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Human microbiome: What's new in scalp diseases

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Nowadays, the study of human microbiome represents a novel diagnostic and therapeutic approach to treat many human conditions, also including that strictly related to skin and scalp. The findings we included in the present work represent just an overview of a larger pioneer study on the involvement of changing of the microbiome in scalp diseases, especially that related to hair growth. Even just preliminary, our results strongly highlighted, for the first time, the role exerted by unbalancing on the normal resident microbial community in hair growth-related conditions.
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... The role of the microbiome has also been reported in hair growth disorders such as non-cicatricial and cicatricial alopecia [39][40][41][49][50][51]. ...
... We further investigated the role of the microbiome in AA and showed, for the first time, the alteration of the "equilibrium" of the composition of the scalp microbiota in subjects affected by AA both at the superficial epidermis level [39] and in the subepidermal compartment of the scalp [39]. Using 16S taxonomic analysis, we revealed that the dysbiosis of the bacterial population on the scalp of subjects affected by AA is mainly due to an increase in Actinobacteria and a decrease in Firmicutes [39], and Propionibacterium and Staphylococcus have been reported as the main genera involved [39]. ...
... We further investigated the role of the microbiome in AA and showed, for the first time, the alteration of the "equilibrium" of the composition of the scalp microbiota in subjects affected by AA both at the superficial epidermis level [39] and in the subepidermal compartment of the scalp [39]. Using 16S taxonomic analysis, we revealed that the dysbiosis of the bacterial population on the scalp of subjects affected by AA is mainly due to an increase in Actinobacteria and a decrease in Firmicutes [39], and Propionibacterium and Staphylococcus have been reported as the main genera involved [39]. ...
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The continuous research advances in the microbiome field is changing clinicians’ points of view about the involvement of the microbiome in human health and disease, including autoimmune diseases such as alopecia areata (AA). Both gut and cutaneous dysbiosis have been considered to play roles in alopecia areata. A new approach is currently possible owing also to the use of omic techniques for studying the role of the microbiome in the disease by the deep understanding of microorganisms involved in the dysbiosis as well as of the pathways involved. These findings suggest the possibility to adopt a topical approach using either cosmetics or medical devices, to modulate or control, for example, the growth of overexpressed species using specific bacteriocins or postbiotics or with pH control. This will favour at the same time the growth of beneficial bacteria which, in turn, can impact positively both the structure of the scalp ecosystem on the host’s response to internal and external offenders. This approach, together with a “systemic” one, via oral supplementation, diet, or faecal transplantation, makes a reliable translation of microbiome research in clinical practice and should be taken into consideration every time alopecia areata is considered by a clinician.
... Among the proposed causes, a link with the gut microbiome has also been hypothesized [5]. Cutibacterium, Staphylococcus, and Corynebacterium were the most common bacteria, while Malassezia was the most common fungus, on healthy scalps [6,7]. Due to its unique features, the scalp is expected to harbor a specific microbiome, which is expected to play a peculiar role in scalp conditions related to hair growth [7]. ...
... Cutibacterium, Staphylococcus, and Corynebacterium were the most common bacteria, while Malassezia was the most common fungus, on healthy scalps [6,7]. Due to its unique features, the scalp is expected to harbor a specific microbiome, which is expected to play a peculiar role in scalp conditions related to hair growth [7]. Several researchers studied the scalp microbiome profile regarding AA and they suggested the notion that an imbalance between skin microbes that maintain skin homeostasis causes inflammation [8][9][10][11][12]. ...
... Several scientific published evidence have reported the strict correlation between microbial disequilibrium and skin conditions [4,5,[7][8][9][10]. Given this growing body of literature, it is becoming increasingly clear that the modulation of the microbiota may be a novel and important adjunct modality. ...
