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New research details how saliva is produced

New research details how saliva is produced. Specifically, it reveals the details of how the salivary glands collectively produce the constellation of proteins found in saliva, which opens the door to important medical research, according to researchers at the journal Cell Reports.

Research traces these vital proteins back to their origin, showing which proteins are produced by each of the three main types of human salivary glands and how individual cells in the same gland can secrete different proteins. The project also identifies proteins in the mouth that appear to come from outside the salivary glands, from places like epithelial tissue or blood plasma.

“Saliva is important to taste, digest, swallow, defend against pathogens that we constantly inhale and consume. The proteins in our mouths form an army, so to speak, that is constantly working to protect us. Before that, scientists had an idea of ​​the proteins present in the mouth, but we did not have a complete idea of ​​their origin. We are filling this gap, ”says Omer Gokcumen, associate professor of biological sciences at the College of Arts and Sciences at the University of Buffalo. , in the USA.

“From a biomedical perspective, our research opens the door to more studies on the functions of saliva and salivary glands, and on the use of saliva as a diagnostic fluid, because it takes a snapshot of functioning. healthy and healthy salivary glands. deviations from this expectation may indicate disease, ”explains Stefan Ruhl, professor of oral biology at the UB School of Dental Medicine.

The first author of the study is Marie Saitou, senior bioscience researcher at the Norwegian University of Life Sciences and former postdoctoral researcher at the University of Chicago and UB. Saitou, Gokcumen, and Ruhl led the study with Sarah Knox, associate professor of cell and tissue biology at the University of California San Francisco School of Dentistry (UCSF).

To explain how our bodies produce saliva, scientists first sought to understand which proteins are produced by each major type of salivary gland: the parotid, submandibular, and sublingual glands (humans have a pair).

To do this, the team used a method called transcriptomics to measure the activity of genes in each type of gland. Genetic activity provides information about the production of proteins, as each gene provides instructions for making a specific protein.

This effort has allowed scientists to understand the proteins produced by each gland and how the glands differ from each other in terms of what they produce.

For example, the study found that the parotid and submandibular glands create a lot of salivary amylase, an enzyme that helps digest starch, while the sublingual gland produces next to nothing. During this time, the sublingual gland produces relatively large amounts of certain GalNAc transferases, a family of enzymes that is important for initiating a process called O-glycosylation that binds a sugar to certain salivary mucin proteins. And these are just a few examples.

“We show how the actions of different glands collectively contribute to producing a complex bodily fluid: our saliva,” says Saitou.

“Our work reveals that even one type of gland itself is not homogeneous: acinar cells that produce saliva, once thought to make the same proteins and therefore the same cells, actually synthesize different proteins from saliva, indicating a new level of cellular diversity, ”adds Knox.

Gokcumen points out that research is a step towards understanding the immense complexity of saliva. Beyond examining the origins of the proteins produced by the salivary glands, the team also concluded that some proteins found adrift in saliva are likely not originating from the salivary glands, and that some important proteins that help regulate The gene expression is mostly active in the salivary glands, but not in a litany of other tissues.

“Salivary proteins are a gateway to our body – Gokcumen recalls – When they don’t work well, we suffer. Our work brings us closer to understanding their complex origins and the complex interaction between them. “

“The much-desired saliva diagnostic applications for monitoring systemic well-being and disease will need to measure the quantitative differences in saliva biomarkers,” says Ruhl. “One obstacle that has always hindered progress in this area was that we weren’t sure exactly what proteins the salivary glands inherently produce and what proteins diffuse into saliva from leaking surrounding tissue. “

“In addition, we were missing a reliable baseline, a standard, if so, that tells us what the normal and healthy values ​​are for the protein components of saliva – he adds -. Our study helps to resolve these conflicting issues, providing information that I hope will stimulate saliva diagnostic applications. “

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