Ethnic variation in vellus hair follicle size and distribution

Investigating the morphology and genetics of scalp and facial hair characteristics for phenotype prediction

Microscopic traits and ultrastructure of hair such as cross-sectional shape, pigmentation, curvature, and internal structure help determine the level of variations between and across human populations. Apart from cosmetics and anthropological applications, such as determining species, somatic origin (body area), and biogeographic ancestry, the evidential value of hair has increased with rapid progression in the area of forensic DNA phenotyping (FDP). Individuals differ in the features of their scalp hair (greying, shape, colour, balding, thickness, and density) and facial hair (eyebrow thickness, monobrow, and beard thickness) features. Scalp and facial hair characteristics are genetically controlled and lead to visible inter-individual variations within and among populations of various ethnic origins. Hence, these characteristics can be exploited and made more inclusive in FDP, thereby leading to more comprehensive, accurate, and robust prediction models for forensic purposes. The present article focuses on understanding the genetics of scalp and facial hair characteristics with the goal to develop a more inclusive approach to better understand hair biology by integrating hair microscopy with genetics for genotype-phenotype correlation research.

Abdominal, perineal, and genital soft tissue reconstruction with pedicled anterolateral thigh perforator flaps

Background

Pedicled perforator flaps have become a contemporary alternative to muscle flaps for soft tissue reconstruction as they have reduced donor site morbidity, avoid the need for microsurgical transfer, and are versatile and reliable. The anterolateral thigh (ALT) flap was first introduced as a free flap and has since gained popularity as a pedicled flap. Here we review our experience using pedicled ALT flaps for regional soft tissue reconstruction.

Methods

We retrospectively reviewed all patients who underwent loco-regional soft tissue reconstruction using pedicled ALT flaps between March 2014 and October 2018, with the goal of identifying potential applications of pedicled ALT flaps. The following aspects of each case were reviewed: patient demographics, defect location and size, comorbidities such as previous radiotherapy, flap details, clinical follow-up, and postoperative complications.

Results

Our analysis demonstrates the versatility of pedicled ALT flaps in a variety of indications to successfully cover large abdominal, perineal, and genital soft tissue defects. Depending on the patient’s needs to achieve more bulk or stability in the reconstruction, the ALT flap was individually tailored with underlying muscle or fascia. The average follow-up was 7 months (range: 3–13 months).

Conclusions

Pedicled ALT flaps are a valuable reconstructive option for soft tissue defects located within the pedicle’s range, from the lower abdomen to the perianal region. These flaps are usually raised from a non-irradiated donor site and are sufficient for covering extensive soft tissue defects. Three-dimensional reconstruction of the defect using pedicled ALT flaps allows for anatomical function and minor donor sites.

Level of evidence: Level IV, therapeutic study.

Incidence of Cutibacterium acnes from shoulder arthroplasties in Asians: ethnic differences should be considered

BACKGROUND

Most studies on Cutibacterium acnes in shoulder surgery have been conducted in the Western population, and studies on Asians are rare. We evaluated the incidence and risk factors of C acnes in shoulder arthroplasty in Asians.

METHODS

We retrospectively analyzed 154 patients between January 2017 and May 2019 who underwent shoulder arthroplasty. Swabs were taken after skin preparation from the skin surface of the anterior acromion, axilla, and joint fluid to study the incidence of C acnes. Before skin preparation we also collected swabs from the anterior acromion, axilla, and thigh from 59 of the 154 patients.

RESULTS

Eight of 154 patients after and 6 of 59 patients before skin preparation were positive for C acnes. C acnes were found in 2 patients at the anterior acromion and in 6 at the synovial joint after skin preparation and in 1 patient at the axilla, in 5 at the anterior acromion, and in 3 at the thigh before preparation. History of steroid injection and number of steroid injections were significantly associated with C acnes isolation (P = .039 and P = .006, respectively), whereas age, sex, body mass index, shoulder surgery history, hypertension, diabetes, and cerebrovascular disease were not, as were serum inflammatory markers, including white blood cell count, C-reactive protein level, and erythrocyte sedimentation rate.

CONCLUSION

A total of 5.2% of the patients after skin preparation and 10.2% of patients before skin preparation were found to be positive for C acnes. The incidence of C acnes in patients who underwent shoulder arthroplasties in Asia was low and, thus, ethnic differences should be considered for C acnes. The history and number of steroid injections were associated with isolation of C acnes.

Preparation, properties and challenges of the microneedles-based insulin delivery system

Microneedle technology relates to pharmacy, polymer chemistry and micromachining. Microneedle can effectively deliver insulin into systemic circulation across the skin. This process does not affect the activity of insulin. Compared to subcutaneous injection, microneedles cause less pain for their special structure. This review thoroughly discusses the preparation technologies of the microneedles-based insulin delivery system including solid, hollow, dissolving, phase transition, glucose-responsive microneedle patches. In the meantime, the properties, challenges and clinical/commercial status of the microneedles-based insulin delivery system are also discussed in this review.