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Little is known about the scalp bacterial composition of alopecia areata (AA) patients. The aim of this study was to investigate the differences in the scalp microbiome of AA patients according to their prognosis, in addition to healthy controls. A total of 33 AA patients and 12 healthy controls (HC) were included in this study. The microbiomes were characterized by sequencing 16S rRNA genes on the Illumina MiSeq platform. The scalp microbiome was more diverse in AA patients compared to HC, but not significantly different according to the severity of AA. Nevertheless, the higher proportion of Corynebacterium species and the lower proportion of Staphylococcus caprae among the Staphylococcus species were noticed in severe AA patients compared to HC or mild AA. The higher ratio of Cutibacterium species to S. caprae was noticed in severe AA. We highlight the potential predictive role of scalp microbiome profiling to a worse prognosis of patients with alopecia areata.
... More recently, scientists have highlighted the crucial role of the microbiome in skin health (Grice, 2014), even though, at present, few studies have focused on hair growth-related conditions. In recent years, researchers' efforts have focused on understanding the unique relationship between the microbial communities inhabiting the human body, from the gut to the oral cavity and skin (Blum, 2017), and more recently, the scalp (Clavaud et al., 2013;Rinaldi et al., 2018;Saxena et al., 2018;Polak-Witka et al., 2020). As the largest organ of the human body, the skin comprises highly diversified ecosystems across different regions of the human body (Byrd et al., 2018;Langan et al., 2018), each of which is characterized by different water and sebum contents, pH values, temperatures, and moisture levels. ...
... Compared to other skin and associated ecosystems, the scalp is thicker, more vascularized, characterized by the presence of more sebaceous glands, and has a more acidic pH. For this reason, the scalp microbial population is of particular interest (Rinaldi et al., 2018). The scalp is inhabited mainly by bacteria belonging to Propionibacterium and Staphylococcus genera (Pinto et al., 2019) and fungi such as Malassezia spp. ...
... Larger studies have been related to dandruff (Clavaud et al., 2013;Xu et al., 2016;Saxena et al., 2018) and seborrheic dermatitis (Park et al., 2012;Soares et al., 2016), whereas other studies have dealt with folliculitis decalvans (Prohic, 2003;Takahata et al., 2007;Zomorodian et al., 2008;Matard et al., 2013;Gomez-Moyano et al., 2014;Rudramurthy et al., 2014). Only recently has the attention of researchers also focused on scalp conditions related to hair growth such as androgenetic alopecia (AGA) (Mahé et al., 2000;Rinaldi et al., 2018) and alopecia areata (AA) (Rinaldi et al., 2018;Ho et al., 2019;Pinto et al., 2019). ...
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Involvement of the microbiome in many different scalp conditions has been investigated over the years. Studies on the role of the scalp microbiome in specific diseases, such as those involving hair growth alterations like non-cicatricial [androgenetic alopecia (AGA), alopecia areata (AA)] and cicatricial alopecia lichen planopilaris, are of major importance. In the present work, we highlighted the differences in microbial populations inhabiting the scalp of AA subjects and a healthy sample cohort by using an integrated approach relying on metagenomic targeted 16S sequencing analysis, urine metabolomics, and human marker gene expression. Significant differences in genera abundances (p < 0.05) were found in the hypodermis and especially the dermis layer. Based on 16S sequencing data, we explored the differences in predicted KEGG pathways and identified some significant differences in predicted pathways related to the AA pathologic condition such as flagellar, assembly, bacterial chemotaxis, mineral absorption, ABC transporters, cellular antigens, glycosaminoglycan degradation, lysosome, sphingolipid metabolism, cell division, protein digestion and absorption, and energy metabolism. All predicted pathways were significantly enhanced in AA samples compared to expression in healthy samples, with the exceptions of mineral absorption, and ABC transporters. We also determined the expression of TNF-α, FAS, KCNA3, NOD-2, and SOD-2 genes and explored the relationships between human gene expression levels and microbiome composition by Pearson's correlation analysis; here, significant correlations both positive (SOD vs. Staphylococcus, Candidatus Aquiluna) and negative (FAS and SOD2 vs. Anaerococcus, Neisseria, and Acinetobacter) were highlighted. Finally, we inspected volatile organic metabolite profiles in urinary samples and detected statistically significant differences (menthol, methanethiol, dihydrodehydro-beta-ionone, 2,5-dimethylfuran, 1,2,3,4, tetrahydro-1,5,7-trimethylnapthalene) when comparing AA and healthy subject groups. This multiple comparison approach highlighted potential traits associated with AA and their relationship with the microbiota inhabiting the scalp, opening up novel therapeutic interventions in such kind of hair growth disorders mainly by means of prebiotics, probiotics, and postbiotics.
