The expression pattern of galectins during human epidermal morphogenesis

INTRODUCTION

Galectins constitute a phylogenetically conserved family of proteins with high binding affinity for glycoconjugates bearing β-galactoside residues. Surprisingly, knowledge of the expression pattern of galectins during human epidermal morphogenesis is very limited.

METHODS

Fifty-eight biopsy skin specimens obtained from human embryos and 10 biopsy specimens obtained from healthy adult volunteers were processed for immunohistochemistry using a panel of antibodies against galectins 1, 3, 7, and 9.

RESULTS

Fetal human epidermis was devoid of any galectin 1 immunoreactivity, whereas clear-cut changes were found in the galectin 3 immunoreactivity of fetal epidermis with advancing gestational age. The expression pattern of galectins 7 and 9 remained constant at all stages of gestation.

CONCLUSIONS

The changes in galectin 3 immunoreactivity of human fetal epidermis with advancing gestational age, which are reported here for the first time, suggest that this galectin and its ligands may be implicated in the molecular events underlying human epidermal morphogenesis. It remains to be elucidated in future investigations whether the expression pattern of galectins, particularly that of galectin 3, in the developing human epidermis reveals alterations in fetuses with inherited cutaneous disorders that may be important for prenatal diagnosis of these disorders.

In contrast to melanocytes, keratinocytes of normal human adult interfollicular epidermis do not express galectin-1

INTRODUCTION

Galectins constitute a phylogenetically conserved family of proteins that specifically bind to glycoconjugates bearing β-galactoside residues. Although galectin-1 (Gal 1), the first identified member of the galectin family, is involved in highly important biological processes at the molecular and cellular level in human skin, its expression in keratinocytes of normal human adult interfollicular epidermis (NHAIE) remains in dispute, whereas that in epidermal melanocytes has drawn very little attention so far. This prompted us to investigate the expression of Gal 1 in the keratinocytes and melanocytes of NHAIE.

METHODS

Biopsy specimens obtained from the buttock skin of 23 healthy adult volunteers of both sexes were processed for single and double immunohistochemical staining using antibodies against Gal 1 and Melan-A.

RESULTS

In contrast to epidermal melanocytes, which revealed a distinct Gal 1 immunoreactivity, keratinocytes of NHAIE were completely devoid of any expression of this galectin.

CONCLUSIONS

This article simultaneously assesses Gal 1 immunoreactivity of keratinocytes and melanocytes in NHAIE for the first time. Our findings may contribute to a better understanding of alterations in Gal 1 expression in various benign and malignant cutaneous disorders and may be of importance for the future design of targeted therapies.

Galectin 3: an extraordinary multifunctional protein in dermatology. Current knowledge and perspectives

Galectin 3 is a unique ~31 kDa protein that recognizes the N-acetyl-lactosamine structure of several glycoconjugates. It mainly occurs in epithelial and myeloid cells, but is also found in a variety of human cell types. In view of the crucial role played by galectin 3 in the regulation of cellular processes of essential importance and in the pathogenetic mechanisms of diverse disorders, it is not surprising that, particularly in the last three decades, the attention of the scientific community has been increasingly drawn to this extraordinary and multifunctional galectin. In this paper the authors summarize current knowledge on the expression of galectin 3 in normal and diseased human skin, its implications in the pathogenesis, diagnosis and prognosis of cutaneous disorders, and the perspectives of a novel approach to the treatment of the latter using galectin 3 or its inhibitors/antagonists.

Galectin 1 in dermatology: current knowledge and perspectives

Galectins are a family of soluble proteins that are widely distributed in nature and bind to a variety of glycoproteins and glycolipids bearing β-galactoside residues. They are involved in highly important processes at the molecular and cellular level in human cutaneous and extracutaneous tissues, and they exert biological effects of paramount importance through their interaction with cytoplasmic and nuclear proteins and the components of the cell surface and extracellular matrix. Galectin 1 (Gal 1), the first galectin isolated, is a noncovalent homodimeric protein with a 14 kDa monomer that contains one carbohydrate-recognition domain (CRD) and preferentially recognizes galactose-β1-4-N-acetyl-glucosamine sequences on N- or O-linked glycans. Gal 1 occurs intracellularly, extracellularly, and on the cell surface. In the last few years Gal 1 has emerged as a multifaceted protein that exerts a wide spectrum of regulatory effects in diverse normal and abnormal tissues and conditions, indicating a tremendous therapeutic potential. This review summarizes current knowledge on the expression of Gal 1 in normal and diseased human skin, its implications in the pathogenesis, diagnosis, and prognosis of cutaneous disorders, and the novel approach to the treatment of these disorders offered by the use of Gal 1 or its inhibitors/antagonists.