Creative Touch Permanent Makeup and Aesthetics

The hallmarks of ageing are a framework of twelve interconnected biological processes that collectively produce the functional decline of ageing tissue. Established by López-Otín and colleagues and updated in 2023 to expand from nine to twelve hallmarks, the framework organises these processes into three tiers: Primary hallmarks that initiate damage, Antagonistic hallmarks that represent compensatory responses which become harmful in excess, and Integrative hallmarks that emerge as the systemic output of accumulated primary and antagonistic dysfunction. The skin is the organ where the hallmarks’ consequences are most directly visible in clinical practice – making the framework not merely academic but a practical map of why skin ages, why it ages faster in some people than others, and where meaningful intervention is possible. Inflammageing – the chronic sterile inflammation covered in its own entity – is not a separate hallmark but the convergence point toward which most of the others contribute.

In 2013, Carlos López-Otín and colleagues published a landmark paper in Cell proposing that the complexity of biological ageing could be organised around nine recurring molecular and cellular events – the hallmarks of ageing – each of which meets three criteria: it manifests during normal ageing; experimentally aggravating it accelerates ageing; and experimentally ameliorating it decelerates ageing or extends healthy lifespan. ^[5] A 2023 update expanded the framework to twelve hallmarks, adding disabled macroautophagy, chronic inflammation, and microbiome disturbance – reflecting a decade of evidence that these processes meet the qualifying criteria and are not merely consequences of other hallmarks but drivers in their own right. ^[4]

The framework matters beyond academic geroscience for two reasons. First, it provides a structured explanation of why ageing is not simply a single process slowing down but a network of interacting dysfunctions compounding each other over time. Second, it identifies specific molecular targets – each hallmark is a potential intervention point – which is why the most promising longevity research, and increasingly the rationale for evidence-based aesthetics treatments, is organised around it.

The Three-Tier Architecture

The 2023 framework organises the twelve hallmarks into three tiers that describe a causal sequence rather than a simple list. Understanding the architecture changes how you read the hallmarks – they are not parallel independent processes but a cascade.

Primary hallmarks are intrinsically harmful from the outset. They represent the fundamental damage that accumulates in biological systems over time – the initiating events from which everything downstream follows. Reducing primary hallmark burden always has beneficial effects; there is no threshold above which they become useful.

Antagonistic hallmarks are the biological responses to primary damage. They are initially protective – designed to maintain tissue function in the face of accumulating damage – but when they are chronically activated or when the damage they respond to becomes too great, they themselves become sources of dysfunction. Cellular senescence is the clearest example: a senescent cell has stopped dividing to prevent damaged DNA from propagating, which is a protective response; but when senescent cells accumulate in large numbers and cannot be cleared, their SASP output becomes a sustained source of pro-inflammatory damage.

Integrative hallmarks emerge from the accumulated burden of primary and antagonistic dysfunction. They represent the systemic-level outputs – the whole-organism consequences of decades of molecular and cellular damage. They are the tier most visible in clinical presentation and most directly connected to age-related disease risk.

Primary Hallmarks: The Origins of Damage

Genomic Instability

DNA damage accumulates throughout life from replication errors, oxidative stress, UV radiation, and environmental mutagens. Cells possess multiple DNA damage response (DDR) mechanisms, but their efficiency declines with age and the rate of unrepaired damage progressively increases. In the skin, UV radiation is the dominant source of genomic instability – generating cyclobutane pyrimidine dimers and 6-4 photoproducts in keratinocyte and fibroblast DNA at a rate that cumulative repair cannot fully match. Unrepaired genomic damage activates persistent DDR signalling that itself promotes NF-κB activation and contributes to the chronic inflammatory environment. Beyond its contribution to skin cancer risk, genomic instability in fibroblasts impairs their proliferative capacity and collagen synthesis output – contributing to the structural dermal thinning of intrinsically aged skin independently of any external exposure. ^[5]

Telomere Attrition

Telomeres – the protective DNA-protein caps on chromosome ends – shorten with each cell division, eventually reaching a critically short length that triggers replicative senescence or apoptosis. Telomere length is considered a partial biomarker of biological age; shorter telomeres correlate with earlier onset of age-related disease across multiple tissue types. In the skin, telomere attrition limits the replicative lifespan of keratinocytes and fibroblasts – progressively reducing the pool of functional cells available for barrier maintenance and wound healing. Chronic stress accelerates telomere shortening through cortisol-mediated mechanisms, providing one of the direct biological links between psychological stress history and premature skin ageing that the individual variation data in the Skin Ageing entity describes clinically.