... A link between LPP and the microbial population inhabiting the scalp has been also recently reported [20]. As reported for the gut [21] and skin microbiome [22], bacteria and fungi are strongly involved in the healthy status, and the host immune system is recognized as a major stress able to modulate the microbial composition [23]. ...
... Although numerous studies stated the role of bacterial populations in many skin conditions [40][41][42][43], the role of the scalp microbiome in LPP has not been investigated yet. In a previously published work, we reported preliminary data on the superficial epidermis of fifteen LPP subjects [20]. In the present study, we showed for the first time, the peculiar features of the core microbiome in cutaneous samples from LPP patients. ...
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Lichen Planopilaris (LPP) is a lymphatic disease affecting the scalp that is characterized by a chronic and destructive inflammation process, named as ‘cicatricial alopecia’ in which the hair follicles are targeted and may involve predominantly lymphocytes or neutrophils. Scalp and biopsy layers have never been used to investigate microbial community composition and its relative taxa abundances in LPP. We sought to examine the significant taxa of this chronic relapsing inflammatory skin disease, together with inspect the existing connections with metabolic pathways featuring this microbial community. We used a multilevel analysis based on 16S rRNA marker sequencing in order to detect OTU abundances in pathologic/healthy samples, real time PCR for measuring the levels of IL-23 interleukin expression and urinary metabolomics to find out volatile organic metabolites (VOMs). By using a linear regression model, we described peculiar taxa that significantly differentiated LPP and healthy samples. We inspected taxa abundances and interleukin mRNA levels and the Microbacteriaceae family resulted negatively correlated with the IL-23 expression. Moreover, starting from 16S taxa abundances, we predicted the metabolic pathways featuring this microbial community. By inspecting microbial composition, sample richness, metabolomics profiles and the relative metabolic pathways in a cohort of LPP and healthy samples we deepened the contribution of significant taxa that are connected to inflammation maintenance and microbiota plasticity in LPP pathology.
... It has long been implicated in the pathogenesis of acne 29 . An unbalancing in the bacterial population, including C. acnes and S. aureus has been also recently reported in other skin conditions such as seborrheic dermatitis 30 , psoriasis, and rosacea 31 , and alopecia [32][33][34][35] . ...
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Human skin is populated by various microorganisms, the so-called microbiota, such as bacteria, viruses, yeasts, fungi, and archaea. The skin microbiota is in constant contact with the surrounding environment which can alter its eubiotic state. Recently it has been also observed that the application of cosmetic products can alter the balance of the skin microbiota. This effect may be attributed to many factors including the residual activity of the preservatives on the skin. In the present work, we studied the effect of eleven preservatives commonly found in cosmetic products on Propionibacterium acnes, Staphylococcus epidermidis, and Staphylococcus aureus in vitro using 3D skin models and culture-dependent methods. Also, the effect on Histone deacetylase 3 (HDAC3) has been investigated. Among tested combinations, three resulted as the best suitable for restoring a pre-existing dysbiosis since they act moderately inhibiting C. acnes and strongly S. aureus without simultaneously inhibiting the growth of S. epidermidis. The other four combinations resulted as the best suitable for use in topical products for skin and scalp in which it is necessary to preserve the eubiosis of the microbiota. Some of the tested were also able to increase HDAC3 expression. Taking together these data highlight the role of preservatives of skin resident microflora dynamics and could provide a reference for correctly choice preservatives and dosage in cosmetic formulations to preserve or restore homeostasis of skin microbiota.
