Advancing Research of Inflammatory Intestinal Diseases

Inflammatory intestinal diseases, such as inflammatory bowel disease and celiac disease, can cause severe symptoms that significantly impact a patient’s quality of life. A lack of human-relevant models has so far limited our understanding of these conditions and hindered the development of effective therapies.

To help advance research of inflammatory intestinal diseases, Emulate recently launched the Colon Intestine-Chip, a comprehensive model that incorporates human colonic organoids and supportive colonic endothelial cells.

We spoke to Dr Lorna Ewart, Emulate’s executive vice president of science, to learn more about the limitations of traditional inflammatory intestinal disease models, what makes the Colon Intestine-Chip a more relevant model and how it can be used to investigate potential drug targets.  

Anna MacDonald (AM): How are inflammatory intestinal diseases traditionally investigated?

Lorna Ewart (LE):

    ● Animal models—primarily mouse models.

    ● Traditional cell culture—primarily cancer-derived cell lines such as Caco-2.

    ● Colonic organoids (colonoids)

AM: What limitations do these approaches present?

LE:

    ● Animal models: species differences—such as differences in the immune system limit translation to human response.

    ● Cancer-derived cell lines: while Caco-2 cell lines are the gold standard for drug permeability studies, they are not appropriate to use for studying colonic inflammation and drug candidate efficacy. Because of their cancerous origin, cell lines:

    ○ Lack the diversity of epithelial cell types found in the human colon

    ○ Have large differences in gene expression

    ○ Are overly resilient to barrier damage

    ○ Lack the donor-to-donor variability found in the patient population.

    ● Organoids: organoids overcome many of the limitations of cell lines and have the diversity of epithelial cell types found in the human colon, but are limited by the lack of mechanical forces, fluid (media) flow and lack of vasculature, which results in limited gene expression compared to humans. Their spherical structure also makes it challenging to measure barrier function as the apical membrane is on the inside.

AM: Can you highlight some of the main features of the Colon Intestine-Chip that make it a more relevant model?

LE: The Colon Intestine-Chip takes the robust cell source that organoids offer, co-cultures them with endothelial cells, and applies colon-relevant mechanical forces through flow and stretch. This results in improved barrier function, enhanced epithelial cell maturation, the formation of a mature brush border with densely packed microvilli and improved gene expression that is closer to in vivo than organoids in suspension culture.

Inside the chip, fragmented colonic organoids are seeded in the top channel on top of a porous membrane, and colon-specific microvascular endothelial cells are seeded in the bottom channel on the other side of the membrane. This structure makes it easier for researchers to measure barrier function compared to intact organoids (as above, organoids are inside out). It also enables researchers to study the movement of immune cells from the vasculature to the epithelial layer, a key function of the inflammatory process.

AM: How important is it to incorporate mechanical forces?

LE: Mechanical forces are crucial in recreating the microenvironment that cells are exposed to inside the human body on the Organ-Chip. For all our Organ-Chips, this includes applying shear stress to the cells with media flow, and for the Colon Intestine-Chip, it also includes applying cyclic stretch to the cells in order to emulate intestinal peristalsis.

One area where we see the advantage of mechanical forces specifically is in epithelial cell polarization. In a recent study, we compared our Colon Intestine-Chip to static cell culture on a permeable support with the exact same cell sources—only in the Colon Intestine-Chip with mechanical forces did we see proper epithelial cell polarization. This matters for researchers because it indicates epithelial cells in the Intestine-Chip are more physiologically respondent than the same cells in static culture (an advantage also confirmed by transcriptomic analysis), and more closely morphologically and functionally resemble colonic cells in the human body.

AM: In what ways can the Colon Intestine-Chip accelerate drug discovery for inflammatory intestinal diseases?

LE: With the Colon Intestine-Chip, researchers can add inflammatory stimuli to study the mechanisms of inflammation and discover the role of various cytokine signaling pathways to identify druggable targets. The fact that the Colon Intestine-Chip model has a transcriptomic profile closer to human tissue, means that there is a greater likelihood of a customer’s target of interest being expressed. Cells can be removed from the chip post-inflammatory stimulus to look at gene expression changes or perform proteomic analysis which may also illuminate new drug targets.

The chip can also be used to evaluate the efficacy of anti-inflammatory drug candidates, and we have demonstrated a physiological response to marketed treatment in a concentration-, time- and donor-dependent manner. This has been demonstrated with on-market targeted therapeutics for ulcerative colitis and Crohn’s disease.

AM: Can you tell us about any plans to further develop the Colon Intestine-Chip?

LE: This year, we will be focusing on two additional applications that will expand the utility of the Colon Intestine-Chip model and relevant targets for IBD:
                
● T-cell recruitment, which will enable users to study the recruitment and activation of circulating T cells to study the role of the immune system in colon inflammation and assess the safety of monoclonal antibody drug candidates.
    
● Microbiome and bacteria; our users have seen early successes studying either complex microbiome consortia or individual bacterial strains on colonic barrier homeostasis. We are working to optimize the colon model and workflow to enable this to a broader community.

AM: Do you think organs-on-chips have the potential in the long-term to completely replace conventional cell culture and animal models?

LE: Eventually, yes. Now organs-on-chips technology is proving to provide utility in recreating complex biology for disease research, drug target validation, mechanism of action and drug toxicity. As the technology develops and scales, its utility in higher throughput drug screening will increase – providing the best biology to pull out the most effective drug candidates and predicating human response.

The drug pipeline is shifting towards modalities, such as biologics, that are incredibly challenging to model in conventional cell culture and for which animal models are often inapplicable due to species differences. While these conventional approaches often worked for traditional small molecule drugs, they are much less translatable for predicting human response to biologics.

Though animal testing may always play a role in the drug development process, the greater human relevance of organs-on-chips technology can help meet the need for more predictive models that align with these new therapeutic modalities and in the long-term, enable researchers to reduce, refine and replace animal testing.

Lorna Ewart was speaking to Anna MacDonald, Science Writer for Technology Networks.