Stiffness of Extracellular Matrix Components Modulates the Phenotype of Human Smooth Muscle Cells in Vitro and Allows for the Control of Properties of Engineered Tissues

AbstractSmooth muscle cells (SMCs) play a significant role in the pathogenesis of atherosclerosis. 2D cultures elucidated valuable information about the interaction between SMCs and extracellular matrix (ECM) components. However, 3D constructs better represent the native vascular environment. Furthermore, a limited number of studies addressed the effect of ECM stiffness on SMCs phenotype. We investigated the effect of stiffness of different ECM substrates by modulating their concentrations, including the effect on morphology, proliferation, expression of the contractile protein α-smooth muscle actin (α-SMA) and deposition of collagen type I (Col I) and collagen type III (Col III) proteins. At low concentrations of Col I gels and Col I gels supplemented with 10% fibronectin (Fn), SMCs exhibited non-elongated, ‘hill-and-valley’ shape and large mean cellular area, indicating a hypertrophic morphology, characteristic of the synthetic phenotype. However, with increasing concentration, mean cellular area and proliferation relative to cells cultured in 2D dropped. Whole protein secretion into the culture media and deposition of Col I and Col III generally decreased with increasing stiffness. Moreover, percentage of α-SMA+ SMCs decreased with increasing gel concentration, pointing to a shift towards the synthetic phenotype. Supplementing Col I with 10% Laminin (Ln) maintained higher cellular area and aspect ratio at all gel concentrations and did not change α-SMA expression significantly, compared to Col I alone or Col I + Fn. Overall, these results demonstrate that ECM components and stiffness could provide the tools to modulate the phenotype and function of SMCs in vitro, which allows for the control of properties of engineered tissues

Engineered Microvessel for Cell Culture in Simulated Microgravity

As the number of manned space flights increase, studies on the effects of microgravity on the human body are becoming more important. Due to the high expense and complexity of sending samples into space, simulated microgravity platforms have become a popular way to study these effects on earth. In addition, simulated microgravity has recently drawn the attention of regenerative medicine by increasing cell differentiation capability. These platforms come with many advantages as well as limitations. A main limitation for usage of these platforms is the lack of high-throughput capability due to the use of large cell culture vessels. Therefore, there is a requirement for microvessels for microgravity platforms that limit waste and increase throughput. In this work, a microvessel for commercial cell culture plates was designed. Four 3D printable (polycarbonate (PC), polylactic acid (PLA) and resin) and castable (polydimethylsiloxane (PDMS)) materials were assessed for biocompatibility with adherent and suspension cell types. PDMS was found to be the most suitable material for microvessel fabrication, long-term cell viability and proliferation. It also allows for efficient gas exchange, has no effect on cell culture media pH and does not induce hypoxic conditions. Overall, the designed microvessel can be used on simulated microgravity platforms as a method for long-term high-throughput biomedical studies

Transdifferentiation of human fibroblasts into skeletal muscle cells: Optimization and assembly into engineered tissue constructs through biological ligands

The development of robust skeletal muscle models has been challenging due to the partial recapitulation of human physiology and architecture. Reliable and innovative 3D skeletal muscle models recently described offer an alternative that more accurately captures the in vivo environment but require an abundant cell source. Direct reprogramming or transdifferentiation has been considered as an alternative. Recent reports have provided evidence for significant improvements in the efficiency of derivation of human skeletal myotubes from human fibroblasts. Herein we aimed at improving the transdifferentiation process of human fibroblasts (tHFs), in addition to the differentiation of murine skeletal myoblasts (C2C12), and the differentiation of primary human skeletal myoblasts (HSkM). Differentiating or transdifferentiating cells were exposed to single or combinations of biological ligands, including Follistatin, GDF8, FGF2, GDF11, GDF15, hGH, TMSB4X, BMP4, BMP7, IL6, and TNF-α. These were selected for their critical roles in myogenesis and regeneration. C2C12 and tHFs displayed significant differentiation deficits when exposed to FGF2, BMP4, BMP7, and TNF-α, while proliferation was significantly enhanced by FGF2. When exposed to combinations of ligands, we observed consistent deficit differentiation when TNF-α was included. Finally, our direct reprogramming technique allowed for the assembly of elongated, cross-striated, and aligned tHFs within tissue-engineered 3D skeletal muscle constructs. In conclusion, we describe an efficient system to transdifferentiate human fibroblasts into myogenic cells and a platform for the generation of tissue-engineered constructs. Future directions will involve the evaluation of the functional characteristics of these engineered tissues

Genome-wide and fine-resolution association analysis of malaria in West Africa

We report a genome-wide association (GWA) study of severe malaria in The Gambia. The initial GWA scan included 2,500 children genotyped on the Affymetrix 500K GeneChip, and a replication study included 3,400 children. We used this to examine the performance of GWA methods in Africa. We found considerable population stratification, and also that signals of association at known malaria resistance loci were greatly attenuated owing to weak linkage disequilibrium (LD). To investigate possible solutions to the problem of low LD, we focused on the HbS locus, sequencing this region of the genome in 62 Gambian individuals and then using these data to conduct multipoint imputation in the GWA samples. This increased the signal of association, from P = 4 × 10(-7) to P = 4 × 10(-14), with the peak of the signal located precisely at the HbS causal variant. Our findings provide proof of principle that fine-resolution multipoint imputation, based on population-specific sequencing data, can substantially boost authentic GWA signals and enable fine mapping of causal variants in African populations