... [13][14][15] Gut microbiota has been recently reported playing a pivotal role in controlling immunomodulation in autoimmune conditions including AA. 16 More recently, a role for the microbial population inhabiting the scalp has also been hypothesized in hair growth disorders. 17 Therefore, microbial dysbiosis has been deeply investigated in subjects affected by AA. 18 Propionibacterium and Staphylococcus have been reported as the main genera involved in microbial shift and a different microbial composition between healthy and AA affected subjects have also been reported at the different area surrounding hair follicle. 18 Understanding the role of the microbial population inhabiting the human body, including the scalp, remain a challenge but the advent of novel technologies as the effort of many research groups on microbiome field could provide in the nearest future a clearest framework about the strict relationship between human healthiness and symbiotic microorganism resident on the different ecosystem of our body. ...
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Nowadays, the involvement of the microbiome in human health and many human diseases, including that strictly related to the scalphas been brought to the light. Indeed, more recently, authors highlighted the presence of a significant microbial shift both in nonscarring (Androgenetic alopecia and Alopecia areata) and scarring Alopecias. The advent of novel technologies together with the effort of many scientists in the microbiome field could provide in the nearest future a clearest framework about the strict relationship between human healthiness and symbiotic microorganism resident on different ecosystem of our body. In this view, the use of Omics approaches has to be considered as no longer negligible when studying the microbiome implication in human health and disease.
... Findings from the scientific community have brought to light the involvement of skin microbiota in human health as in dermatological conditions [10][11][12][13][14]. ...
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The skin microbiome is in a very close mutualistic relationship with skin cells, influencing their physiology and immunology and participating in many dermatological conditions. Today, there is much interest in cosmetic ingredients that may promote a healthy microbiome, especially postbiotics, mainly derived from fermented products. In the present work, we studied the effects on skin microbiota of new patented natural oils obtained by unique fermentation technology in vivo. Three fermented oils were evaluated: F-Shiunko (FS), F-Artemisia® (FA) and F-Glycyrrhiza® (FG). The active components were included as single active component or in combination (FSAG) in an emulsion system. A total of 20 healthy women were recruited, and skin microbiota from cheek were analyzed by mean of swab sampling at T0 and T1 (after 4 weeks of a one-day treatment). 16S sequencing revealed that the treatment with fermented oils improved microbiome composition and alpha-diversity. It was shown that higher biodiversity reflects in a healthier microbial ecosystem since microbial diversity decreases in the presence of a disease or due to aging. The treatment also resulted in a more “beneficial” and “younger” microbial community since a significant decrease in Proteobacteria and the increase in Staphylococcus were reported after the treatment with fermented oils.
... Topically applied minoxidil and orally administered finasteride have been shown to be effective in countering the effects of DHT and reducing the production of DHT, respectively [5] [6] [7]. It has also been suggested that abnormal propagation of pathogens such as dermal bacteria and their toxins induce hair loss [8]. ...
... But poor knowledge is currently available about the impact of changing in scalp microbial communities in hair disorders Xu et al., 2016). In a recently published work (Rinaldi et al., 2018) we reported, for the first time, evidence about a microbial shift in hair loss disorder, such as Alopecia androgenetica, AA and Lichen planopilaris. In the present work, we reported data on patients affected by Alopecia areata, with the aim to study the impact of the diet on microbiome changing related to scalp disease Thirty subjects affected by Alopecia Areata (20-60 years old; 30% male) were included in the study. ...
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Introduction: The impact of diet on hair growth disorder is well established as the influence of diet on the gut microbiome. Poor information is still available as regards the link between microbiome, especially scalp microbiome and hair diseases. Aim: In the present work, we reported data on patients affected by Alopecia areata with the aim to study the impact of the diet on microbiome changing related to scalp disease. Methodology: Data from the dietary survey, qRT-PCR on main bacterial strains inhabiting the scalp were matched and compared each other and with healthy population. Results: Beyond the diet’s well-known impact on general human health, our results highlighted the role of one’s diet in modifying scalp microbiome, which in turn seems to have an impact on AA evolution. Conclusions: Our results provide the first evidence of strict intercorrelation between microbial dysbiosis on the scalp of patients with AA and dietary habits.
