Porous honeycomb film membranes enhance endothelial barrier integrity in human vascular wall bilayer model compared to standard track-etched membranes.

In vitro vascular wall bilayer models for drug testing and disease modeling must emulate the physical and biological properties of healthy vascular tissue and its endothelial barrier function. Both endothelial cell (EC)-vascular smooth muscle cell (SMC) interaction across the internal elastic lamina (IEL) and blood vessel stiffness impact endothelial barrier integrity. Polymeric porous track-etched membranes (TEM) typically represent the IEL in laboratory vascular bilayer models. However, TEM stiffness exceeds that of diseased blood vessels, and the membrane pore architecture limits EC-SMC interaction. The mechanical properties of compliant honeycomb film (HCF) membranes better simulate the Young's modulus of healthy blood vessels, and HCFs are thinner (4 vs. 10 µm) and more porous (57 vs. 6.5%) than TEMs. We compared endothelial barrier integrity in vascular wall bilayer models with human ECs and SMCs statically cultured on opposite sides of HCFs and TEMs (5 µm pores) for up to 12 days. Highly segregated localization of tight junction (ZO-1) and adherens junction (VE-cadherin) proteins and quiescent F-actin cytoskeletons demonstrated superior and earlier maturation of interendothelial junctions. Quantifying barrier integrity based on transendothelial electrical resistance (TEER), membranes showed only minor but significant TEER differences despite enhanced junctional protein localization on HCF. Elongated ECs on HCF likely experienced greater paracellular diffusion than blocky ECs on TEM. Also, larger populations of plaques of connexin 43 subunit-containing gap junctions suggested enhanced EC-SMC communication across the more porous, thinner HCF. Compared with standard TEMs, engineered vascular wall bilayers cultured on HCFs better replicate physiologic endothelial barrier integrity.

The Characteristics and Survival Potential Under Sub-lethal Stress of Mesenchymal Stromal/Stem Cells Isolated from the Human Vascular Wall.

Mesenchymal stromal/stem cells (MSCs) have been identified in multiple human tissues, including the vascular wall. High proliferative potential, multilineage, and immunomodulatory properties make vascular MSCs promising candidates for regenerative medicine. Indeed, their location is strategic for controlling vascular and extra-vascular tissue homeostasis. However, the clinical application of MSCs, and in particular vascular MSCs, is still challenging. Current studies are focused on developing strategies to improve MSC therapeutic applications, like priming MSCs with stress conditions (hypoxia, nutrient deprivation) to achieve a higher therapeutic potential. The goal of the present study is to review the main findings regarding the MSCs isolated from the human vascular wall. Further, the main priming strategies tested on MSCs from different sources are reported, together with the experience on vascular MSCs isolated from healthy cryopreserved and pathological arteries. Stress induction can be a priming approach able to improve MSC effectiveness through several mechanisms that are discussed in this review. Nevertheless, these issues have not been completely explored in vascular MSCs and potential side effects need to be investigated.

Differentiation and plasticity of human vascular wall mesenchymal stem cells, dermal fibroblasts and myofibroblasts: a critical comparison including ultrastructural evaluation of osteogenic potential.

Mesenchymal stem cells (MSCs) share many properties with other tissue stromal cells, including cell morphology, immunophenotype, differentiation and immunologic properties. In this study, we compared the immunophenotype and the differentiation potential of human vascular wall mesenchymal stem cells (hVW-MSCs) with those of human dermal fibroblasts and myofibroblasts. Cell morphology and surface markers were evaluated by immunofluorescence and flow cytometry; functional assays for immunomodulation, angiogenesis, adipogenesis and osteogenesis were performed, together with the mRNA analysis of the critical differentiation genes. hVW-MSCs, dermal fibroblasts and myofibroblasts were all negative to CD34, whereas the expression of CD44 stemness marker was more intense in hVW-MSCs. As expected, hVW-MSC plasticity was wide and the angiogenic, adipogenic, osteogenic features were confirmed. Fibroblasts were the less effective in terms of immunomodulation, angiogenesis and adipogenic differentiation; differently from fibroblasts, the myofibroblasts showed a poor angiogenic commitment. The mineralization assay was positive in all the three cell types, but ultrastructure interestingly evidenced differential osteogenic patterns among them. Our study supports the higher anti-inflammatory and wound healing repair features of hVW-MSCs, in comparison to the other stromal cells investigated. Moreover, we underline the importance of ultrastructure for investigating the specific osteogenic pattern for each cell type.