Contribution de Galectine-7 à la cicatrisation de l'épiderme

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Overexpression of galectin-7 in mouse epidermis leads to loss of cell junctions and defective skin repair.

International audienceThe proteins of the galectin family are implicated in many cellular processes, including cell interactions, polarity, intracellular trafficking, and signal transduction. In human and mouse, galectin-7 is almost exclusively expressed in stratified epithelia, notably in the epidermis. Galectin-7 expression is also altered in several human tumors of epithelial origin. This study aimed at dissecting the consequences of galectin-7 overexpression on epidermis structure and functions in vivo. We established transgenic mice specifically overexpressing galectin-7 in the basal epidermal keratinocytes and analyzed the consequences on untreated skin and after UVB irradiation or mechanical injury. The intercellular cohesion of the epidermis is impaired in transgenic animals, with gaps developing between adjacent keratinocytes, associated with loss of adherens junctions. The epidermal architecture is aberrant with perturbations in the multilayered cellular organisation of the tissue, and structural defects in the basement membrane. These transgenic animals displayed a reduced re-epithelialisation potential following superficial wound, due to a defective collective migration of keratinocytes. Finally, a single mild dose of UVB induced an abnormal apoptotic response in the transgenic epidermis. These results indicate that an excess of galectin-7 leads to a destabilisation of adherens junctions associated with defects in epidermal repair. As this phenotype shares similarities with that of galectin-7 null mutant mice, we conclude that a critical level of this protein is required for maintaining proper epidermal homeostasis. This study brings new insight into the mode of action of galectins in normal and pathological situations

Aberrant epidermal response in transgenic mice after UVB irradiation.

<p>Mice were depilated on their back and irradiated with a single dose of UVB (2000J/m²). (A) Kinetic of apoptotic response. The number of sunburn cells per cm of epidermis was determined in unirradiated depilated skin (no UV) and in irradiated skin between 6h and 48h post-UVB exposure. A total of 61 mice were used for these experiments (N<i>wt</i> = 25; N<i>tg</i>_<i>34</i> = 11; N<i>tg</i>_<i>46</i> = 25) i.e. 3 to 4 mice per genotype and per time point. Each bar represents the mean value ± sem. Statistical differences between <i>wt</i> and transgenic animals are noted **p<0.01 and ***p<0.001. (B) Histology. Representative hematoxylin-eosin sections of irradiated skin samples at 9h post-UVB. Apoptotic sunburn cells are indicated by black arrowheads. (C) Confocal analysis of E-Cadherin immunostaining on skin samples at 9h post-UVB. The signal is very weak and diffuse in <i>tg</i>_<i>34</i> and <i>tg</i>_<i>46</i> tissues compared to the <i>wt</i>. Three mice were used for each genotype. Scale bar: 20μm.</p

Defects in epidermal markers in <i>tg</i>_<i>34</i> and <i>tg</i>_<i>46</i> epidermis.

<p>Representative immunofluorescent stainings of keratin14 (K14), specific for basal cells (panel A), keratin10 (K10), specific for suprabasal cells (panel B), and loricrin, specific for terminally differentiated cells (panel C), were performed on paraffin sections of tail skin and analysed by confocal microscopy. Abnormal K14 staining is observed in cells above the basal layer, while K10 staining appears less intense in suprabasal cells of transgenic samples compared to <i>wt</i>. Three to five mice were used for each genotype. White lines delineate the dermo-epidermal junction. Scale bar: 20μm.</p

Delayed wound closure in transgenic mice.

<p>Superficial scratches were made along the sagittal axis of the tail. (A) Wound closure measurement. The distance between the two wound margins was determined 18h after injury. Results were calculated as a mean of at least three independent measurements per animal. A total of 49 mice were used for these experiments (N<i>wt</i> = 20; N<i>tg</i>_<i>34</i> = 14; N<i>tg</i>_<i>46</i> = 15). Each bar represents the mean value ± sem. Statistical differences between <i>wt</i> and transgenic animals are noted *p<0.05, ***p<0.001. (B) Histology. All pictures are focused on the “left” side of the migrating wound margin (yellow arrows). Transverse tail sections of the wound site stained with hematoxylin and eosin revealed abnormal migrating epithelial tongues in transgenic tissue compared to control, including signs of microblistering (yellow arrowheads). Scale bar: 10μm. (C, D, E) Confocal analysis. Immunostainings are performed either on paraffin sections for anti-E-cadherin Ab (C), or on cryosections for anti-laminin (D) or anti-cortactin (E) Abs. White lines delineate the dermo-epidermal junction. Scale bar: 10μm.</p