Background

Red foxes carry a wide range of infectious agents, including lungworms, parasitic worms that live in the lungs and airways. Studying how these parasites interact with their host normally means working with animals, since the tissues involved are difficult to reproduce in the lab.

Dr Andreas Oehm built an alternative at the University of Zurich: a cell culture model of the fox respiratory tract, grown at an air-liquid interface. The cells sit with liquid below and air above, as they would in a real airway, which lets them develop into the kind of surface tissue a parasite would actually encounter. The lab uses it to study which genes and proteins the tissue switches on in response to lungworm infection.

The gut is the other major site of parasite infection, and needs a different approach. Organoids are small three-dimensional structures grown from stem cells that organise themselves into something resembling a real organ. The Glasgow host lab specialises in intestinal organoids, and this stay aimed to bring those techniques back to Zurich.

Together, the two models would let the lab study parasites in both the airway and the gut, compare how different host species respond, and build a tissue bank for future work, without the animal experiments those questions would otherwise require.

Aims

• Learn to isolate intestinal crypts and grow organoids from them, across several host species.
• Learn to freeze and revive crypts and organoids, so that tissue can be stored and used later rather than sourced afresh.
• Learn to grow organoids together with parasitic nematodes, and to develop the parasites through their life stages in culture.
• Bring the methods back to Zurich, alongside the existing fox respiratory model, and extend them to canid intestinal tissue.

Outcome

The stay provided hands-on training in a full set of intestinal organoid techniques. Organoids are grown from crypts, the small pockets of stem cells in the gut lining that constantly renew it. Andreas learned to isolate crypts from cattle, sheep and mice and grow organoids from them, to freeze and revive both crypts and organoids, and to keep bovine organoid lines going over the long term. Being able to freeze them matters: it means a lab can build a stored collection of tissue from different species and revive it when needed, rather than returning to animals each time.

The stay also covered the part specific to parasitology. Andreas learned to grow organoids together with parasitic nematodes, and to take Teladorsagia circumcincta, a worm that infects the stomachs of sheep, from its infective larval stage through to near-adult and adult worms in culture. Being able to grow the parasite alongside host tissue makes it possible to watch an infection develop, and to see how the tissue responds, without the animal in which that would normally have to happen.

Back in Zurich, the techniques are being prepared for use rather than running yet. Andreas has written the organoid work into the lab’s research plans and drawn up what it needs, from the growth factors specific to each species to the imaging equipment. A workshop with the team will set the first aims, expected to include establishing canid intestinal organoid lines, getting the culture conditions right and a first attempt at growing parasites alongside them. Two things have to be settled before the cultures can start. Funding is one. The other is biosafety: foxes carry pathogens that can infect people, so working with their intestinal tissue requires additional containment measures.