The seasonal development dynamics of the yak hair cycle transcriptome.

BACKGROUND: Mammalian hair play an important role in mammals' ability to adapt to changing climatic environments. The seasonal circulation of yak hair helps them adapt to high altitude but the regulation mechanisms of the proliferation and differentiation of hair follicles (HFs) cells during development are still unknown. Here, using time series data for transcriptome and hormone contents, we systematically analyzed the mechanism regulating the periodic expression of hair development in the yak and reviewed how different combinations of genetic pathways regulate HFs development and cycling. RESULTS: This study used high-throughput RNA sequencing to provide a detailed description of global gene expression in 15 samples from five developmental time points during the yak hair cycle. According to clustering analysis, we found that these 15 samples could be significantly grouped into three phases, which represent different developmental periods in the hair cycle. A total of 2316 genes were identified in these three consecutive developmental periods and their expression patterns could be divided into 9 clusters. In the anagen, genes involved in activating hair follicle growth are highly expressed, such as the WNT pathway, FGF pathway, and some genes related to hair follicle differentiation. In the catagen, genes that inhibit differentiation and promote hair follicle cell apoptosis are highly expressed, such as BMP4, and Wise. In the telogen, genes that inhibit hair follicle activity are highly expressed, such as DKK1 and BMP1. Through co-expression analysis, we revealed a number of modular hub genes highly associated with hormones, such as SLF2, BOP1 and DPP8. They may play unique roles in hormonal regulation of events associated with the hair cycle. CONCLUSIONS: Our results revealed the expression pattern and molecular mechanisms of the seasonal hair cycle in the yak. The findings will be valuable in further understanding the alpine adaptation mechanism in the yak, which is important in order to make full use of yak hair resources and promote the economic development of pastoral plateau areas.

Assessment of markers expressed in human hair follicles according to different skin regions.

BACKGROUND: Body region-dependent hair follicle (HF) characteristics are concerned with follicular size and distribution, and have been demonstrated to have characteristics for each region of the body. OBJECTIVES: The aim of the present study was to investigate the expression patterns of the markers called cytokeratin 15 (K15), cytokeratin 6 (K6) and monoclonal antibody Ki-67, and also apoptosis in HFs, which can be observed in different parts of the human body. MATERIAL AND METHODS: In this study, healthy human HFs were taken by biopsy from 5 various donor sites of the human body: the scalp, the leg, the abdomen, the back and waist. HF-containing skin specimens taken using cryosection were stained with hematoxylin & eosin (H&E) and K15, K6, Ki-67 and terminal deoxynucleotidyl transferase-mediated digoxigenin-dNTP nick end-labelling (TUNEL) immunofluorescence staining protocol was performed. RESULTS: Different skin regions from the human body were examined histologically. While the HFs of scalp tissue showed anatomically obvious hair layers, some hair sections from other regions, like the leg, the abdomen, back and waist, were not as distinct as in the scalp region. According to our findings, K15 expression was highest in the scalp. In addition, the immunoreactivity (IR) intensity of K15 was significantly decreased in the HFs on the waist and abdominal regions, compared to the scalp and back regions (p < 0.001). However, the IR intensity of K6 in the scalp region was statistically significantly higher than the IR intensity of K6 in the abdomen region (p < 0.05). Moreover, we showed intraepithelial apoptosis and proliferation of keratinocytes in the bulge of HF. In the study, Ki-67-positive and TUNEL-positive cell numbers were not statistically significant (p > 0.05). CONCLUSIONS: Our findings are important for further investigation of molecular aspects of the human hair follicle stem cells compartments in health and disease, which might be a promising model for comparative studies with different human diseases.

Carcinogenicity assessment of the Hedgehog pathway inhibitor, vismodegib in Tg.rasH2 mice and Sprague-Dawley rats.

Vismodegib (also known as GDC-0449) is a novel small molecule inhibitor of the Hedgehog (Hh) signaling pathway currently approved for the treatment of metastatic or locally advanced basal cell carcinoma (BCC) in humans. Its tumorigenic potential was assessed in dedicated carcinogenicity studies in rasH2 transgenic (Tg.rasH2) mice and Sprague Dawley (SD) rats. Tumorigenicity potential of vismodegib was identified in rats only and was limited to benign hair follicle tumors, including pilomatricomas and keratoacanthomas at exposures of ≥0.1-fold and ≥0.6-fold, respectively, of the steady-state exposure (AUC0-24h) of the recommended human dose. No malignant tumors were identified in either species. Overall, the totality of pharmacology and nonclinical safety data (lack of genotoxicity, in vitro secondary pharmacological binding, and immunoregulatory effects, and limited effects on the endocrine system) suggests that the development of the benign hair follicle tumors may be related to pharmacologically-mediated disruption of hair follicle morphogenesis, although the exact mechanism of tumorigenesis is unclear. Hair follicle tumors have not been reported in vismodegib-treated patients. The relevance of this finding in rats to patients is uncertain.

