Previous Article |
Table of Contents
| Next Article 
* L'Oreal, Life Sciences Advanced Research, Centre C. Zviak, 90, Rue du Général Roguet, 92583 Clichy, France;
Communicated by Philip C. Hanawalt, Stanford University,
Stanford, CA, May 4, 2001 (received for review October 17, 2000)
Sun exposure has been clearly implicated in premature skin aging
and neoplastic development. These features are exacerbated in patients
with xeroderma pigmentosum (XP), a hereditary disease, the biochemical
hallmark of which is a severe deficiency in the nucleotide excision
repair of UV-induced DNA lesions. To develop an organotypic model of
DNA repair deficiency, we have cultured several strains of primary XP
keratinocytes and XP fibroblasts from skin biopsies of XP patients. XP
skin comprising both a full-thickness epidermis and a dermal equivalent
was succesfully reconstructed in vitro. Satisfactory
features of stratification were obtained, but the expression of
epidermal differentiation products, such as keratin K10 and loricrin,
was delayed and reduced. In addition, the proliferation of XP
keratinocytes was more rapid than that of normal keratinocytes.
Moreover, increased deposition of cell attachment proteins, three-dimensional skin model | xeroderma pigmentosum | UVB
radiation | DNA damage | keratinocyte differentiation
The major consequences of UV
(ultraviolet) radiation from sunlight are skin photoaging and cancer
development (1, 2). The dramatic effects of UV radiation are
demonstrated in patients affected with the genetic disease xeroderma
pigmentosum (XP) (3), the cellular biochemical hallmark of which is a
defect in nucleotide excision repair (NER) for UV-induced mutagenic DNA
lesions (4). NER is the most versatile repair process of UVB-induced
DNA lesions, such as 6-4 pyrimidine pyrimidone photoproducts and
cyclobutane pyrimidine dimers (CPDs). It involves five enzymatic steps:
(i) recognition of the DNA lesion; (ii) DNA
unwinding to form a "bubble;" (iii) 5' and 3'
single-strand DNA incision in the DNA strand bearing the UV lesion;
(iv) DNA gap filling by repair replication, with the intact
strand as template; and, ultimately, (v) ligation of the
newly synthesized DNA patch. Alteration of some of the early steps of
the NER process results in one of the seven XP complementation groups
(XP-A to XP-G), defined biochemically by somatic cell fusion (5). The
persistence of UV-induced DNA lesions is mutagenic during DNA
replication and may result in tumor development (6). Indeed, the NER
deficiency in XP patients results in a high predisposition (×2,000,
compared with the general population) to developing epidermal skin
tumors in sun-exposed body areas (3). The study of the responses of XP
skin cells in their natural three-dimensional environment is precluded
by ethical considerations, ruling out experimental trials that include
UV irradiation of XP volunteers. In addition, because of their limited
thickness and consequent poor differentiation capacity, classical
keratinocyte cultures (i.e., on plastic) do not take into account the
three-dimensional tissue architecture in epithelial-mesenchymal
interaction-mediated effects on UV-induced skin aging and cancer
development. Finally, introducing DNA repair defects by genetic
recombination in laboratory mice may result in phenotypic traits that
sometimes are at variance with those of the corresponding human
syndromes (7).
Alternative attempts to analyze tissue and cell damage induced by UV
radiation in normal individuals (8-10) and photoprevention (11) have
ensued from engineering fully differentiated normal human skin in
vitro. Actually, skin reconstructed in vitro was shown
to reproduce most stages of the stepwise epidermal differentiation program, starting with basal, undifferentiated keratinocytes, up to the
ultimate steps of maturation, illustrated by the formation of cornified
layers as in normal epidermis in vivo (12, 13). Nevertheless, in vitro organotypic human systems able to
reliably mimic photosensitive skin have never been developed, despite
their numerous potential fundamental applications.
In this report, we present the development of an in
vitro photosensitive human skin model developed from cells from
several independent primary (i.e., not transformed) strains of
epidermal keratinocytes and dermal fibroblasts obtained from skin
biopsies of unexposed body areas of XP patients (14). All of these
belong to the XP-C complementation group, the clinical hallmarks of
which are photosensitivity, skin aging, and proneness to cancer, but which are not associated with the neurodegenerative symptoms sometimes found in XP-D and -A patients (15).
