Topological defects in self-assembled patterns of mesenchymal stromal cells in vitro are predictive attributes of condensation and chondrogenesis.

Mesenchymal stromal cells (MSCs) are promising therapeutic agents for cartilage regeneration, including the potential of cells to promote chondrogenesis in vivo. However, process development and regulatory approval of MSCs as cell therapy products benefit from facile in vitro approaches that can predict potency for a given production run. Current standard in vitro approaches include a 21 day 3D differentiation assay followed by quantification of cartilage matrix proteins.

Mechanical regulation of oligodendrocyte biology.

Oligodendrocytes (OL) are a subset of glial cells in the central nervous system (CNS) comprising the brain and spinal cord. The CNS environment is defined by complex biochemical and biophysical cues during development and response to injury or disease. In the last decade, significant progress has been made in understanding some of the key biophysical factors in the CNS that modulate OL biology, including their key role in myelination of neurons.

High-resolution Imaging of Nuclear Dynamics in Live Cells under Uniaxial Tensile Strain.

Extracellular mechanical strain is known to elicit cell phenotypic responses and has physiological relevance in several tissue systems. To capture the effect of applied extracellular tensile strain on cell populations in vitro via biochemical assays, a device has previously been designed which can be fabricated simply and is small enough to fit inside tissue culture incubators, as well as on top of microscope stages. However, the previous design of the polydimethylsiloxane substratum did not allow high-resolution subcellular imaging via oil-immersion objectives.

Mechanical Strain Alters Cellular and Nuclear Dynamics at Early Stages of Oligodendrocyte Differentiation.

Mechanical and physical stimuli including material stiffness and topography or applied mechanical strain have been demonstrated to modulate differentiation of glial progenitor and neural stem cells. Recent studies probing such mechanotransduction in oligodendrocytes have focused chiefly on the biomolecular components. However, the cell-level biophysical changes associated with such responses remain largely unknown.

PREP1 tumor suppressor protects the late-replicating DNA by controlling its replication timing and symmetry.

The synthesis of middle-to-late-replicating DNA can be affected independently of the rest of the genome by down-regulating the tumor suppressor PREP1 (PKNOX1). Indeed, DNA combing shows that PREP1 down-regulation affects DNA replication rate, increases the number of simultaneously firing origins and the asymmetry of DNA replication, leading to DNA damage. Genome-wide analysis of replication timing by Repli-seq shows that, upon PREP1 down-regulation, 25% of the genome is replicated earlier in the S-phase.

Mechanical Strain Promotes Oligodendrocyte Differentiation by Global Changes of Gene Expression.

Differentiation of oligodendrocyte progenitor cells (OPC) to oligodendrocytes and subsequent axon myelination are critical steps in vertebrate central nervous system (CNS) development and regeneration. Growing evidence supports the significance of mechanical factors in oligodendrocyte biology. Here, we explore the effect of mechanical strains within physiological range on OPC proliferation and differentiation, and strain-associated changes in chromatin structure, epigenetics, and gene expression.

How cells respond to environmental cues - insights from bio-functionalized substrates.

Biomimetic materials have long been the (he)art of bioengineering. They usually aim at mimicking in vivo conditions to allow in vitro culture, differentiation and expansion of cells. The past decade has witnessed a considerable amount of progress in soft lithography, bio-inspired micro-fabrication and biochemistry, allowing the design of sophisticated and physiologically relevant micro- and nano-environments.

Reduced Insulin Receptor Expression Enhances Proximal Tubule Gluconeogenesis.

Reduced insulin receptor protein levels have been reported in the kidney cortex from diabetic humans and animals. We recently reported that, targeted deletion of insulin receptor (IR) from proximal tubules (PT) resulted in hyperglycemia in non-obese mice. To elucidate the mechanism, we examined human proximal tubule cells (hPTC) and C57BL/6 mice fed with high-fat diet (HFD, 60% fat for 20 weeks).

Nuclear deformability and telomere dynamics are regulated by cell geometric constraints.

Forces generated by the cytoskeleton can be transmitted to the nucleus and chromatin via physical links on the nuclear envelope and the lamin meshwork. Although the role of these active forces in modulating prestressed nuclear morphology has been well studied, the effect on nuclear and chromatin dynamics remains to be explored. To understand the regulation of nuclear deformability by these active forces, we created different cytoskeletal states in mouse fibroblasts using micropatterned substrates.

Micropillar displacements by cell traction forces are mechanically correlated with nuclear dynamics.

Cells sense physical cues at the level of focal adhesions and transduce them to the nucleus by biochemical and mechanical pathways. While the molecular intermediates in the mechanical links have been well studied, their dynamic coupling is poorly understood. In this study, fibroblast cells were adhered to micropillar arrays to probe correlations in the physical coupling between focal adhesions and nucleus.

Insulin regulates nitric oxide production in the kidney collecting duct cells.

The kidney is an important organ for arterial blood pressure (BP) maintenance. Reduced NO generation in the kidney is associated with hypertension in insulin resistance. NO is a critical regulator of vascular tone; however, whether insulin regulates NO production in the renal inner medullary collecting duct (IMCD), the segment with the greatest enzymatic activity for NO production in kidney, is not clear.

The regulation of dynamic mechanical coupling between actin cytoskeleton and nucleus by matrix geometry.

Cells sense their physical microenvironment and transduce these signals through actin-nuclear links to regulate nuclear functions including gene expression. However, the spatio-temporal coupling between perinuclear actin and nucleus and their functional importance are still unclear. Using micropatterned substrates to control cell geometry, we show that perinuclear actin organization at the apical plane remodels from mesh-like structure to stress fibers.