Comprehensive assessment of shockwave intensity: Transcriptomic biomarker discovery for primary blast-induced mild traumatic brain injury using the mammalian hair follicle.

OBJECTIVE: Primary blast-induced mild traumatic brain injury (mTBI) is an injury experienced during modern warfare due to exposure to the pressure waves produced by the detonation of explosives. With virtually no apparent physical damage or symptoms presented, there is a need for more objective and accessible mTBI biomarkers posing minimal invasiveness risk. METHODS: We measured the transcriptomic sensitivity of the hair follicles in relation to the severity of primary blast-derived TBI. An Advanced Blast Simulator system was used to expose male rats to single pulse shock waves (intensities ranging from 15 to 30 psi) in a head-only fashion. Gene differential expression (DE) and gene set (GS) analyses were conducted in the rat whisker hair follicles and the whole blood samples. RESULTS: While shared cellular function, themes were found across the exposure groups, some gene sets under such themes were unique to the exposure conditions. Intensity-specific pathway enrichment patterns within shared GS themes were also identified. Furthermore, while exhibited shared pathways, the blood transcriptome showed substantially fewer enriched gene sets compared with the hair follicles across all exposure conditions. CONCLUSIONS: Accordingly, we demonstrate the potential of mammalian hair follicles serving as an additional source for biomarker discovery and for diagnosing mTBI with high accessibility.

Assessment of penetration of Ascorbyl Tetraisopalmitate into biological membranes by molecular dynamics.

The present work, involves the simulation of the transport of a vitamin C derivative, Ascorbyl Tetraisopalmitate (ATI), through human skin by molecular dynamics. Percutaneous absorption of the ATI molecule through the infundibulum, an important route of absorption into the hair follicle of the human skin, has been modeled and compared with the stratum corneum membrane. The comparative study was done using molecular dynamics with Martini force field. In infundibulum, a single ATI molecule require more time to penetrate, and the data obtained suggested that a high concentration of ATI molecule accelerated the process of penetration. In conclusion, the ATI molecule was found to have more affinity towards the stratum corneum as compared with the infundibulum, and it followed a straight pathway to penetrate (until 600ns of simulation). In the infundibulum, it showed less affinity, more mobility and followed a lateral pathway. Thus, this work contributes to a better understanding of the different molecular interactions during percutaneous absorption of active molecules in these two different types of biological membranes.

Lentivirus Live Cell Array for Quantitative Assessment of Gene and Pathway Activation during Myogenic Differentiation of Mesenchymal Stem Cells.

Stem cell differentiation involves multiple cascades of transcriptional regulation that govern the cell fate. To study the real-time dynamics of this complex process, quantitative and high throughput live cell assays are required. Herein, we developed a lentiviral library of promoters and transcription factor binding sites to quantitatively capture the gene expression dynamics over a period of several days during myogenic differentiation of human mesenchymal stem cells (MSCs) harvested from two different anatomic locations, bone marrow and hair follicle. Our results enabled us to monitor the sequential activation of signaling pathways and myogenic gene promoters at various stages of differentiation. In conjunction with chemical inhibitors, the lentiviral array (LVA) results also revealed the relative contribution of key signaling pathways that regulate the myogenic differentiation. Our study demonstrates the potential of LVA to monitor the dynamics of gene and pathway activation during MSC differentiation as well as serve as a platform for discovery of novel molecules, genes and pathways that promote or inhibit complex biological processes.

The concept of the onychodermis (specialized nail mesenchyme): an embryological assessment and a comparative analysis with the hair follicle.

