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Pritinder Kaur

Publications and source records attributed to Pritinder Kaur.

15 recordsLinked to original sources
PubMed2006

Identification of candidate murine esophageal stem cells using a combination of cell kinetic studies and cell surface markers.

The identification and characterization of esophageal stem cells are critical to our understanding of the biology of the esophageal epithelium in health and disease. However, the proliferative compartment within the mouse esophageal epithelium remains poorly characterized. Here, we report that the basal cells of the mouse esophagus can be separated into three phenotypically and functionally distinct subpopulations based on the expression of alpha(6) integrin and transferrin receptor (CD71). Cells that express high levels of alpha(6) integrin and low levels of CD71, termed alpha(6)(bri)CD71(dim), are a minor subpopulation of small and undifferentiated cells that are enriched for label-retaining cells and thus represent a putative esophageal stem cell population. Conversely, cells expressing high levels of both alpha(6) integrin and CD71 (alpha(6)(bri)CD71(bri)), the majority of basal esophageal cells, are enriched for actively cycling cells and therefore represent a transit-amplifying population. Kinetic analyses revealed that a third cell population, which is alpha(6) integrin-dim and CD71-bright (alpha(6)(dim)), is destined to leave the basal layer and differentiate.

Animals↗
PubMed2006

Side population in adult murine epidermis exhibits phenotypic and functional characteristics of keratinocyte stem cells.

Based on functional studies in the bone marrow, it has been suggested that the ability to efflux Hoechst 33342 may represent a universal stem cell trait. In this phenotypic and functional characterization of the Hoechst side population (SP) in adult murine epidermis, we demonstrate that these cells are a rare subset of the keratinocyte stem cell-enriched alpha(6)(bri)CD71(dim) fraction comprising SSC(low)/K14(+)/CD34(-)/Oil red O(-)/c-kit(-)/CD45(-) keratinocytes. Epidermal SPs have the smallest cell and nuclear size but exhibit the highest nuclear-to-cytoplasmic ratio of any fraction examined, consistent with a primitive cell type. Although SPs demonstrated poor cumulative in vitro proliferative output, they exhibited sustained epidermal tissue-regenerative activity in vivo compared with unfractionated and non-SP cells. Collectively, these results indicate that the epidermal SP contains the most potent keratinocyte stem cell population in skin epithelium.

Animals↗
PubMed2006

Epidermal stem cells.

Our understanding of adult epidermal stem cells has increased substantially over the last two decades especially; however even more detailed knowledge is imperative for realizing potential medical therapies. We need to know how to identify these cells and what regulates their function. In this review, we describe the literature to date and elucidate the clinical relevance of these findings.

Aging↗
PubMed2006

Interfollicular epidermal stem cells: identification, challenges, potential.

Homeostatic epidermal tissue renewal is the result of the combined activity of rare but potent stem cells, and a large pool of short-lived progenitor cells termed transit amplifying cells. Although the existence of epidermal stem cells has been known for some decades, their specific role in the processes of wound repair, skin diseases, and carcinogenesis remains unelucidated. Nevertheless, significant advances have been made in the identification and functional characterization of both murine and human epidermal stem cells, which place investigators in an exciting position to gain further insights into the fundamental processes of tissue renewal and repair in the epidermis.

Animals↗
PubMed2005

A homolog of Drosophila grainy head is essential for epidermal integrity in mice.

The Drosophila cuticle is essential for maintaining the surface barrier defenses of the fly. Integral to cuticle resilience is the transcription factor grainy head, which regulates production of the enzyme required for covalent cross-linking of the cuticular structural components. We report that formation and maintenance of the epidermal barrier in mice are dependent on a mammalian homolog of grainy head, Grainy head-like 3. Mice lacking this factor display defective skin barrier function and deficient wound repair, accompanied by reduced expression of transglutaminase 1, the key enzyme involved in cross-linking the structural components of the superficial epidermis. These findings suggest that the functional mechanisms involving protein cross-linking that maintain the epidermal barrier and induce tissue repair are conserved across 700 million years of evolution.

