Hair Follicle: Differentiation Under the Electron Microscope - An Atlas PDF
Preview Hair Follicle: Differentiation Under the Electron Microscope - An Atlas
K. Morioka Hair Follicle Differentiation Under the Electron Microscope An Atlas K. Morioka Hair Follicle Differentiation Under the Electron Microscope An Atlas With 83 Figures, Including 6 in Color 1 3 Kiyokazu Morioka, Ph.D. The Tokyo Metropolitan Institute of Medical Science 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan Library of Congress Control Number: 2004 112646 ISBN 4-431-22429-7 Springer-Verlag Tokyo Berlin Heidelberg New York Printed on acid-free paper This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publisher can give no guarantee for information about drug dosage and application thereof contained in this book. In every individual case the respective user must check its accuracy by consulting other pharmaceutical literature. Springer is a part of Springer Science+Business Media springeronline.com © Springer-Verlag Tokyo 2005 Printed in Japan Typesetting: SNP Best-set Typesetter Ltd., Hong Kong Printing and binding: Nikkei Printing Inc., Japan Foreword Each and every hair is much more than just the visible shaft—there are also associated complex sheath structures of epidermal and dermal origin. In the hair follicle, cells undergo a variety of differentiation processes, mostly depending on their layers and positions therein, and electron microscopy reveals a very complex architecture. The structure of a particular layer, such as Henle’s layer of the inner root sheath, is not uniform. Rather, cells drastically change during the course of differentiation. By simply comparing electron micrographs of cells of a layer at different degrees of differentiation, one can hardly recognize them as belonging to the same layer. As readers will see, this book contains many superb electron micro- graphs, from low-magnification panoramic views for orientation to high- power views showing ultrastructural detail. Captions and schematic drawings are also very helpful in “reading” electron micrographs and un- derstanding the structural detail. In this way, Dr. Morioka has succeeded in dissecting the complex hair follicle at the ultrastructural level. Dr. Morioka started his career as a biologist when he was a graduate student in the Laboratory of Developmental Physiology and Biochemistry at the Zoological Institute of the University of Tokyo. He continued to work in the field of biochemistry of cellular differentiation of blood cells before moving on to hair follicles. About 10 years ago he visited our labo- ratory to take a course in electron microscopy. I am sure that he learned not only the techniques of microscopy, but also the structural marvel of cells and tissues of the body. After the completion of genome projects at the beginning of this cen- tury, complex tissue systems will provide a new challenge to biomedical researchers. Structurally, while hair is compact, it is one of the most com- plex cellular systems in the body. Hair serves as one of the outstanding models for studying cell renewal, proliferation, differentiation, migration, and death. Comprehensive understanding of the structure of hair consti- tutes the basis for the advancement of research in this field. Dr. Morioka’s work on the hair follicle sets the stage for even deeper ultrastructural re- search into hair. VI Foreword Advances in electron microscope technology and the use of diamond knives have made thin-section electron microscopy much easier in most specimens. However, some tissues are still difficult to process. Making smooth ultrathin sections from specimens containing different textures and degrees of hardness is not easy. Skin is one such composite tissue. High-quality electron micrographs can be obtained by highly skilled elec- tron microscopists only by sectioning and processing with utmost care. It is felt that Dr. Morioka’s achievement offers an admirable and compre- hensive reference work and will benefit many researchers working in this field. Kuniaki Takata, Ph.D., D.M.Sc. Professor and Head Department of Anatomy and Cell Biology Gunma University Graduate School of Medicine Gunma Japan Preface New approaches to the study of hair, involving growth factors, differentiation inducers, cell signaling pathways, and transcription factors, have vastly increased our understanding of hair growth in recent years. Each hair contains stem cells and the hair’s distinctive progenitors, primarily the medulla, cortex, cuticle, and three inner root sheath layers. The differentiation of these components is controlled by complicated systems, including epidermis–dermis interactions, which are known to function in a variety of developmental processes in humans and animals. It suggests that advances in hair research contribute not only to the artificial control of hair growth, but also to the elucidation of core problems in biology and medicine. About 10 years ago, my friend Prof. S. Ihara (Faculty of Life and Envi- ronmental Science, Shimane University), who had studied hair reproduc- tion in vitro, introduced me into his mysterious and fascinating field. His work and thinking facilitated my early studies, but I soon noticed that the structure of hair is highly complex and, therefore, sufficiently detailed descriptions of the morphological changes in each hair-cell lineage and the interactions of cells of different lineages were not available. Many questions emerged. How and when do uniform placode cells differentiate? What conditions are needed to induce the intrusion of dermal papilla cells into the hair rod? How do connective tissue follicle (dermal sheath) cells transform into the papilla? How does the hair bulb stem cell differentiate into several lines of very different types of cells? How do medulla cells differentiate and undergo programmed cell death (and is this a common apoptotic event)? How are the hard keratins assembled in the hair cortex and hair cuticle? How are the distinctive cornifications of the three inner root sheath layers accomplished? Many more questions appear in the