Hanz Blatt

Bio: Hanz Blatt is an academic researcher from Northwestern University. The author has contributed to research in topics: Cellular differentiation & Hair follicle. The author has an hindex of 10, co-authored 11 publications receiving 959 citations. Previous affiliations of Hanz Blatt include Loyola University Chicago & University of Pennsylvania.

Bald scalp in men with androgenetic alopecia retains hair follicle stem cells but lacks CD200-rich and CD34-positive hair follicle progenitor cells

Abstract: Androgenetic alopecia (AGA), also known as common baldness, is characterized by a marked decrease in hair follicle size, which could be related to the loss of hair follicle stem or progenitor cells. To test this hypothesis, we analyzed bald and non-bald scalp from AGA individuals for the presence of hair follicle stem and progenitor cells. Cells expressing cytokeratin15 (KRT15), CD200, CD34, and integrin, α6 (ITGA6) were quantitated via flow cytometry. High levels of KRT15 expression correlated with stem cell properties of small cell size and quiescence. These KRT15hi stem cells were maintained in bald scalp samples. However, CD200hiITGA6hi and CD34hi cell populations — which both possessed a progenitor phenotype, in that they localized closely to the stem cell–rich bulge area but were larger and more proliferative than the KRT15hi stem cells — were markedly diminished. In functional assays, analogous CD200hiItga6hi cells from murine hair follicles were multipotent and generated new hair follicles in skin reconstitution assays. These findings support the notion that a defect in conversion of hair follicle stem cells to progenitor cells plays a role in the pathogenesis of AGA.

Mitochondrial reactive oxygen species promote epidermal differentiation and hair follicle development.

Abstract: Proper regulation of keratinocyte differentiation within the epidermis and follicular epithelium is essential for maintenance of epidermal barrier function and hair growth. The signaling intermediates that regulate the morphological and genetic changes associated with epidermal and follicular differentiation remain poorly understood. We tested the hypothesis that reactive oxygen species (ROS) generated by mitochondria are an important regulator of epidermal differentiation by generating mice with a keratinocyte-specific deficiency in mitochondrial transcription factor A (TFAM), which is required for the transcription of mitochondrial genes encoding electron transport chain subunits. Ablation of TFAM in keratinocytes impaired epidermal differentiation and hair follicle growth and resulted in death 2 weeks after birth. TFAM-deficient keratinocytes failed to generate mitochondria-derived ROS, a deficiency that prevented the transmission of Notch and β-catenin signals essential for epidermal differentiation and hair follicle development, respectively. In vitro keratinocyte differentiation was inhibited in the presence of antioxidants, and the decreased differentiation marker abundance in TFAM-deficient keratinocytes was partly rescued by application of exogenous hydrogen peroxide. These findings indicate that mitochondria-generated ROS are critical mediators of cellular differentiation and tissue morphogenesis.

Prostaglandin D2 inhibits hair growth and is elevated in bald scalp of men with androgenetic alopecia

Abstract: Testosterone is necessary for the development of male pattern baldness, known as androgenetic alopecia (AGA); yet, the mechanisms for decreased hair growth in this disorder are unclear. We show that prostaglandin D2 synthase (PTGDS) is elevated at the mRNA and protein levels in bald scalp compared to haired scalp of men with AGA. The product of PTGDS enzyme activity, prostaglandin D2 (PGD2), is similarly elevated in bald scalp. During normal follicle cycling in mice, Ptgds and PGD2 levels increase immediately preceding the regression phase, suggesting an inhibitory effect on hair growth. We show that PGD2 inhibits hair growth in explanted human hair follicles and when applied topically to mice. Hair growth inhibition requires the PGD2 receptor G protein (heterotrimeric guanine nucleotide)–coupled receptor 44 (GPR44), but not the PGD2 receptor 1 (PTGDR). Furthermore, we find that a transgenic mouse, K14-Ptgs2, which targets prostaglandin-endoperoxide synthase 2 expression to the skin, demonstrates elevated levels of PGD2 in the skin and develops alopecia, follicular miniaturization, and sebaceous gland hyperplasia, which are all hallmarks of human AGA. These results define PGD2 as an inhibitor of hair growth in AGA and suggest the PGD2-GPR44 pathway as a potential target for treatment.

Accuracy of self-report in assessing Fitzpatrick skin phototypes I through VI.