We show that XP skin can be reliably reconstructed in vitro
from XP keratinocytes and XP fibroblasts and, most importantly, that it
retains the DNA repair deficiency of XP skin in vivo (3). Although it exhibits mostly normal morphological features, the in
vitro reconstructed XP skin exhibited alterations in the
keratinocyte differentiation program, accompanied by an increased rate
of proliferation. Still more significantly, the in vitro
reconstructed XP skin displayed striking epidermal invasions within the
dermis, a characteristic of early steps of epidermal neoplastic
development. The XP skin model reported in this paper thus opens
prospects for the study of tissue factors that contribute to UV-induced
skin carcinogenesis and aging. It may also provide clues to the
development of tissue gene therapy of XP.
Patients.
All patients presented a marked photosensitivity. Unless otherwise
indicated, all patients were independent. Patient XP148VI had developed
multiple skin tumors from the age of 9 years, as described (14).
Patients XP374VI (4 years old), XP373VI (3 years old) (XP 374VI's
brother), and XP399VI (5 years old) had developed several cutaneous
tumors from the age of 2. Patient XP424VI (18 years old) had developed
three basal cell carcinomas from the age of 15 and presented numerous
freckles and nevi on sun-exposed skin.
Skin Biopsies and Cell Culture.
Normal human skin was obtained from mammary plastic surgery.
Cell Biology
Clues to epidermal cancer proneness revealed by
reconstruction of DNA repair-deficient xeroderma pigmentosum skin
in vitro
,
,, and,§
Department of Dermatology, Centre
Hospitalo-Universitaire, Bab-El-Oued, Algeria; and
Genetic Instability and Cancer Unit, Centre National de
la Recherche Scientifique Unité Propre de Recherche 2169, 7, Rue Guy Môquet, 94801 Villejuif, France
Abstract
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusions
References
-6 and
-1 integrins, was observed in the basement membrane zone, and -1
integrin subunit, the expression of which is normally confined to basal
keratinocytes, extended into several suprabasal cell layers. Most
strikingly, the in vitro reconstructed XP skin displayed
numerous proliferative epidermal invasions within dermal equivalents.
Epidermal invasion and higher proliferation rate are reminiscent of
early steps of neoplasia. Compared with normal skin, the DNA repair
deficiency of in vitro reconstructed XP skin was
documented by long-lasting persistence of UVB-induced DNA damage in all
epidermal layers, including the basal layer from which carcinoma
develops. The availability of in vitro reconstructed XP
skin provides opportunities for research in the fields of photoaging,
photocarcinogenesis, and tissue therapy.
Introduction
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusions
References
Materials and Methods
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusions
References
Determination of XP Complementation Group. XP keratinocytes were infected by retroviral particles expressing wild-type XP cDNAs, and the complementation groups were determined by described procedures (17, 18).
Reconstructed Skin in Vitro. In all experiments, fibroblasts and keratinocytes were used at the same passages, P4 and P2, respectively. Reconstructed skin was prepared essentially as described in detail (12), except for minor modifications according to related XP strain (see below). The principle of skin reconstruction relied on the production of lattice in which fibroblasts were embedded in a type I collagen gel. After contraction of the lattice, 5 × 104 normal, to up to 3 × 105 XP keratinocytes (AS148, 3 × 105; AS374, 1 × 105; AS399, AS424, 2 × 105) were seeded onto a 1.5-cm2 lattice. Keratinocytes overlying the dermal equivalent (lattice) were then incubated for 7 (normal) to 8 days (XP) immersed in culture medium before being raised at the air-liquid interface (emersion period) for a time ranging from 7 days for normal and XP AS374A cells to 8 (AS148) or 9 days for AS399 and AS424.
Irradiation Sources and Procedures. UVB irradiation was performed with Philips TL20W/12 fluorescent tubes (Lumiéres Service, Paris) equipped with a Kodacel filter. UV spectra and procedures were as described (10).