BACKGROUND: Recently, an intriguing concept was introduced into the literature that defines the area underlying the nail bed as a specific mesenchymal substructure unique to the nail organ. It has been termed onychodermis. The onychodermis expresses CD10 with remarkable specificity. Herein, we compare adult and fetal human hair follicles with fetal nail organs in an attempt to draw analogies for the mesenchyme associated with both adnexal structures. METHODS: We examined immunohistochemically samples from adult and fetal hair follicles for the expression of CD10, CD34 and the mesenchymal stem cell marker nestin and compared the antigen profile with that of the fetal nail organ. RESULTS: The CD10-positive/CD34-negative onychodermis is prominently visible at the end of the second trimester. A corresponding follicular structure was not identified, either in the adult or in the developing hair follicle. Nestin staining does not define the onychodermis. CONCLUSIONS: The concept of the onychodermis is equally valid in the developing nail organ where it is also defined by its expression for CD10. Its function may be related to the anchorage of the overlying nail bed but may also involve a more dynamic role in the induction of hard keratins in the latter, contributing to the formation of the nail plate.

Retinoic acid and dimethyl sulfoxide promote efficient delivery of transgenes to mouse skin by topically transdermal penetration.

Simple and efficient gene transfer to the skin would facilitate many local and systemic gene therapy applications. This study reports a novel approach that allows expression of plasmid DNA in epidermis and hair follicle cells with dimethyl sulfoxide (DMSO) after pre-treatment with depilation and retinoic acid (RA) for the purposes of gene therapy. This study investigated the transdermal efficacy of gene to mouse skin when utilizing DMSO after RA pre-treatment. Retinoic acid pre-treatment can increase the efficiency of transfection. This finding indicates that one can more effectively and much less expensively make use of genes therapy to treat diseases of the hair and skin.

Human percutaneous absorption of a direct hair dye comparing in vitro and in vivo results: implications for safety assessment and animal testing.

Although in vitro skin absorption studies often detect small residues of applied test material in the epidermis/dermis, it is uncertain whether the residue is within the living skin. We studied the dermal absorption of a hair dye hydroxyanthraquinone-aminopropyl methyl morpholinium methosulphate (HAM) in human skin in vivo and in vitro. In vivo, skin (back and scalp) received 0.5% HAM in a commercial formulation at 20microg/cm2 After 0.5 or 48h, skin was tape stripped, followed by cyanoacrylate biopsies (CAB). Sebum from scalp sites was collected for 48h. In vitro, skin was treated with 20mg/cm2 dye for 0.5h, penetration determined after 24h. In vivo, at 0.5h, total recovery (back) was 0.67microg/cm2 (tape strips+CAB). Fluorescence microscopy showed HAM in the hair follicle openings (HFO). At 0.5h, scalp tape strips contained 1.80microg/cm2, HFO 0.82microg/cm2. At 48h, HFO contained 0.21microg/cm2, sebum 0.80microg/cm2. In vivo, skin residues were in the non-living skin and eliminated via desquamation and sebum secretion. In vitro, the SC contained 1.50microg/cm2, epidermis/dermis 0.86microg/cm2, receptor fluid<0.04microg/cm2, a total of 0.90microg/cm2 was considered to be bioavailable. In vitro epidermis/dermis residues were nearly identical to those located in non-living skin in vivo. In conclusion, in vitro percutaneous penetration studies may produce seemingly bioavailable material , which raises the need for a Threshold of Skin Absorption (TSA) addressing a negligible dermal absorption in order to avoid unnecessary in vivo toxicity studies on substances that produce no significant human systemic exposure.

The human hair follicle: glycoprotein-related antigenic profile of distinct keratinocyte populations in vivo and their alterations in vitro.

The cell surface expression of three glycoprotein antigens, as defined by the monoclonal antibodies BT 15, T 43, and MH 99, was investigated in follicular keratinocyte populations in vivo. In addition, the regulation of glycoprotein synthesis was studied in follicular and interfollicular keratinocytes cultured in vitro. The BT 15 antigen was strongly expressed in the inner root sheath and the area above Auber's line of the hair bulb, whereas the T43 antigen was mainly seen in the outer root sheath. Selectively high expression of the MH 99 antigen was found only in outgrowing germ buds of early anagen follicles. Radioimmunoprecipitation revealed strong signals with BT 15 in freshly prepared follicular keratinocytes, two to three times stronger than those in interfollicular keratinocytes, but the signals clearly decreased by 80% under continuing culture conditions. The T 43 antigen was found by FACS analysis and radioimmunoprecipitation in initially low amounts in both populations, but the signals increased dramatically (up to 50 times) in long-term cultures and in subcultures. The MH 99 antigen was also initially present only in low amounts, in interfollicular rather than in follicular keratinocytes, but its expression increased up to 15-fold with continuing culture and any differences between the two populations disappeared. Our investigation revealed that at least three populations of hair follicle keratinocytes are characterized by different surface glycoprotein antigens, clearly related to their state of differentiation and proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)