Quantification of Hair Follicles in the Scalp in Mexican Mestizo Population

Introduction

There are no reports of the density of hair follicles in the scalp of Mexican mestizo population, necessitating the determination of normal references values for this population compared with other ethnic groups.

Objective

To determine the average hair follicle count on the scalp in Mexican mestizo population.

Materials and Methods

A total of 50 scalp samples (25 men and 25 women) from Mexican mestizo individuals aged between 19 and 60 years, with no clinical evidence of hair disease, obtained by biopsy punch at General Hospital "Dr. Manuel Gea González" were collected over 2 years. The total follicular density, vellus and terminal hair follicles, and the percentage in anagen and catagen-telogen phase were measured. χ² was used as the basic statistical test.

Results

The mean number of total hair follicles in our Mexican mestizo population was 23.2 ± 4.2, which is lower compared with Thais, Iranians, and Caucasians. However, the ratio of terminal and vellus hair follicles was higher than in Thais, Caucasians, and African-Americans. The percentage of terminal hairs in anagen phase was lower than in the other populations, and higher in telogen, without exceeding 15%, established as the normal reference value. There was an association between sex and terminal hairs in telogen phase (p < 0.05). The average follicular density per mm² was slightly higher compared with African-Americans and Asians. Women had more terminal hairs than men.

Conclusions

The density of total follicles is lower in the Mexican mestizo population compared with Iranians, Thais, and Caucasians. However, the greater number of terminal hairs compared to vellus hairs gives the appearance of greater overall volume. The results of this study can be used as a reference for diseases of the scalp in the Mexican population.

The biology and genetics of curly hair

Hair fibres show wide diversity across and within all human populations, suggesting that hair fibre form and colour have been subject to much adaptive pressure over thousands of years. All human hair fibres typically have the same basic structure. However, the three-dimensional shape of the entire fibre varies considerably depending on ethnicity and geography, with examples from very straight hair with no rotational turn about the long axis, to the tightly sprung coils of African races. The creation of the highly complex biomaterials in hair follicle and how these confer mechanical functions on the fibre so formed is a topic that remains relatively unexplained thus far. We review the current understanding on how hair fibres are formed into a nonlinear coiled form and which genetic and biological factors are thought to be responsible for hair shape. We report on a new GWAS comparing low and high curl individuals in South Africa, revealing strong links to polymorphic variation in trichohyalin, a copper transporter protein CUTC and the inner root sheath component keratin 74. This builds onto the growing knowledge base describing the control of curly hair formation.

Scalp as a donor site in children: Is it really the best option?

BACKGROUND

Since 2003 we have used the scalp as a donor site for split skin grafts (SSGs) in major burns when there was a shortage of conventional donor areas. However, we seen a high incidence of complications, contrary to international experience.

OBJECTIVE

The aim of this study was to analyze the results and complications related to the scalp as a donor site and to determine whether there is an association between our specific patient population and the complications encountered.

METHODS

A retrospective review of our scalp donor site outcomes over a 12-year period was conducted. The cohort included 25 patients, 15 of black African descent, nine of mixed race and one Caucasian. The various hair types were identified based on ethnicity and classified into eight types. Most of our patients had hair types VI-VIII. None of these patients had scalp burns and all received standard burn treatment. The SSGs were taken with an electric dermatome with a standard micrometric setting of 0.2mm. Complications were categorized into short- or long-term, with a mean follow-up time of 1.59years.

RESULTS

The mean age of the 25 children was 5.7years. Nineteen sustained flame burns and 6 sustained hot water burns, with a mean total body surface area of 44.9%. A total of 43 scalp procurements were performed in the 25 patients studied. The group of 15 black African patients (hair types VI-VIII) had a total of 22 procurements, the nine patients of mixed race (hair types III-V) had 18 procurements and the single Caucasian patient (hair types II-III) had two procurements. The median healing time was 15days, 11.8days and 8.5days, respectively, per group. Significant complications were encountered, including folliculitis 44%, non-healing wounds 52%, alopecia 16% and visible, hypopigmented scars 3%. One patient had a hypertrophic scar and no hair transfers to the recipient areas were observed. The various hair types correlated with the complications encountered. Five children, with an average burn size of 65.2% (range: 40-85%) died of sepsis. Due to the small sample size, the only statistically significant findings were related to the total body surface area of the burn and the number of times skin was harvested from the scalp, with a p-value of 0.005. The p-values for the healing times related to the first, second and third croppings, were p=0.022, p=0.00032 and p<0.001 respectively.

