The Experts below are selected from a list of 16707 Experts worldwide ranked by ideXlab platform
Alexa Patzelt - One of the best experts on this subject based on the ideXlab platform.
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Hair Follicles as a target structure for nanoparticles
Journal of Innovative Optical Health Sciences, 2015Co-Authors: Jurgen Lademann, Fanny Knorr, H Richter, Sora Jung, Martina C Meinke, E Ruhl, Ulrike Alexiev, Marcelo Calderon, Alexa PatzeltAbstract:For at least two decades, nanoparticles have been investigated for their capability to deliver topically applied substances through the skin barrier. Based on findings that nanoparticles are highly suitable for penetrating the blood–brain barrier, their use for drug delivery through the skin has become a topic of intense research. In spite of the research efforts by academia and industry, a commercial product permitting the nanoparticle-assisted delivery of topically applied drugs has not yet been developed. However, nanoparticles of approximately 600 nm in diameter have been shown to penetrate efficiently into the Hair Follicles, where they can be stored for several days. The successful loading of nanoparticles with drugs and their triggered release inside the Hair follicle may present an ideal method for localized drug delivery. Depending on the particle size, such a method would permit targeting specific structures in the Hair Follicles such as stem cells or immune cells or blood vessels found in the vicinity of the Hair Follicles.
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approach towards developing a novel procedure to selectively quantify topically applied substances in the Hair Follicles of the model tissue porcine ear skin
Experimental Dermatology, 2013Co-Authors: Fanny Knorr, H Richter, Alexa Patzelt, Wolfram Sterry, Sabine Schanzer, J LademannAbstract:Hair Follicles represent reservoirs for localized drug therapy and transport pathways for systemic drug delivery. This study describes an approach towards developing a novel procedure for quantifying topically applied substances located in the Hair Follicles of porcine ear skin, a model for human in vivo skin, using a fluorescent dye. Approximately 5% of the topically applied dye was recovered from the Hair Follicles, which is in accordance with a previous study.
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Drug delivery to Hair Follicles
Expert Opinion on Drug Delivery, 2013Co-Authors: Alexa Patzelt, Jurgen LademannAbstract:Introduction: The optimization of drug delivery to and via the Hair Follicles is gaining more and more importance as it has been recognized that the Hair Follicles are an interesting target site for topical applications. They are closely surrounded by capillaries and antigen-presenting cells, are associated with the sebaceous glands and are the host of stem cells in the bulge region of the Hair follicle. Areas covered: The present review shortly summarizes the complexity of the structure, biology and functions of the Hair follicle and presents the models and methods suitable to investigate follicular penetration. Drug delivery to Hair Follicles was clearly shown to be dependent on the physicochemical properties of the applied substances and vehicles as well as on the activity status, size and density of the Hair Follicles. Especially particulate substances were demonstrated to be proficient drug carriers into the Hair Follicles, whereas dependent data for transfollicular penetration into the deeper viable...
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Hair Follicles contribute significantly to penetration through human skin only at times soon after application as a solvent deposited solid in man
British Journal of Clinical Pharmacology, 2011Co-Authors: Xin Liu, Alexa Patzelt, Nina Otberg, J Lademann, Jeffrey E Grice, Sindy Trauer, Michael S RobertsAbstract:WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Depending on the body site and the substances, the Hair Follicles can contribute significantly to the penetration of topically applied substances. However, the quantitative and selective description of the follicular and intercellular penetration kinetics is difficult due to the lack of suitable models to differentiate between the different penetration pathways. Recently, for the first time, the follicular transport was measured directly in man in vivo indicating that the Hair Follicles are responsible for a fast delivery of topically applied substances. WHAT THIS STUDY ADDS • In the present study, pharmacokinetic principles were applied to define the underlying relative penetration of caffeine through Follicles and through intact stratum corneum with time in vivo. Absorption from Hair Follicles was found to contribute more than one third of the total percutaneous absorption of caffeine. Additionally, it was observed that the uptake by the Hair Follicles appeared at early times and was transient. AIMS The aim of this study was to define the underlying relative penetration of caffeine through Hair Follicles and through intact stratum corneum with time in vivo through pharmacokinetic modelling. METHODS Caffeine plasma concentration–time profiles after topical application into skin with or without Hair follicle blocking were modelled using the Wagner–Nelson method or a compartmental model with first order absorption and elimination. Pharmacokinetic parameters describing absorption rate and extent of absorption through Hair Follicles or the stratum corneum were determined separately and compared with each other. RESULTS The obtained pharmacokinetic parameters from the two methods were similar. The absorption rate constant of caffeine for Hair Follicles was nearly 10 times higher than that for the stratum corneum and the percentage of absorption from Hair Follicles was more than half of that of the stratum corneum. In addition, the absorption from the stratum corneum showed an approximately 10 min delay while there was no delay for absorption from Hair Follicles. All caffeine absorbed by Hair Follicles occurs within 30 min of application and accounts for 10.5 to 33.8% of the total amount absorbed across the skin for all subjects, whereas absorption of caffeine through the stratum corneum can occur over several hours. CONCLUSION Hair Follicles contribute significantly to percutaneous absorption of caffeine after topical application in man in vivo only at times soon after application.