Epigenetic Alterations

The epigenome – the system of DNA methylation, histone modification, and chromatin remodelling that regulates gene expression without changing the DNA sequence – undergoes characteristic changes with age. Epigenetic clocks, based on DNA methylation patterns at specific CpG sites, can estimate biological age more accurately than chronological age and are increasingly used as ageing biomarkers in longevity research. In skin, age-related epigenetic changes alter the expression patterns of structural proteins, growth factor receptors, and inflammatory regulators in fibroblasts and keratinocytes – producing cells that are genomically intact but functionally aged in their gene expression output. UV radiation accelerates epigenetic ageing in sun-exposed skin, and the gap between epigenetic age at sun-exposed and sun-protected sites has been used to quantify the epigenetic burden of photoageing specifically.

Loss of Proteostasis

Proteostasis – the maintenance of the proteome in a correctly folded, functional state – depends on the integrated activity of protein synthesis machinery, molecular chaperones (heat shock proteins), and two degradation systems: the ubiquitin-proteasome system and autophagy. With age, proteasome activity declines, chaperone capacity is increasingly overwhelmed, and damaged or misfolded proteins accumulate in cells. In skin fibroblasts, the accumulation of damaged proteins impairs cellular function broadly and activates the unfolded protein response (UPR), which triggers ER stress signalling that has both pro-apoptotic and pro-inflammatory downstream effects. The heat shock protein induction that radiofrequency treatments produce – through controlled thermal stress – is mechanistically relevant here: HSP47 and HSP70 induction stimulates not only collagen synthesis but the broader proteostasis maintenance machinery, providing partial cellular rejuvenation at the proteostasis level.

Disabled Macroautophagy (new in 2023)

Macroautophagy – the cellular process by which damaged organelles, protein aggregates, and cytoplasmic debris are sequestered in autophagosomes and delivered to lysosomes for degradation – declines in efficiency with age. This is now recognised as a primary hallmark rather than simply a consequence of proteostasis loss, because autophagy impairment accelerates ageing across multiple systems independently of protein aggregate accumulation. In skin, autophagy is critical for melanocyte homeostasis – regulating melanosome processing and the disposal of oxidatively damaged melanin synthesis components. Age-related autophagy impairment in melanocytes contributes to the dysfunctional pigmentation changes of aged skin, including the irregular melanin distribution that produces uneven tone. Caloric restriction and intermittent fasting both upregulate autophagy through AMPK and mTOR inhibition – the clearest mechanistic link between dietary patterns and skin pigmentation ageing.

Antagonistic Hallmarks: Responses That Overshoot

Deregulated Nutrient Sensing

Four nutrient-sensing pathways regulate cellular metabolism in response to available energy and growth signals: mTORC1, AMPK, IGF-1/ insulin signalling, and sirtuins. In youth, these pathways are appropriately calibrated – activating anabolic processes when nutrients are available, conserving resources when they are not. With age, mTORC1 becomes chronically overactivated and AMPK and sirtuin activity declines, shifting the balance toward persistent anabolic drive without the compensatory conservation periods that maintain cellular health. ^[3]

In skin, this has two clinically visible consequences. Chronic mTORC1 overactivation drives sebaceous gland hyperactivity – the mechanism through which high glycaemic index diets and elevated IGF-1 promote sebaceous dysfunction and acne. Conversely, IGF-1 and growth hormone signalling support fibroblast collagen synthesis; the decline in these signals with age contributes to reduced collagen production beyond the direct senescence and TGFβ effects described elsewhere. Caloric restriction, time-restricted eating, and rapamycin (the most studied mTOR inhibitor) all demonstrably extend healthy lifespan in animal models through nutrient sensing pathway recalibration; human evidence is accumulating but not yet sufficient for clinical prescribing outside trials.

