Cardiovascular diseases are the most distributed cause of death worldwide. Stenting of arteries as a percutaneous transluminal angioplasty procedure became a promising minimally invasive therapy based on re-opening narrowed arteries by stent insertion. In order to improve and optimize this method, many research groups are focusing on designing new or improving existent stents. Since the beginning of the stent development in 1986, starting with bare-metal stents (BMS), these devices have been continuously enhanced by applying new materials, developing stent coatings based on inorganic and organic compounds including drugs, nanoparticles or biological components such as genes and cells, as well as adapting stent designs with different fabrication technologies. Drug eluting stents (DES) have been developed to overcome the main shortcomings of BMS or coated stents. Coatings are mainly applied to control biocompatibility, degradation rate, protein adsorption, and allow adequate endothelialization in order to ensure better clinical outcome of BMS, reducing restenosis and thrombosis. As coating materials (i) organic polymers: polyurethanes, poly(ε-caprolactone), styrene-b-isobutylene-b-styrene, polyhydroxybutyrates, poly(lactide-co-glycolide), and phosphoryl choline; (ii) biological components: vascular endothelial growth factor (VEGF) and anti-CD34 antibody and (iii) inorganic coatings: noble metals, wide class of oxides, nitrides, silicide and carbide, hydroxyapatite, diamond-like carbon, and others are used. DES were developed to reduce the tissue hyperplasia and in-stent restenosis utilizing antiproliferative substances like paclitaxel, limus (siro-, zotaro-, evero-, bio-, amphi-, tacro-limus), ABT-578, tyrphostin AGL-2043, genes, etc. The innovative solutions aim at overcoming the main limitations of the stent technology, such as in-stent restenosis and stent thrombosis, while maintaining the prime requirements on biocompatibility, biodegradability, and mechanical behavior. This paper provides an overview of the existing stent types, their functionality, materials, and manufacturing conditions demonstrating the still huge potential for the development of promising stent solutions.

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Background: Mesenchymal stem cells (MSCs) secrete a cocktail of growth factors and cytokines, which could promote tissue regeneration and wound healing. Therefore, in clinical practice, post-culture MSC supernatant treatment could be a more attractive alternative to autologous stem cell transplantation. In this study, we compared the regenerative properties of supernatants harvested from four newly established human adipose tissue mesenchymal stem cell lines (HATMSCs) derived from chronic wound patients or healthy donors. Methods: HATMSC supernatants were produced in a serum-free medium under hypoxia and their content was analyzed by a human angiogenesis antibody array. The regenerative effect of HATMSCs supernatants was investigated in an in vitro model of chronic wound, where cells originating from human skin, such as microvascular endothelial cells (HSkMEC.2), keratinocytes (HaCaT), and fibroblasts (MSU-1.1), were cultured in serum-free and oxygen-reduced conditions. The effect of supernatant treatment was evaluated using an MTT assay and light microscopy. In addition, fibroblasts and HATMSCs were labeled with PKH67 and PKH26 dye, respectively, and the effect of supernatant treatment was compared to that obtained when fibroblasts and HATMSCs were co-cultured, using flow cytometry and fluorescent microscopy. Results: A wide panel of angiogenesis-associated cytokines such as angiogenin, growth-regulated oncogene (GRO), interleukin-6 and 8 (IL-6, IL-8), vascular endothelial growth factor (VEGF), insulin growth factor 1 (IGF-1), and matrix metalloproteinase (MMP) were found in all tested HATMSCs supernatants. Moreover, supernatant treatment significantly enhanced the survival of fibroblasts, endothelial cells, and keratinocytes in our chronic wound model in vitro. Importantly, we have shown that in in vitro settings, HATMSC supernatant treatment results in superior fibroblast proliferation than in the case of co-culture with HATMSCs. Conclusions: Our results suggest that therapy based on bioactive factors released by the immortalized atMSC into supernatant has important effect on skin-derived cell proliferation and might preclude the need for a more expensive and difficult cell therapy approach to improve chronic wound healing.

Endothelial progenitor cells (EPCs) and mesenchymal stem/stromal cells (MSCs) are associated with maintaining tissue homeostasis and tissue repair. Both types of cells contribute to tissue regeneration through the secretion of trophic factors (alone or in the form of microvesicles). This study investigated the isolation and biological properties of microvesicles (MVs) derived from human immortalized MSC line HATMSC1 of adipose tissue origin and EPC line. The human immortalized cell line derived from the adipose tissue of a patient with venous stasis was established in our laboratory using the hTERT and pSV402 plasmids. The human EPC line originating from cord blood (HEPC-CB.1) was established in our previous studies. Microvesicles were isolated through a sequence of centrifugations. Analysis of the protein content of both populations of microvesicles, using the Membrane-Based Antibody Array and Milliplex ELISA showed that isolated microvesicles transported growth factors and pro- and antiangiogenic factors. Analysis of the miRNA content of isolated microvesicles revealed the presence of proangiogenic miRNA (miR-126, miR-296, miR-378, and miR-210) and low expression of antiangiogenic miRNA (miR-221, miR-222, and miR-92a) using real-time RT-PCR with the TaqMan technique. The isolated microvesicles were assessed for their effect on the proliferation and proangiogenic properties of cells involved in tissue repair. It was shown that both HEPC-CB.1- and HATMSC1-derived microvesicles increased the proliferation of human endothelial cells of dermal origin and that this effect was dose-dependent. In contrast, microvesicles had a limited impact on the proliferation of fibroblasts and keratinocytes. Both types of microvesicles improved the proangiogenic properties of human dermal endothelial cells, and this effect was also dose-dependent, as shown in the Matrigel assay. These results confirm the hypothesis that microvesicles of HEPC-CB.1 and HATMSC1 origin carry proteins and miRNAs that support and facilitate angiogenic processes that are important for cutaneous tissue regeneration.