Tracking and Predicting Human Somatic Cell Reprogramming Using Nuclear Characteristics.

Reprogramming of human somatic cells to induced pluripotent stem cells (iPSCs) generates valuable resources for disease modeling, toxicology, cell therapy, and regenerative medicine. However, the reprogramming process can be stochastic and inefficient, creating many partially reprogrammed intermediates and non-reprogrammed cells in addition to fully reprogrammed iPSCs. Much of the work to identify, evaluate, and enrich for iPSCs during reprogramming relies on methods that fix, destroy, or singularize cell cultures, thereby disrupting each cell's microenvironment. Here, we develop a micropatterned substrate that allows for dynamic live-cell microscopy of hundreds of cell subpopulations undergoing reprogramming while preserving many of the biophysical and biochemical cues within the cells' microenvironment. On this substrate, we were able to both watch and physically confine cells into discrete islands during the reprogramming of human somatic cells from skin biopsies and blood draws obtained from healthy donors. Using high-content analysis, we identified a combination of eight nuclear characteristics that can be used to generate a computational model to predict the progression of reprogramming and distinguish partially reprogrammed cells from those that are fully reprogrammed. This approach to track reprogramming in situ using micropatterned substrates could aid in biomanufacturing of therapeutically relevant iPSCs and be used to elucidate multiscale cellular changes (cell-cell interactions as well as subcellular changes) that accompany human cell fate transitions.

RosetteArray® Platform for Quantitative High-Throughput Screening of Human Neurodevelopmental Risk.

Neural organoids have revolutionized how human neurodevelopmental disorders (NDDs) are studied. Yet, their utility for screening complex NDD etiologies and in drug discovery is limited by a lack of scalable and quantifiable derivation formats. Here, we describe the RosetteArray® platform's ability to be used as an off-the-shelf, 96-well plate assay that standardizes incipient forebrain and spinal cord organoid morphogenesis as micropatterned, 3-D, singularly polarized neural rosette tissues (>9000 per plate). RosetteArrays are seeded from cryopreserved human pluripotent stem cells, cultured over 6-8 days, and immunostained images can be quantified using artificial intelligence-based software. We demonstrate the platform's suitability for screening developmental neurotoxicity and genetic and environmental factors known to cause neural tube defect risk. Given the presence of rosette morphogenesis perturbation in neural organoid models of NDDs and neurodegenerative disorders, the RosetteArray platform could enable quantitative high-throughput screening (qHTS) of human neurodevelopmental risk across regulatory and precision medicine applications.

Engineering induction of singular neural rosette emergence within hPSC-derived tissues.

Human pluripotent stem cell (hPSC)-derived neural organoids display unprecedented emergent properties. Yet in contrast to the singular neuroepithelial tube from which the entire central nervous system (CNS) develops in vivo, current organoid protocols yield tissues with multiple neuroepithelial units, a.k.a. neural rosettes, each acting as independent morphogenesis centers and thereby confounding coordinated, reproducible tissue development. Here, we discover that controlling initial tissue morphology can effectively (>80%) induce single neural rosette emergence within hPSC-derived forebrain and spinal tissues. Notably, the optimal tissue morphology for observing singular rosette emergence was distinct for forebrain versus spinal tissues due to previously unknown differences in ROCK-mediated cell contractility. Following release of geometric confinement, the tissues displayed radial outgrowth with maintenance of a singular neuroepithelium and peripheral neuronal differentiation. Thus, we have identified neural tissue morphology as a critical biophysical parameter for controlling in vitro neural tissue morphogenesis furthering advancement towards biomanufacture of CNS tissues with biomimetic anatomy and physiology.

Multifunctional drug nanocarriers formed by cRGD-conjugated ßCD-PAMAM-PEG for targeted cancer therapy.

Polyamidoamine (PAMAM) dendrimer was conjugated with both carboxymethyl-ß-cyclodextrin (ßCD) and poly(ethylene glycol) (PEG). Cyclic RGD peptide, used as a tumor targeting ligand, was then selectively conjugated onto the distal ends of the PEG arms. The resulting ßCD-PAMAM-PEG-cRGD polymer was able to form stable and uniform nanoparticles (NPs) in aqueous solution. Doxorubicin (Dox), a model hydrophobic anticancer drug, was effectively encapsulated in the NPs via an inclusion complex formed between the drug and ßCD. The Dox loading level was 16.8 wt%. The cellular uptake of cRGD-conjugated Dox-loaded NPs in the U87MG cell line was much higher than that of non-targeted NPs. Furthermore, the anti-proliferative effect of the cRGD-conjugated NPs was superior to that of free drug and non-targeted NPs. These results suggest that NPs formed by ßCD-PAMAM-PEG-cRGD with a high drug payload may significantly improve the anticancer efficacy by tumor-targeted delivery and enhanced cellular uptake.

