Shear stress induces osteogenic differentiation of human mesenchymal stem cells

Aim: To determine whether fluid flow-induced shear stress affects the differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) into osteogenic cells. Materials & methods: hMSCs cultured with or without osteogenic differentiation medium were exposed to fluid flow-induced shear stress and analyzed for alkaline phosphatase activity and expression of osteogenic genes. Results: Immediately following shear stress, alkaline phosphatase activity in osteogenic medium was significantly increased. At days 4 and 8 of culture the mRNA expression of bone morphogenetic protein-2 and osteopontin was significantly higher in hMSCs subjected to shear stress than those cultured in static conditions. However, hMSCs cultured in osteogenic differentiation medium were less responsive in gene expression of alkaline phosphatase and bone morphogenetic protein-2. Conclusion: These data demonstrate that shear stress stimulates hMSCs towards an osteoblastic phenotype in the absence of chemical induction, suggesting that certain mechanical stresses may serve as an alternative to chemical stimulation of stem cell differentiation

A Combined Synthetic-Fibrin Scaffold Supports Growth and Cardiomyogenic Commitment of Human Placental Derived Stem Cells

Aims: A potential therapy for myocardial infarction is to deliver isolated stem cells to the infarcted site. A key issue with this therapy is to have at one\u27s disposal a suitable cell delivery system which, besides being able to support cell proliferation and differentiation, may also provide handling and elastic properties which do not affect cardiac contractile function. In this study an elastic scaffold, obtained combining a poly(ether)urethane-polydimethylsiloxane (PEtU-PDMS) semi-interpenetrating polymeric network (s-IPN) with fibrin, was used as a substrate for in vitro studies of human amniotic mesenchymal stromal cells (hAMSC) growth and differentiation. Methodology/Principal Findings: After hAMSC seeding on the fibrin side of the scaffold, cell metabolic activity and proliferation were evaluated by WST-1 and bromodeoxyuridine assays. Morphological changes and mRNAs expression for cardiac differentiation markers in the hAMSCs were examined using immunofluorescence and RT-PCR analysis. The beginning of cardiomyogenic commitment of hAMSCs grown on the scaffold was induced, for the first time in this cell population, by a nitric oxide (NO) treatment. Following NO treatment hAMSCs show morphological changes, an increase of the messenger cardiac differentiation markers [troponin I (TnI) and NK2 transcription factor related locus 5 (Nkx2.5)] and a modulation of the endothelial markers [vascular endothelial growth factor (VEGF) and kinase insert domain receptor (KDR)]. Conclusions/Significance: The results of this study suggest that the s-IPN PEtU-PDMS/fibrin combined scaffold allows a better proliferation and metabolic activity of hAMSCs cultured up to 14 days, compared to the ones grown on plastic dishes. In addition, the combined scaffold sustains the beginning of hAMSCs differentiation process towards a cardiomyogenic lineage

Numerical methods for the design and description of in vitro expansion processes of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are a valuable source of cells for clinical applications (e.g., treatment of acute myocardial infarction or inflammatory diseases), especially in the field of regenerative medicine. However, for autologous (patient-specific) and allogeneic (off-the-shelf) hMSC-based therapies, in vitro expansion is necessary prior to the clinical application in order to achieve the required cell numbers. Safe, reproducible, and economic in vitro expansion of hMSCs for autologous and allogeneic therapies can be problematic because the cell material is restricted and the cells are sensitive to environmental changes. It is beneficial to collect detailed information on the hydrodynamic conditions and cell growth behavior in a bioreactor system, in order to develop a so called “Digital Twin” of the cultivation system and expansion process. Numerical methods, such as Computational Fluid Dynamics (CFD) which has become widely used in the biotech industry for studying local characteristics within bioreactors or kinetic growth modelling, provide possible solutions for such tasks. In this review, we will present the current state-of-the-art for the in vitro expansion of hMSCs. Different numerical tools, including numerical fluid flow simulations and cell growth modelling approaches for hMSCs, will be presented. In addition, a case study demonstrating the applicability of CFD and kinetic growth modelling for the development of an microcarrier-based hMSC process will be shown

A mathematical model of mechanotransduction reveals how mechanical memory regulates mesenchymal stem cell fate decisions

Abstract Background Mechanical and biophysical properties of the cellular microenvironment regulate cell fate decisions. Mesenchymal stem cell (MSC) fate is influenced by past mechanical dosing (memory), but the mechanisms underlying this process have not yet been well defined. We have yet to understand how memory affects specific cell fate decisions, such as the differentiation of MSCs into neurons, adipocytes, myocytes, and osteoblasts. Results We study a minimal gene regulatory network permissive of multi-lineage MSC differentiation into four cell fates. We present a continuous model that is able to describe the cell fate transitions that occur during differentiation, and analyze its dynamics with tools from multistability, bifurcation, and cell fate landscape analysis, and via stochastic simulation. Whereas experimentally, memory has only been observed during osteogenic differentiation, this model predicts that memory regions can exist for each of the four MSC-derived cell lineages. We can predict the substrate stiffness ranges over which memory drives differentiation; these are directly testable in an experimental setting. Furthermore, we quantitatively predict how substrate stiffness and culture duration co-regulate the fate of a stem cell, and we find that the feedbacks from the differentiating MSC onto its substrate are critical to preserve mechanical memory. Strikingly, we show that re-seeding MSCs onto a sufficiently soft substrate increases the number of cell fates accessible. Conclusions Control of MSC differentiation is crucial for the success of much-lauded regenerative therapies based on MSCs. We have predicted new memory regions that will directly impact this control, and have quantified the size of the memory region for osteoblasts, as well as the co-regulatory effects on cell fates of substrate stiffness and culture duration. Taken together, these results can be used to develop novel strategies to better control the fates of MSCs in vitro and following transplantation