Classical Histology. Samples were fixed in neutral formalin. Paraffin sections were stained with hematoxylin, eosin, and saffron (8).
Immunostaining. Immunolabeling was performed on air-dried vertical 5-µm cryosections as described (8).
Mouse monoclonal antibodies against various proteins were obtained from the following sources: keratin 10/RKSE 60 (1:5), Sanbio, Uden, The Netherlands; human filaggrin (1:100) and keratinocyte transglutaminase (1:20), Biomedical Technologies, Stoughton, MA; thymine dimers (H3) (1:50): L. Roza, Netherlands Organization for Applied Scientific Research, Zeist, The Netherlands (19); human vimentin (1:10), Monosan, Unden, The Netherlands; Ki-67 (1:20), NovoCastra, Newcastle, U.K.; integrin-6 (1:10): GoH3, Immunotech, Luminy, France; integrin -1
(1:50): K20, Immunotech.
Rabbit polyclonal antiserum was against human loricrin (1:40) (T. Magnaldo et al., ref. 20).
FITC-conjugated rabbit anti-mouse or swine anti-rabbit immunoglobulins
(Dako) were used as secondary antibodies (1:100). (1:X) indicates the
appropriate dilution of antibodies in PBS.
Detection of thymine dimers was carried out (19) on methanol/acetic
acid (3:1) fixed sections, followed by denaturation with NaOH (0.07 M
in 70% ethanol) and partial digestion with proteinase K (1 µg/ml).
| |
Results and Discussion |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusions
References
|
|---|
Reconstruction of XP Epidermis on a DNA Repair-Proficient Dermal Equivalent Reveals Altered Keratinocyte Differentiation and Proliferation. XP epidermis displaying apparent satisfactory features of stratification and differentiation (21) could be reconstructed on a DNA repair-proficient dermis. An increased (×2-×6) number of cells was seeded onto the dermal equivalent, compared with the normal skin model. The capacity of the epidermal cells to divide and their life span could be realized quite faithfully in vitro by their ability to form colonies (16, 22). Despite the higher amounts of XP-C keratinocytes required to fully reconstruct epidermis in vitro, their colony-forming efficiency (CFE) values were in a range similar to that of normal cells [e.g., CFE values from NHK9 (normal) and AS374 A (XP-C) keratinocyte strains were both 10%]. This apparent discrepancy suggested that three-dimensional culture conditions might reveal intrinsic alterations in the control of XP keratinocyte proliferation that are not detectable under standard culture conditions.
Histology of reconstructed XP epidermis made from epidermal XP keratinocytes revealed a stratum corneum (outermost terminally differentiated layers) with a significantly reduced thickness, suggesting an impaired capacity of XP-C keratinocytes to terminally differentiate, compared with normal controls (12, 21) (Fig. 1). Nevertheless, the stratum corneum of in vitro reconstructed XP epidermis did not contain persisting nuclei, an abnormality called parakeratosis, which accompanies some cutaneous hyperproliferative syndromes (23).
|
|
|
-1 and -6
specific to basal keratinocytes. Immunolabeling revealed that
deposition of these proteins at the basement membrane zone was
increased in XP epidermis compared with normal epidermis reconstructed in vitro (Fig. 3). In addition to a much brighter signal at
the basement membrane zone than in normal epidermis, -1 integrin was
also not restricted to basal keratinocytes but extended to several
suprabasal cell layers in reconstructed XP epidermis (Fig. 3).
Furthermore, staining of both -6 and -1 integrins underscored slight nascent epidermal invaginations within the dermal equivalent, the importance of which was amplified in the presence of a dermal equivalent containing XP fibroblasts (see below).
Higher levels of -1 integrin have been ascribed to keratinocytes
with characteristics of stem cells (30-33). Conversely, ectopic expression of -1 integrin in the suprabasal keratinocytes of transgenic mice and in the in vitro reconstructed epidermis
has resulted in epidermal alterations resembling psoriatic epidermis, such as keratinocyte hyperproliferation and delayed onset of
differentiation (34, 35). Although transient keratinocyte
hyperproliferation has been correlated with suprabasal expression of
integrins (-3 and -1) in normal in vitro reconstructed
human epidermis (36), it remains to be determined whether suprabasal
integrin expression may result in, or is only secondary to,
keratinocyte hyperproliferation in in vitro reconstructed XP epidermis.