CONCLUSION

Our study suggests that in pediatric patients of black African descent (hair types VI-VIII) the scalp is not an ideal donor area, due to the unacceptably high incidence of complications. Hence, every precaution should be taken when it becomes necessary to harvest donor skin from the scalp.

Towards a body hair atlas of women of caucasian ethnicity

OBJECTIVE

A preliminary study was conducted in 17 female volunteers (mean age 29.8 years) to gain deeper insights into the characteristics of terminal Caucasian female body hair of different body parts. The focus on Caucasian women was driven by the high number of different scalp hair phenotypes in this ethnicity and intended to identify relevant differences between body areas to improve body hair removal approaches.

METHODS

Multiple growth parameters and structural parameters were assessed for hair on the upper arm, forearm, upper leg, lower leg, axilla and intimate area and compared to scalp data.

RESULTS

In particular, macroscopic and much less microscopic or hair surface properties differ strikingly in the investigated body areas. Hair density on the body is much lower than on scalp with the highest hair density in the axilla and intimate area. Multihair follicular units are described for scalp but were also found to a smaller proportion in the axilla and the intimate area. Substantial percentages of hair triplets are only found on the scalp and intimate area. Hair diameter is highest in the intimate area, followed by axillary and lower leg hair and correlates with a faster hair growth rate. The angle of emerging hair is smallest in the intimate area, axilla and on the lower leg. Hair shafts on the lower leg and in the axilla have most overlapping cuticle layers, but independent of body region, no significant differences in the mean thickness of cuticle layers were detectable. In addition, no differences were found in the mean distance between cuticle layer edges along the hair shaft and the hair surface roughness. Hair on the scalp, forearm, upper arm and upper leg had an almost round shape, whereas hair of the lower leg, intimate area and axilla had more elliptical shape. Hairs on the arm showed the highest luminance values and no visible medulla. The darkest hairs were in the axilla and intimate area containing the highest level of visible medulla in hair shafts.

CONCLUSION

To our knowledge, this is the first systematic study comparing terminal hair properties in all cosmetically relevant body regions in Caucasian women.

Understanding engineered nanomaterial skin interactions and the modulatory effects of ultraviolet radiation skin exposure

The study of engineered nanomaterials for the development of technological applications, nanomedicine, and nano-enabled consumer products is an ever-expanding discipline as is the concern over the impact of nanotechnology on human environmental health and safety. In this review, we discuss the current state of understanding of nanomaterial skin interactions with a specific emphasis on the effects of ultraviolet radiation (UVR) skin exposure. Skin is the largest organ of the body and is typically exposed to UVR on a daily basis. This necessitates the need to understand how UVR skin exposure can influence nanomaterial skin penetration, alter nanomaterial systemic trafficking, toxicity, and skin immune function. We explore the unique dichotomy that UVR has on inducing both deleterious and therapeutic effects in skin. The subject matter covered in this review is broadly informative and will raise awareness of potential increased risks from nanomaterial skin exposure associated with specific occupational and life style choices. The UVR-induced immunosuppressive response in skin raises intriguing questions that motivate future research directions in the nanotoxicology and nanomedicine fields.

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.

Toxicokinetics of captan and folpet biomarkers in dermally exposed volunteers

To better assess biomonitoring data in workers exposed to captan and folpet, the kinetics of ring metabolites [tetrahydrophthalimide (THPI), phthalimide (PI) and phthalic acid] were determined in urine and plasma of dermally exposed volunteers. A 10  mg kg(-1) dose of each fungicide was applied on 80  cm(2) of the forearm and left without occlusion or washing for 24  h. Blood samples were withdrawn at fixed time periods over the 72  h following application and complete urine voids were collected over 96  h post-dosing, for metabolite analysis. In the hours following treatment, a progressive increase in plasma levels of THPI and PI was observed, with peak levels being reached at 24  h for THPI and 10  h for PI. The ensuing elimination phase appeared monophasic with a mean elimination half-life (t(½) ) of 24.7 and 29.7 h for THPI and PI, respectively. In urine, time courses PI and phthalic acid excretion rate rapidly evolved in parallel, and a mean elimination t(½) of 28.8 and 29.6  h, respectively, was calculated from these curves. THPI was eliminated slightly faster, with a mean t(½) of 18.7  h. Over the 96  h period post-application, metabolites were almost completely excreted, and on average 0.02% of captan dose was recovered in urine as THPI while 1.8% of the folpet dose was excreted as phthalic acid and 0.002% as PI, suggesting a low dermal absorption fraction for both fungicides. This study showed the potential use of THPI, PI and phthalic acid as key biomarkers of exposure to captan and folpet.

