8 research outputs found
Thyroxine differentially modulates the peripheral clock: lessons from the human hair follicle
No full textThe human hair follicle (HF) exhibits peripheral clock activity, with knock-down of clock genes (BMAL1 and PER1) prolonging active hair growth (anagen) and increasing pigmentation. Similarly, thyroid hormones prolong anagen and stimulate pigmentation in cultured human HFs. In addition they are recognized as key regulators of the central clock that controls circadian rhythmicity. Therefore, we asked whether thyroxine (T4) also influences peripheral clock activity in the human HF. Over 24 hours we found a significant reduction in protein levels of BMAL1 and PER1, with their transcript levels also decreasing significantly. Furthermore, while all clock genes maintained their rhythmicity in both the control and T4 treated HFs, there was a significant reduction in the amplitude of BMAL1 and PER1 in T4 (100 nM) treated HFs. Accompanying this, cell-cycle progression marker Cyclin D1 was also assessed appearing to show an induced circadian rhythmicity by T4 however, this was not significant. Contrary to short term cultures, after 6 days, transcript and/or protein levels of all core clock genes (BMAL1, PER1, clock, CRY1, CRY2) were up-regulated in T4 treated HFs. BMAL1 and PER1 mRNA was also up-regulated in the HF bulge, the location of HF epithelial stem cells. Together this provides the first direct evidence that T4 modulates the expression of the peripheral molecular clock. Thus, patients with thyroid dysfunction may also show a disordered peripheral clock, which raises the possibility that short term, pulsatile treatment with T4 might permit one to modulate circadian activity in peripheral tissues as a target to treat clock-related disease
Divergent proliferation patterns of distinct human hair follicle epithelial progenitor niches in situ and their differential responsiveness to prostaglandin D2
No full textHuman scalp hair follicles (hHF) harbour several epithelial stem (eHFSC) and progenitor cell sub-populations organised into spatially distinct niches. However, the constitutive cell cycle activity of these niches remains to be characterized in situ. Therefore, the current study has studied these characteristics of keratin 15+ (K15), CD200+ or CD34+ cells within anagen VI hHFs by immunohistomorphometry, using Ki-67 and 5-ethynyl-2'-deoxyuridine (EdU). We quantitatively demonstrate in situ the relative cell cycle inactivity of the CD200+/K15+ bulge compared to other non-bulge CD34+ and K15+ progenitor compartments and found that in each recognized eHFSC/progenitor niche, proliferation associates negatively with eHFSC-marker expression. Furthermore, we also show how prostaglandin D2 (PGD2), upregulated in balding scalp, differentially impacts on the proliferation of distinct eHFSC populations. Namely, 24h organ-cultured hHFs treated with PGD2 resulted in reduced Ki-67 expression and EdU incorporation in bulge resident K15+ cells, but not in supra/proximal bulb outer root sheath K15+ progenitors. This study emphasises clear differences between the cell cycle behaviours of spatially distinct stem/progenitor cell niches in the hHF, and demonstrates a possible link between PGD2 and perturbed proliferation dynamics in epithelial stem cells
Oxidative damage control in a human (mini-) organ:Nrf2 activation protects against oxidative stress-induced hair growth inhibition
No full textThe in situ control of redox insult in human organs is of major clinical relevance, yet remains incompletely understood. Activation of Nrf2, the “master regulator” of genes controlling cellular redox homeostasis, is advocated as a therapeutic strategy for diseases with severely impaired redox balance. It remains to be shown whether this strategy is effective in human organs, rather than isolated human cell types. We have therefore explored the role of Nrf2 in a uniquely accessible human (mini-) organ, human scalp hair follicles (HFs). Microarray and qPCR analysis of human HFs following Nrf2 activation using sulforaphane identified the modulation of phase II metabolism, ROS clearance, the pentose phosphate pathway and glutathione homeostasis. Nrf2 knockdown (siRNA) in cultured human HFs confirmed the regulation of key Nrf2 target genes (i.e. HO-1, NQO1, GSR, GCLC, ABCC1, PRDX1). Importantly, Nrf2 activation significantly reduced ROS levels and associated lipid peroxidation. Nrf2 pre-activation reduced oxidative stress-stimulated (H2O2 or menadione) premature catagen and hair growth inhibition, significantly ameliorated the H2O2-dependent increase in matrix keratinocyte apoptosis and reversed the ROS-induced reduction in proliferation. This study thus provides direct evidence for the crucial role of Nrf2 in protecting human organ function (i.e. scalp HFs) against redox insult
Core Curriculum for Hair Restoration Surgery, Recommended by the International Society of Hair Restoration Surgery (ISHRS)
No full textGene expression studies of lytic infection and chromosomal integration of human herpesvirus 6.
No full textHuman herpesvirus 6 (HHV-6) was discovered in 1986 in patients with lymphoproliferative diseases and it has a predominant tropism for CD4+ T cells in vitro and in vivo. The virus can be divided into two variants: HHV-6A and 6B, based on the differences in biological properties and DNA sequences. HHV-6B has been shown to be the causative agent of exanthem subitum while HHV-6A has no clear association with any disease yet. The genome for both variants has been defined and each encodes just over 100 open readings frames (ORFs). However, there is limited knowledge regarding the functions and transcription kinetics of most ORFs. This thesis discusses the development of DNA microarrays for HHV-6 and the application of the arrays to characterise HHV-6B gene expression in the SupT1 cell line. The expression pattern of individual viral genes over a 60h time course (<1 replication cycle) was profiled. Viral genes were further classified into three kinetic groups: immediately-early (IE), early (E), and late (L), according to their transcriptional activity in the absence of de novo protein synthesis or DNA replication. In addition, HHV-6 presents an atypical stage in the herpesvirus life cycle in which the viral genome is integrated into host chromosomes. The prevalence of HHV-6 integration was estimated to be between 0.21% to 3%. An individual harbouring integrated HHV-6 was previously identified. The molecular biology and gene expression of this integrated HHV-6 DNA were characterised. Expression of viral genes belonging to all three kinetic classes (IE, E, and L) was detected in vitro and ex vivo. The data strongly suggest that the chromosomal HHV-6 sequence is transcriptionally active and the implications of this are discussed