text of this book. I thought that some of these questions might be answered, at least partially, by recourse to electron microscopy. At that time I determined to begin the study of ultrastructure. I was not young, but Prof. M. Sameshima (Faculty of Agriculture and Life Science, Hirosaki University) took me under his wing as a rank beginner and tutored me broadly on the methods of electron microscopy, from the fixation of samples to the VIII Preface printing of photographs. Prof. K. Takata (Gunma University, Graduate School of Medicine) also gave me many useful suggestions on his profes- sional training course in this field. With their lessons absorbed, I entered into an intensive investigation of hair. Because it is refractory to the penetration of resins, hair is one of the most difficult organs to deal with in electron microscopy. I decided to use neonatal rats, partly because their relatively soft hair is easier to work with, but more importantly, because the use of animals at this stage of life allows us to see the developmental process of the hair follicle. Hair shafts regenerate throughout the life of humans and animals, but hair follicles are not formed in adults. The hair follicle of a rat from birth to seven days does not contain two (old and new) hair shafts because it is in the first growth stage, the first anagen. The advantage of this characteristic is that it obviates the need to identify old and new hair shafts in the small viewing field of the electron microscope. Electron microscopy research of hair has a history of some 50 years, but it has become difficult to gather and integrate the fragmented knowl- edge so far accumulated. Some has been lost or become inaccessible dur- ing the age of molecular biology. So, I chose to provide various new and original photographs of all basic hair cells, from their birth to death. As for the intended audience for this book, first and foremost, I recom- mend this collection to molecular biologists who are interested in hair. A hair is a minute organ, but it has a fine structure consisting of many dis- tinctive tissues and cells and is produced through the collaboration of these constituent members. All those who study hair should know the morphological and developmental details of the organ. Some photo- graphs that contain novel findings may also be useful to advanced stu- dents and experts conducting morphological or dermatological research. Chapter 1 will be of benefit to students or novices in this field. It provides a brief history of hair and hair research as well as a short summary of recent progress in the field. It also contains basic information and nomen- clature to facilitate the beginner’s study. The following chapters contain brief explanations of the photographs, but it is important to emphasize that the photographs likely contain more information than I have de- scribed. I therefore expect that the readers will discover new possibilities and questions in the photographs themselves, aside from any explana- tions I have offered. I express my sincere thanks and appreciation to the following people for their support and interest during the course of this work: Prof. M. Sameshima and Prof. K. Takata for teaching me the principles and tech- niques of electron microscopy and for writing the foreword to this book; Prof. S. Ihara and Dr. T. Matsuzaki for their many helpful suggestions; Dr. I. Yahara for leaving his electron microscope for us when he retired; Dr. H. Sakuraba, the director of our laboratory, for allowing me to undertake this research; Dr. H. Takano-Ohmuro, Dr. M. Mukaida, Dr. E. Kominami, Dr. T. Ueno, Dr. M. Sameshima, Dr. K. Sato-Kusubata, Dr. S. Kawashima, Dr. H. Sakuraba, and Dr. S. Ihara for their collaboration on the immuno- IX histochemical study shown in Chapter 1; Mr. M. Kawasaki for his goodwill in allowing the use of his original drawings of ancient animals; Dr. S. Kimura-Nozawa for her generous gift of the book Hair, written by M. L. Ryder and translated into Japanese by Dr. Kimura-Nozawa with the late Dr. T. Kato; and Mrs. S. Yasutomi-Sakaizumi for the schematic of the hair follicle structure and Dr. G. Harris for his rewriting and editing of the text, both of whom worked above and beyond the call of duty. I also thank the editorial and production staff of Springer-Verlag Tokyo, who provided exceptional help in the publication of this book. To all of you, I gratefully acknowledge your efforts. Finally, I express special thanks to Dr. M. Morioka for her encourage- ment throughout this study and my gratitude also goes to my experimen- tal animals, which died in their infancy. I dedicate this book to them. Kiyokazu Morioka Shiroi, Chiba Japan Contents Foreword V Preface VII 1 Introduction 1 Why Study Hair? 1 Growth and Development 4 General Structure 9 Electron Microscopy 12 Life and Death 14 Materials and Methods 20 References 21 2 Medulla 25 Variety 25 Early Stages 26 Trichohyalin 28 Unique Exocytosis 28 Granules and Vesicles 34 Groove 36 Programmed Cell Death 40 References 43 XII Contents 3 Hair Cortex and Hair Cuticle 45 Initial Signs of Keratinization 45 Accumulation of Keratin Fibers 48 Keratin Filament Bundles 50 Morphological Change of the Nucleus 54 Mitochondria 56 Keratinization of the Hair Cuticle 58 Granules 60 References 62 4 Inner Root Sheath 63 Near the Skin Surface 63 Precursors of the Inner Root Sheath 65 Formation of Trichohyalin Granules and Tonofilaments 67 Special Adherence of Henle’s Layer Cells 67 Decomposition of Trichohyalin Granules and Cornification 70 Cellular Junctions 74 Huxley Versus Henle Versus Cuticle 74 Degeneration of the Nucleus 76 Specifics of the Cuticle of the Inner Root Sheath 78 Relationship Between the Cuticle of the Inner Root Sheath and the Hair Cuticle 82 Final Steps in Cornification 82 Alternative Ways of Hair Emergence 86 References 88 5 Outer Root Sheath and Companion Layer 89 Conundrums 89 Outer Root Sheath in the Hair Bulb 91 Identification of the Companion Layer 91 Boundary and Overlapping of the Outer Root Sheath and Companion Layer 93
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