Senescence and ageing skin
Research has identified the skin as a common site for the accumulation of senescent cells, a hallmark of ageing. Senescent cells are those that have ceased replication but continue living. Within the skin, they contribute to ageing further by damaging neighbouring cells, degrading the extracellular matrix and increasing tissue fibrosis. Conversely, skin damage also influences the ageing process by promoting systemic inflammation and encouraging
cellular senescence.
Factors which trigger the ageing process
Cellular senescence refers to the irreversible arrest of cellular differentiation and accompanying altered, inflammatory metabolism known as the senescence associated secretory phenotype (SASP).
Acute senescence occurs in response to cellular lifespan, tissue damage or tumour growth, and is protective and time limited. In contrast, chronic or accelerated senescence due to environmental stimuli (e.g. pollutants, ultra-violet B radiation, gut dysfunction) compromises tissue repair and contributes to tissue damage and organ ageing (see Figure 1).
Immune surveillance and clearance of senescent cells is fundamental to reducing senescent cellular accumulation and collateral tissue damage. During ageing, senescent cells increase exponentially, in line with deteriorating immune function and telomere attrition. The three major contributors to senescent cell accumulation include:
1. Increased damage from environmental stimuli;
2. Natural accumulation due to the ageing process;
3. Impaired immune clearance due to ageing or compromised immune function
When the normal process of ageing is combined with increased senescence from environmental stimuli, and compromised immune clearance, the ageing process is fast-tracked.
The bidirectional gut-skin axis
The gut and skin share many histological and functional features, including a resident microbiome, being comprised of epithelial cells and in direct contact with the external environment. Emerging research has revealed the existence of the gut-skin axis, where communication through inflammatory signalling, microbial metabolites and the immune system impact the health of each organ. For example, metabolites from Clostridioides dificile, which are markers for dysbiosis, have been found to aggregate in the skin and affect epidermal integrity, skin cell differentiation, reduce skin moisture and impact keratinisation. Equally, damage to epidermal cells causes increased intestinal permeability, mast cell expansion and sensitivity to food allergens.
A healthy gut is key to ageing well
The ageing gut loses dominant commensals which are replaced by less favourable commensals and pathobionts – a microbial signature that is associated with age-related disease. Improving the microbiome and intestinal barrier health, on the other hand, reduces the ageing process and in particular skin ageing by:
• Producing short-chain fatty acids (SCFAs) which promote skin barrier function;
• Reducing inflammation;
• Promoting a healthy skin pH;
• Supporting immune function; and
• Attenuating cellular senescence.
In addition to causing direct damage to the skin, local epidermal inflammation has been found to result in increased levels of circulating inflammatory cytokines, suggesting that skin dysfunction contributes to age-associated systemic inflammation.
Conclusion
Skin is a refection of the internal environment and can be considered a biomarker for the ageing process. By using key nutrients to support healthy senescence, immune surveillance, skin integrity and gut health, qualified naturopaths are able to support their patient’s beauty to emerge from the inside whilst simultaneously delaying the ageing process.
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