Hepatocyte growth factor (HGF), a pleiotropic cytokine of mesenchymal origin promoting migration, proliferation, and survival in a wide spectrum of cells, can also modulate different biological responses in stem cells, but the mechanisms involved are not completely understood so far. In this context, we show that short-term exposure of mesenchymal stem cells (MSCs) to HGF can induce the activation of its cognate Met receptor and the downstream effectors ERK1/2, p38MAPK, and PI3K/Akt, while long-term exposure to HGF resulted in cytoskeletal rearrangement, cell migration, and marked inhibition of proliferation through the arrest in the G 1 -S checkpoint.When added to MSCs, the K252A tyrosine kinase inhibitor prevented HGF-induced responses. HGF's effect on MSC proliferation was reversed by p38 inhibitor SB203580, while the effects on cell migration were abrogated by PI3K inhibitor Wortmannin, suggesting that HGF acts through different pathways to determine its complex effects on MSCs. Prolonged treatment with HGF induced the expression of cardiac-specific markers (GATA-4, MEF2C, TEF1, desmin, ␣-MHC, ␤-MHC, and nestin) with the concomitant loss of the stem cell markers nucleostemin, c-kit, and CD105. STEM CELLS 2006;24: 23-33

Background: In late December 2019, Chinese health authorities reported an outbreak of pneumonia of unknown origin in Wuhan, Hubei Province. Summary: A few days later, the genome of a novel coronavirus was released (http://virological.org/t/novel-2019-coronavirus-genome/319; Wuhan-Hu-1, GenBank accession No. MN908947) and made publicly available to the scientific community. This novel coronavirus was provisionally named 2019-nCoV, now SARS-CoV-2 according to the Coronavirus Study Group of the International Committee on Taxonomy of Viruses. SARS-CoV-2 belongs to the Coronaviridae family, Betacoronavirus genus, subgenus Sarbecovirus. Since its discovery, the virus has spread globally, causing thousands of deaths and having an enormous impact on our health systems and economies. In this review, we summarize the current knowledge about the epidemiology, phylogenesis, homology modeling, and molecular diagnostics of SARS-CoV-2. Key Messages: Phylogenetic analysis is essential to understand viral evolution, whereas ho-mology modeling is important for vaccine strategies and therapies. Highly sensitive and specific diagnostic assays are key to case identification, contact tracing, identification of the animal source, and implementation of control measures.

Cardiac progenitor cells (CPCs) are a promising autologous source of cells for cardiac\ud regenerative medicine. However, CPC culture in vitro requires the presence of microenvironmental\ud conditions (a complex array of bioactive substance concentration, mechanostructural\ud factors, and physicochemical factors) closely mimicking the natural cell surrounding in vivo,\ud including the capability to uphold reactive oxygen species (ROS) within physiological levels\ud in vitro. Cerium oxide nanoparticles (nanoceria) are redox-active and could represent a potent\ud tool to control the oxidative stress in isolated CPCs. Here, we report that 24 h exposure to 5, 10,\ud and 50 !g/mL of nanoceria did not a!ect cell growth and function in cardiac progenitor cells,\ud while being able to protect CPCs from H2O2-induced cytotoxicity for at least 7 days, indicating\ud that nanoceria in an e!ective antioxidant. Therefore, these "ndings con"rm the great\ud potential of nanoceria for controlling ROS-induced cell damage

a b s t r a c tA novel (scalable) electrospinning process was developed to fabricate bio-inspired multiscale threedimensional scaffolds endowed with a controlled multimodal distribution of fiber diameters and geared towards soft tissue engineering. The resulting materials finely mingle nano-and microscale fibers together, rather than simply juxtaposing them, as is commonly found in the literature. A detailed proof of concept study was conducted on a simpler bimodal poly(e-caprolactone) (PCL) scaffold with modes of fiber distribution at 600 nm and 3.3 lm. Three conventional unimodal scaffolds with mean diameters of 300 nm and 2.6 and 5.2 lm, respectively, were used as controls to evaluate the new materials. Characterization of the microstructure (i.e. porosity, fiber distribution and pore structure) and mechanical properties (i.e. stiffness, strength and failure mode) indicated that the multimodal scaffold had superior mechanical properties (Young's modulus $40 MPa and strength $1 MPa) in comparison with the controls, despite the large porosity ($90% on average). A biological assessment was conducted with bone marrow stromal cell type (mesenchymal stem cells, mTERT-MSCs). While the new material compared favorably with the controls with respect to cell viability (on the outer surface), it outperformed them in terms of cell colonization within the scaffold. The latter result, which could neither be practically achieved in the controls nor expected based on current models of pore size distribution, demonstrated the greater openness of the pore structure of the bimodal material, which remarkably did not come at the expense of its mechanical properties. Furthermore, nanofibers were seen to form a nanoweb bridging across neighboring microfibers, which boosted cell motility and survival. Lastly, standard adipogenic and osteogenic differentiation tests served to demonstrate that the new scaffold did not hinder the multilineage potential of stem cells.