Liver injury-on-a-chip

Soon Sung HongCEM Laboratory

BBC News

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BioMEMS (Bio-Micro-Electro-Mechanical-Systems)

Biology Microfabrication & Microfluidics

Bioapplications

Introduction• Liver fibrosis

• Caused by exposure to toxicants, such as alcohol

• Aberrant deposition of extracellular matrix to form scar tissue

• Loss of hepatic function

• Transforming growth factor (TGF)-B• Key fibrogenic cytokine

• Associated with activation of stellate cells by hepatic TGF-B

Traditional Techniques

Conditioned media Transwell Co-culture

Problem• Difficult to monitor paracrine interactions using traditional culture

techniques (ie. Conditioned media and transwell co-cultures)

• Unable to replicate the high local concentrations of secreted signals present in vivo

• Secreted molecules diluted rapidly in the large volume of media

Hypothesis

“Close proximity of the two cell types in the microfluidic co-culture system may better recapitulate local concentrations of signaling molecules produced during liver injury”

Co-cultivated Microfluidic Device

Cell-culture chamber: 10 mm x 1 mm x 0.1mm

Sensing Chamber: 10mm x 0.2mm x 0.1mm

Glass plate

PDMS: flow layer

Actuation layer

Cell-culture chamber: 8 mm x 1.8 mm x 0.075mm

Real Device Fabrication

Experiments MethodConditioned Media Transwell Plate Microfluidic Device

ethanol

Step 1 Hepatocytes induced with alcohol for 48 hours

Experiments MethodConditioned Media Transwell Plate Microfluidic Device

stellate cells treated with conditioned

media from injured hepatocytes

stellate cells on top of a transwell insert

introduced to well with injured hepatocytes

the wall was raised to start cell communication

ethanol

Step 1

Step 2

Hepatocytes induced with alcohol for 48 hours

Figure 1

Shortcomings

“The role of hepatic TGF-B on stellate cell activation is not shown directly”

“Difficult to characterize dynamics of reciprocal signaling using molecular biology approaches”

Microfluidic Device with Integrated Biosensors• For better understanding of the dynamics behind TGF-B secretion• Aptamer-based biosensors integrated • Sensing chambers with gold electrodes implemented

Figure 4

BiosensorsFigure 5

Monoculture ExperimentFigure 6

Hypothesis

“ injured hepatocytes send TGF-B molecules to activate neighboring stellate cells”

ResultsFigure 7

Conclusion

• The importance of hepatocytes as early inducers of liver injury• Alcohol injures the cells that can metabolize it – the hepatocytes- who

in turn send injury signals to neighboring stellate cells

Overall Quality

• Straightforward• Leads to the conclusion in a succinct manner • Doesn’t include the controls and other comparable data • Lacks consistency in terms of experimental materials

• Rat hepatocytes and human stellate cells used• Immortalized human stellate cell line and primary rat hepatocytes• Dimensions of the two types of microfluidic device are different • Difference in levels between the media chamber • Difference in the volume of media that they use between the 3 models

Pg. 4469

Rat hepatocytes and human stellate cells used

Co-cultivated Microfluidic Device

Cell-culture chamber: 10 mm x 1 mm x 0.1mm

Sensing Chamber: 10mm x 0.2mm x 0.1mm

Glass plate

PDMS: flow layer

Actuation layer

Cell-culture chamber: 8 mm x 1.8 mm x 0.075mm

Real Device Fabrication