Preferential amplification of CD8 effector-T cells after transcutaneous application of an inactivated influenza vaccine: a randomized phase I trial

BACKGROUND

Current conventional vaccination approaches do not induce potent CD8 T-cell responses for fighting mostly variable viral diseases such as influenza, avian influenza viruses or HIV. Following our recent study on vaccine penetration by targeting of vaccine to human hair follicular ducts surrounded by Langerhans cells, we tested in the first randomized Phase-Ia trial based on hair follicle penetration (namely transcutaneous route) the induction of virus-specific CD8 T cell responses.

METHODS AND FINDINGS

We chose the inactivated influenza vaccine - a conventional licensed tetanus/influenza (TETAGRIP) vaccine - to compare the safety and immunogenicity of transcutaneous (TC) versus IM immunization in two randomized controlled, multi-center Phase I trials including 24 healthy-volunteers and 12 HIV-infected patients. Vaccination was performed by application of inactivated influenza vaccine according to a standard protocol allowing the opening of the hair duct for the TC route or needle-injection for the IM route. We demonstrated that the safety of the two routes was similar. We showed the superiority of TC application, but not the IM route, to induce a significant increase in influenza-specific CD8 cytokine-producing cells in healthy-volunteers and in HIV-infected patients. However, these routes did not differ significantly for the induction of influenza-specific CD4 responses, and neutralizing antibodies were induced only by the IM route. The CD8 cell response is thus the major immune response observed after TC vaccination.

CONCLUSIONS

This Phase Ia clinical trial (Manon05) testing an anti-influenza vaccine demonstrated that vaccines designed for antibody induction by the IM route, generate vaccine-specific CD8 T cells when administered transcutaneously. These results underline the necessity of adapting vaccination strategies to control complex infectious diseases when CD8 cellular responses are crucial. Our work opens up a key area for the development of preventive and therapeutic vaccines for diseases in which CD8 cells play a crucial role.

TRIAL REGISTRATION

Clinicaltrials.gov NCT00261001.

Percutaneous absorption and exposure assessment of pesticides

Dermal exposure to a diverse range of chemicals may result from various uses. In order to assess exposure and estimate potential risks, accurate quantitative data on absorption are required. Various factors will influence the final results and interpretations of studies designed to assess the ability of compounds to penetrate the skin. This overview will discuss skin penetration by pesticides, emphasizing key parameters to be considered from the perspective of exposure assessment.

Physicochemical factors that affect metal and metal oxide nanoparticle passage across epithelial barriers

The diversity of nanomaterials in terms of size, shape, and surface chemistry poses a challenge to those who are trying to characterize the human health and environmental risks associated with incidental and unintentional exposures. There are numerous products that are already commercially available that contain solid metal and metal oxide nanoparticles, either embedded in a matrix or in solution. Exposure assessments for these products are often incomplete or difficult due to technological challenges associated with detection and quantitation of nanoparticles in gaseous or liquid carriers. The main focus of recent research has been on hazard identification. However, risk is a product of hazard and exposure, and one significant knowledge gap is that of the target organ dose following in vivo exposures. In order to reach target organs, nanoparticles must first breach the protective barriers of the respiratory tract, gastrointestinal tract, or skin. The fate of those nanoparticles that reach physiological barriers is in large part determined by the properties of the particles and the barriers themselves. This article reviews the physiological properties of the lung, gut, and skin epithelia, the physicochemical properties of metal and metal oxide nanoparticles that are likely to affect their ability to breach epithelial barriers, and what is known about their fate following in vivo exposures.

Transcutaneous anti-influenza vaccination promotes both CD4 and CD8 T cell immune responses in humans

Induction of T cell responses has become one of the major goals in therapeutic vaccination against viral diseases and cancer. The use of the skin as target organ for vaccine has been spurred by recent implication of epithelial dendritic cells in CD8 cell cross-priming and suggests that vaccination via the transcutaneous (TC) route may be relevant in the induction of cellular immune responses. We have previously shown that TC application of nanoparticles, on human skin explants, allows targeting of epidermal dendritic cells, possibly via hair follicles. In this study, we have investigated cellular immune responses against an influenza protein-based vaccine by TC vaccination, compared with i.m. vaccination in humans. In this study on 11 healthy volunteers, we found that a newly developed protocol based on cyanoacrylate skin surface stripping induced a significant increase in IFN-gamma-producing T cells specific for influenza vaccine by ELISPOT assays. Interestingly, TC vaccination induced both effector CD4 and CD8 T cell responses, whereas i.m. injection induced strong effector CD4 in the absence of CD8 T cells, as assessed by intracellular cytokine staining and tetramer analyses. This study proposes new perspectives for the development of vaccination strategies that trigger T cell immune responses in humans.