Physiological Impact of a Synthetic Elastic Protein in Arterial Diseases Related to Alterations of Elastic Fibers: Effect on the Aorta of Elastin-Haploinsufficient Male and Female Mice.

Elastic fibers, made of elastin (90%) and fibrillin-rich microfibrils (10%), are the key extracellular components, which endow the arteries with elasticity. The alteration of elastic fibers leads to cardiovascular dysfunctions, as observed in elastin haploinsufficiency in mice (Eln+/-) or humans (supravalvular aortic stenosis or Williams-Beuren syndrome). In Eln+/+ and Eln+/- mice, we evaluated (arteriography, histology, qPCR, Western blots and cell cultures) the beneficial impact of treatment with a synthetic elastic protein (SEP), mimicking several domains of tropoelastin, the precursor of elastin, including hydrophobic elasticity-related domains and binding sites for elastin receptors. In the aorta or cultured aortic smooth muscle cells from these animals, SEP treatment induced a synthesis of elastin and fibrillin-1, a thickening of the aortic elastic lamellae, a decrease in wall stiffness and/or a strong trend toward a reduction in the elastic lamella disruptions in Eln+/- mice. SEP also modified collagen conformation and transcript expressions, enhanced the aorta constrictive response to phenylephrine in several animal groups, and, in female Eln+/- mice, it restored the normal vasodilatory response to acetylcholine. SEP should now be considered as a biomimetic molecule with an interesting potential for future treatments of elastin-deficient patients with altered arterial structure/function.

MiR-30a-5p Alters Epidermal Terminal Differentiation during Aging by Regulating BNIP3L/NIX-Dependent Mitophagy.

Chronological aging is characterized by an alteration in the genes' regulatory network. In human skin, epidermal keratinocytes fail to differentiate properly with aging, leading to the weakening of the epidermal function. MiR-30a is particularly overexpressed with epidermal aging, but the downstream molecular mechanisms are still uncovered. The aim of this study was to decipher the effects of miR-30a overexpression in the human epidermis, with a focus on keratinocyte differentiation. We formally identified the mitophagy receptor BNIP3L as a direct target of miR-30a. Using a 3D organotypic model of reconstructed human epidermis overexpressing miR-30a, we observed a strong reduction in BNIP3L expression in the granular layer. In human epidermal sections of skin biopsies from donors of different ages, we observed a similar pattern of BNIP3L decreasing with aging. Moreover, human primary keratinocytes undergoing differentiation in vitro also showed a decreased expression of BNIP3L with age, together with a retention of mitochondria. Moreover, aging is associated with altered mitochondrial metabolism in primary keratinocytes, including decreased ATP-linked respiration. Thus, miR-30a is a negative regulator of programmed mitophagy during keratinocytes terminal differentiation, impairing epidermal homeostasis with aging.

Design and characterization of an in vivo injectable hydrogel with effervescently generated porosity for regenerative medicine applications.

Injectable hydrogels that polymerize directly in vivo hold significant promises in clinical settings to support the repair of damaged or failing tissues. Existing systems that allow cellular and tissue ingrowth after injection are limited because of deficient porosity and lack of oxygen and nutrient diffusion inside the hydrogels. Here is reported for the first time an in vivo injectable hydrogel in which the porosity does not pre-exist but is formed concomitantly with its in situ injection by a controlled effervescent reaction. The hydrogel tailorable crosslinking, through the reaction of polyethylene glycol with lysine dendrimers, allows the mixing and injection of precursor solutions from a dual-chamber syringe while entrapping effervescently generated CO2 bubbles to form highly interconnected porous networks. The resulting structures allow preserving modular mechanical properties (from 12.7 ± 0.9 to 29.9 ± 1.7 kPa) while being cytocompatible and conducive to swift cellular attachment, proliferation, in-depth infiltration and extracellular matrix deposition. Most importantly, the subcutaneously injected porous hydrogels are biocompatible, undergo tissue remodeling and support extensive neovascularisation, which is of significant advantage for the clinical repair of damaged tissues. Thus, the porosity and injectability of the described effervescent hydrogels, together with their biocompatibility and versatility of mechanical properties, open broad perspectives for various regenerative medicine or material applications, since effervescence could be combined with a variety of other systems of swift crosslinking. STATEMENT OF SIGNIFICANCE: A major challenge in hydrogel design is the synthesis of injectable formulations allowing easy handling and dispensing in the site of interest. However, the lack of adequate porosity inside hydrogels prevent cellular entry and, therefore, vascularization and tissue ingrowth, limiting the regenerative potential of a vast majority of injectable hydrogels. We describe here the development of an acellular hydrogel that can be injected directly in situ while allowing the simultaneous formation of porosity. Such hydrogel would facilitate handling through injection while providing a porous structure supporting vascularization and tissue ingrowth.