To establish that the observed alteration of epidermal
differentiation and proliferation was not because of culture
conditions, a small number of biopsies from normal and XP skins were
analyzed. Histological stainings did not reveal major differences (or
alteration) of epidermal structures in normal versus XP skin biopsies.
In contrast, labeling of differentiation markers revealed slight alterations (delayed and reduced expression) of K10 keratin and a
slight decrease in loricrin in XP skin as compared with normal skin
maintained in the same conditions before analysis (i.e., up to 4 days
in serum containing medium, as sometimes happens with shipment of
biopsies to the laboratory). Furthermore, the expression of -1
integrin was increased and detected in several suprabasal keratinocyte
layers in XP but not in normal epidermis (data not shown). We conclude
that in vitro reconstructed XP epidermis closely resembles
XP epidermis ex vivo. Our model of reconstructed XP skin
thus appears as a faithful physiological system, able to reproduce
subtle and as-yet-unreported traits of the XP skin phenotype in the
absence of UV irradiation.
XP Fibroblasts Provoke Epidermal Invasions of Normal and XP Keratinocytes Within the Dermal Equivalent. According to their tissue origin or their association with cutaneous abnormalities, dermal fibroblasts have been shown to influence the behavior (differentiation and proliferation) of epidermal keratinocytes in organotypic cultures (37-40). To assess their influence on keratinocyte growth and epidermal morphogenesis, XP fibroblasts from three independent strains (AS148, AS374, AS424) were introduced into a dermal equivalent overlaid with either normal or XP keratinocytes.
Normal keratinocytes seeded onto XP dermal equivalents formed a fully differentiated epidermis and displayed a normal histological appearance (i.e., presence of spinous, granular, and horny layers), as well as a pattern of expression of differentiation markers similar to that of controls. However, frequent invaginations of normal keratinocytes within the XP dermal equivalent were observed by histology and immunolabeling of-6 and -1 integrins (Fig. 4). When XP keratinocytes were seeded
onto a XP dermal equivalent to reconstruct a complete XP skin,
epidermal invaginations were larger and more frequent than in
heterologous skins comprising solely a XP dermal equivalent.
|
XP Fibroblasts Spontaneously Orient Abnormally in the Dermal Equivalent and Lead to Retraction of Dermal Equivalents. The possible role of XP fibroblasts in the formation of epidermal invasions was assessed by studying their behavior at the macro- and microscopic levels in the three-dimensional dermal equivalent. Strikingly, the presence of XP fibroblasts resulted in significantly smaller diameters of the lattices (23.3 ± 3.3% at 24 h; 24.7 ± 3.3% at 96 h) than with control cells. Histology and staining of vimentin, a marker of mesenchymal cells, revealed that XP fibroblasts tend to massively orient perpendicular to the plane of the dermal-epidermal junction. In comparison, normal fibroblasts appeared mostly in random orientations (Fig. 5). These differences in the XP compared with a normal dermal equivalent strongly suggested that XP fibroblasts provoke profound modifications of the content and/or the organization of extracellular matrix components. In this respect, Scott et al. (41) have shown that a potent inhibitor of matrix metalloproteases, Marimastat, inhibited fibroblast-mediated contraction of a dermal equivalent populated by normal dermal fibroblasts, hence suggesting by analogy that in an XP dermal equivalent, increased matrix metalloproteases (42) may be produced.
|
In Vitro Reconstructed XP Epidermis as a Unique Three-Dimensional Model of DNA Repair Deficiency. As an attempt to evaluate the capacity of XP keratinocytes to repair UVB-induced DNA lesions within in vitro reconstructed epidermis, biologically efficient UVB doses (BEDs) were determined as described (8). BED was defined as the minimal UVB dose able to induce the formation of sunburn cells in suprabasal cell layers of in vitro reconstructed normal epidermis 24 h after exposure to a single UVB irradiation. There is a narrow correspondence between BED or sunburn cell formation in vitro and mean minimal erythemal dose as measured after UVB irradiation of normal volunteers (8, 46).
