Predictive Metagenomic Profiling, Urine Metabolomics, and Human Marker Gene Expression as an Integrated Approach to Study Alopecia Areata

Abstract

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.

‘Omics’ Approaches for Studying the Microbiome in Alopecia Areata

“…For example, some of the human gut bacteria can produce biotin 29 and the balance between biotin-producing and biotin-eating bacteria could determine how much biotin is available also for the hair follicle. We can also assume a role for bacteria of the scalp as regards biotin metabolism and our preliminary findings 30 strongly suggest a strict correlation between microbial population inhabiting the scalp of AA subjects and biotin biosynthesis, as predicted by KEGG analysis. This is also true as regards other important pathways related to the immunomodulatory, inflammatory response, and other cellular pathways (eg: ion channels, pores ion channels, inorganic ion transport and metabolism, and so on).…”

Effect of commonly used cosmetic preservatives on skin resident microflora dynamics

“…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 – 35 .…”

Lichen Planopilaris: The first biopsy layer microbiota inspection

“…The findings of the present work are in line with our previous investigation on another form of auto-immune disease affecting the scalp, Alopecia areata [ 63 ]. Indeed, the alterations of GAG degradation have been reported as responsible of abnormalities in hair morphology [ 39 ] and of the alteration of the morphology of the connective tissue surrounding the HF [ 64 ]. Bacteria themselves can use GAGs, as a mask to avoid the recognition by the immune system collaborators [ 65 ].…”

“…The e following step of extraction was carried out with a CombiPAL system injector autosampler (CTC Analytics). The extracted compounds were desorbed in splitless for 3 min at 280°C [ 39 ]. A Clarus 680 (PerkinElmer, Waltham, MA, USA) gas chromatograph equipped with an Elite-624Sil MS Capillary Column (30 m × 0.25 mm i.d., 1.4-μm film thickness; PerkinElmer) was used.…”