Biomedical Engineering Reference
In-Depth Information
among those proteins is crucial in the understanding of underlying disease mechan-
isms and hopefully in developing new treatment methods.
Saliva is the watery and usually frothy substance produced in the oral cavity of
humans and most other animals. It is an unique clear fluid, composed of a complex
mixture of electrolytes and proteins, and represented by enzymes, immunoglobulins
and other antimicrobial factors, such as mucosal glycoproteins, traces of albumin and
some polypeptides and oligopeptides, of importance for oral health [9].
Whole saliva is secreted mainly from three pairs of major salivary glands: the paro-
tid, the submandibular and the sublingual glands. Approximately 90% of total salivary
volume results from the activity of these three pairs of glands, with the bulk of the
remainder from minor salivary glands located at various oral mucosal sites [10].
Whole saliva also contains proteins from gingival crevicular fluid, oral mucosa and
oral microbiota. The various components of saliva from these sources, together with
the plasma proteins that appear in saliva, define the physiological behaviour of the
oral cavity, the oral physiome (Oralome).
Saliva is an ideal translational research tool and diagnostic medium and is being
used in novel ways to provide molecular biomarkers for a variety of oral conditions,
such as oral cancer [11, 12], dental caries [13] and periodontitis [13, 14], as well as
systemic disorders such as breast cancer [15], Sjögren's syndrome [16], diabetes mel-
litus [17], cystic fibrosis [18] and diffuse systemic sclerosis [19]. The ability to ana-
lyse saliva to monitor health and disease is a highly desirable goal for oral health
promotion and research [20, 21]. The most important advantage in collecting saliva is
that it is obtained in a non-invasive way and is easily accessible.
Over the past thirty years, there have been many efforts to determine and identify
the main salivary proteins and peptides. Nevertheless, the fluctuating nature of saliva
from different individuals, huge dynamic protein concentration ranges and the protein
detection limits of most proteomic techniques have made the saliva proteome difficult
to define [22]. Even when a healthy individual's saliva is considered, with multi-
dimensional separations and advanced bioinformatics search software tools, proteins
identified in different saliva proteomics experiments are often inconsistent with each
other except for the most abundant proteins. To overcome the poor coverage, poten-
tial bias and complementary nature of each experimental measurement of the human
saliva proteome, it is necessary for biomedical researchers to collect and evaluate all
reliable publicly available saliva protein data sets generated from different analytical
and computational platforms for healthy individuals as well as in disease conditions.
A comprehensive integrated resource of the saliva proteins would provide a great
amount of comparative power for interpreting proteomics profile changes in patients'
saliva, and may supplement or compensate the limitations and biases associated with
the set of controls for a given study. It would also improve the ability to find protein
biomarkers that are known to occur in healthy human saliva, for instance where a
protein is differentially expressed in a patient sample related to the quantities ob-
served in the study control.
Oralome will have as a vital component an integrated database, by compiling and
manually reviewing all the existing experimental data performed on healthy individu-
al samples as well as in several oral and systemic diseases. It will include a collection
of microbial proteins expected to be present in saliva due to their presence in the ge-
nomes of the oral microbiota [23, 24] and a subset of microbial proteins determined
experimentally [25].
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