Abstract: Importance Determining Fitzpatrick skin phototypes (FST) allows physicians to assess a person’s risk of developing sunburn and, by extension, the need for sun protection to prevent the development of skin cancer. Reflectance spectrophotometry objectively measures the melanin index and can assist in determining the accuracy of self-report of FST compared with dermatologist-determined FST. Objectives To assess whether self-reported or dermatologist-determined FST is more accurate in identifying a participant’s FST for FST I through VI and to assess the relevance of the burning and tanning measures for a range of skin types among ethnically diverse participants. Design and Setting A convenience sample of participants in an observational study from June 2, 2010, through December 15, 2010, at an ambulatory academic dermatologic practice and employee health center in an urban city. Participants Participants, staff, and students of Northwestern University, who self-identified as being non-Hispanic white, Hispanic or Latino, Asian or Pacific Islander, or black. Main Outcomes and Measures Melanin index as measured with reflectance spectrophotometry compared with dermatologist- and participant-determined FST. Results Forty-two percent (114 of 270) of the participants’ responses to the burning and tanning questions could not be classified using standard FST definitions. The spectrophotometry measurements for dermatologist-determined FST were significantly different for FST III and IV ( P P P P = .90). Participant responses to burning and the dermatologist-determined FST were significantly correlated (Spearman ρ, 0.764; P P = .15). Spectrophotometry measurements assessing FST were statistically significantly different for FST III through VI ( P Conclusions and Relevance Dermatologist-determined FST is more accurate than self-report for FST III through VI. Rephrasing the questions using specific descriptors that have meaning to people with skin of color, such as skin irritation, tenderness, itching, or skin becoming darker, may allow physicians to more accurately assign a skin phototype and, by inference, assess the risk of these participants developing skin cancer. Trial Registration clinicaltrials.gov Identifier:NCT01124513

microRNA-31/factor-inhibiting hypoxia-inducible factor 1 nexus regulates keratinocyte differentiation

Abstract: Notch plays a critical role in the transition from proliferation to differentiation in the epidermis and corneal epithelium. Furthermore, aberrant Notch signaling is a feature of diseases like psoriasis, eczema, nonmelanoma skin cancer, and melanoma where differentiation and proliferation are impaired. Whereas much is known about the downstream events following Notch signaling, factors responsible for negatively regulating Notch receptor signaling after ligand activation are incompletely understood. Notch can undergo hydroxylation by factor-inhibiting hypoxia-inducible factor 1 (FIH-1); however, the biological significance of this phenomenon is unclear. Here we show that FIH-1 expression is up-regulated in diseased epidermis and corneal epithelium. Elevating FIH-1 levels in primary human epidermal keratinocytes (HEKs) and human corneal epithelial keratinocytes (HCEKs) impairs differentiation in submerged cultures and in a “three-dimensional” organotypic raft model of human epidermis, in part, via a coordinate decrease in Notch signaling. Knockdown of FIH-1 enhances keratinocyte differentiation. Loss of FIH-1 in vivo increased Notch activity in the limbal epithelium, resulting in a more differentiated phenotype. microRNA-31 (miR-31) is an endogenous negative regulator of FIH-1 expression that results in keratinocyte differentiation, mediated by Notch activation. Ectopically expressing miR-31 in an undifferentiated corneal epithelial cell line promotes differentiation and recapitulates a corneal epithelium in a three-dimensional raft culture model. Our results define a previously unknown mechanism for keratinocyte fate decisions where Notch signaling potential is, in part, controlled through a miR-31/FIH-1 nexus.

