Jean Krutmann

• Leibniz Research Institute for Environmental Medicine

Pregnancy is associated with physiological skin changes, altered response to UV exposure and increased risk of pigmentary disorders such as melasma and linea nigra, which can impact quality of life. This review explores the effects of photoprotection during pregnancy, focusing on safety, efficacy, and the role of sunscreens in preventing pregnancy-...

Introduction Human skin serves as a dynamic habitat for a diverse microbiome, including a complex array of viruses whose diversity and roles are not fully understood. Objectives This study aims to enhance our understanding of this skin viral diversity through the construction of a detailed, non-redundant DNA viral reference catalog. Methods A total...

Objective To evaluate the awareness of and attitudes toward various aspects of sun-exposure risks and protection methods among Canadians. Methods An online survey conducted from September 28 to October 18, 2021, included 17,001 participants aged 18 years and above from 17 countries across 5 continents; the data presented are those of the Canadian...

This article provides an evidence-driven classification of non-filtering photoprotective ingredients that modulate skin's biological response to sunlight.

Background: There is no doubt that global warming, with its extreme heat events, is having an increasing impact on human health. Heat is not independent of ambient temperature but acts synergistically with relative humidity (RH) to increase the risk of several diseases, such as cardiovascular and pulmonary diseases. Although the skin is the organ i...

Human induced pluripotent stem cells (iPSCs) have great potential in research, but pluripotency testing faces challenges due to non-standardized methods and ambiguous markers. Here, we use long-read nanopore transcriptome sequencing to discover 172 genes linked to cell states not covered by current guidelines. We validate 12 genes by qPCR as unique...

Skin aging is a dynamic process involving a spectrum of phenotypic changes, making it an attractive model for studying microbiome‐phenotype interactions. Therefore, 822 facial microbial samples and 14 skin phenotypes from corresponding areas were assessed in a Chinese cohort. Porphyrins and the chronological age exhibited the most significant micro...

Characterizing the metabolite fingerprint from the skin surface provides invaluable insights into skin biology and microbe-host interactions. To ensure data accuracy and reproducibility, it is essential to develop standard operating procedures for skin surface metabolomics. However, there is a notable lack of studies in this area. In this study, we...

Cockayne Syndrome B (CSB) is a hereditary multiorgan syndrome which—through largely unknown mechanisms—can affect the brain where it clinically presents with microcephaly, intellectual disability and demyelination. Using human induced pluripotent stem cell (hiPSC)-derived neural 3D models generated from CSB patient-derived and isogenic control line...

Secondary prevention of skin cancer consists in early detection of malignant lesions through patients’ mole self-examination and medical examination. The objective of this study was to assess the self-reported frequency of mole examination in a large, representative sample of the adult general population of 17 countries from all continents. Of a to...

This study conducted a comprehensive online survey across 17 countries to assess the influence of fear of skin cancer versus fear of photoaging on photoprotection practices. Revealing significant differences in sun protection behaviors, the research found that individuals concerned about photoaging are more likely to adopt comprehensive sun protect...

The skin microbiome undergoes constant exposure to solar radiation (SR), with its effects on health well‐documented. However, understanding SR's influence on host‐associated skin commensals remains nascent. This review surveys existing knowledge on SR's impact on the skin microbiome and proposes innovative sun protection methods that safeguard both...

The objective of our study was to assess the attitudes and behaviors in Japan regarding sun exposure and compare them to those in Europe and North America. The study population was a representative sample of individuals aged >18 years from Ipsos panels in Japan ( N = 1000), North America ( N = 1000), and Europe ( N = 6000) using the quota method. Q...

Background Standardized methods for sun protection factor (SPF) testing are still beset with endpoint and method‐driven issues, and can be influenced by multiple factors. The purpose of this analysis is to explore the factors influencing the results of sun protection factor (SPF) testing in human subjects according to the ISO 24444:2019 standard. I...

The skin is a barrier organ and thus exposed to environmental factors from birth, which essentially determine skin aging. In order to describe and understand this complex process exactly, we applied the concept of the "exposome" to the environmentally induced skin aging process. In this review, we summarize current knowledge on the skin aging expos...

Background Behavioural interventions can improve attitudes towards sun protection but the impact remains inconsistent worldwide. Objective To assess awareness of and attitudes towards the multiple facets of sun exposure and suggest ways to improve prevention from overexposure to the sun in all geographical zones and multiple skin types. Methods O...

