Identifying quality control mechanisms in human skin and their role in the hallmarks of ageing

Hallmarks of Ageing was first published in 2013 identifying nine key elements of the ageing process with an additional three hallmarks added 10 years later. Of these, five are believed to be primary hallmarks; genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, and disabled macroautophagy. Impairment of macroautophagy (hereafter autophagy) with age is now considered one of the main factors driving progression of other hallmarks, impacting protein, organelle and overall cellular functions. Indeed, the function of autophagy in ensuring cellular quality control by degrading damaged components is essential for organismal health and the majority of interventions extending healthspan in a variety of laboratory models require activation of autophagy for their effect. Autophagy works in concert with other components of the proteostasis network to ensure protein quality control by appropriate synthesis, folding and degradation. These quality control systems to maintain cellular health exist in young cells/tissues yet they are obviously not sufficient to prevent the hallmarks of ageing. One example is the loss of mitochondrial quality control by autophagy (process termed mitophagy) with age which prevents recycling of damaged mitochondria. We recently demonstrated that reactivation of mitophagy with small molecules developed by us was sufficient to revert old primary fibroblasts to a younger phenotype (reference 1). Unfortunately, our understanding of this and other cellular quality control mechanisms in human tissues is still very limited with most research relying on animal models or in vitro 2D cell cultures. For example, virtually nothing is known about mitochondrial degradation by mitophagy in human tissue, and this is also true about other aspects of cellular quality control pathways.
In the past two years we developed an experimental pipeline allowing continuous generation of human skin organoids (explants from surplus surgical tissue) aiming to develop these into a robust platform for molecular biology studies in a physiologically relevant context. We started adapting experimental tools for the genetic and pharmacological modulation of pathways under study in the tissue settings allowing us to perform mechanistic investigations in these 3D models. In this project we will capitalise on skin explants with the overall aim to discover the extent and the role of quality control mechanisms in living human tissue. We will particularly focus on selective autophagy pathways degrading damaged proteins and organelles to understand how organellar quality and proteostasis are maintained in young skin and how it is perturbed with ageing. The unique feature of this project is that instead of starting from 2D cell culture or animal models we will investigate principles of basic biology directly in human tissue. We will combine a range of experimental approaches, from exploratory multiomics which will shed the light on the gene and protein expression profiles of young and old skin, biochemical methods to isolate cellular components such as mitochondria to characterise changes in their function with age, which will be followed by targeted/hypothesis driven questions which will be answered by the application of pharmacogenetic tools to modulate protein/cell/tissue function.