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distribution of bacteria in the epidermal layers and Hair Follicles of the human skin
Skin Pharmacology and Physiology, 2011Co-Authors: Bernhard Langeasschenfeldt, Alexa Patzelt, D Marenbach, C Lang, M Ulrich, A Maltusch, Dorothea Terhorst, Eggert Stockfleth, Wolfram Sterry, J LademannAbstract:Previous studies over recent years have revealed the presence of a resident bacterial population in the human skin throughout the entire body. However, the localization and composition of the bacteria within the epidermis and the skin appendages have not been fully investigated. Using differential tape stripping, cyanoacrylate skin surface biopsies and mapping of Hair Follicles, bacteria on the forearms of study participants were isolated, mapped, cultured and identified with respect to their origin within the epidermis and the Hair Follicles. Our studies showed that 85% of the bacteria were found within the first 6 corneocyte layers and roughly 25% of the cutaneous bacterial population were localized within the Hair Follicles. The microbial flora of the skin between individuals is subject to considerable fluctuations. Micrococcaceae represent the biggest fraction of Hair-follicle-associated bacteria. The techniques developed for this study allowed us to selectively investigate the bacterial population within the Hair Follicles. Our results point out the role of skin appendages as potential microbial reservoirs and the need to develop new antiseptic formulations that sufficiently penetrate into the Hair Follicles.
J Lademann - One of the best experts on this subject based on the ideXlab platform.
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approach towards developing a novel procedure to selectively quantify topically applied substances in the Hair Follicles of the model tissue porcine ear skin
Experimental Dermatology, 2013Co-Authors: Fanny Knorr, H Richter, Alexa Patzelt, Wolfram Sterry, Sabine Schanzer, J LademannAbstract:Hair Follicles represent reservoirs for localized drug therapy and transport pathways for systemic drug delivery. This study describes an approach towards developing a novel procedure for quantifying topically applied substances located in the Hair Follicles of porcine ear skin, a model for human in vivo skin, using a fluorescent dye. Approximately 5% of the topically applied dye was recovered from the Hair Follicles, which is in accordance with a previous study.
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Hair Follicles contribute significantly to penetration through human skin only at times soon after application as a solvent deposited solid in man
British Journal of Clinical Pharmacology, 2011Co-Authors: Xin Liu, Alexa Patzelt, Nina Otberg, J Lademann, Jeffrey E Grice, Sindy Trauer, Michael S RobertsAbstract:WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Depending on the body site and the substances, the Hair Follicles can contribute significantly to the penetration of topically applied substances. However, the quantitative and selective description of the follicular and intercellular penetration kinetics is difficult due to the lack of suitable models to differentiate between the different penetration pathways. Recently, for the first time, the follicular transport was measured directly in man in vivo indicating that the Hair Follicles are responsible for a fast delivery of topically applied substances. WHAT THIS STUDY ADDS • In the present study, pharmacokinetic principles were applied to define the underlying relative penetration of caffeine through Follicles and through intact stratum corneum with time in vivo. Absorption from Hair Follicles was found to contribute more than one third of the total percutaneous absorption of caffeine. Additionally, it was observed that the uptake by the Hair Follicles appeared at early times and was transient. AIMS The aim of this study was to define the underlying relative penetration of caffeine through Hair Follicles and through intact stratum corneum with time in vivo through pharmacokinetic modelling. METHODS Caffeine plasma concentration–time profiles after topical application into skin with or without Hair follicle blocking were modelled using the Wagner–Nelson method or a compartmental model with first order absorption and elimination. Pharmacokinetic parameters describing absorption rate and extent of absorption through Hair Follicles or the stratum corneum were determined separately and compared with each other. RESULTS The obtained pharmacokinetic parameters from the two methods were similar. The absorption rate constant of caffeine for Hair Follicles was nearly 10 times higher than that for the stratum corneum and the percentage of absorption from Hair Follicles was more than half of that of the stratum corneum. In addition, the absorption from the stratum corneum showed an approximately 10 min delay while there was no delay for absorption from Hair Follicles. All caffeine absorbed by Hair Follicles occurs within 30 min of application and accounts for 10.5 to 33.8% of the total amount absorbed across the skin for all subjects, whereas absorption of caffeine through the stratum corneum can occur over several hours. CONCLUSION Hair Follicles contribute significantly to percutaneous absorption of caffeine after topical application in man in vivo only at times soon after application.