A biomaterials approach to influence stem cell fate in injectable cell-based therapies

Background Numerous stem cell therapies use injection-based administration to deliver high-density cell preparations. However, cell retention rates as low as 1% have been observed within days of transplantation. This study investigated the effects of varying administration and formulation parameters of injection-based administration on cell dose recovery and differentiation fate choice of human mesenchymal stem cells. Methods The impact of ejection rate via clinically relevant Hamilton micro-syringes and biomaterial-assisted delivery was investigated. Cell viability, the percentage of cell dose delivered as viable cells, proliferation capacity as well as differentiation behaviour in bipotential media were assessed. Characterisation of the biomaterial-based cell carriers was also carried out. Results A significant improvement of in-vitro dose recovery in cells co-ejected with natural biomaterials was observed, with ejections within 2% (w/v) gelatin resulting in 87.5 ± 14% of the cell dose being delivered as viable cells, compared to 32.2 ± 19% of the dose ejected in the commonly used saline vehicle at 10 μl/min. Improvement in cell recovery was not associated with the rheological properties of biomaterials utilised, as suggested by previous studies. The extent of osteogenic differentiation was shown to be substantially altered by choice of ejection rate and cell carrier, despite limited contact time with cells during ejection. Collagen type I and bone-derived extracellular matrix cell carriers yielded significant increases in mineralised matrix deposited at day 21 relative to PBS. Conclusions An enhanced understanding of how administration protocols and biomaterials influence cell recovery, differentiation capacity and choice of fate will facilitate the development of improved administration and formulation approaches to achieve higher efficacy in stem cell transplantation

What Are the Hydroecological Drivers of Water Security in an Agricultural and Snowmelt-Dominated Region?

Water is a cornerstone of human productivity. A water-secure region has access to water in sufficient quantities, of adequate quality, and at the right time to meet the needs of humans and ecosystems. Over the 21st century, the combination of warming-induced shifts in hydrological regimes and greater water demands for food and energy due to rapid economic growth is likely to create water security challenges across the globe. The goal of this dissertation is to investigate how and to what extent the processes of land-use change, climate warming, and crop transpiration drive changes in water supply and demand in regions where the hydrology is strongly influenced by snow accumulation and melt. The research is focused on a commonly neglected element of water security in snow-dominated basins, that is, the seasonal alignment of meltwater flow and irrigation demand. The implications of shifts in water supply and demand timing for agricultural production, energy production, and instream flows for fish are evaluated and discussed. The geographical setting of this work is the Pacific Northwest Region, particularly the Columbia River Basin.Analysis of the role played by water rights in moderating the impact of land-use/cover change on food, energy, and water subsystems showed that expanding irrigated area can enhance the productivity of food and energy crops, but it may do so at the cost of greater instream flow deficits and less hydropower production in summer. Analysis of shifts in irrigation demand timing for a variety of annual and perennial crops resulted in greater shifts in demand toward earlier timing among annuals compared to perennials. A partial-correlation analysis revealed that crop phenology, followed by sowing date, followed by growing season precipitation, are the primary contributing factors to shifts in water demand timing. Shifts in streamflow timing were found to be strongly associated with the fraction of runoff derived from snowmelt and the mean winter temperature. Watersheds most vulnerable to increasing separation between supply and demand timing are those with a large contribution from snowmelt, winter temperatures near 0°C, and a high proportion of cropland planted to annuals. Earlier water demand timing showed potential to mitigate increasing water right curtailment frequency due to earlier streamflow timing by a small amount. Finally, priority-based water right curtailment was shown to augment streamflow by an amount equal to or larger than curtailment in favor of instream flows

Effects of differentiation and shears stress on stem cell gene expression and nanomechanics.

Effects of differentiation and shears stress on stem cell gene expression and nanomechanics

An Investigation of Crop Senescence Patterns Observed in Palouse Region Fields Using Satellite Remote Sensing and Hydrologic Modeling

Precision agriculture (PA) recognizes that every area of a field does not respond equally to equal inputs. Growers in the Palouse region know this from the yields they obtain. Scientists know this from carefully designed experiments, and casual observers know this from the patchwork of green, yellow, and brown they see within the rolling wheat fields come July. Crop yields are driven by water in this dryland farming region, and the colors are senescence (or ageing) patterns caused mainly by water stress. Soils, topography, and climate all combine to form the unique micro-environments in which crops grow in Palouse fields, producing a high level of spatial complexity. In this thesis, intensive field monitoring and soil mapping are used to parameterize and evaluate a modified version of the SMR hydrologic model. A linkage is investigated between soil measurements, landscape hydrology, and crop patterns observed by the high-resolution RapidEyeTM multispectral imager.Thesis (M.S., Biological & Agricultural Engineering) -- University of Idaho, 201