Decision aids for people facing health treatment or screening decisions

Abstract: Background Decision aids are intended to help people participate in decisions that involve weighing the benefits and harms of treatment options often with scientific uncertainty. Objectives To assess the effects of decision aids for people facing treatment or screening decisions. Search methods For this update, we searched from 2009 to June 2012 in MEDLINE; CENTRAL; EMBASE; PsycINFO; and grey literature. Cumulatively, we have searched each database since its start date including CINAHL (to September 2008). Selection criteria We included published randomized controlled trials of decision aids, which are interventions designed to support patients' decision making by making explicit the decision, providing information about treatment or screening options and their associated outcomes, compared to usual care and/or alternative interventions. We excluded studies of participants making hypothetical decisions. Data collection and analysis Two review authors independently screened citations for inclusion, extracted data, and assessed risk of bias. The primary outcomes, based on the International Patient Decision Aid Standards (IPDAS), were: A) 'choice made' attributes; B) 'decision-making process' attributes. Secondary outcomes were behavioral, health, and health-system effects. We pooled results using mean differences (MD) and relative risks (RR), applying a random-effects model. Main results This update includes 33 new studies for a total of 115 studies involving 34,444 participants. For risk of bias, selective outcome reporting and blinding of participants and personnel were mostly rated as unclear due to inadequate reporting. Based on 7 items, 8 of 115 studies had high risk of bias for 1 or 2 items each. Of 115 included studies, 88 (76.5%) used at least one of the IPDAS effectiveness criteria: A) 'choice made' attributes criteria: knowledge scores (76 studies); accurate risk perceptions (25 studies); and informed value-based choice (20 studies); and B) 'decision-making process' attributes criteria: feeling informed (34 studies) and feeling clear about values (29 studies). A) Criteria involving 'choice made' attributes: Compared to usual care, decision aids increased knowledge (MD 13.34 out of 100; 95% confidence interval (CI) 11.17 to 15.51; n = 42). When more detailed decision aids were compared to simple decision aids, the relative improvement in knowledge was significant (MD 5.52 out of 100; 95% CI 3.90 to 7.15; n = 19). Exposure to a decision aid with expressed probabilities resulted in a higher proportion of people with accurate risk perceptions (RR 1.82; 95% CI 1.52 to 2.16; n = 19). Exposure to a decision aid with explicit values clarification resulted in a higher proportion of patients choosing an option congruent with their values (RR 1.51; 95% CI 1.17 to 1.96; n = 13). B) Criteria involving 'decision-making process' attributes: Decision aids compared to usual care interventions resulted in: a) lower decisional conflict related to feeling uninformed (MD -7.26 of 100; 95% CI -9.73 to -4.78; n = 22) and feeling unclear about personal values (MD -6.09; 95% CI -8.50 to -3.67; n = 18); b) reduced proportions of people who were passive in decision making (RR 0.66; 95% CI 0.53 to 0.81; n = 14); and c) reduced proportions of people who remained undecided post-intervention (RR 0.59; 95% CI 0.47 to 0.72; n = 18). Decision aids appeared to have a positive effect on patient-practitioner communication in all nine studies that measured this outcome. For satisfaction with the decision (n = 20), decision-making process (n = 17), and/or preparation for decision making (n = 3), those exposed to a decision aid were either more satisfied, or there was no difference between the decision aid versus comparison interventions. No studies evaluated decision-making process attributes for helping patients to recognize that a decision needs to be made, or understanding that values affect the choice. C) Secondary outcomes Exposure to decision aids compared to usual care reduced the number of people of choosing major elective invasive surgery in favour of more conservative options (RR 0.79; 95% CI 0.68 to 0.93; n = 15). Exposure to decision aids compared to usual care reduced the number of people choosing to have prostate-specific antigen screening (RR 0.87; 95% CI 0.77 to 0.98; n = 9). When detailed compared to simple decision aids were used, fewer people chose menopausal hormone therapy (RR 0.73; 95% CI 0.55 to 0.98; n = 3). For other decisions, the effect on choices was variable. The effect of decision aids on length of consultation varied from 8 minutes shorter to 23 minutes longer (median 2.55 minutes longer) with 2 studies indicating statistically-significantly longer, 1 study shorter, and 6 studies reporting no difference in consultation length. Groups of patients receiving decision aids do not appear to differ from comparison groups in terms of anxiety (n = 30), general health outcomes (n = 11), and condition-specific health outcomes (n = 11). The effects of decision aids on other outcomes (adherence to the decision, costs/resource use) were inconclusive. Authors' conclusions There is high-quality evidence that decision aids compared to usual care improve people's knowledge regarding options, and reduce their decisional conflict related to feeling uninformed and unclear about their personal values. There is moderate-quality evidence that decision aids compared to usual care stimulate people to take a more active role in decision making, and improve accurate risk perceptions when probabilities are included in decision aids, compared to not being included. There is low-quality evidence that decision aids improve congruence between the chosen option and the patient's values. New for this updated review is further evidence indicating more informed, values-based choices, and improved patient-practitioner communication. There is a variable effect of decision aids on length of consultation. Consistent with findings from the previous review, decision aids have a variable effect on choices. They reduce the number of people choosing discretionary surgery and have no apparent adverse effects on health outcomes or satisfaction. The effects on adherence with the chosen option, cost-effectiveness, use with lower literacy populations, and level of detail needed in decision aids need further evaluation. Little is known about the degree of detail that decision aids need in order to have a positive effect on attributes of the choice made, or the decision-making process.

Cellular mechanisms and physiological consequences of redox-dependent signalling

Abstract: Reactive oxygen species (ROS), which were originally characterized in terms of their harmful effects on cells and invading microorganisms, are increasingly implicated in various cell fate decisions and signal transduction pathways. The mechanism involved in ROS-dependent signalling involves the reversible oxidation and reduction of specific amino acids, with crucial reactive Cys residues being the most frequent target. In this Review, we discuss the sources of ROS within cells and what is known regarding how intracellular oxidant levels are regulated. We further discuss the recent observations that reduction-oxidation (redox)-dependent regulation has a crucial role in an ever-widening range of biological activities - from immune function to stem cell self-renewal, and from tumorigenesis to ageing.

Mitochondrial ROS in cancer: initiators, amplifiers or an Achilles' heel?

Abstract: Mitochondria cooperate with their host cells by contributing to bioenergetics, metabolism, biosynthesis, and cell death or survival functions. Reactive oxygen species (ROS) generated by mitochondria participate in stress signalling in normal cells but also contribute to the initiation of nuclear or mitochondrial DNA mutations that promote neoplastic transformation. In cancer cells, mitochondrial ROS amplify the tumorigenic phenotype and accelerate the accumulation of additional mutations that lead to metastatic behaviour. As mitochondria carry out important functions in normal cells, disabling their function is not a feasible therapy for cancer. However, ROS signalling contributes to proliferation and survival in many cancers, so the targeted disruption of mitochondria-to-cell redox communication represents a promising avenue for future therapy.