The history of using saliva as an indicator of what’s taking place within the human body dates back centuries. In ancient China, an inability to swallow a handful of rice whole, was a sign of guilt, because if an individual was nervous (as a result of lying for example) and their salivary secretions dried up, it would be difficult to swallow. In the early 20th century, cytochemical tests of saliva were used to study such conditions as gout and rheumatism.
Early scientific research in saliva was mainly concerned with determining it’s makeup, and in supporting a patient’s ability to speak, lubricate, masticate and function.
In early 2002, the National Institute of Dental and Craniofacial research (NIDCR), began supporting and investing in research of saliva as a Biofluid for molecular diagnostics. Technological advances in engineering, chemistry and advanced computerized genetic analysis for the first time merged in such a way as to allow researchers to begin to understand that the same genomic information found throughout the body is also found in saliva. This is what makes saliva so effective in testing for various systemic conditions.
The initiative by the NIDCR has created a roadmap through the use of oral fluids as the diagnostic medium to scrutinize the health and disease status of patients. State-of-the-art saliva-based biosensors and disease discriminatory salivary biomarkers can be used in diagnostic applications regarding Periodontal disease, Cardiac disease, Atherosclerosis, Hypertension, Diabetes, Kidney disease, Inflammatory disease and Low Birth Weight Babies. Oral fluid, often called the “Mirror of the Body”, is a perfect medium to be explored for health and disease surveillance. The opportunities for diagnosis of severe diseases are enormous.
The salivary glands are exocrine glands, glands with ducts, that produce saliva. They also secrete Amlase, an enzyme that breaks down starch into maltose.
There are over 600 minor salivary glands located throughout the oral cavity within the submucosal layer of the oral mucosa. They are 1-2 mm in diameter and unlike other glands, they are not encapsulated by connective tissue, only surrounded by it. A minor salivary gland is usually made up of a number of Acini, connected in a tiny lobule. A minor salivary gland may have a common excretory duct with another gland, or may have its own excretory duct.
Acinus is Latin for berry. An Acini is any cluster of cells that resembles a many-lobed “berry”. The berry shaped termination of an exocrine gland, where secretion is produced, is said to be acinar in form.
Their secretion is mainly mucous in nature and has many functions such as coating the oral mucosa with saliva to keep it moist. Estimates of the average amount of saliva produced by an adult per day range from 0.75 to 1.5 liters per day. During sleep the amount of saliva produced drops to almost zero. In humans, the submandibular gland contributes around 70% of secretion, while the parotid gland secretes about 25% and 5% are secreted from the other salivary glands.
On a molecular level, saliva contains mostly water. It is a biofluid that is the vehicle for many vital functions. Saliva is also composed of various constituents, such as gingival crevicular fluid, epithelial cells, immune cells, electrolytes, mucopolysaccharides, glycoproteins, antibacterial compounds (thiocyanate, hydrogen peroxide and secretory immunoglobulin A), epidermal growth factor and various enzymes that confer numerous properties to this diagnostically rich medium.
Many of these properties are crucial in the human activities of daily living. Among the top functions of saliva are the antibacterial roles through peroxidases, mucins, and cystatins; buffering roles using carbonic anhydrases and histatins; digestive functions using amylases, mucins and lipases; and the more obvious role of lubrication through mucins and statherins. It should be noted that it was the discovery of epidermal growth factor (EGF) and nerve growth factor (NGF) in saliva in 1986 by Stanely Cohen and Rita Levi-Montalcini that won them the Nobel Prize in Physiology and Medicine.
Because of the intimate relationship of the blood supply (in the capillaries) to the salivary glands, the transport of ions and proteins from the serum into the salivary ducts occurs routinely through osmosis.
Human saliva contains human DNA and RNA as well as becrial and viral DNA. Both types of DNA can be extracted and analyzed through a laboratory process called Polymerase Chain Reaction (PCR), which is a technique for cloning DNA in a test tube. Cloning is necessary to ensure that a large enough DNA sample is obtained to perform a detailed lab analysis. More than 1 billion DNA strands are produced from the original single strand after approximately 90 minutes of laboratory preparation.
Not only does the genetic information derived from the PCR process play an integral part in the early diagnosis of diseases, but also in confirming the presence of a genetic polymorphism, which can indicate whether a person has a predisposition or increased susceptibility to a specific disease or condition.
Dr. Raul Garcia and Dr. Conchi Sanchez-Garcia have partnered with Oral DNA Labs (http://oraldna.com/index.html), the global leader in salivary-based diagnostic testing, which is a subsidiary of Quest Diagnostics. This Los Angels based company performs laboratory testing for more than half a million patients each day, serving approximately half of the physicians, dentists and hospitals in the United States.
If you have a patient whom you suspect may have a problem with Periodontal disease, Cardiac disease, Atherosclerosis, Hypertension, Diabetes, Kidney disease, HPV (human papillomavirus) or is pregnant and you would like to have them tested for inflammatory biomarkers like Interleukin-1 (IL-1), elevated levels of Immunoglobulin (IgA) or Substance P (the marker for inflammatory diseases), call our office at (305) 595-4616 or email us at email@example.com.
TH HUMAN SLAIVARY PROTEOME (HSP)
For those of you who are interested in the details of the bioengineering research of Salivary Diagnositics, there is an interesting article on mapping the DNA genome of human saliva called the Human Salivary Proteome Project at UCLA. You can read more about it by clicking here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2674509/