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distribution of bacteria in the epidermal layers and Hair Follicles of the human skin
Skin Pharmacology and Physiology, 2011Co-Authors: Bernhard Langeasschenfeldt, Alexa Patzelt, D Marenbach, C Lang, M Ulrich, A Maltusch, Dorothea Terhorst, Eggert Stockfleth, Wolfram Sterry, J LademannAbstract:Previous studies over recent years have revealed the presence of a resident bacterial population in the human skin throughout the entire body. However, the localization and composition of the bacteria within the epidermis and the skin appendages have not been fully investigated. Using differential tape stripping, cyanoacrylate skin surface biopsies and mapping of Hair Follicles, bacteria on the forearms of study participants were isolated, mapped, cultured and identified with respect to their origin within the epidermis and the Hair Follicles. Our studies showed that 85% of the bacteria were found within the first 6 corneocyte layers and roughly 25% of the cutaneous bacterial population were localized within the Hair Follicles. The microbial flora of the skin between individuals is subject to considerable fluctuations. Micrococcaceae represent the biggest fraction of Hair-follicle-associated bacteria. The techniques developed for this study allowed us to selectively investigate the bacterial population within the Hair Follicles. Our results point out the role of skin appendages as potential microbial reservoirs and the need to develop new antiseptic formulations that sufficiently penetrate into the Hair Follicles.
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which skin model is the most appropriate for the investigation of topically applied substances into the Hair Follicles
Skin Pharmacology and Physiology, 2010Co-Authors: J Lademann, H Richter, Martina C Meinke, Wolfram Sterry, Alexa PatzeltAbstract:It has recently been demonstrated by the utilization of different techniques, such as differential stripping and laser scanning microscopy, that the Hair Follicles represent an efficient long-term reservoir for topically applied substances. In the present paper, the different in vivo techniques are compared to those of in vitro analysis. It was found that in vitro measurements on pig ear skin are highly superior for the analysis of follicular penetration, as compared to in vitro investigations on excised human skin, mainly due to the fact that the human skin contracts after removal. Restretching of the skin to its original size mainly stretches the interfollicular fibres, whereas the fibres around the Hair Follicles remain contracted. In contrast to excised human skin, pig ear tissue does not contract when the cartilage is not removed. Moreover, it has an intact barrier on both sides of the ear. Regardless of the fact that the Hair Follicles on pig ear skin are larger than those of humans, the porcine ear skin represents a more suitable in vitro model for the analysis of the penetration and storage of topically applied substances in the Hair Follicles than excised human skin.
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Hair Follicles an efficient storage and penetration pathway for topically applied substances
Skin Pharmacology and Physiology, 2008Co-Authors: J Lademann, Fanny Knorr, H Richter, Ulrike Blumepeytavi, Wolfram Sterry, Annika Vogt, Christina Antoniou, Alexa PatzeltAbstract:In the past, it was assumed that the intercellular route was the only relevant penetration pathway for topically applied substances. Recent results on follicular penetration obtained at the Center for Experimental and Applied Cutaneous Physiology, Charite – Universitatsmedizin Berlin, Germany, emphasize that the Hair Follicles represent a highly relevant and efficient penetration pathway and reservoir for topically applied substances.
Danelle Devenport - One of the best experts on this subject based on the ideXlab platform.
