The Hidden Beauty of Intestinal Villi
Posted on by Dr. Francis Collins
The human small intestine, though modest in diameter and folded compactly to fit into the abdomen, is anything but small. It measures on average about 20 feet from end to end and plays a big role in the gastrointestinal tract, breaking down food and drink from the stomach to absorb the water and nutrients.
Also anything but small is the total surface area of the organ’s inner lining, where millions of U-shaped folds in the mucosal tissue triple the available space to absorb the water and nutrients that keep our bodies nourished. If these folds, packed with finger-like absorptive cells called villi, were flattened out, they would be the size of a tennis court!
That’s what makes this this microscopic image so interesting. It shows in cross section the symmetrical pattern of the villi (its cells outlined by yellow) that pack these folds. Each cell’s nucleus contains DNA (teal), and the villi themselves are fringed by thousands of tiny bristles, called microvilli (magenta), which are too small to see individually here. Collectively, microvilli make up an absorptive surface, called the brush border, where digested nutrients in the fluid passing through the intestine can enter cells via transport channels.
Amy Engevik, a researcher at the Medical University of South Carolina, Charleston, took this snapshot to show what a healthy intestinal cellular landscape looks like in a young mouse. The Engevik lab studies the dynamic movement of ions, water, and proteins in the intestine—a process that goes wrong in humans born with a rare disorder called microvillus inclusion disease (MVID).
MVID causes chronic gastrointestinal problems in newborn babies, due to defects in a protein that transports various cellular components. Because they cannot properly absorb nutrition from food, these tiny patients require intravenous feeding almost immediately, which carries a high risk for sepsis and intestinal injury.
Engevik and her team study this disease using a mouse model that replicates many of the characteristics of the disorder in humans [1]. Interestingly, when Engevik gets together with her family, she isn’t the only one talking about MVID and villi. Her two sisters, Mindy and Kristen, also study the basic science of gastrointestinal disorders! Instead of sibling rivalry, though, this close alliance has strengthened the quality of her research, says Amy, who is the middle child.
Beyond advancing science and nurturing sisterhood in science, Engevik’s work also captured the fancy of the judges for the Federation of American Societies for Experimental Biology’s annual BioArt Scientific Image and Video Competition. Her image was one of 10 winners announced in December 2020.
Because multiple models are useful for understanding fundamentals of diseases like MVID, Engevik has also developed a large-animal model (pig) that has many features of the human disease [2]. She hopes that her efforts will help to improve our understanding of MVID and other digestive diseases, as well as lead to new, potentially life-saving treatments for babies suffering from MVID.
References:
[1] Loss of MYO5B Leads to reductions in Na+ absorption with maintenance of CFTR-dependent Cl- secretion in enterocytes. Engevik AC, Kaji I, Engevik MA, Meyer AR, Weis VG, Goldstein A, Hess MW, Müller T, Koepsell H, Dudeja PK, Tyska M, Huber LA, Shub MD, Ameen N, Goldenring JR. Gastroenterology. 2018 Dec;155(6):1883-1897.e10.
[2] Editing myosin VB gene to create porcine model of microvillus inclusion disease, with microvillus-lined inclusions and alterations in sodium transporters. Engevik AC, Coutts AW, Kaji I, Rodriguez P, Ongaratto F, Saqui-Salces M, Medida RL, Meyer AR, Kolobova E, Engevik MA, Williams JA, Shub MD, Carlson DF, Melkamu T, Goldenring JR. Gastroenterology. 2020 Jun;158(8):2236-2249.e9.
Links:
Microvillus inclusion disease (Genetic and Rare Diseases Center/NIH)
Digestive Diseases (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)
Amy Engevik (Medical University of South Carolina, Charleston)
Podcast: A Tale of Three Sisters featuring Drs. Mindy, Amy, and Kristen Engevik (The Immunology Podcast, April 29, 2021)
BioArt Scientific Image and Video Competition (Federation of American Societies for Experimental Biology, Bethesda, MD)
NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases
It’s a great read.
A very interesting article. Then I get to “sisterhood”-REALLY! Yes, I know you want to get more women into science but let’s do away with more of this type of addition. A women did the research and follow through along with a staff which I am sure had a few men. I am a women and I find this type of breakdown unnecessary Do we get “manhood or male hood”. when discussion of a paper by a man?
Are you really going to pull the female card on science? Man-phobia has no place here. This is the only way females and males can work for the better good! There are good and bad in either of the sexes.
I think the primary reason for the phrase was because there were three sisters working in the same subfield, and it sounded to me like it was perhaps meant as a gentle joke about it, even as “sisterhood” in STEM is also considered worthy of endorsement. I too think that the women-in-STEM push can be overdone, but when they actually are talking about literal sisters, this seems like an awfully picky battle to pick.
Normally I would be annoyed by the sisterhood commentary. Like everyone else, I have had it up to my eyebrows with everyone broadcasting to the world how woke they are. But in this case, I agree with you; I think the writer was mostly emphasizing that there were three siblings working together on the project. That’s pretty unusual, and I bet had they been three brothers, that would have been pointed out as well.
In the search to resolve this severe clinical picture that dramatically afflicts the onset of life, will we be able to find the hidden solution in Aquaporins or in the carbohydrates of cell membranes?
Would an altered pH regulation affect the assembly of glycans, with repercussions on the bioelectric balance of the membrane, altering the formation of gel domains and the transport functions?