Salivary MicroRNA

Salivary mircroRNA and early diagnosis of periodontal problems

Pic Courtesy: Medical Express

Regarded as the mirror of the body, 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 diseases and conditions. Although many putative biomarkers have been discovered using proteomic, transcriptomic, epigenetic, and metabolomic technologies, transcriptomic analyses have so far achieved the most progress in terms of sensitivity and specificity and translation into clinical practice. Identifying alterations in salivary transcriptomic signatures using microarray or sequencing technologies will help to find novel biomarkers for diagnosing oral diseases including oral cancer and periodontal diseases and also improve personalized approaches that can be used to individualize treatment plans for these patients.
MicroRNAs (miRNAs) are a large family of about 22-nucleotide-long, non-coding, single-stranded RNA molecules that that inhibit gene expression post-transcriptionally by pairing with complementary sequences in their target mRNA. miRNAs are a pivotal component of host-pathogen interactions and host immune responses toward microorganisms. The similarity between miRNA profiles of saliva and other body fluids strongly supports the potential of using miRNAs from human cell-free saliva as biomarkers for various human diseases.
Oral Squamous Cell Carcinoma (OSCC) is ranked as sixth most common cancer worldwide.Despite the advent of new technology, there is a lack of comprehensive screening procedure for this disease. It has been reported that the patient’s survival rate will approach 80% if the cancer has been diagnosed at initial stages, and survival rate decreases to 20–40% if diagnosed at final stages. To date, histopathology remains as the golden standard for reporting cancer risk of pre-malignant disorders. Th invasiveness of histopathology leads to poor compliance for patients and is impossible to be used for monitoring the disease progression. There comes the importance of a distinctive marker which can be utilized to detect the disease at the earliest possible stages.
The discovery of microRNAs has identified a new layer of gene regulation mechanisms, which play a pivotal role in development as well as in various cellular processes, such as proliferation, differentiation, cell growth, and cell death. Deregulated microRNA expression favors acquisition of cancer hallmark traits as well as transforms the tumor microenvironment, leading to tumor development and progression. Many recent studies have
revealed altered expression of microRNAs in oral carcinoma with several microRNAs shown to have key biological role in tumorigenesis functioning either as tumor suppressors or as
tumor promoters. MicroRNA expression levels correlate with clinicopathological variables and have a diagnostic and prognostic value in oral carcinomas. Few studies have identified a variety of salivary miRNAs as promising non-invasive diagnostic biomarkers of oral cancers.
One of the most frequently occurring oral disease, Periodontitis, is a multifactorial infectious and immuno-inflammatory disease that results from a complex interaction between
colonizing microorganisms and host immuno-inflammatory response, being characterized by irreversible histopathological changes, such as destruction of the periodontal ligament, bone destruction, and deepening of periodontal pockets, which can converge to tooth loss. Periodontal disease is time consuming and expensive to treat and therefore its prevention, early detection and management yield considerable health-care benefit. However, despite numerous advances in our understanding of the pathogenesis of chronic inflammatory diseases, periodontitis is still only diagnosed once connective tissue and bone destruction has occurred. Furthermore, monitoring disease progression using clinical measurements and radiographs is a highly skilled and technically demanding process. Recent advances in transcriptomic high-throughput technologies are shedding new light on salivary biomarker discovery, which can elevate salivary diagnosis of periodontal diseases to a higher level.
Profiling of healthy and periodontal transcriptomes will help to find the most significant candidate genes for the onset and progression of periodontal diseases. Those discriminatory
candidate genes must be validated for their sensitivity and specificity as salivary biomarkers. Promising salivary diagnostic tools that may exist in the near future would be chair-side
point-of-care devices that has the ability to analyse a patient’s salivary fluid sample and supply the dental professional with a quick result. Not only will these tools optimize therapy
and risk assessment with personalized dental medicine, they will also likely open the door for expanded health care services that will impact patients on a global level.

Dr. Nisha K. J., Head Of The Department, Dept. Of Periodontics, Vydehi Institute Of Dental Sciences And Research Centre, Bangalore, Karnataka, India.

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