Primary and secondary prevention of skin cancer varies considerably from one country to another. This survey investigates knowledge and behaviours regarding sun exposure in the UK. This UK survey (n = 1000) was conducted online from 28 September to 18 October 2021 and was part of a worldwide survey (n = 17 001) conducted in 17 countries (five conti...

e21578 Background: This survey investigates knowledge and behaviors regarding sun exposure among population who have been treated with immunosuppressive anti-graft rejection drugs because of an organ transplantation. Methods: The survey (N = 17,001) was conducted online in 17 countries (5 continents) from 28 September-18 October 2021. Automated sel...

e21575 Background: This survey investigates knowledge and behaviors regarding sun exposure among population who have been treated for skin cancer (melanoma/non melanoma) or pre-cancerous lesions in 17 countries. Methods: The survey (N = 17,001) was conducted online in 17 countries (5 continents) from 28 September-18 October 2021. Automated selectio...

Background: Acne pathophysiology includes a complex interaction among inflammatory mediators, hyperseborrhea, alteration of keratinization and follicular colonization by Propionibacterium acnes. Aims: To describe the impact of the exposome on acne and how photoprotection can improve outcomes. Methods: A narrative review of the literature was c...

Previous studies have found associations between chromium exposure and skin damage. However, few studies have focused on both chromium and skin aging. This study aimed to assess the degree of skin aging symptoms and estimate the relationship between hair chromium and skin aging among rural housewives. We recruited 405 subjects in Shanxi Province of...

Background and Aims Female pattern hair loss affects females of all ages with a trend to increase after menopause. This disorder may have significant psychological impact and lead to anxiety and depression. Objective In a single center, double blind, randomized, placebo‐controlled study, the effects of oral Pycnogenol® intake (3 × 50 mg/day for a...

Genetic and exposomal factors contribute to the development of human aging. For example, genetic polymorphisms and exposure to environmental factors (air pollution, tobacco smoke, etc.) influence lung and skin aging traits. For prevention purposes it is highly desirable to know the extent to which each category of the exposome and genetic factors c...

Solar lentigines are a hallmark of human skin aging. They result from chronic exposure to sunlight and other environmental stressors. Recent studies also imply genetic factors, but findings are partially conflicting and lack replication. Via a multi-trait based analysis strategy, we discovered that genetic variants in telomerase reverse transcripta...

The medical literature on aesthetic dermatology has primarily focused on a light-skinned patient population, yet patients of darker skin types have different needs and priorities. In Chinese individuals, key concerns include altered pigmentation, which is perceived to age the individual, and also relates to the Chinese cultural standard of beauty o...

Skin of colour or pigmented skin has unique characteristics: it has a higher eumelanin-to-pheomelanin ratio, more mature melanosomes, an increased amount of melanin distributed in the upper layers of the epidermis, and more efficient DNA repair compared with lighter skin. However, individuals with skin of colour are at a significant risk of skin da...

Skin is a complex ecosystem colonized by millions of microorganisms, including bacteria, fungi, and viruses. Skin microbiota is believed to exert critical functions in maintaining host skin health. Profiling the structure of skin microbial community is the first step to overview the ecosystem. However, the community composition is highly individual...

IntroductionThe shortcomings of standardized sunscreen testing have been discussed in recent years, noting differences between how sunscreens perform in indoor clinical (in vivo) laboratory testing compared with real-life conditions. We previously developed an outdoor clinical method for ranking sunscreens by performance level. We used this method...

Cystic fibrosis is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) that can lead to terminal respiratory failure. Ultrafine carbonaceous particles, which are ubiquitous in ambient urban and indoor air, are increasingly considered as major contributors to the global health burden...

Transcriptome analysis experiments enable researchers to gain extensive insights into the molecular mechanisms underlying cell physiology and disease. Oxford Nanopore Technologies (ONT) has recently been developed as a fast, miniaturized, portable, and cost-effective alternative to next-generation sequencing (NGS). However, RNA-Seq data analysis so...

Biogeography (body site) is known to be one of the main factors influencing the composition of the skin microbial community. However, site-associated microbial variability at a fine-scale level was not well-characterized since there was a lack of high-resolution recognition of facial microbiota across kingdoms by shotgun metagenomic sequencing. To...

Sunscreens provide excellent protection against erythema and against chronic damage such as photoaging and skin cancer. Today’s challenges concern safety of the products and improved methods for standardizing the evaluation of their efficacy. Other important topics are the further development of sunscreen products, as well as personalization of use...

To understand the importance of terrestrial solar exposure on human skin, not only individual spectral components need to be considered in biomedical studies, but also the relevance of the combined action profile of the complete solar spectrum (cSS) must be established. We therefore developed a novel irradiation device that combines the emission of...