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counter rotational cell flows drive morphological and cell fate asymmetries in mammalian Hair Follicles
Nature Cell Biology, 2018Co-Authors: Maureen Cetera, Liliya Leybova, Bradley Joyce, Danelle DevenportAbstract:Organ morphogenesis is a complex process coordinated by cell specification, epithelial–mesenchymal interactions and tissue polarity. A striking example is the pattern of regularly spaced, globally aligned mammalian Hair Follicles, which emerges through epidermal-dermal signaling and planar polarized morphogenesis. Here, using live-imaging, we discover that developing Hair Follicles polarize through dramatic cell rearrangements organized in a counter-rotational pattern of cell flows. Upon Hair placode induction, Shh signaling specifies a radial pattern of progenitor fates that, together with planar cell polarity, induce counter-rotational rearrangements through myosin and ROCK-dependent polarized neighbour exchanges. Importantly, these cell rearrangements also establish cell fate asymmetry by repositioning radial progenitors along the anterior–posterior axis. These movements concurrently displace associated mesenchymal cells, which then signal asymmetrically to maintain polarized cell fates. Our results demonstrate how spatial patterning and tissue polarity generate an unexpected collective cell behaviour that in turn, establishes both morphological and cell fate asymmetry. Cetera et al. show that Hair follicle development is characterised by counter-rotational cell rearrangements, which depend on myosin and Shh signalling, and direct cell fate asymmetry.
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planar polarization in embryonic epidermis orchestrates global asymmetric morphogenesis of Hair Follicles
Nature Cell Biology, 2008Co-Authors: Danelle Devenport, Elaine FuchsAbstract:Mammalian Hair Follicles are aligned along the anterior–posterior axis. The planar cell polarity genes Vangl2 and Celsr1 are essential for Hair follicle polarization and orientation.
Michael S Howard - One of the best experts on this subject based on the ideXlab platform.
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survivin p53 mac complement c3 fibrinogen and hla abc within Hair Follicles in central and centrifugal cicatricial alopecia
North American Journal of Medical Sciences, 2011Co-Authors: Ana Maria Abreuvelez, Deo A Klein, Michael S HowardAbstract:Central centrifugal cicatricial alopecia (CCCA; originally entitled follicular degeneration syndrome, or hot comb alopecia) was first described in African American women utilizing hot combs and/or strong chemical Hair care products. Case Report: A 67 year old African American female was evaluated for the presence of alopecic areas occurring on the scalp vertex, and spreading centrifugally. The alopecic lesions appeared as diffuse patches, including atrophic small areas surrounding individual Hair Follicles. Patients and Methods: Skin biopsies for hematoxylin and eosin examination, as well as for direct immunofluorescence and immunohistochemistry analyses were performed. Results: hematoxylin and eosin staining demonstrated histopathologic findings of premature desquamation of the inner root sheath and eccentric thinning of the follicular epithelium, supporting the diagnosis of CCCA. Direct immunofluorescence revealed strong depositions of Complement/C3, fibrinogen and kappa light chains around the Hair Follicles. Immunohistochemistry demonstrated increased expressions of HLA-ABC (as in African American patients with insulin independent diabetes mellitus). We also detected positive p53, bcl-2 and MAC staining in the Hair follicle areas. Conclusions: Follicular degeneration syndrome may have an important immunological component previously not described, and multicolor immunofluorescence may be useful in establishing an early diagnosis.
Wolfram Sterry - One of the best experts on this subject based on the ideXlab platform.
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approach towards developing a novel procedure to selectively quantify topically applied substances in the Hair Follicles of the model tissue porcine ear skin
Experimental Dermatology, 2013Co-Authors: Fanny Knorr, H Richter, Alexa Patzelt, Wolfram Sterry, Sabine Schanzer, J LademannAbstract:Hair Follicles represent reservoirs for localized drug therapy and transport pathways for systemic drug delivery. This study describes an approach towards developing a novel procedure for quantifying topically applied substances located in the Hair Follicles of porcine ear skin, a model for human in vivo skin, using a fluorescent dye. Approximately 5% of the topically applied dye was recovered from the Hair Follicles, which is in accordance with a previous study.