BEDs of in vitro reconstructed XP-C epidermis were found in the range of BEDs of reconstructed normal epidermis (i.e., 500-800 J/m2) (BEDs of XP-C epidermis: AS148, 300 J/m2; AS374A, 800 J/m2; AS399, 600 J/m2; AS424, 600 J/m2), which is in agreement with results obtained from laboratory mice with disrupted XPC alleles (XPC
/), which exhibit minimal erythemal dose
values similar to those of normal or heterozygous animals
(XPC+/) (47, 48). In contrast,
XPA/ or CSB/ mice exhibit
minimal erythemal dose values three to four times lower than those of
wild-type or XPC/ mice. These differences
presumably result from the persistence of UVB lesions on the
transcribed strand of active genes in XP-A/ and
CSB/ (47, 48) but not in
XPC/ mice, whose DNA repair defect only concerns
the global repair pathway (49).
The lowest BED value was found in the XP-C keratinocyte strain
with the poorest capacity to develop thick horny layers (AS148, Fig.
1), suggesting a protective role of stratum corneum. UVB penetration
and absorption throughout the stratum corneum and normal epidermis,
however, seem to be far less significant (50) than assumed (51).
Nevertheless, our previous investigations in classical cultures (i.e.,
on plastic) had shown that a particular UVB irradiation induced twice
as many DNA lesions (6-4 pyrimidine pyrimidone photoproducts and CPDs)
in normal fibroblasts as in keratinocytes (14). In skin epidermal
keratinocytes in vivo, at least 70% of protein synthesis is
devoted to keratins. We had suggested that normal expression of these
proteins might help to shield against UVB and perhaps lead to epidermal
cancer protection (14). Impaired K10 expression observed in all XP-C
epidermal cultures in our study might alter this natural protection.
XP and normal epidermis reconstructed in vitro on a normal
dermal equivalent were then exposed to appropriate UVB BEDs and harvested at various times after irradiation. CPD DNA lesions were
detected with the use of the H3 monoclonal antibody (8, 19).
Immediately after irradiation, CPD lesions were detected similarly in
all nuclei throughout both normal and XP epidermis, regardless of the
depth (Fig. 6). Twenty-four hours after
UVB irradiation, CPD lesions were no longer detected in the basal layer
of normal reconstructed epidermis, whereas in suprabasal layers most
nuclei remained clearly positive. In contrast, 24 h after UVB
irradiation of XP epidermis, CPD lesions in the basal layer remained at
a level similar to that observed initially. Ninety-six hours after
irradiation, DNA lesions were no longer detectable in any viable layers
of normal epidermis (i.e., basal and suprabasal layers), whereas they
persisted in an amount virtually identical in all layers of XP
epidermis. In comparison with other XP-C epidermis, epidermis
reconstructed from AS424 keratinocytes showed a slight attenuation of
DNA lesions 96 h after irradiation. This finding could be
correlated with the relatively moderate photosensitivity and cancer
proneness of this XP-C patient (only three basal cell carcinomas at the
age of 18). Likewise, residual NER DNA repair of AS424 fibroblasts was
relatively high (about 20%) compared with other XP-C fibroblasts
(AS148, AS399, and AS374A) that exhibited about 10% residual repair)
(not shown). In addition, in the four XP-C keratinocyte strains tested,
exposure to UVB led to parakeratosis that was more pronounced than in
normal epidermis (8) 96 h after irradiation. In one of the four
XP-C strains (AS374A), suprabasal sunburn cells remained visible
96 h after irradiation, whereas they had disappeared in other
cultures.
