Aplicarea Microarray in medicină

Introduction

Microarray is the final outcome of progressive combination of molecular techniques and clinical Bioinformatics^(1,2). Microarrays are microminiaturized technologies originated from dot blotting techniques of Northern/Southern blots. The procedures of microarray involve a vast range of applications (Figure 1)^(3-7).
 

Target molecules in microarrays include DNA, RNA and proteins. Microarray is a powerful molecular diagnostic method which can manage an enormous volume of information and data. Thousands of RNA or DNA target sequences are detectable at the same time via microarray^(3,4,8).

DNA microarray comprises fabrication, process of target labeling, probe designing, hybridization and image scanning and data interpretation (Figure 2)^(1,3,7).
 

DNA microarray is an accurate, rapid, reliable, sensitive and specific diagnostic technology, which has influential and effective treating management^(1,6).

DNA microarrays are divided into PCR and Oligonucleotide arrays. Oligonucleotide DNA microarrays introduce a definite diagnostic tool for different diseases, including infectious diseases, autoimmune diseases, inflammatory diseases, metabolic and genetic disorders⁽⁶⁾.

In this review, we have a bald look at medical applications of Microarrays.

Gene Expression Profiling

Precise detection, identification and measurement of gene function and expression is possible via microarrays through the extraction of RNA molecules in clinical samples of cells and tissues. Gene expression profiling may lead to more accurate prognosis, diagnosis, control, and definite treatment of various diseases^(1,4-6,8-10).

According to different studies, microarray techniques are known as appropriate and powerful screening procedures for identifying and detecting genes clusters associated with a determinant biological process. The advantage of microarray technology for profiling gene expressions is to measure the function and the pattern similarities of tens of thousands of genes in the form of a single assay^(6,8,11,12).

Data analyses relating to gene expressions show the functional and the pattern of gene clusters which may lead to categorize and mapping different classes of the genes. Each set of gene cluster will be identified via negative and positive labeling^(1,6,12).

The secret of gene expression profiling is to screen the biomarkers relating to an individual disease. Therefore, the use of DNA microarray is a prompt approach to diagnose a wide range of non-infectious diseases such as cancers, leukemia, lymphoma, melanoma, diabetes, arthritis, systemic lupus erythematosis (SLE), rheumatoid arthritis (RA), and Crohn’s disease via biomarker genes^(6,8,13).

So, mapping the appeared changes in gene coding regions related to gene regulation and expression via DNA microarray technology is a great revolution in molecular diagnostic methods^(1,6).

Diagnosis of Genetic Disorders

Chromosomal malformations and DNA mutations (including SNPs) are categorized as inherited genetic disorders. DNA mutations may lead to protein deformities, protein malfunctions, absence of protein products, and the appearance of phenotypic genetic diseases. SNPs are helpful to detect genetic disorders in various life stages. DNA microarray technology is an advanced molecular-bioinformatics diagnostics for diagnosing genetic diseases and disorders. Also chromosomal diseases, including Down’s syndrome, Edward syndrome, and Turner’s syndrome are detectable via designed DNA microarray bacterial artificial chromosome (BAC) chips^(6,14,15).

Diagnosis of Infectious Diseases

One of the most important factors relating to human death is the appearance of infectious diseases. There are different clinical diagnostics which have their advantages and disadvantages. Traditional diagnostic methods, including culture media, biochemical, immunological and serological tests are time consuming and show a wide range of false positive or negative results. Thus, the use of traditional microbiological assays may lead to weak diagnoses and uncertain treating management of infectious diseases^(6,16).

On the other hand, molecular-bioinformatics approaches such as microarrays are accurate, rapid, and reliable diagnostics which have high levels of sensitivity and specificity. Therefore, clinical diagnostics based on nucleic acids are suitable and progressive tests which have bright promise in future^(6,8,16,17).

Detection of pathogenic microbial agents

Pathogenic microorganisms, including bacteria, fungi, and viruses are detectable in a variety of clinical samples like blood, cerebral spinal fluid, sputum, stool, and urine via different microbiological tools. According to aforementioned part, traditional diagnostic techniques are not suitable methods for detecting pathogenic microorganisms. The traditional diagnostics are even weaker for detecting and identifying multidrug-resistant pathogenic microbial agents. For these reasons, the nucleic acid based technologies and in particular microarray techniques are the best choice for detecting pathogens; because they are reliable, rapid, accurate, sensitive and specific clinical tests^(1,3,6).

Also, the microarray tools are appropriate for determining bacterial agents comprising Methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis, Escherichia coli etc. in species level. Today, there is a wide range of bacteria that can be detected via microarrays^(1,6,8).

The range of fungal diseases has significantly increased. That is why, there are several pathogenic fungi, including Aspergillus, Candida, Mucor, Penicillium (particularly Penicillium marneffei), and Rhizopus which are detectable in species levels via microarrays^(3,6,18).

And finally, the important pathogenic viruses like hepatitis viruses, and human papilloma viruses as obligate endoparasites are detected via microarrays^(1,6).

Conclusions

Microarray technologies are predominant and powerful clinical tests because of their high accuracy, rapidity, reliability, sensitivity, and specificity. These techniques are suitable to identify gene expressions, biomarkers, genetic disorders, infectious and non-infectious diseases and pathogenic microbial agents. The basis of microarrays is funded on probes, nucleic acid labeling and hybridization. Although the microarray procedures are obvious and determined, but the interpretation of data analyses is the most important part of microarray tools. Currently, the cost of technology, tools, data analyzers and specialists are too expensive to be used in every routine medical center. So, it takes time for using microarray technologies in public medical centers, clinical laboratories and hospitals.