Animals↗
PubMed2005

Optimization of a transplant model to assess skin reconstitution from stem cell-enriched primary human keratinocyte populations.

Given that an important functional attribute of stem cells in vivo is their ability to sustain tissue regeneration, we set out to establish a simple and easy technique to assess this property from candidate populations of human keratinocyte stem cells in an in vivo setting. Keratinocytes were inoculated into devitalized rat tracheas and transplanted subcutaneously into SCID mice, and the epithelial lining regenerated characterized to establish the validity of this heterotypic model. Furthermore, the rate and quality of epidermal tissue reconstitution obtained from freshly isolated unfractionated vs. keratinocyte stem cell-enriched populations was tested as a function of (a) cell numbers inoculated; and (b) the inclusion of irradiated support keratinocytes and dermal cells. Rapid and sustained epidermal tissue regeneration from small numbers of freshly isolated human keratinocyte stem cells validates the utilization of this simple and reliable model system to assay for enrichment of epidermal tissue-reconstituting cells.

Animals↗
PubMed2005

Serial cultivation of primary adult murine keratinocytes.

In vitro cell culture is a necessary prerequisite in acquiring a thorough understanding of the biology and behavior of the cells of interest and is a critical first step in developing cellular therapies. Somatic stem cell biology is concerned with stem cells of the adult and how they may be utilized in regenerating tissue and ameliorating disease. Moreover, the incidence of disease increases with age, hence the demand for therapeutics is greatest among mature individuals. Therefore, an ability to grow and manipulate primary adult epithelial keratinocytes in vitro is of paramount importance in gaining insights into the biology of skin that may have clinical implications. A methodology has been developed that will enable investigators to isolate and serially culture adult basal keratinocytes from the epidermis of the mouse in a supplemented culture medium that selects for epithelial lineages and enhances their proliferation while inhibiting differentiation through many passages.

Animals↗
PubMed2005

FACS enrichment of human keratinocyte stem cells.

Recent work from our laboratory has led to the development and validation of fluorescence-activated cell sorting (FACS)-based techniques to prospectively isolate viable keratinocyte stem cells from both human and murine skin. Here we describe a step-by-step method to apply our technique to isolate epidermal keratinocytes from skin tissue, process them for immunofluorescent staining for cell surface markers, and subject them to fluorescence-activated cell sorting to obtain the stem, transient amplifying, and early differentiating keratinocyte fractions. These viable cells can then be placed into culture for further analysis or directly into keratinocyte assays, such as organotypic cultures or in vivo transplantation. This method will be useful for the complete biological characterization of keratinocyte progenitors with respect to wound healing, carcinogenesis, and therapeutic manipulation.

Animals↗
PubMed2004

An in vivo comparative study of sonic, desert and Indian hedgehog reveals that hedgehog pathway activity regulates epidermal stem cell homeostasis.

Despite the well-characterised role of sonic hedgehog (Shh) in promoting interfollicular basal cell proliferation and hair follicle downgrowth, the role of hedgehog signalling during epidermal stem cell fate remains largely uncharacterised. In order to determine whether the three vertebrate hedgehog molecules play a role in regulating epidermal renewal we overexpressed sonic (Shh), desert (Dhh) and Indian (Ihh) hedgehog in the basal cells of mouse skin under the control of the human keratin 14 promoter. We observed no overt epidermal morphogenesis phenotype in response to Ihh overexpression, however Dhh overexpression resulted in a range of embryonic and adult skin manifestations indistinguishable from Shh overexpression. Two distinct novel phenotypes were observed amongst Shh and Dhh transgenics, one exhibiting epidermal progenitor cell hyperplasia with the other displaying a complete loss of epidermal tissue renewal indicating deregulation of stem cell activity. These data suggest that correct temporal regulation of hedgehog activity is a key factor in ensuring epidermal stem cell maintenance. In addition, we observed Shh and Dhh transgenic skin from both phenotypes developed lesions reminiscent of human basal cell carcinoma (BCC), indicating that BCCs can be generated despite the loss of much of the proliferative (basal) compartment. These data suggest the intriguing possibility that BCC can arise outside the stem cell population. Thus the elucidation of Shh (and Dhh) target gene activation in the skin will likely identify those genes responsible for increasing the proliferative potential of epidermal basal cells and the mechanisms involved in regulating epidermal stem cell fate.