|
| |
Conclusions |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusions
References
|
|---|
This study demonstrates that XP skin could now reliably be reconstructed in vitro and thus defines a human model suitable for the study of a genetic DNA repair defect (photosensitivity) with accurate three-dimensional tissue architecture in vivo. The high UV sensitivity of the reconstructed XP skin model allows us to analyze the effects of UVs, including low doses, with special attention to early molecular events involved in skin photoaging and cancer. In this respect, this model should contribute to the enhancement of the efficiency of sun protection (11) against broad UV ranges. In vitro reconstruction of complex XP skin, including melanocytes and immune skin cells (Langerhans cells), should further improve the biological relevance of our model. Finally, the possibility of reverting to the DNA repair deficiency of XP epidermal keratinocytes as well as of XP fibroblasts (54, 55) allows the reconstruction of DNA repair proficient XP skins and provides perspectives on tissue therapy.
| |
Acknowledgements |
|---|
We are indebted to Dr. J. Leclaire for his continuous support and encouragement. T.M. is supported by the Association pour la Recherche sur le Cancer (ARC 1711; ARC 9500) and the Fondation pour la Recherche Médicale.
| |
Abbreviations |
|---|
XP, xeroderma pigmentosum; NER, nucleotide excision repair; CPDs, cyclobutane pyrimidine dimers; BED, biologically efficient UVB dose.
| |
Footnotes |
|---|
§ To whom reprint requests should be addressed. E-mail: magnaldo{at}infobiogen.fr.
| |
References |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results and Discussion
Conclusions
References
|
|---|
| 1. | Brash, D. E. (1997) Trends Genet. 13, 410-414[CrossRef][ISI][Medline] . |
| 2. |
Kraemer, K. H.
(1997)
Proc. Natl. Acad. Sci. USA
94,
11-14 |
| 3. | Kraemer, K. , Lee, M. & Scotto, J. (1987) Arch. Dermatol. 123, 241-250[Abstract]. |
| 4. | Ford, J. M. & Hanawalt, P. C. (1997) Curr. Top. Microbiol. Immunol. 221, 47-70[ISI][Medline] . |
| 5. |
de Boer, J.
& Hoeijmakers, J. H.
(2000)
Carcinogenesis
21,
453-460 |
| 6. |
Kraemer, K. H.
, Lee, M. M.
& Scotto, J.
(1984)
Carcinogenesis
5,
511-514 |
| 7. | Friedberg, E. C. (1999) Cancer J. Sci. Am. 5, 257-263[Medline] . |
| 8. | Bernerd, F. & Asselineau, D. (1997) Dev. Biol. 183, 123-138[CrossRef][Medline] . |
| 9. | Haake, A. & Polakowska, R. (1995) Cell Death Differ. 2, 183-193. |
| 10. |
Bernerd, F.
, Sarasin, A.
& Magnaldo, T.
(1999)
Proc. Natl. Acad. Sci. USA
96,
11329-11334 |
| 11. | Bernerd, F. , Vioux, C. & Asselineau, D. (2000) Photochem. Photobiol. 71, 314-320[CrossRef][Medline] . |
| 12. | Asselineau, D. , Bernard, B. , Bailly, C. & Darmon, M. (1985) Exp. Cell Res. 159, 536-539[CrossRef][Medline] . |
| 13. | Fuchs, E. & Byrne, C. (1994) Curr. Opin. Genet. Dev. 4, 725-736[CrossRef][Medline] . |
| 14. |
Otto, A.
, Riou, L.
, Marionnet, C.
, Mori, T.
, Sarasin, A.
& Magnaldo, T.
(1999)
Cancer Res.
59,
1212-1218 |
| 15. | Bootsma, D. , Kraemer, K. , Cleaver, J. & Hoeijmaker, J. (1998) in The Genetic Basis of Human Cancer, eds. Vogelstein, B. & Kinzler, K. (McGraw-Hill, New York), pp. 245-274. |
| 16. | Rheinwald, J. G. & Green, H. (1975) Cell 6, 331-344[CrossRef][ISI][Medline] . |
| 17. | Carreau, M. , Quilliet, X. , Eveno, E. , Salvetti, A. , Danos, O. , Heard, J. M. , Mezzina, M. & Sarasin, A. (1995) Hum. Gene Ther. 6, 1307-1315[Medline] . |
| 18. | Zeng, L. , Sarasin, A. & Mezzina, M. (1999) Methods Mol. Biol. 113, 87-100[Medline] . |
| 19. | Roza, L. , De Gruijl, F. R. , Bergen Henegouwen, J. B. , Guikers, K. , Van Weelden, H. , Van Der Schans, G. P. & Baan, R. A. (1991) J. Invest. Dermatol. 96, 903-907[CrossRef][ISI][Medline] . |
| 20. | Magnaldo, T. , Bernerd, F. , Asselineau, D. & Darmon, M. (1992) Differentiation (Berlin) 49, 39-46. |
| 21. |
Fuchs, E.
