25 years of epidermal stem cell research.

This is a chronicle of concepts in the field of epidermal stem cell biology and a historic look at their development over time. The past 25 years have seen the evolution of epidermal stem cell science, from first fundamental studies to a sophisticated science. The study of epithelial stem cell biology was aided by the ability to visualize the distribution of stem cells and their progeny through lineage analysis studies. The excellent progress we have made in understanding epidermal stem cell biology is discussed in this article. The challenges we still face in understanding epidermal stem cells include defining molecular markers for stem and progenitor sub-populations, determining the locations and contributions of the different stem cell niches, and mapping regulatory pathways of epidermal stem cell proliferation and differentiation. However, our rapidly evolving understanding of epidermal stem cells has many potential uses that promise to translate into improved patient therapy

Eccentric lamellar keratolimbal grafts harvested with a manually guided microkeratome

Background: To perform lamellar keratolimbal allograft transplantation in a one- step procedure with a single graft, we investigated the feasibility of harvesting eccentric lamellar keratolimbal grafts from conventionally processed corneoscleral buttons using a manually guided microkeratome in conjunction with an artificial anterior chamber system. Methods: We used the Moria LSK- One microkeratome and the automated lamellar therapeutic keratoplasty ( ALTK) system ( Antony, France). Ten human donor eyes were used to obtain single- piece lamellar keratolimbal grafts. Specimens were processed for light and electron microscopy. Results: Eccentric keratolimbal grafts could be obtained from all human donor buttons. Grafts include a crescent- shaped limbal and a large corneal portion. No visible damage to the limbal region was discernible. Conclusion: Our data show that the LSK- One microkeratome in conjunction with the ALTK system allows harvesting eccentric keratolimbal grafts from donor corneoscleral buttons. Copyright (c) 2007 S. Karger AG, Basel

Corneal Limbal Microenvironment Can Induce Transdifferentiation of Hair Follicle Stem Cells into Corneal Epithelial-like Cells

The aim of this study was to investigate the transdifferentiation potential of murine vibrissa hair follicle (HF) stem cells into corneal epithelial-like cells through modulation by corneal- or limbus-specific microenvironmental factors. Adult epithelial stem cells were isolated from the HF bulge region by mechanical dissection or fluorescence-activated cell sorting using antibodies to α6 integrin, enriched by clonal expansion, and subcultivated on various extracellular matrices (type IV collagen, laminin-1, laminin-5, fibronectin) and in different conditioned media derived from central and peripheral corneal fibroblasts, limbal stromal fibroblasts, and 3T3 fibroblasts. Cellular phenotype and differentiation were evaluated by light and electron microscopy, real-time reverse transcription-polymerase chain reaction, immunocytochemistry, and Western blotting, using antibodies against putative stem cell markers (K15, α6 integrin) and differentiation markers characteristic for corneal epithelium (K12, Pax6) or epidermis (K10). Using laminin-5, a major component of the corneo-limbal basement membrane zone, and conditioned medium from limbal stromal fibroblasts, clonally enriched HF stem and progenitor cells adhered rapidly and formed regularly arranged stratified cell sheets. Conditioned medium derived from limbal fibroblasts markedly upregulated expression of cornea-specific K12 and Pax6 on the mRNA and protein level, whereas expression of the epidermal keratinocyte marker K10 was strongly downregulated. These findings suggest that adult HF epithelial stem cells are capable of differentiating into corneal epithelial-like cells in vitro when exposed to a limbus-specific microenvironment. Therefore, the HF may be an easily accessible alternative therapeutic source of autologous adult stem cells for replacement of the corneal epithelium and restoration of visual function in patients with ocular surface disorders

An Ideal Society? Neighbors of Diverse Origins Interact to Create and Maintain Complex Mini-Organs in the Skin

Hair follicles are the focus of this primer on mammalian skin development

Effects of Murine Dermal Cells on the Regulation of Hair Growth Is Dependent on the Cell Number and Post-Natal Age of Newborn Mice

Dermal cells from neonatal mice can initiate the formation of hair follicles (HFs) when combined with adult mouse epidermal cells and transplanted subcutaneously into athymic mice. In the present study, the effects of dermal cells on HF formation were tested in terms of total cell number and the time course of cell harvest. Results demonstrated that the number of dermal cells is critical to the formation of HF. Furthermore, hair forming ability is rapidly decreasing as the neonatal mice age. To examine potential differences in gene expression, cDNA array was performed. Results demonstrate that numerous molecules which are directly involved in receptor and signaling correlated with decreased hair inductivity in early time points after delivery. It is reported that bone morphogenic protein (BMP)-6 and Wnt3a treatment increased hair inductivity of dermal papilla cells. But in our study, no changes were observed in the expression levels of BMP-6 and Wnt3a. However, several Wnt related genes demonstrate increased or decreased expression levels. Thus, our results suggest that co-ordinated regulation of these molecules will be important in hair neogenesis within our model system

