MicroRNA (miRNA) molecules play a complex and quite indirect role in the process of producing proteins from genetic blueprints, their activities adjusting the amount of protein produced for a range of genes. Since protein levels change in aging, we should expect to also see changes in miRNAs also. The system reacts to the cellular and molecular damage that causes aging, and this is another part of the reaction:
Human ageing is a complex and integrated gradual deterioration of cellular processes. There are nine major hallmarks of ageing, that include changes in DNA repair and DNA damage response, telomere shortening, changes in control over the expression and regulation of genes brought about by epigenetic and mRNA processing changes, loss of protein homeostasis, altered nutrient signaling, mitochondrial dysfunction, stem cell exhaustion, premature cellular senescence and altered intracellular communication.
MicroRNAs are estimated to regulate as many as 60% of all human mRNAs, which represent practically all cellular and molecular functions. MiRNAs are known to be key players in the regulation of transcripts involved in processes as diverse as embryonic development, differentiation, cellular proliferation, apoptosis, metabolism and adaptation to environmental stress. Given the involvement of miRNA regulation in multiple cellular processes, it is unsurprising that this process plays a part in complex, multifactorial and environmentally-influenced cellular processes such as human disease and cellular and organismal ageing.
In this review, I will outline each of the features of ageing, together with examples of specific miRNAs that have been demonstrated to be involved in each one. This will demonstrate the interconnected nature of the regulation of transcripts involved in human ageing, and the role of miRNAs in this process. Definition of the factors involved in degeneration of organismal, tissue and cellular homeostasis may provide biomarkers for healthy ageing and increase understanding of the processes that underpin the ageing process itself.