LAMINITIS

Major Foot Forward

Making Breakthroughs in Understanding Laminitis

Tory Moore

A joint study between the Universities of Florida (UF) and Pennsylvania (PennVet) made a major breakthrough in understanding laminitis. They looked at genetic information specific to hoof tissues to see what genes and proteins are involved in the process with the hope that there will 1 day be not only a noninvasive test for the disease, but treatments that target the inflammatory process itself.

“We have very few tools in our arsenal to manage the disease itself. We treat symptoms, pain and mechanical instability but do not have anything to target the cause just yet,” said Samantha Brooks, PhD, an associate professor of equine physiology at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS).

That’s because studies have been hindered by the scarcity of genetic information specific to hoof tissues. Scientists from the UF/IFAS and the University of Pennsylvania School of Veterinary Medicine tapped into PennVet’s New Bolton Center Laminitis Discovery Database, an archive of data and sample sets from naturally occurring laminitis cases collected since 2008. They examined 36 archived tissues of 20 Thoroughbred horses treated for laminitis.

There are 3 types of laminitis, and all impair the structure and function of the horse’s foot. This research provided a snapshot of the active pathways and functions of the hoof, with a focus on supporting limb laminitis—the laminitis that lead to the death of the famous racehorse, Barbaro, in 2007.

“We understand the situations that trigger an episode of laminitis, but we do not have a good understanding of what is happening in the hoof,” said Dr. Brooks, who specializes in equine genetics. “This study took a very comprehensive view of the processes early in the development of laminitis.”

Using gene expression analysis, Dr. Brooks and her colleagues catalogued the changes in gene transcription in archived lamellar tissue from 20 Thoroughbred racehorses to identify trends in the disease process. They looked at tissue from horses with healthy hooves, horses with early disease and others with more severe disease.

“By tapping into my lab’s database and incorporating Dr. Brooks’ unparalleled expertise in equine genetics and transcriptome analysis, we have identified new and promising pathways in cell stress and inflammatory response that significantly enhance our understanding of supporting limb laminitis and its disease processes,” said Hannah Galantino-Homer, VMD, PhD, DACT, a senior investigator in laminitis research at New Bolton.

They found alterations in cell replication and growth, as well as gene expression and proteins that could serve as biomarkers for laminitis disease. In addition, nuclear receptor subfamily 1 group D member 1 (NR1D1) and other important inflammatory genes offer the promise of novel medical treatments.

Laminitis research new bolton: The horse’s hoof lamellae consist of primary and secondary folds or "lamellae" (PELs and SELs) that increase the contact area between the hoof and underlying tissues, allowing the transfer of the horse’s weight from the bones of the limb to the hoof. In this confocal (laser technology) microscopic image, the basal cells of the SELs are stained green using an antibody against an epithelial basal cell keratin, K14.

Image courtesy of New Bolton Center

Red-green-blue-lamellae: The "axial" end (away from the hoof, close to the coffin bone/distal phalanx bone) of a single primary fold or "lamella" (PEL) of the inner surface of a horse's hoof that has been stained using a blue DNA stain to identify the cell nuclei of the lamella and adjacent dermis, a red counterstain to help visualize the microanatomy of the lamellae, and a monoclonal antibody that identifies a keratin specific to the basal cells of the lamella (green).

Image courtesy of New Bolton Center

“This is a big step in improving our understanding of laminitis,” Dr. Brooks said. “Something that could be completely untreatable 10 years ago; in another 10 years we may be able to intervene and make a significant difference in the disease early on.”

Scientists found a collection of genes responsible for triggering that inflammation that could pave the way for future medications to treat the inflammation. For instance, NR1D1 functions as a transcriptional repressor and has a role in rheumatoid arthritis; it was also seen in the laminitic tissues. The genes led researchers to think that some human medications for autoimmune disorders might help horses with laminitis.

Changes in gene expression in diseased tissue are often reflected in changes in the proteins that can be detected in the blood as the disease progresses. For example, increases in specific biomarkers, which can be seen in people following traumatic brain injury, were expressed in the samples from the horses with laminitis in this study.

Medical doctors have used these compounds to understand the severity of these injuries in people without using imaging or more invasive testing. Dr. Brooks hopes this could be used as a tool to monitor the progression of laminitis in the horse and will lead to a blood test to detect laminitis-related biomarkers.

“We don’t always recognize that a horse has severe laminitis until things have gotten quite bad,” Dr. Brooks said. “Early monitoring tools and ways to combat the disease were exciting findings, but we need further research before these new tools will be ready for use in the field.”

Dr. Galantino-Hoomer added that the new findings will point “toward a more targeted approach for future exploration that we hope will help uncover novel solutions for preventing and treating this debilitating disease.”

Funding for the study came from The Foundation for the Horse.

For more information:

Holl HM, Armstrong C, Galantino-Homer H, et al. Transcriptome diversity and differential expression in support limb laminitis. Vet Immunol Immunopathol. 2022 Jan;243:110353. doi: 10.1016/j.vetimm.2021.110353.Epub 2021 Nov 9. https://www.sciencedirect.com/science/article/abs/pii/S0165242721001719?via%3Dihub

Original article appeared on the UF/IFAS website; used with permission. It has been edited for style. https://blogs.ifas.ufl.edu/news/2021/12/01/breakthrough-laminitis-research-shows-promise-for-the-future/