Immunopathology of the human hair follicle

Hair Loss and Telogen Effluvium Related to COVID-19: The Potential Implication of Adipose-Derived Mesenchymal Stem Cells and Platelet-Rich Plasma as Regenerative Strategies

The diffusion of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inducing coronavirus disease 2019 (COVID-19) has increased the incidence of several dermatological disorders, including hair loss (HL). This article aims to review the literature regarding the incidence of HL and telogen effluvium (TE) in COVID-19 patients and critically appraise the available evidence regarding the role of regenerative strategies like Platelet-Rich Plasma (PRP) and Human Follicle Stem Cells (HFSCs). A literature review regarding the correlation of HL and TE in COVID-19 patients analyzing the biomolecular pathway involved and the role of regenerative strategies was performed using PubMed, MEDLINE, Embase, PreMEDLINE, Scopus, and the Cochrane databases. Observational studies revealed an escalated incidence of pattern HL and TE in COVID-19 patients. Psychological stress, systemic inflammation, and oxidative stress are potential culprits. Proinflammatory cytokines and stress hormones negatively affect the normal metabolism of proteoglycans. Reduced anagenic expression of proteoglycans is a potential mediating mechanism that connects HL to COVID-19. Currently, only one study has been published on PRP against HL in COVID-19 patients. Further controlled trials are required to confirm PRP and HFSCs efficacy in COVID-19 patients.

Linear Lichen Planopilaris of the Face: Case Report and Review

We describe the case of a 45-year-old man who presented with a 5-month history of unilateral pruritic linear erythematous papules and atrophy on the chin and mandibular area. Dermoscopy showed areas of cicatricial alopecia with absence of follicular openings, perifollicular erythema and pigment. Lichen planopilaris of the face is a rare variant with only 13 cases reported in the literature.

Immunohistochemistry: relevance in dermatology

Use of immunohistochemical technique is increasing in diagnosing various diseases. In many situations it may not be possible to differentiate entities with overlapping clinical and histopathological features. Immunostaining of cellular antigens is immensely helpful in such cases. Immunohistochemistry (IHC) has also been in use for targeted cancer therapy. In this article, the discussion will be restricted to use of IHC in dermatological disorders and use of classical antigens with brief updating of some important newly discovered antigens.

Drug delivery into the skin by degradable particles

Recently, it was demonstrated that particles could be utilized as carrier systems for drugs into the hair follicles. In the present study, a two-component drug delivery system is presented consisting of degradable particles loaded with fluorescein isothiocyanate and a separate protease formulation for degradation. The particles were applied alone, 30 min previous to the protease application and simultaneously with the protease onto porcine skin. Subsequently, biopsies were removed, and the penetration depths of the particles were analyzed using laser scanning microscopy. The obtained results demonstrate that the particles alone achieved a penetration depth of around 900 μm. Similar results were obtained for the successive application of particles and protease, whereas a release of the fluorescent dye was only observed in the upper 250 μm corresponding to the penetration depth of the protease. In the case of the simultaneous application, the particles were partly dissolved before application, leading to a reduced particle size and diminished penetration depth. The results revealed that degradable particles are a promising tool for drug delivery into the skin.

Increased hair shedding may be associated with the presence of Pityrosporum ovale

BACKGROUND AND OBJECTIVE

Although the available data show that hair loss is an important cosmetic problem worldwide, the pathogenesis of common hair shedding is not fully understood. The aim of this study was to evaluate the association between hair shedding and cutaneous Malassezia infection. Malassezia fungi have been the suspected cause of dandruff for more than a century. Previously referred to as Pityrosporum ovale or P. orbiculare, these fungi are now known to consist of at least seven species.

METHODS

Over a 4-year period, we obtained 300 hair samples from medical students. Based on the clinical history and a hair-pull test, the participants were divided into two groups: normal subjects and subjects with hair shedding. The students' scalp skin was gently scraped, smeared on a slide, colored by methylene blue, and observed under 10x magnification.

RESULTS

All participants who had positive smears with >or=3 P. ovale organisms per low-power microscopic field (10x) were defined as 'carriers.' Seventy-six percent of students were Malassezia carriers. The prevalence of positive smears was significantly higher among subjects with hair shedding than among normal subjects (89.92% vs 9.52%, p<0.001). Furthermore, participants with positive smears had a significantly higher frequency of hair loss complaints and positive hair-pull tests.

CONCLUSION

The proportion of subjects who were carriers of Malassezia yeasts was significantly higher in the group with hair shedding, and our results therefore raise the possibility of a relationship between this unicellular organism and hair loss. Our study findings should be explored in a larger series of patients.

Langerhans cell microgranulomas (pseudo-pautrier abscesses): morphologic diversity, diagnostic implications and pathogenetic mechanisms

The term 'Langerhans cell microgranuloma' (LCM) was introduced a decade ago to draw attention to focal collections of these cells within the epidermal layer that develops during certain immune reactions. In spite of a growing awareness of this phenomenon during the past decade, few reports have focused on the development and phenotype of LCM. In this commentary, we review the historical development of the concept of LCM, demonstrate the salient immunomorphologic characteristics of LCM, and advance a hypothesis to explain their sequential evolution and formation.

Mechanism of apoptotic regulation of follicular regression: toward understanding the molecular basis for tissue remodeling and regeneration

“There are one hundred and ninety-three living species of monkeys and apes. One hundred and ninety-two of them are covered with hair. The exception is a naked ape self-named Homo sapiens.” —Desmond Morris, The Naked Ape (1967)

Controls of hair follicle cycling

Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.