(1990)
J. Cell Biol.
111,
2807-2814 |
| 22. |
Barrandon, Y.
& Green, H.
(1987)
Proc. Natl. Acad. Sci. USA
84,
2302-2306 |
| 23. | Grosshans, E. & Caussade, P. (1991) in Dermatologie et Vénéréologie, eds. Saurat, J., Grosshans, E., Laugier, P. & Lachapelle, J. (Masson, Paris), pp. 13-19. |
| 24. | Jiang, C. K. , Epstein, H. S. , Tomic, M. , Freedberg, I. M. & Blumenberg, M. (1991) J. Invest. Dermatol. 96, 162-167[CrossRef][Medline] . |
| 25. | Bernerd, F. , Magnaldo, T. & Darmon, M. (1992) J. Invest. Dermatol. 98, 902-910[CrossRef][ISI][Medline] . |
| 26. | Juhlin, L. , Magnaldo, T. & Darmon, M. (1992) Acta Dermatol. Venereol. 72, 407-409[Medline] . |
| 27. | Schroeder, W. T. , Thacher, S. M. , Stewart-Galetka, S. , Annarella, M. , Chema, D. , Siciliano, M. J. , Davies, P. J. , Tang, H. Y. , Sowa, B. A. & Duvic, M. (1992) J. Invest. Dermatol. 99, 27-34[CrossRef][ISI][Medline] . |
| 28. | Bernard, B. A. , Reano, A. , Darmon, Y. M. & Thivolet, J. (1986) Br. J. Dermatol. 114, 279-283[CrossRef][ISI][Medline] . |
| 29. |
Giancotti, F.
& Ruoslaahti, E.
(1999)
Science
285,
1028-1032 |
| 30. | Jones, P. H. & Watt, F. M. (1993) Cell 73, 713-724[CrossRef][ISI][Medline] . |
| 31. | Jones, P. H. , Harper, S. & Watt, F. (1995) Cell 80, 83-93[CrossRef][ISI][Medline] . |
| 32. | Jensen, U. B. , Lowell, S. & Watt, F. M. (1999) Development (Cambridge, U.K.) 126, 2409-2418[Abstract]. |
| 33. | Jones, P. H. (1997) BioEssays 19, 683-690[CrossRef][ISI][Medline] . |
| 34. | Carroll, J. M. , Romero, M. R. & Watt, F. M. (1995) Cell 83, 957-968[CrossRef][ISI][Medline] . |
| 35. | Romero, M. R. , Carroll, J. M. & Watt, F. M. (1999) Exp. Dermatol. 8, 53-67[ISI][Medline] . |
| 36. | Rikimaru, K. , Moles, J. P. & Watt, F. M. (1997) Exp. Dermatol. 6, 214-221[CrossRef][Medline] . |
| 37. |
Smola, H.
, Thiekotter, G.
& Fusenig, N. E.
(1993)
J. Cell Biol.
122,
417-429 |
| 38. | Konstantinova, N. V. , Lemak, N. A. , Duong, D. M. , Chuang, A. Z. , Urso, R. & Duvic, M. (1998) Plast. Reconstr. Surg. 101, 385-391[CrossRef][ISI][Medline] . |
| 39. | Fusenig, N. E. (1994) in The Keratinocyte Handbook, eds. Leigh, I., Lane, E. & Watt, F. M. (Cambridge Univ. Press, Cambridge, U.K.), pp. 71-94. |
| 40. |
Saiag, P.
, Coulomb, B.
, Lebreton, C.
, Bell, E.
& Dubertret, L.
