Reversible Host–Guest Crosslinks in Supramolecular Hydrogels for On‐Demand Mechanical Stimulation of Human Mesenchymal Stem Cells

Stem cells are regulated not only by biochemical signals but also by biophysical properties of extracellular matrix (ECM). The ECM is constantly monitored and remodeled because the fate of stem cells can be misdirected when the mechanical interaction between cells and ECM is imbalanced. A well-defined ECM model for bone marrow-derived human mesenchymal stem cells (hMSCs) based on supramolecular hydrogels containing reversible host–guest crosslinks is fabricated. The stiffness (Young\u27s modulus E) of the hydrogels can be switched reversibly by altering the concentration of non-cytotoxic, free guest molecules dissolved in the culture medium. Fine-adjustment of substrate stiffness enables the authors to determine the critical stiffness level E* at which hMSCs turn the mechano-sensory machinery on or off. Next, the substrate stiffness across E* is switched and the dynamic adaptation characteristics such as morphology, traction force, and YAP/TAZ signaling of hMSCs are monitored. These data demonstrate the instantaneous switching of traction force, which is followed by YAP/TAZ signaling and morphological adaptation. Periodical switching of the substrate stiffness across E* proves that frequent applications of mechanical stimuli drastically suppress hMSC proliferation. Mechanical stimulation across E* level using dynamic hydrogels is a promising strategy for the on-demand control of hMSC transcription and proliferation

Genome Sequencing of SHH Medulloblastoma Predicts Genotype-Related Response to Smoothened Inhibition

SummarySmoothened (SMO) inhibitors recently entered clinical trials for sonic-hedgehog-driven medulloblastoma (SHH-MB). Clinical response is highly variable. To understand the mechanism(s) of primary resistance and identify pathways cooperating with aberrant SHH signaling, we sequenced and profiled a large cohort of SHH-MBs (n = 133). SHH pathway mutations involved PTCH1 (across all age groups), SUFU (infants, including germline), and SMO (adults). Children >3 years old harbored an excess of downstream MYCN and GLI2 amplifications and frequent TP53 mutations, often in the germline, all of which were rare in infants and adults. Functional assays in different SHH-MB xenograft models demonstrated that SHH-MBs harboring a PTCH1 mutation were responsive to SMO inhibition, whereas tumors harboring an SUFU mutation or MYCN amplification were primarily resistant

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Marine and freshwater conservation planning: from representation to persistence

[Extract] Most of the science and practice of conservation planning has focused on terrestrial environments (Vance-Borland et al. 2008), just as this book has, with similarly threatened marine and freshwater systems receiving less attention. In contrast to land, anthropogenic changes to marine and freshwater systems are less easily observed and, until recently, the phrase "out of sight, out of mind" aptly applied to the conservation of these systems. As human impacts on marine and freshwater systems have become increasingly apparent (e.g., fisheries collapses), there has been an increasing realization that these ecosystems require protection, better resource management, and conservation (Nel et al. 2009; Sala and Knowlton 2006). Biodiversity in marine and freshwater is declining alarmingly, and humans are starting to feel the effects of reductions in ecosystem services (Worm et al. 2006). Increased conservation of marine and freshwater systems is therefore necessary, and a key part of these efforts will be conservation planning

Comparison of 6-month outcomes of sepsis versus non-sepsis critically ill patients receiving mechanical ventilation

Abstract Background Data on long-term outcomes after sepsis-associated critical illness have mostly come from small cohort studies, with no information about the incidence of new disability. We investigated whether sepsis-associated critical illness was independently associated with new disability at 6 months after ICU admission compared with other types of critical illness. Methods We conducted a secondary analysis of a multicenter, prospective cohort study in six metropolitan intensive care units in Australia. Adult patients were eligible if they had been admitted to the ICU and received more than 24 h of mechanical ventilation. There was no intervention. Results The primary outcome was new disability measured with the WHO Disability Assessment Schedule 2.0 (WHODAS) 12 level score compared between baseline and 6 months. Between enrollment and follow-up at 6 months, 222/888 (25%) patients died, 100 (35.5%) with sepsis and 122 (20.1%) without sepsis (P < 0.001). Among survivors, there was no difference for the incidence of new disability at 6 months with or without sepsis, 42/106 (39.6%) and 106/300 (35.3%) (RD, 0.00 (− 10.29 to 10.40), P = 0.995), respectively. In addition, there was no difference in the severity of disability, health-related quality of life, anxiety and depression, post-traumatic stress, return to work, financial distress or cognitive function. Conclusions Compared to mechanically ventilated patients of similar acuity and length of stay without sepsis, patients with sepsis admitted to ICU have an increased risk of death, but survivors have a similar risk of new disability at 6 months. Trial registration NCT03226912, registered July 24, 2017.http://deepblue.lib.umich.edu/bitstream/2027.42/173930/1/13054_2022_Article_4041.pd