Fabricating complex culture substrates using robotic microcontact printing (R-µCP) and sequential nucleophilic substitution.

In tissue engineering, it is desirable to exhibit spatial control of tissue morphology and cell fate in culture on the micron scale. Culture substrates presenting grafted poly(ethylene glycol) (PEG) brushes can be used to achieve this task by creating microscale, non-fouling and cell adhesion resistant regions as well as regions where cells participate in biospecific interactions with covalently tethered ligands. To engineer complex tissues using such substrates, it will be necessary to sequentially pattern multiple PEG brushes functionalized to confer differential bioactivities and aligned in microscale orientations that mimic in vivo niches. Microcontact printing (µCP) is a versatile technique to pattern such grafted PEG brushes, but manual µCP cannot be performed with microscale precision. Thus, we combined advanced robotics with soft-lithography techniques and emerging surface chemistry reactions to develop a robotic microcontact printing (R-µCP)-assisted method for fabricating culture substrates with complex, microscale, and highly ordered patterns of PEG brushes presenting orthogonal 'click' chemistries. Here, we describe in detail the workflow to manufacture such substrates.

High-precision robotic microcontact printing (R-µCP) utilizing a vision guided selectively compliant articulated robotic arm.

Increased realization of the spatial heterogeneity found within in vivo tissue microenvironments has prompted the desire to engineer similar complexities into in vitro culture substrates. Microcontact printing (µCP) is a versatile technique for engineering such complexities onto cell culture substrates because it permits microscale control of the relative positioning of molecules and cells over large surface areas. However, challenges associated with precisely aligning and superimposing multiple µCP steps severely limits the extent of substrate modification that can be achieved using this method. Thus, we investigated the feasibility of using a vision guided selectively compliant articulated robotic arm (SCARA) for µCP applications. SCARAs are routinely used to perform high precision, repetitive tasks in manufacturing, and even low-end models are capable of achieving microscale precision. Here, we present customization of a SCARA to execute robotic-µCP (R-µCP) onto gold-coated microscope coverslips. The system not only possesses the ability to align multiple polydimethylsiloxane (PDMS) stamps but also has the capability to do so even after the substrates have been removed, reacted to graft polymer brushes, and replaced back into the system. Plus, non-biased computerized analysis shows that the system performs such sequential patterning with <10 µm precision and accuracy, which is equivalent to the repeatability specifications of the employed SCARA model. R-µCP should facilitate the engineering of complex in vivo-like complexities onto culture substrates and their integration with microfluidic devices.

Micropattern width dependent sarcomere development in human ESC-derived cardiomyocytes.

In this study, human embryonic stem cell-derived cardiomyocytes were seeded onto controlled two-dimensional micropatterned features, and an improvement in sarcomere formation and cell alignment was observed in specific feature geometries. High-resolution photolithography techniques and microcontact printing were utilized to produce features of various rectangular geometries, with areas ranging from 2500 µm(2) to 160,000 µm(2). The microcontact printing method was used to pattern non-adherent poly(ethylene glycol) regions on gold coated glass slides. Matrigel and fibronectin extracellular matrix (ECM) proteins were layered onto the gold-coated glass slides, providing a controlled geometry for cell adhesion. We used small molecule-based differentiation and an antibiotic purification step to produce a pure population of immature cardiomyocytes from H9 human embryonic stem cells (hESCs). We then seeded this pure population of human cardiomyocytes onto the micropatterned features of various sizes and observed how the cardiomyocytes remodeled their myofilament structure in response to the feature geometries. Immunofluorescence was used to measure α-actinin expression, and phalloidin stains were used to detect actin presence in the patterned cells. Analysis of nuclear alignment was also used to determine how cell direction was influenced by the features. The seeded cells showed clear alignment with the features, dependent on the width rather than the overall aspect ratio of the features. It was determined that features with widths between 30 µm and 80 µm promoted highly aligned cardiomyocytes with a dramatic increase in sarcomere alignment relative to the long axis of the pattern. This creation of highly-aligned cell aggregates with robust sarcomere structures holds great potential in advancing cell-based pharmacological studies, and will help researchers to understand the means by which ECM geometries can affect myofilament structure and maturation in hESC-derived cardiomyocytes.