Animals↗
PubMed2004

Keratinocyte stem cell assays: an evolving science.

Although the existence of epithelial stem cells in the skin has been known for some decades from cell kinetic studies performed in vivo, attempts to prospectively isolate these cells for further biological characterization have been made possible relatively recently facilitated by the availability of antibodies that detect cell surface markers on epidermal cells. Elegant gene marking studies in vivo have provided confirmation of the patterns of epithelial tissue replacement predicted by classical cell turnover studies. But, the identification of candidate epidermal stem cells ex vivo remains an area of great controversy, requiring the re-evaluation of current experimental approaches that rely of necessity on predicted epidermal stem cell behavior in culture. Here we review the diverse experimental approaches utilized to identify keratinocyte stem cells and their underlying assumptions. We conclude that hair follicles and interfollicular epidermis each have their own self-renewing stem cell populations, contributing to distinct regions of the epithelium during homeostasis, although this is perturbed during wound healing. The need for the development of more rigorous assays for stem cell activity is highlighted given our recent observations using current assays and the discovery of new surface markers that identify putative epidermal stem cells.

Animals↗
PubMed2004

Location and phenotype of human adult keratinocyte stem cells of the skin.

The location and identity of interfollicular epidermal stem cells of adult human skin remain undefined. Based on our previous work in both adult murine and neonatal human foreskin, we demonstrate that cell surface levels of the alpha6 integrin and the transferrin receptor (CD71) are valid markers for resolving a putative stem cell, transit amplifying and differentiating compartment in adult human skin by flow cytometry. Specifically, epidermal cells expressing high levels of alpha6 integrin and low levels of the transferrin receptor CD71 (phenotype alpha6 (bri)CD71(dim)) exhibit several stem cell characteristics, comprising a minor population (2%-5%) of the K14(bri) fraction, enriched for quiescent and small blast-like cells with high clonogenic capacity, lacking the differentiation marker K10. Conversely, the majority of K14(bri) K10(neg) epidermal cells express high levels of CD71 (phenotype alpha6 (bri)CD71(bri)), and represent the actively cycling fraction of keratinocytes displaying greater cell size due to an increase in cytoplasmic area, consistent with their being transient amplifying cells. The alpha6 (bri)CD71(bri) population exhibited intermediate clonogenic capacity. A third population of K14(dim) but K10 positive epidermal cells could be identified by their low levels of alpha6 integrin expression (i.e. alpha6 (dim) cells), representing the differentiation compartment; predictably, this subpopulation exhibited poor clonogenic efficiency. Flow cytometric analysis for the hair follicle bulge region (stem cell) marker K15 revealed preferential expression of this keratin in alpha6 (bri) cells (i.e., both stem and transient amplifying fractions), but not the alpha6 (dim) population. Given that K15 positive cells could only be detected in the deep rete ridges of adult skin in situ, we conclude that stem and transient amplifying cells reside in this location, while differentiating (K15 negative) cells are found in the shallow rete ridges.

Adult↗
PubMed2004

The transcription factors c-rel and RelA control epidermal development and homeostasis in embryonic and adult skin via distinct mechanisms.