Introduction: Polymorphic light eruption (PLE) is the most common idiopathic, acquired photodermatosis. The pathophysiology of PLE is not yet fully understood but seems to involve immunological mechanisms, UVA-induced oxidative stress, and the subsequent elicitation of a cellular stress response affecting keratinocyte gene expression and skin immu...

Genome engineering-induced cleavage sites can be resolved by non-homologous end joining (NHEJ) or homology-directed repair (HDR). Identifying genetically modified clones at the target locus remains an intensive and laborious task. Different workflows and software that rely on deep sequencing data have been developed to detect and quantify targeted...

Background: Chronic exposure to air pollution can negatively affect skin health. Aims: To assess the efficacy of the LUMIVIVE® System (LVS), a skincare system consisting of individual day and night serums, in Chinese women exposed to air pollution. Patients/methods: In this single-center, vehicle-controlled study, eligible females (mean age, 4...

Sunscreens provide excellent protection against erythema and against chronic damage such as photoaging and skin cancer. Today's challenges concern safety of the products and improved methods for standardizing the evaluation of their efficacy. Other important topics are the further development of sunscreen products, as well as personalization of use...

Cutaneous squamous cell carcinoma (SCC) is one of the most frequent malignancies in humans and academia as well as public authorities expect a further increase of its incidence in the next years. The major risk factor for the development of SCC of the general population is the repeated and unprotected exposure to ultraviolet (UV) radiation. Another...

Background: Skin aging is a process regulated by chronological aging and amplified by exposome factors including chronic UV exposure and pollution, which both induce reactive oxygen species. Topical antioxidants have the potential to counteract this process and to improve skin aging signs, including wrinkles and hyperpigmentation. Objective: To...

Background Cosmetic products are widely used in daily life and can cause skin reactions. However, to date, few studies have investigated the prevalence and associated factors of skin reactions to different types of cosmetic products using patch test results. Objectives To investigate the frequency and associated factors of skin reactions to sunscr...

Genome-wide analysis of transcriptomes offers extensive insights into the molecular mechanisms underlying the physiology of all known species and discover those that are still hidden. Oxford Nanopore Technologies (ONT) has recently been developed as a fast, miniaturized, portable and a cost effective alternative to Next Generation Sequencing. Howev...

Urea is a hygroscopic molecule (capable of absorbing water) present in the epidermis as a component of the natural moisturizing factor (NMF) and is essential for the adequate hydration and integrity of the stratum corneum. Urea improves skin barrier function including antimicrobial defense by regulating gene expression in keratinocytes relevant for...

The transcription factor Hypoxia-Inducible Factor-1alpha (HIF-1a) regulates cellular metabolism under hypoxia but also immune responses and UVB-induced skin reactions. In keratinocytes, HIF-1a is an environmental sensor orchestrating the adaptation to environmental changes. Here, we investigated the role of HIF-1a in keratinocytes for skin reaction...

Ultraviolet (UV) B irradiation of keratinocytes results in the formation of the tryptophan photoproduct 6-formylindolo[3,2-b]carbazole (FICZ) which is a high-affinity ligand for the aryl hydrocarbon receptor (AHR). The resulting activation of AHR signaling induces the expression of cytochrome P450 (CYP) 1A1 which subsequently metabolizes FICZ. Impo...

Introduction: Bathing in the Blue Lagoon (BL) in Iceland benefits patients with psoriasis. Accordingly, the BL water contains algae with biological activities that improve skin barrier function and affect T-cell responses relevant for psoriasis. Bathing in the BL is also becoming increasingly popular among healthy individuals and anecdotal evidenc...

Human fibroblasts from a Cockayne Syndrome (CS) patient carrying the compound heterozygous c.1131 A>T and c.2571C>T within ERCC Excision Repair 6 (ERCC6) were reprogramed to generate integration-free induced pluripotent stem cells (iPSCs). Characterization of IUFi001-iPSCs demonstrated that this iPSC line is free of exogenous reprogrammed genes and...

Background Patch test, as a helpful tool in clinic diagnosis and safety assessment of cosmetics, is affected by many factors. Objectives To investigate the influencing factors of patch test reactions in a highly standardized large-scale dataset of Chinese. Methods Patch test data (n=151,280) from safety assessments of cosmetic products were obtai...

The absorption of topically applied substances is challenging due to the effective skin barrier. Encapsulation of substances into nanoparticles was expected to be promising to increase the bioavailability of topically applied products. Since nanoparticles cannot traverse the intact skin barrier, but penetrate into the hair follicles, they could be...