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distribution of bacteria in the epidermal layers and Hair Follicles of the human skin
Skin Pharmacology and Physiology, 2011Co-Authors: Bernhard Langeasschenfeldt, Alexa Patzelt, D Marenbach, C Lang, M Ulrich, A Maltusch, Dorothea Terhorst, Eggert Stockfleth, Wolfram Sterry, J LademannAbstract:Previous studies over recent years have revealed the presence of a resident bacterial population in the human skin throughout the entire body. However, the localization and composition of the bacteria within the epidermis and the skin appendages have not been fully investigated. Using differential tape stripping, cyanoacrylate skin surface biopsies and mapping of Hair Follicles, bacteria on the forearms of study participants were isolated, mapped, cultured and identified with respect to their origin within the epidermis and the Hair Follicles. Our studies showed that 85% of the bacteria were found within the first 6 corneocyte layers and roughly 25% of the cutaneous bacterial population were localized within the Hair Follicles. The microbial flora of the skin between individuals is subject to considerable fluctuations. Micrococcaceae represent the biggest fraction of Hair-follicle-associated bacteria. The techniques developed for this study allowed us to selectively investigate the bacterial population within the Hair Follicles. Our results point out the role of skin appendages as potential microbial reservoirs and the need to develop new antiseptic formulations that sufficiently penetrate into the Hair Follicles.
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which skin model is the most appropriate for the investigation of topically applied substances into the Hair Follicles
Skin Pharmacology and Physiology, 2010Co-Authors: J Lademann, H Richter, Martina C Meinke, Wolfram Sterry, Alexa PatzeltAbstract:It has recently been demonstrated by the utilization of different techniques, such as differential stripping and laser scanning microscopy, that the Hair Follicles represent an efficient long-term reservoir for topically applied substances. In the present paper, the different in vivo techniques are compared to those of in vitro analysis. It was found that in vitro measurements on pig ear skin are highly superior for the analysis of follicular penetration, as compared to in vitro investigations on excised human skin, mainly due to the fact that the human skin contracts after removal. Restretching of the skin to its original size mainly stretches the interfollicular fibres, whereas the fibres around the Hair Follicles remain contracted. In contrast to excised human skin, pig ear tissue does not contract when the cartilage is not removed. Moreover, it has an intact barrier on both sides of the ear. Regardless of the fact that the Hair Follicles on pig ear skin are larger than those of humans, the porcine ear skin represents a more suitable in vitro model for the analysis of the penetration and storage of topically applied substances in the Hair Follicles than excised human skin.
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Hair Follicles an efficient storage and penetration pathway for topically applied substances
Skin Pharmacology and Physiology, 2008Co-Authors: J Lademann, Fanny Knorr, H Richter, Ulrike Blumepeytavi, Wolfram Sterry, Annika Vogt, Christina Antoniou, Alexa PatzeltAbstract:In the past, it was assumed that the intercellular route was the only relevant penetration pathway for topically applied substances. Recent results on follicular penetration obtained at the Center for Experimental and Applied Cutaneous Physiology, Charite – Universitatsmedizin Berlin, Germany, emphasize that the Hair Follicles represent a highly relevant and efficient penetration pathway and reservoir for topically applied substances.
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morphometry of human terminal and vellus Hair Follicles
Experimental Dermatology, 2007Co-Authors: Annika Vogt, Wolfram Sterry, J Lademann, Sabrina Hadam, Marc Heiderhoff, Heike Audring, Ulrike BlumepeytaviAbstract:Previous studies suggest that drug delivery systems based on particles can be used to deposit active compounds in Hair Follicles and to target Hair follicle-associated cell populations. The development of application protocols is complicated by the fact that there is no information available on the size and the position of key target structures in the different Hair follicle types and their intra- and interindividual variation. Therefore, we performed morphometric measurements on histological sections of human terminal (THF) and vellus Hair Follicles (VHF) from the scalp and the retroauricular region. With 3864 +/- 605 microm and 580 +/- 84 microm in THF compared to 646 +/- 140 microm and 225 +/- 34 microm in VHF, the total length and the length of the infundibulum differed significantly as determined by paired t-test (P < 0.0001). The same level of significance was observed for the position and the length of the bulge region. The thickness of the epithelial lining was lowest in VHF (45 +/- 14 microm at 100 microm from skin surface) compared to 65 +/- 20 microm at 150 microm in THF, while the thickness of the interfollicular epidermis ranged between 64 +/- 12 microm and 99 +/- 18 microm in VHF-bearing skin and 72 +/- 16 microm and 136 +/- 37 microm in THF-bearing skin. In addition, the diameter of the Hair follicle opening was determined at 50 microm intervals from the skin surface. Our data suggest that Hair follicle types in defined body regions represent rather homogenous groups and that particle-based drug delivery may be a feasible approach, also in larger numbers of individuals. We provide precise information on the size and the position of key target structures in VHF and THF.
