing and drug screening, may open new avenues for the treatment of stretch marks.

OBJECTIFS: Les vergetures sont des lésions cutanées défigurantes qui posent souvent des problèmes d'estime de soi, mais peu d'efforts ont été consacrés dans l'étude de cette pathologie. Nous avons donc analysé des cultures cellulaires de fibroblastes dermiques isolés d'un stria alba, afin de reconstruire ensuite un modèle de peau avec une pleine épaisseur. METHODES: Des fibroblastes dermiques humains (FDH) ont été isolés d'une lésion de Stria distensae (SD) et d'une peau adjacente sans lésion. Le derme de deux modèles de peau de pleine épaisseur a été reconstruit avec du HDF striae- ou normal, tandis que l'épiderme était reconstruit avec des kératinocytes humains normaux. RESULTATS: Principales observations et données pertinentes: L'analyse de l'expression génique de cultures cellulaires a révélé une décomposition généralisée de la matrice extra-cellulaire (MEC) car les collagènes de types I et III, la lysyl oxydase, le biglycane, le lumican et la fibronectine étaient régulés négativement, tandis que la MMP3 augmentait ses inhibiteurs naturels diminuaient (TIMP1, TIMP2 et PAI-1). Ces résultats ont été corroborés statistiquement pour les éléments clés de la MEC au niveau de la protéine (COL1, MMP1 et TGFB1). Il est intéressant de noter que les fibroblastes de Striae albae ont conservé un phénotype proinflammatoire, comme le suggère l'augmentation de l'expression des gènes de CXCL8, HAS1 et TNFA. Nous avons ensuite reconstruit un modèle de peau de pleine épaisseur (Stria Reconstructed) avec des fibroblastes dermiques de Striae albae. L'analyse de l'expression génique a montré que la reconstruction de Striae induisait non seulement la décomposition de la MEC, mais également le vieillissement de la peau, comme l'indique la régulation à la hausse de P16, PTGS2 et SOD2. Points de discussion : Bien que l'épiderme ait été construit avec des kératinocytes humains normaux, les stries reconstruites présentaient une atrophie épidermique et une augmentation spectaculaire du taux de ß1-intégrine au niveau de la jonction épidermo-dermique, fournissant pour la première fois une explication rationnelle qui démontre que les cellules principales impliquées dans la pathologie de la Striae sont les fibroblastes et non les kératinocytes. CONCLUSION: Nouvelles connaissances: Ensemble, nos résultats donnent une nouvelle lumière sur l'étiologie des vergetures et indiquent que le Striae Reconstructed, un nouveau modèle de test in vitro et de dépistage du médicament, pourrait être une avancée pour le traitement des vergetures.

The three α1-adrenoceptor subtypes show different spatio-temporal mechanisms of internalization and ERK1/2 phosphorylation.

We analyzed the kinetic and spatial patterns characterizing activation of the MAP kinases ERK 1 and 2 (ERK1/2) by the three α1-adrenoceptor (α1-AR) subtypes in HEK293 cells and the contribution of two different pathways to ERK1/2 phosphorylation: protein kinase C (PKC)-dependent ERK1/2 activation and internalization-dependent ERK1/2 activation. The different pathways of phenylephrine induced ERK phosphorylation were determined by western blot, using the PKC inhibitor Ro 31-8425, the receptor internalization inhibitor concanavalin A and the siRNA targeting ß-arrestin 2. Receptor internalization properties were studied using CypHer5 technology and VSV-G epitope-tagged receptors. Activation of α1A- and α1B-ARs by phenylephrine elicited rapid ERK1/2 phosphorylation that was directed to the nucleus and inhibited by Ro 31-8425. Concomitant with phenylephrine induced receptor internalization α1A-AR, but not α1B-AR, produced a maintained and PKC-independent ERK phosphorylation, which was restricted to the cytosol and inhibited by ß-arrestin 2 knockdown or concanavalin A treatment. α1D-AR displayed constitutive ERK phosphorylation, which was reduced by incubation with prazosin or the selective α1D antagonist BMY7378. Following activation by phenylephrine, α1D-AR elicited rapid, transient ERK1/2 phosphorylation that was restricted to the cytosol and not inhibited by Ro 31-8425. Internalization of the α1D-AR subtype was not observed via CypHer5 technology. The three α1-AR subtypes present different spatio-temporal patterns of receptor internalization, and only α1A-AR stimulation translates to a late, sustained ERK1/2 phosphorylation that is restricted to the cytosol and dependent on ß-arrestin 2 mediated internalization.

Different ß-adrenoceptor subtypes coupling to cAMP or NO/cGMP pathways: implications in the relaxant response of rat conductance and resistance vessels.

BACKGROUND AND PURPOSE: To analyse the relative contribution of ß1 -, ß2 - and ß3 -adrenoceptors (Adrb) to vasodilatation in conductance and resistance vessels, assessing the role of cAMP and/or NO/cGMP signalling pathways. EXPERIMENTAL APPROACH: Rat mesenteric resistance artery (MRA) and aorta were used to analyse the Adrb expression by real-time-PCR and immunohistochemistry, and for the pharmacological characterization of Adrb-mediated activity by wire myography and tissue nucleotide accumulation. KEY RESULTS: The mRNAs and protein for all Adrb were identified in endothelium and/or smooth muscle cells (SMCs) in both vessels. In MRA, Adrb1 signalled through cAMP, Adrb3 through both cAMP and cGMP, but Adrb2, did not activate nucleotide formation; isoprenaline relaxation was inhibited by propranolol (ß1 , ß2 ), CGP20712A (ß1 ), and SQ22536 (adenylyl cyclase inhibitor), but not by ICI118,551 (ß2 ), SR59230A (ß3 ), ODQ (soluble guanylyl cyclase inhibitor), L-NAME or endothelium removal. In aorta, Adrb1 signalled through cAMP, while ß2 - and ß3 -subtypes through cGMP; isoprenaline relaxation was inhibited by propranolol, ICI118,551, ODQ, L-NAME, and to a lesser extent, by endothelium removal. CL316243 (ß3 -agonist) relaxed aorta, but not MRA. CONCLUSION AND IMPLICATION: Despite all three Adrb subtypes being found in both vessels, Adrb1, located in SMCs and acting through the adenylyl cyclase/cAMP pathway, are primarily responsible for vasodilatation in MRA. However, Adrb-mediated vasodilatation in aorta is driven by endothelial Adrb2 and Adrb3, but also by the Adrb2 present in SMCs, and is coupled to the NO/cGMP pathway. These results could help to understand the different physiological roles played by Adrb signalling in regulating conductance and resistance vessels.