Figuratively speaking, laymen are regularly told that scientists need to use “guinea pigs” to test their theories – yet few would imagine that a giant version of the familiar pet animal could one day help human stroke victims.
Step forward the capybara (Hydrochoeris hydrochaeris), the world’s largest rodent and a native of the South American wetlands that can reach 40 kilograms in weight. It is a distant relative of the coypu, but closer to the guinea pig, also a native of South America. The flow of oxygenated blood to the creature’s brain is unique – and models what happens when human brains experience a stroke or ischemic cerebrovascular accident (CVA).
An article published in the journal Cells Tissues Organs explains how and why this giant rodent is being used. When the animal reaches sexual maturity at approximately one year of age, one of the main arteries that carries blood to its brain closes off. Simultaneously, another doubles in size and undergoes a process of remodelling to meet the brain’s demand for oxygen and nutrients.
This process is astonishingly like the process taking place more suddenly during a CVA. So scientists at the University of São Paulo (USP) and University College London (UCL), have proposed using the capybara as a model for study.
When a capybara reaches six months, its internal carotid artery naturally begins to undergo a process of fibrosis. At 12 months, the blood vessel is completely obstructed by conjunctive tissue, similar to a fibrous string. At the same time the basilar artery takes its place as the main supplier of blood to the animal’s brain.
According to professor Augusto Coppi, of the Laboratory of Stochastic Stereology and Chemical Anatomy (LSSCA) and USP’s Department of Surgery and School of Veterinary Medicine and Zootechny (FMVZ), this makes the capybara an ideal “guinea pig” for use by the pharmaceutical industry to test new drugs to treat CVA in humans.
Together with UK reseachers, prof. Coppi is undertaking a study to whether atheromatous plaque (formed by cholesterol and calcium) in human brains, could eventually be made less deadly if the secrets of the capybara were unlocked to help remodel to supply the brain’s blood needs.
The FAPESP-funded study is the latest in a series of cooperations and partnership with researchers at University College London has already spanned more than a decade, resulting resulted in three publications. In 2004, in the periodical Anatomia, Histologia, Embryologia, the group structurally described the obstruction process of the internal carotid artery and the remodeling of the basilar artery in the capybara.
In 2005, in the Journal of Molecular Histology, the authors discussed the possible presence of endothelin-1 and its receptor in the basilar artery of capybaras.
A study published in 2006 in Cell and Tissue Research described, with a great wealth of details, the structural alterations of the obstructed internal carotid artery and the increase of calibre and structural remodelling of the basilar artery.
You can read a full article on the capybara research by Brazilian journalist Karina Toledo by clicking here .
The article Immunoreactive Endothelin-1 and Endothelin A Receptor in Basilar Artery Perivascular Nerves of Young and Adult Capybaras (doi: 10.1159/000348617) can be read at www.karger.com/Article/FullText/348617