Mitochondrial Dysfunction

Mitochondrial efficiency declines with age through accumulation of mitochondrial DNA mutations, reduced biogenesis, and impaired mitophagy (the selective autophagy of damaged mitochondria). Dysfunctional mitochondria produce increased reactive oxygen species (ROS) whilst generating less ATP – an accelerating cycle, since mitochondrial ROS itself damages mitochondrial DNA, producing further dysfunction. In skin, mitochondrial ROS drives oxidative modification of collagen and elastin, directly contributing to ECM structural degradation independently of MMP activity. Critically, mitochondrial membrane permeability increases with age, allowing mitochondrial DNA to leak into the cytoplasm where it activates cGAS-STING – the molecular bridge to the inflammageing cycle described in the Inflammageing entity. Mitochondrial dysfunction is therefore not a parallel ageing mechanism but an upstream driver of chronic inflammatory activation. ^[2]

Cellular Senescence

Cellular senescence is the permanent cell cycle arrest that prevents damaged cells from replicating. In youth, senescent cells are rapidly cleared by immune surveillance; with age, both senescent cell production increases and immune clearance declines, producing progressive accumulation of SASP-secreting cells in tissue. As covered in detail in the Inflammageing and Subcutaneous Tissue entities, SASP cytokines ( IL-6, IL-8, TNF-α, MMP-3) create a pro-inflammatory microenvironment that suppresses adjacent stem and progenitor cell function, degrades extracellular matrix, and perpetuates senescence in neighbouring cells through paracrine signalling. The senolytic research programme – developing drugs that selectively eliminate senescent cells – represents one of the most active areas of longevity therapeutics, with compounds including dasatinib/quercetin combinations and navitoclax in clinical trials for multiple age-related conditions. ^[1]

Integrative Hallmarks: The Systemic Output

Stem Cell Exhaustion

Adult tissue stem cells – epidermal stem cells in the basal layer, hair follicle stem cells in the bulge region, dermal papilla cells – maintain tissue homeostasis through regulated self-renewal and differentiation. Their functional capacity declines with age through the accumulated burden of upstream hallmarks: genomic instability limits replicative capacity, telomere attrition triggers senescence, and the SASP-driven inflammatory environment suppresses stem cell activation and differentiation. The clinical consequences in skin are reduced epidermal renewal rate (contributing to dullness and impaired barrier recovery), slower wound healing, and – most visibly – progressive hair follicle miniaturisation as dermal papilla cell populations decline. The PNAS 2019 study referenced in the Tissue Regeneration entity demonstrated that stem cell exhaustion is partially environmentally reversible – reducing the inflammatory environment restored stem cell function without directly manipulating the stem cells themselves.

Altered Intercellular Communication

Tissue function depends on precisely regulated paracrine and endocrine signalling between cell populations. With age, these communication networks are disrupted in two directions: pro-inflammatory signals increase (SASP, NF-κB-driven cytokine secretion) whilst homeostatic signals decline (reduced growth factor secretion, impaired gap junction function, altered exosome cargo). In skin, the disrupted communication between fibroblasts and keratinocytes – normally a tightly regulated bidirectional signalling relationship that coordinates barrier maintenance, collagen production, and epidermal renewal – produces functional uncoupling. Keratinocytes receive fewer synthesis-stimulating signals from aged fibroblasts; fibroblasts lose the mechanical and paracrine cues from well-functioning epithelium that normally sustain their activity. Polynucleotide treatments address this hallmark most directly – through adenosine receptor activation and growth factor receptor stimulation, they partially restore the paracrine signalling environment that aged intercellular communication has degraded.

