BIONÆR-Bionæringsprogram

The skeleton in the limbs consists mainly of long bones and small, so-called cuboidal bones found in the knee and hock joints. Both types of bone can suffer from developmental diseases, characterised by the fact that they arise while the animal is still growing, even if they often are discovered after the animal is skeletally mature. In long bones, the understanding of developmental diseases has benefitted greatly from studies of the blood supply to growth cartilage. The most common developmental disease: osteochondrosis (meaning: "bone-cartilage-disease") is defined as a focal, i.e. limited delay in skeletal growth by so-called endo-chondral or within-cartilage ossification. Research has shown that the blood supply can fail, leading to necrosis or small infarcts in growth cartilage, and it is these little infarcts that cause the delay in endochondral ossification, or osteochondrosis. Cuboidal bones suffer from osteochondrosis, but the hock joint also gets other developmental diseases such as joint inflammation or osteoarthritis, known as bone spavin. The main aim for the project was to determine whether the understanding of developmental diseases such as osteochondrosis and osteoarthritis/spavin could be increased through studying the blood supply to the growth cartilage of cuboidal bones in the hock. Historically, it has only been possible to study the blood supply to growth cartilage systematically through breeding animals for research, but technology evolves rapidly, and an important part of the project was to determine if the blood supply to growth cartilage could be studied in limbs donated to research from dead foals, if new, advanced techniques were used. Hind limb pairs from foals donated to research after having died or been euthanased for various reasons were therefore examined using computer tomography, also known as CT or CAT-scanning, and magnetic resonance imaging, known as MRI. Observations were later confirmed by histological examination in the microscope. Results were as follows: MRI showed the blood supply better than CT in examination of bones donated from foals after death. This was because for blood vessels to show up in CT scans, they first have to be filled with contrast medium and the bones did not tolerate this well, as blocks and leakages arose. It is not necessary to fill vessels for them to be visible in MRI scans, but the technique is sensitive and must be done right: it turned out to make a difference whether limbs were suspended or lay flat before scanning; the latter was best. The blood supply to the growth cartilage of the cuboidal bones comprised mainly vertical and horizontal vessels. As growth slows, the cartilage thins and vessels regress, and this happened by about 120 days of age. In the cuboidal bones of 61 % of examined foals, there were CT changes that in other bones have corresponded to osteochondrosis lesions. Microscopic examination has so far confirmed that the CT-changes actually correspond to osteochondrosis, and that that osteochondrosis is the result of failure of the blood supply, for 30 % of the CT changes. The reason why this has so far only been confirmed for 30 % of the changes is that they are so small that it is difficult to capture them when one has to cut extremely thin slices for examination in the microscope. However, there was a match between the three-dimensional shape of the CT changes, and the direction and branching of vertical and horizontal vessels, making it likely that the majority of them represent failure of the blood supply to growth cartilage and osteochondrosis. The conclusions were that MR is recommended for examination of vessels, but CT remains useful for identification of lesions. Due to the high prevalence of 61 %, osteochondrosis is a likely cause of osteoarthritis/spavin in the hock joint. This should be confirmed in more animals, and confirmation can now potentially be done by translating the current project results to CT and MRI of live foals, and following them from before 3 months old when the disease process starts.

Flere prosjektdeltagere har tilegnet seg veilederkompetanse, som kreves for professoropprykk. Forskning og publisering påvirker institusjonenes finansiering, kvalitet og akkreditering. Kun akkrediterte institusjoner har stemmerett i The European Association of Establishments for Veterinary Education, hvor NMBU og SLU skal re-akkrediteres i hhv. 2024 og 2027. Prosjektet markerer et skille mellom historiske teknikker som krever bruk av sterke kjemikalier, og nye teknikker uten kjemikalier. Teknikkene gir bedre forskningsresultater, men som bivirkning reduseres risiko forbundet med anskaffelse, bruk og avhending av kjemikalier, for forskere og nærmiljø. Prosjektet markerer også at forskningen beveger seg stadig lenger bort fra å undersøke forsøksdyr, til å følge levende dyr med minimalt invasive teknikker. Dette er fordelaktig for forskningen, men det forventes også at hestenæringen vil se fordelen ved å fange opp sykdom tidlig mens den ennå kan styres positivt bort fra lidelse.

Prosjektet det søkes om har en grunnforskningsdel og en klinisk relevansdel. Hovedmål for prosjektet er å beskrive blodtilførselen til vekstbrusken i de små haseknoklene hos unge Islandshester. Lignende studier av blodtilførselen til de lange knoklene som forbeines fra tre sentre har gitt et fullstendig nytt svar på at osteochondrose, som kan gi løse biter i ledd (osteochondrosis dissecans) oppstår når en liten del av denne blodtilførselen svikter. Det er ikke kjent om blodtilførselen til de små haseknoklene, som forbeines fra ett enkelt senter, er organisert på samme måte. I relevansdelen vil man undersøke forholdet mellom blodtilførselen og feilvokste, kileformede knokler som gir sigdhaser. Man vil også se på forholdet mellom blodtilførsel og utviklingsmessig, arvelig predisponert leddbetennelse/osteoarthritt eller spatt, som er svært vanlig hos Islandshest. Dette kan gi verdifull informasjon som potensielt også er relevant for leddbetennelse generelt.