(1985)
Science
230,
669-672 |
| 41. | Scott, K. A. , Wood, E. J. & Karran, E. H. (1998) FEBS Lett. 441, 137-140[CrossRef][ISI][Medline] . |
| 42. | Curran, S. & Murray, G. I. (1999) J. Pathol. 189, 300-308[CrossRef][ISI][Medline] . |
| 43. | Johansson, N. & Kahari, V. M. (2000) Histol. Histopathol. 15, 225-237[Medline] . |
| 44. | Fisher, G. J. , Datta, S. C. , Talwar, H. S. , Wang, Z. Q. , Varani, J. , Kang, S. & Voorhees, J. J. (1996) Nature (London) 379, 335-339[CrossRef][Medline] . |
| 45. | Lehmann, A. R. & Bridges, B. A. (1990) Br. J. Dermatol. 35, Suppl. 122, 115-119. |
| 46. | Van de Leun, J. (1965) Photochem. Photobiol. 4, 459-464[Medline] . |
| 47. | Berg, R. J. , Ruven, H. J. , Sands, A. T. , de Gruijl, F. R. & Mullenders, L. H. (1998) J. Invest. Dermatol. 110, 405-409[CrossRef][ISI][Medline] . |
| 48. |
Berg, R. J.
, Rebel, H.
, van der Horst, G. T.
, van Kranen, H. J.
, Mullenders, L. H.
, van Vloten, W. A.
& de Gruijl, F. R.
(2000)
Cancer Res.
60,
2858-2863 |
| 49. | Sarasin, A. (1999) Mutat. Res. 428, 5-10[ISI][Medline] . |
| 50. | Chadwick, C. A. , Potten, C. S. , Nikaido, O. , Matsunaga, T. , Proby, C. & Young, A. R. (1995) J. Photochem. Photobiol. B 28, 163-170[CrossRef][Medline] . |
| 51. | Bruls, W. A. G. , Slaper, H. , van der Leun, J. & Berrens, L. (1984) Photochem. Photobiol. 40, 485-494[ISI][Medline] . |
| 52. | Barrandon, Y. (1993) Dev. Biol. 4, 209-215. |
| 53. |
Dumaz, N.
, Drougard, C.
, Sarasin, A.
& Daya-Grosjean, L.
(1993)
Proc. Natl. Acad. Sci. USA
90,
10529-10533 |
| 54. | Quilliet, X. , Chevallier-Lagente, O. , Eveno, E. , Stojkovic, T. , Destee, A. , Sarasin, A. & Mezzina, M. (1996) Mutat. Res. 364, 161-169[CrossRef][Medline] . |
| 55. | Zeng, L. , Quilliet, X. , Chevallier-Lagente, O. , Eveno, E. , Sarasin, A. & Mezzina, M. (1997) Gene Ther. 4, 1077-1084[CrossRef][ISI][Medline] . |
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg What's this?
This article has been cited by other articles in HighWire Press-hosted journals:
|
|
 |
|
  R. Maurelli, G. Zambruno, L. Guerra, C. Abbruzzese, G. Dimri, M. Gellini, S. Bondanza, and E. Dellambra Inactivation of p16INK4a (inhibitor of cyclin-dependent kinase 4A) Immortalizes Primary Human Keratinocytes By Maintaining Cells in the Stem Cell Compartment FASEB J, July 1, 2006; 20(9): 1516 - 1518. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. J. Stout, D. Westdijk, D. M. Calkhoven, O. Pijper, C. M. P. Backendorf, R. Willemze, L. H. F. Mullenders, and F. R. de Gruijl Epidermal transit of replication-arrested, undifferentiated keratinocytes in UV-exposed XPC mice: An alternative to in situ apoptosis PNAS, December 27, 2005; 102(52): 18980 - 18985. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Baldeschi, Y. Gache, A. Rattenholl, P. Bouille, O. Danos, J.-P. Ortonne, L. Bruckner-Tuderman, and G. Meneguzzi Genetic correction of canine dystrophic epidermolysis bullosa mediated by retroviral vectors Hum. Mol. Genet., August 1, 2003; 12(15): 1897 - 1905. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
