Kacey Ronaldson

Micropatterned mammalian cells exhibit phenotype-specific left-right asymmetry

Left-right (LR) asymmetry (handedness, chirality) is a well-conserved biological property of critical importance to normal development. Changes in orientation of the LR axis due to genetic or environmental factors can lead to malformations and disease. While the LR asymmetry of organs and whole organisms has been extensively studied, little is known about the LR asymmetry at cellular and multicellular levels. Here we show that the cultivation of cell populations on micropatterns with defined boundaries reveals intrinsic cell chirality that can be readily determined by image analysis of cell alignment and directional motion. By patterning 11 different types of cells on ring-shaped micropatterns of various sizes, we found that each cell type exhibited definite LR asymmetry (p value down to 10-185) that was different between normal and cancer cells of the same type, and not dependent on surface chemistry, protein coating, or the orientation of the gravitational field. Interestingly, drugs interfering with actin but not microtubule function reversed the LR asymmetry in some cell types. Our results show that micropatterned cell populations exhibit phenotype-specific LR asymmetry that is dependent on the functionality of the actin cytoskeleton. We propose that micropatterning could potentially be used as an effective in vitro tool to study the initiation of LR asymmetry in cell populations, to diagnose disease, and to study factors involved with birth defects in laterality.

Bioengineering methods for myocardial regeneration

The challenging task of heart regeneration is being pursued in three related directions: derivation of cardiomyocytes from human stem cells, in vitro engineering and maturation of cardiac tissues, and development of methods for controllable cell delivery into the heart. In this review, we focus on tissue engineering methods that recapitulate biophysical signaling found during normal heart development and maturation. We discuss the use of scaffold-bioreactor systems for engineering functional human cardiac tissues, and the methods for delivering stem cells, cardiomyocytes and engineered tissues into the heart.

Micropatterning of Cells Reveals Chiral Morphogenesis

Invariant left-right (LR) patterning or chirality is critical for embryonic development. The loss or reversal of LR asymmetry is often associated with malformations and disease. Although several theories have been proposed, the exact mechanism of the initiation of the LR symmetry has not yet been fully elucidated. Recently, chirality has been detected within single cells as well as multicellular structures using several in vitro approaches. These studies demonstrated the universality of cell chirality, its dependence on cell phenotype, and the role of physical boundaries. In this review, we discuss the theories for developmental LR asymmetry, compare various in vitro cell chirality model systems, and highlight possible roles of cell chirality in stem cell differentiation. We emphasize that the in vitro cell chirality systems have great promise for helping unveil the nature of chiral morphogenesis in development.

Hierarchically Ordered Nanopatterns for Spatial Control of Biomolecules

The development and study of a benchtop, high-throughput, and inexpensive fabrication strategy to obtain hierarchical patterns of biomolecules with sub-50 nm resolution is presented. A diblock copolymer of polystyrene-b-poly(ethylene oxide), PS-b-PEO, is synthesized with biotin capping the PEO block and 4-bromostyrene copolymerized within the polystyrene block at 5 wt %. These two handles allow thin films of the block copolymer to be postfunctionalized with biotinylated biomolecules of interest and to obtain micropatterns of nanoscale-ordered films via photolithography. The design of this single polymer further allows access to two distinct superficial nanopatterns (lines and dots), where the PEO cylinders are oriented parallel or perpendicular to the substrate. Moreover, we present a strategy to obtain hierarchical mixed morphologies: a thin-film coating of cylinders both parallel and perpendicular to the substrate can be obtained by tuning the solvent annealing and irradiation conditions.

Microgravity and Microgravity Analogue Studies of Cartilage and Cardiac Tissue Engineering

Space is the ultimate frontier, and the International Space Station (ISS) has been serving as a platform for creative science, developing technologies, and testing materials, instruments and processes under extreme conditions. One of the areas of greatest interest is human health, due to the important changes in human physiology during spaceflight: cardiovascular deconditioning, loss of bone and muscle, changes in immune system and vision, among many others. Studies in astronauts are revealing some of the underlying mechanisms of these changes and helping develop new modalities to prevent or treat the adverse effects of the space environment. However, controllable studies of tissue function under the conditions of microgravity remain critical for understanding the effect of spaceflight on human health, and dissecting—under controllable conditions—the factors affecting the development and function of our tissues and organs. The ability of engineered tissue constructs to recapitulate some of the critical and physiological functions opened many exciting avenues of research.