Effects of temperature and doxorubicin exposure on keratinocyte damage in vitro

Cancer chemotherapy treatment often leads to hair loss, which may be prevented by cooling the scalp during drug administration. The current hypothesis for the hair preservative effect of scalp cooling is that cooling of the scalp skin reduces blood flow (perfusion) and chemical reaction rates. Reduced perfusion leads to less drugs available for uptake, whereas the reduced temperature decreases uptake of and damage by chemotherapy. Altogether, less damage is exerted to the hair cells, and the hair is preserved. However, the two mechanisms in the hypothesis have not been quantified yet. To quantify the effect of reduced drug damage caused by falling temperatures, we investigated the effect of local drug concentration and local tissue temperature on hair cell damage using in vitro experiments on keratinocytes. Cells were exposed for 4 h to a wide range of doxorubicin concentrations. During exposure, cells were kept at different temperatures. Cell viability was determined after 3 d using a viability test. Control samples were used to establish a concentration–viability curve. Results show that cell survival is significantly higher in cooled cells (T < 22° C) than in non-cooled cells (T = 37° C), but no significant differences are visible between T = 10° C and T = 22° C. Based on this result and previous work, we can conclude that there is an optimal temperature in scalp cooling. Further cooling will only result in unnecessary discomfort for the patient and should therefore be avoided

Detection of putative stem cells markers, CD44/CD133, in primary and lymph node metastases in head and neck squamous cell carcinomas. A preliminary immunohistochemical and in vitro study.

investigators hypothesized that cancer stem cells (CSCs) could play a role in determining cancer progression by metastasizing to cervical lymph node (N+) and then influencing prognosis of head-and-neck-squamous-cell carcinomas-(HNSCCs) patients.putative CSCs from 29 primary HNSCCs, and 19 corresponding node metastases were identified by immunohistochemical (IHC) and their clonogenic in vivo capacity was tested; ones epithelial nature of cancer cells forming colonies was confirmed by a second IHC, fluorescence-activated-cell-sorting-(FACS) analysis helped in counting CD44/CD133-CSCs markers percentage expression in HNSCC tumor-derived cultures.IHC showed CD44 (93.1\%) and CD133 (10.34\%) expression; FACS-analysis showed the enrichment of CD44/CD133 cancer cells, with the highest clonogenic capacity of CD44+-subpopulation; a higher CD44 rates were documented from N+ subcultures than from original tumors (p<0.05).A putative cancer-stem-like-cell-population is detectable in HNSCCs and our findings show their in vitro clonogenic capacity by demonstrating that CD44+ cultured cells are the main population proliferating obtained by N+ HNSCC metastases, emphasizing their possible role in tumor progression. This article is protected by copyright. All rights reserved

Normal stem cells in cancer prone epithelial tissues

The concept of a cancer stem cell is not a new one, being first suggested over 100 years ago. Over recent years the concept has enjoyed renewed enthusiasm, partly because of our growing understanding of the nature of somatic stem cells, but also because of a growing realisation that the development of strategies that target cancer stem cells may offer considerable advantages over conventional approaches. However, despite this renewed enthusiasm the existence of cancer stem cells remains controversial in many tumour types and any potential relationship to the normal stem cell pool remains poorly defined. This review summarises key elements of our understanding of the normal stem cell populations within animal models of the predominant cancer prone epithelial tissues, and further investigates the potential links between these populations and putative cancer stem cells

Localization of Putative Stem Cells in Dental Epithelium and Their Association with Notch and Fgf Signaling

The continuously growing mouse incisor is an excellent model to analyze the mechanisms for stem cell lineage. We designed an organ culture method for the apical end of the incisor and analyzed the epithelial cell lineage by 5-bromo-2′-deoxyuridine and DiI labeling. Our results indicate that stem cells reside in the cervical loop epithelium consisting of a central core of stellate reticulum cells surrounded by a layer of basal epithelial cells, and that they give rise to transit-amplifying progeny differentiating into enamel forming ameloblasts. We identified slowly dividing cells among the Notch1-expressing stellate reticulum cells in specific locations near the basal epithelial cells expressing lunatic fringe, a secretory molecule modulating Notch signaling. It is known from tissue recombination studies that in the mouse incisor the mesenchyme regulates the continuous growth of epithelium. Expression of Fgf-3 and Fgf-10 were restricted to the mesenchyme underlying the basal epithelial cells and the transit-amplifying cells expressing their receptors Fgfr1b and Fgfr2b. When FGF-10 protein was applied with beads on the cultured cervical loop epithelium it stimulated cell proliferation as well as expression of lunatic fringe. We present a model in which FGF signaling from the mesenchyme regulates the Notch pathway in dental epithelial stem cells via stimulation of lunatic fringe expression and, thereby, has a central role in coupling the mitogenesis and fate decision of stem cells