Background Currently, sunscreens’ sun protection factor (SPF) and ultraviolet (UV) A protection are tested separately under indoor conditions, without considering external conditions that may affect performance. Studies are often conducted in Caucasian individuals; other racial groups may respond differently. Methods An outdoor, double-blind, intr...

Exposome factors that lead to stressed skin can be defined as any disturbance to homeostasis from environmental (meteorological factors, solar radiation, pollution or tobacco smoke) and/or internal exposure (unhealthy diet, hormonal variations, lack of sleep, psychosocial stress). The clinical and biological impact of chronic exposome effects on sk...

In the last decade, transcription activator-like effector nucleases and CRISPR-based genome engineering have revolutionized our approach to biology. Because of their high efficiency and ease of use, the development of custom knock-out and knock-in animal or cell models is now within reach for almost every laboratory. Nonetheless, the generation of...

Visible light (VL) can induce pigmentary alterations, especially in dark-skinned individuals, and exacerbate photodermatoses and pigmentary disorders. Currently, there is no standardized method for assessing sunscreen protection against VL. On the basis of a critical review of published in vitro and in vivo methods, a VL photoprotection assessment...

The importance given to the cumulative effects of incidental, non‐extreme solar irradiation has lagged behind that given to severe episodic sunburn. Cumulative exposure is a contributor to precancerous skin lesions and carcinomas and plays a decisive role in (facial) skin aging.

Background Melanism is more frequent in animals living in polluted areas at urban‐industrial sites. Given that a growing part of the human population is exposed to elevated air pollution levels, we wondered if environmental pollutants might affect melanogenesis in human skin likewise. Epidemiological studies in Caucasians and East Asians indeed sho...

Ultraviolet radiation (UVR) damages the dermis and fibroblasts; and increases melanoma incidence. Fibroblasts and their matrix contribute to cancer, so we studied how UVR modifies dermal fibroblast function, the extracellular matrix (ECM) and melanoma invasion. We confirmed UVR-damaged fibroblasts persistently upregulate collagen-cleaving matrix me...

Carotenoids, a class of phytonutrients, have been well established to boost skin’s innate resistance against Ultraviolet (UV) B‐induced erythema (sunburn). Many of the published clinical studies thus far have focused on measurement of erythema as the primary clinical indicator of skin protection against UVB radiation. More recent studies have shown...

Background: Extrinsic skin aging or photoaging was previously thought to be almost exclusively due to solar ultraviolet (UV) radiation. However, recent literature has described other contributing factors and clarification is thus required as to what extent and what type of daily photoprotection is needed to mitigate extrinsic skin aging. Methods:...

Background: Oral supplementation with a standardized extract from the bark of the French pine (Pycnogenol®) has been reported to benefit the skin. It might thus represent an easy-to-use strategy to improve the skin health of individuals who are exposed to considerable environmental stress in large urban areas. Objective: We investigated if oral...

Increasing evidence on the impact of the different wavelengths of sunlight on the skin demonstrates the need for tailored recommendations of sunscreen according to skin phototype and dermatoses, which is now possible due to advances in the filters and formulations of sunscreens. A selective literature search was performed by an international expert...

Background The human skin microbiota is considered to be essential for skin homeostasis and barrier function. Comprehensive analyses of its function would substantially benefit from a catalog of reference genes derived from metagenomic sequencing. The existing catalog for the human skin microbiome is based on samples from limited individuals from a...

As a barrier organ, the skin is an ideal model to study environmentally-induced (extrinsic) aging. In this review, we explain the development of extrinsic skin aging as a consequence of skin exposure to specific exposomal factors, their interaction with each other, and the modification of their effects on the skin by genetic factors. We also review...

Ultraviolet radiation (UVR) increases the incidence of cutaneous melanoma1-4. The ageing, sun-exposed dermis accumulates UVR damage5, and older patients develop more melanomas at UVR-exposed sites4,6,7. As fibroblasts are functionally heterogeneous and play key roles in the stromal contribution to cancer8,9, we asked whether UVR modifies dermal fib...

In the last decade, Transcription Activator-Like Effector Nucleases (TALEN) and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) based genome engineering have revolutionized our approach to biology. Due to their high efficiency and ease of use, the development of custom knock-out and knock-in animal or cell models is now within re...

Skin aging results from the interaction of genetic and nongenetic so-called exposomal, factors. Among the exposomal factors, chronic, life-long exposure to sunlight is of eminent importance for the development of skin aging characteristics. Importantly, photoaging of human skin is not only caused by ultraviolet (UV) B and A radiation, but is also t...