Function of hepatocyte spheroids in bioactive microcapsules is enhanced by endogenous and exogenous hepatocyte growth factor

The ability to maintain functional hepatocytes has important implications for bioartificial liver development,cell-based therapies,drug screening,and tissue engineering.Several approaches can be used to restore hepatocyte function in vitro,including coating a culture substrate with extracellular matrix(ECM),encapsulating cells within biomimetic gels(Collagen-or Matrigel-based),or co-cultivation with other cells.This paper describes the use of bioactive heparin-based core-shell microcapsules to form and cultivate hepatocyte spheroids.These microcapsules are comprised of an aqueous core that facilitates hepatocyte aggregation into spheroids and a heparin hydrogel shell that binds and releases growth factors.We demonstrate that bioactive microcapsules retain and release endogenous signals thus enhancing the function of encapsulated hepatocytes.We also demonstrate that hepatic function may be further enhanced by loading exogenous hepatocyte growth factor(HGF)into microcapsules and inhibiting transforming growth factor(TGF)-β1 signaling.Overall,bioactive microcapsules described here represent a promising new strategy for the encapsulation and maintenance of primary hepatocytes and will be beneficial for liver tissue engineering,regenerative medicine,and drug testing applications.

Modeling gut neuro-epithelial connections in a novel microfluidic device

The intestinal lumen is filled with diverse chemical and physical stimuli.Intestinal epithelial cells sense these stimuli and signal to enteric neurons which coordinate a range of physiologic processes required for normal digestive tract function.Yet,the neuro-epithelial connections remain poorly resolved,in part because the tools for orchestrating interactions between these cellular compartments are lacking.We describe the development of a two-compartment microfluidic device for co-culturing enteric neurons with intestinal epithelial cells.The device contains epithelial and neuronal compartments connected by microgrooves.The epithelial compartment was designed for cell seeding via injection and confinement of intestinal epithelial cells derived from human intestinal organoids.We demonstrated that organoids planarized effectively and retained epithelial phenotype for over a week.In the second chamber we dissociated and cultured intestinal myenteric neurons including intrinsic primary afferent neurons(IPANs)from transgenic mice that expressed the fluorescent protein tdTomato.IPANs extended projections into microgrooves,surrounded and frequently made contacts with epithelial cells.The density and directionality of neuronal projections were enhanced by the presence of epithelial cells in the adjacent compartment.Our microfluidic device represents a platform that may,in the future,be used to dissect structure and function of neuro-epithelial connections in the gut and other organs(skin,lung,bladder,and others)in health and disease.

Bioactive hydrogel microcapsules for guiding stem cell fate decisions by release and reloading of growth factors

Human pluripotent stem cells(hPSC)hold considerable promise as a source of adult cells for treatment of diseases ranging from diabetes to liver failure.Some of the challenges that limit the clinical/translational impact of hPSCs are high cost and difficulty in scaling-up of existing differentiation protocols.In this paper,we sought to address these challenges through the development of bioactive microcapsules.A co-axial flow focusing microfluidic device was used to encapsulate hPSCs in microcapsules comprised of an aqueous core and a hydrogel shell.Importantly,the shell contained heparin moieties for growth factor(GF)binding and release.The aqueous core enabled rapid aggregation of hPSCs into 3D spheroids while the bioactive hydrogel shell was used to load inductive cues driving pluripotency maintenance and endodermal differentiation.Specifically,we demonstrated that one-time,1 h long loading of pluripotency signals,fibroblast growth factor(FGF)-2 and transforming growth factor(TGF)-β1,into bioactive microcapsules was sufficient to induce and maintain pluripotency of hPSCs over the course of 5 days at levels similar to or better than a standard protocol with soluble GFs.Furthermore,stem cell-carrying microcapsules that previously contained pluripotency signals could be reloaded with an endodermal cue,Nodal,resulting in higher levels of endodermal markers compared to stem cells differentiated in a standard protocol.Overall,bioactive heparin-containing core-shell microcapsules decreased GF usage five-fold while improving stem cell phenotype and are well suited for 3D cultivation of hPSCs.

Functional imaging of neuron-astrocyte interactions in a compartmentalized microfluidic device

Traditional approaches in cultivating neural cells in a dish without orienting their interactions have had only limited success in revealing neural network properties.To enhance the experimental capabilities of studying neural circuitry in vitro,we designed an experimental system combining concepts of micropatterned surfaces,microfluidic devices and genetically encoded biosensors.Micropatterning was used to position neurons and astrocytes in defined locations and guide interactions between the two cell types.Microfluidic chambers were placed atop micropatterned surfaces to allow delivery of different pharmacological agents or viral vectors to the desired cell types.In this device,astrocytes and neurons communicated through grooves molded into the floor of the microfluidic device.By combining microfluidics with genetically encoded calcium indicators as functional readouts,we further demonstrated the utility of this device for analyzing neuron–neuron and neuron–astrocyte interactions in vitro under both healthy and pathophysiological conditions.We found that both spontaneous and evoked calcium dynamics in astrocytes can be modulated by interactions with neurons.In the future,we foresee employing the microdevices described here for studying mechanisms of neurological disorders.

A microfluidic platform for cultivating ovarian cancer spheroids and testing their responses to chemotherapies

There is increasing interest in utilizing in vitro cultures as patient avatars to develop personalized treatment for cancer.Typical cultures utilize Matrigel-coated plates and media to promote the proliferation of cancer cells as spheroids or tumor explants.However,standard culture conditions operate in large volumes and require a high concentration of cancer cells to initiate this process.Other limitations include variability in the ability to successfully establish a stable line and inconsistency in the dimensions of these microcancers for in vivo drug response measurements.This paper explored the utility of microfluidics in the cultivation of cancer cell spheroids.Six patient-derived xenograft(PDX)tumors of high-grade serous ovarian cancer were used as the source material to demonstrate that viability and epithelial marker expression in the microfluidic cultures was superior to that of Matrigel or large volume 3D cultures.To further demonstrate the potential for miniaturization and multiplexing,we fabricated multichamber microfluidic devices with integrated microvalves to enable serial seeding of several chambers followed by parallel testing of several drug concentrations.These valve-enabled microfluidic devices permitted the formation of spheroids and testing of seven drug concentrations with as few as 100,000 cancer cells per device.Overall,we demonstrate the feasibility of maintaining difficul-to-culture primary cancer cells and testing drugs in a microfluidic device.This microfluidic platform may be ideal for drug testing and personalized therapy when tumor material is limited,such as following the acquisition of biopsy specimens obtained by fine-needle aspiration.

Detecting cell-secreted growth factors in microfluidic devices using bead-based biosensors

Microfluidic systems provide an interesting alternative to standard macroscale cell cultures due to the decrease in the number of cells and reagents as well as the improved physiology of cells confined to small volumes.However,the tools available for cell-secreted molecules inside microfluidic devices remain limited.In this paper,we describe an integrated microsystem composed of a microfluidic device and a fluorescent microbead-based assay for the detection of the hepatocyte growth factor(HGF)and the transforming growth factor(TGF)-β1 secreted by primary hepatocytes.This microfluidic system is designed to separate a cell culture chamber from sensing chambers using a permeable hydrogel barrier.Cell-secreted HGF and TGF-β1 diffuse through the hydrogel barrier into adjacent sensing channels and are detected using fluorescent microbead-based sensors.The specificity of sensing microbeads is defined by the choice of antibodies;therefore,our microfluidic culture system and sensing microbeads may be applied to a variety of cells and cell-secreted factors.