Determining the roles of Rel/NF-kappaB transcription factors in mouse skin development with loss-of-function mutants has been limited by redundancy among these proteins and by embryonic lethality associated with the absence of RelA. Using mice lacking RelA and c-rel, which survive throughout embryogenesis on a tumor necrosis factor alpha (TNF-alpha)-deficient background (rela(-/-) c-rel(-/-) tnfalpha(-/-)), we show that c-rel and RelA are required for normal epidermal development. Although mutant fetuses fail to form tylotrich hair and have a thinner epidermis, mutant keratinocyte progenitors undergo terminal differentiation to form an outer cornified layer. Mutant basal keratinocytes are abnormally small, exhibit a delay in G(1) progression, and fail to form keratinocyte colonies in culture. In contrast to the reduced proliferation of mutant keratinocytes during embryogenesis, skin grafting experiments revealed that the mutant epidermis develops a TNF-alpha-dependent hyperproliferative condition. Collectively, our findings indicate that RelA and c-rel control the development of the epidermis and associated appendages during embryogenesis and regulate epidermal homeostasis in a postnatal environment through the suppression of innate immune-mediated inflammation.

Age Factors↗
PubMed2004

Extensive tissue-regenerative capacity of neonatal human keratinocyte stem cells and their progeny.

Given our recent discovery that it is possible to separate human epidermal stem cells of the skin from their more committed progeny (i.e., transit-amplifying cells and early differentiating cells) using FACS techniques, we sought to determine the comparative tissue regeneration ability of these keratinocyte progenitors. We demonstrate that the ability to regenerate a fully stratified epidermis with appropriate spatial and temporal expression of differentiation markers in a short-term in vitro organotypic culture system is an intrinsic characteristic of both epidermal stem and transit-amplifying cells, although the stem cell fraction is most capable of achieving homeostasis. Early differentiating keratinocytes exhibited limited short-term tissue regeneration under specific experimental conditions in this assay, although significant improvement was obtained by manipulating microenvironmental factors, that is, coculture with minimally passaged dermal cells or exogenous supply of the ECM protein laminin-10/11. Importantly, transplantation of all classes of keratinocyte progenitors into an in vivo setting demonstrated that tissue regeneration can be elicited from stem, transit-amplifying, and early differentiating keratinocytes for up to 10 weeks. These data illustrate that significant proliferative and tissue-regenerative capacity resides not only in keratinocyte stem cells as expected, but also in their more committed progeny, including early differentiating cells.

Cell Differentiation↗
PubMed2002

Laminin 10/11: an alternative adhesive ligand for epidermal keratinocytes with a functional role in promoting proliferation and migration.

We have investigated the expression and function of the isoforms of laminin bearing the alpha5 chain, i.e. laminin-10/11 in neonatal and adult human skin. By immunostaining human skin derived from a variety of anatomic sites, we found that the laminin-alpha5 chain is expressed abundantly in the basement membrane underlying the interfollicular epidermis and the blood vessels in the dermis. Interestingly, while the expression level of the well-studied laminin-5 isoform did not change significantly with age, laminin-10/11 (alpha5 chain) appeared to decrease in the basement membrane underlying the epidermis, in adult skin. In contrast, the levels of laminin-10/11 in the basement membrane underlying blood vessels remained unchanged in neonatal vs. adult skin. Importantly, in vitro cell adhesion assays demonstrated that laminin-10/11 is a potent adhesive substrate for both neonatal and adult keratinocytes and that this adhesion is mediated by the alpha3beta1 and alpha6beta4 integrins. Adhesion assays performed with fractionated basal keratinocytes showed that stem cells, transit amplifying cells and early differentiating cells all adhere to purified laminin-10/11 via these receptors. Further, laminin-10/11 provided a proliferative signal for neonatal foreskin keratinocytes, adult breast skin keratinocytes, and even a human papillomavirus type-18 transformed tumorigenic keratinocyte cell line in vitro. Finally, laminin-10/11 was shown to stimulate keratinocyte migration in an in vitro wound healing assay. These results provide strong evidence for a functional role for laminin-10/11 in epidermal proliferation during homeostasis, wound healing and neoplasia.

Adult↗