Evaluation of senolytic interventions in skin ageing

The skin is our largest organ. Ageing of the skin leads to its thinning, loss of barrier function, loss of wound healing efficiency and increased irritability. These are not just 'cosmetic' problems but are extremely important for health and wellbeing in adult and old age. Recent progress in the field including work from the applicants has indicated a major role for cellular ageing (cell senescence) as a cause of age-associated dysfunction and disease in many organs. In fact, this research has shown that suppressing cellular senescence or outright killing the senescent cells that accumulate during ageing can prolong healthy life expectancy in mice. However, it is neither clear whether such a senolytic approach can actually 'rejuvenate' skin nor whether it might work in man.
The present project aims to answer these questions. It is well known that senescent cells accumulate in ageing skin. Previously, in work together with Procter&Gamble, largely funded by BBSRC, we have generated a suite of human-based in-vitro and ex-vivo skin models, in which we can modify the numbers of senescent cells. We will now use these tools to examine the consequences of senescent skin cell accumulation for skin function. We know already that skin containing more senescent cells becomes thinner and less able to act as an efficient barrier. We hypothesize that this occurs because senescent cells compromise the differentiation capabilities of the two major cell types in skin: fibroblasts in the dermis and keratinocytes in the epidermis. We will test whether reduction of senescent cell numbers results in more 'youthful' (papillary) dermal fibroblasts and in better proliferation and/or differentiation of epidermal keratinocytes. We will develop and validate a very novel technology to identify senescent cells and to characterize their interactions with neighbouring cells in tissues by combination of an unprecedented number of functional markers in a single image at subcellular resolution. We will examine whether prior reduction of senescent cell numbers in samples of aged skin improves their ability to heal after wounding. Finally, we will test novel candidate substances for senolytic drugs in our human skin models. Presently, not more than a handful of such candidate drugs are known. Our collaboration partner used an in-silico systems pharmacology approach to predict novel senolytics, which we validate in a cell culture screen in a separate industry collaboration. Promising novel candidates will be transferred into the present project and their effect onto skin cell differentiation, skin thickness, barrier function and wound healing efficiency will be established.
Our project will show for the first time whether it is possible to ameliorate ageing in a human organ (model) by reducing numbers of senescent cells. It will develop a novel technique to visualise senescent cells in their tissue context with unprecedented specificity and thus improve the understanding of their tissue-specific impact. The project will further provide improved screening tools for the development of scientifically evidence-based skin anti-ageing interventions, and it will validate novel senolytic drugs for use in human skin.

Cell senescence has very recently been shown to be a significant cause of ageing in mice, but its role in skin is unclear, as is its role in ageing of any human organ. We propose senescence of skin cells, and especially dermal fibroblasts as a significant and malleable driver of skin ageing. We have developed a suite of human in vitro and ex-vivo ageing skin models and will use these to test whether suppression of cell senescence can improve function of aged human skin. In proof-of-principle experiments, we will reduce frequencies of senescent skin cells in organotypic in-vitro culture and by using senolytic drugs on skin samples ex vivo and measure the impact on skin morphology, dermal fibroblast papillary-to-reticular (trans-)differentiation, epidermal keratinocyte differentiation, barrier function and wound healing. We will validate a novel technique for the specific and sensitive detection of senescent cells in a tissue context by combining up to 14 low-specificity senescence marker antibodies in a single image at subcellular resolution using Imaging Mass Cytometry. Further combination with cell type- and differentiation-specific antibodies and nearest neighbour analysis will enable unprecedented understanding of associations and possible interactions of senescent with non-senescent tissue-resident cells. We will combine a 2D human cell culture senolytic screen that we developed in a separate industry collaboration with our 3D skin models to create a screening pipeline for small molecules that postpone or revert human skin ageing. We will validate this pipeline by screening > 100 potential novel senolytics predicted by a systems pharmacology approach by our collaborator Nuchido Ltd.

The project described here will have impact in three main areas: 1) General population. 2) Scientists studying the ageing process or molecular processes and pathways implicated in ageing, 3) Industry with an interest in ageing and skin care. In particular, Procter & Gamble already exploit anti-oxidants in their skin ageing and beauty consumer products for which they hold substantive market shares. They also have proprietary rights on thousands of similar products. This research program has the potential to inform the development of more effective rejuvenation products that are better able to promote healthy skin ageing through the generation of ectopically applied senolytic products. The juxtaposition of the Newcastle, Durham and Manchester teams to the P&G Open Innovation Partnership within Durham University's Chemistry Department will positively influence this outcome. Further industrial impact will be generated through the collaboration with Nuchido (KTP application under review), which enables us to test an unprecedented range of novel potential senolytics and opens a further route to market through Nuchido. The newly generated National Innovation Centre for Ageing is associated to Newcastle University and is fast becoming an important enabling structure for outreach to industry and the general public.
To facilitate impact of our work we will publish our findings as open access articles in high impact broad readership journals. The data generated during the project will also be publicized in scientific meetings by oral and poster presentations. Impact will also be generated at the level of local scientific infrastructure by contributing to the development of participating Universities as strategic centres in ageing-related research.
The project will also provide scope for public engagement having impact on better understanding and appreciation of basic science among the local communities. This is an area in which the participating institutions have demonstrated proactive approach which has been recognised on different occasions including a runner-up of the 'Greatest Delivery of Impact' in the BBSRC Excellence with Impact awards to Newcastle, in recognition of the influence at both national and local level. A range of activities in public relations within the Changing Age initiative, the first of three Grand Challenges adopted by the University to affect wider socioeconomic change in areas in which it has research excellence, has been established in the past (for example, a Debating Matters competition on ageing). We are actively engaging with school children by allowing access to the research infrastructure for educational purposes. Thus labs of the applicants have been involved in the past, and will continue to participate, in the Newcastle University's Leading Edge programme (offering groups from local schools invaluable experience in laboratory projects), local and national Science festivals etc. Access to the scientific equipment is always the highlight of such projects and leaves an important impact on children's development and choice of future career. The websites of our Universities and laboratories as well as social media and web-based discussion platforms with national and international reach will also be actively used to highlight our findings and the Press offices are well set up to disseminate the most exciting findings to the national media.
One of the more immediate outcomes will be the professional training of the staff involved in the project. They will have an opportunity to learn and improve a wide range of techniques in bioinformatics, molecular and cell biology as well as in vivo techniques. This will equip them well for a career as a scientist in academia or in a private sector.