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en Objective The human scalp harbours a vast community of microbiotal mutualists. Androgenetic alopecia (AGA), the most common form of hair loss in males, is a multifactorial condition involving genetic predisposition and hormonal changes. The role of microflora during hair loss remains to be understood. After having characterized the scalp microbiota of 12 healthy male subjects and 12 AGA male subjects (D0), the aim of this investigation was to evaluate the capacity of Lindera strychnifolia root extract (LsR) to restore a healthy bacterial and fungal scalp microflora after 83 days (D83) of treatment. Material and methods The strategy used was based on high‐throughput DNA sequencing targeting the encoding 16S ribosomal RNA for bacteria and Internal Transcribed Spacer 1 ribosomal DNA for fungi. Results Test analysis of relative abundance comparing healthy and AGA subjects showed a significant increase of Cutibacterim acnes (P < 0.05) and Stenotrophomonas geniculata (P < 0.01) in AGA subjects. AGA scalp condition was also associated with a significant (P < 0.05) decrease of Staphylococcus epidermidis relative abundance. A lower proportion of Malassezia genus in samples corresponding to AGA scalps and an increase of other bacterial genera (Wallemia, Eurotium) were also noted. At the species level, mean relative abundance of Malassezia restricta and Malassezia globosa were significantly lower (P < 0.05) in the AGA group. Eighty‐three days of treatment induced a significant decrease in the relative abundance of C. acnes (P < 0.05) and S. geniculata (P < 0.01). S. epidermidis increased significantly (P < 0.05). At the same time, LsR treatment induced a significant increase in the proportion of M. restricta and M. globosa (P < 0.05). Conclusion Data from sequencing profiling of the scalp microbiota strongly support a different microbial composition of scalp between control and AGA populations. Findings suggest that LsR extract may be a potential remedy for scalp microbiota re‐equilibrium. Resume Francais fr Objectif Le cuir chevelu humain abrite une vaste communauté microbienne. L'alopécie androgénétique (AGA), la forme la plus courante de perte de cheveux chez l'homme, est une pathologie multifactorielle impliquant une prédisposition génétique et des changements hormonaux. Le rôle de la microflore lors de la chute des cheveux reste à comprendre. Après avoir caractérisé le microbiote du cuir chevelu de 12 hommes sans alopecie et 12 hommes porteur d'une alopécie, (J0), l'objectif de cette étude était d'évaluer la capacité de l'extrait de racine de Lindera strychnifolia (LsR) à restaurer une microflore bactérienne et fongique saine du cuir chevelu après 83 jours (D83) de traitement. Matériel et méthodes La stratégie utilisée était basée sur un séquençage d'ADN à haut débit ciblant l'ARN ribosomal 16S codant pour les bactéries et l'ADN ribosomal de l'espaceur transcrit interne 1 pour les champignons. Résultats Une augmentation significative de Cutibacterim acnes (P < 0,05) et Stenotrophomonas geniculata (P < 0,01) chez les sujets AGA a ete note a J0 comparativement aux sujets non alopecique. L'état du cuir chevelu AGA était également associé à une diminution significative (P < 0,05) de l'abondance relative de Staphylococcus epidermidis. Une plus faible proportion du genre Malassezia dans les échantillons correspondant aux cuirs chevelus AGA et une augmentation d'autres genres bactériens (Wallemia, Eurotium) ont également été notées. Au niveau des espèces, l'abondance relative moyenne de Malassezia restricta et Malassezia globosa était significativement plus faible (P < 0,05) dans le groupe AGA. Quatre‐vingt‐trois jours de traitement ont induit une diminution significative de l'abondance relative de C. acnes (P < 0,05) et S. geniculata (P < 0,01). S. epidermidis a augmenté de manière significative (P < 0,05). Dans le même temps, le traitement LsR a induit une augmentation significative de la proportion de M. restricta et M. globosa (P < 0,05). Conclusion Les données de séquençage soutiennent fortement une composition microbienne différente du cuir chevelu entre les populations témoin et AGA. Les résultats suggèrent que l'extrait de LsR peut être un remède potentiel pour le rééquilibre du microbiote du cuir chevelu.
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