Chronic Inflammation (Inflammageing) (new in 2023)

The inclusion of chronic inflammation as a hallmark in its own right – rather than simply a consequence of other hallmarks – reflects the 2023 recognition that it meets all three qualifying criteria: it is universal in ageing; experimentally increasing it accelerates ageing; and interventions that reduce it (anti-inflammatory dietary patterns, IL-6 blockade, senolytics) meaningfully attenuate age-related decline. The full mechanism – cGAS-STING, NF-κB amplification, NLRP3 inflammasome, SASP convergence, and the fibroblast-as-orchestrator circuit – is covered in the Inflammageing entity. In the hallmarks framework, its position as an Integrative hallmark correctly identifies it as an output of accumulated upstream damage that then becomes an independent amplifier of that damage. ^[4]

Microbiome Disturbance (new in 2023)

The gut microbiome undergoes characteristic age-related changes – reduced diversity, loss of keystone species, increased gram-negative bacterial dominance – that increase intestinal permeability and systemic LPS translocation, driving TLR4-mediated inflammatory activation as described in the Inflammageing entity. In skin specifically, the cutaneous microbiome also shifts with age: reduced Lactobacillus and commensal staphylococci, increased opportunistic colonisation, and the Demodex density changes relevant to rosacea pathogenesis. Microbiome disturbance is included as an Integrative hallmark because it reflects the cumulative disruption of the ecological relationships that evolved alongside mammalian immunity – its impairment amplifies inflammatory signalling and impairs immune regulation simultaneously.

The Skin as the Hallmarks’ Most Visible Read-Out

The skin has a unique position among the body’s organ systems: it externalises what is otherwise invisible. Every primary, antagonistic, and integrative hallmark described above produces cutaneous phenotypes that are directly observable – fine lines and laxity from fibroblast collagen decline, uneven pigmentation from melanocyte dysfunction, reduced wound healing from stem cell exhaustion, reactive sensitivity from barrier disruption and inflammatory skewing. The skin is not merely affected by the hallmarks of ageing – it is the organ where their consequences are most accessible to clinical observation and intervention.

This gives the hallmarks framework a practical value in aesthetics that goes beyond academic context. A client whose skin appears to be ageing faster than their chronological age is demonstrating accelerated hallmark progression – the question is which hallmarks and which accelerants. UV history drives genomic instability and epigenetic ageing. Chronic stress drives telomere attrition and NF-κB activation. Poor sleep dysregulates autophagy and circadian NF-κB rhythm. Metabolic syndrome amplifies mTORC1 and NLRP3. Each of these is a modifiable accelerant, and identifying the primary drivers in an individual client changes the intervention priority.

The skin’s biological age and chronological age diverge precisely because hallmark progression rates are not fixed – they are substantially determined by the exposome: the cumulative sum of environmental, lifestyle, and psychological exposures across a lifetime. Clinically, this means that the gap between how a client’s skin looks and how it might look under different conditions is not a fixed genetic destination but a partially recoverable distance. The evidence for partial recovery – through UV protection, sleep optimisation, metabolic health, barrier support, and appropriately targeted regenerative treatments – is the most honest version of what aesthetics practice can offer.

Therapeutic Implications: Targeting the Hallmarks

Each hallmark is a potential intervention point, and the most promising longevity therapeutics are organised around them. Honest evidence calibration is essential here – the research landscape ranges from robust human evidence to compelling preclinical findings that have not yet translated.

Senolytics (cellular senescence). Compounds that selectively eliminate senescent cells – currently dasatinib/quercetin combinations and fisetin – have demonstrated lifespan extension in multiple mouse models and are in early human clinical trials for conditions including frailty, diabetic kidney disease, and osteoarthritis. Human skin-specific senolytic trials are not yet reporting. The mechanism is well-established; the human clinical evidence is genuinely early. ^[1]

NAD+ precursors – NMN and NR (mitochondrial dysfunction, genomic instability). NAD+ declines with age, impairing sirtuin activity, mitochondrial biogenesis, and DNA repair mechanisms that require it. Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) raise cellular NAD+ levels; animal data consistently shows metabolic and longevity benefits. Human trials show modest metabolic improvements, but skin-specific data at meaningful doses is limited. The supplement market substantially outruns the evidence for this class. ^[3]

mTOR inhibition (nutrient sensing, proteostasis, autophagy). Caloric restriction, intermittent fasting, and rapamycin all inhibit mTORC1, reducing cellular senescence accumulation, upregulating autophagy, and extending healthy lifespan across multiple species. Intermittent fasting’s effects on human skin specifically – through autophagy upregulation and reduced IGF-1 – are mechanistically sound. Rapamycin in healthy humans is in trials; its use for longevity outside research settings is not yet clinically established.