Expression and Regulation of mRNA Coding for Acidic and Basic Fibroblast Growth Factor and Transforming Growth Factor^ in Cells Derived from Human Skin
Paul W. Cook, Robert J. Coffey, Jr., Bruce E. Magun, Mark R. Pittelkow, and Gary D. Shipley Department of Cell Biology and Anatomy Oregon Health Sciences University Portland, Oregon 97201 Department of Dermatology Mayo Clinic/Foundation (M.R.P.) Rochester, Minnesota 55905 Departments of Cell Biology and Medicine Vanderbilt University School of Medicine (R.J.C.) Nashville, Tennessee 37232
in the presence or absence of TGF/3 or serum. Collectively, our results demonstrate thaf distinct patterns of growth factor gene expression occur in different normal cell types isolated from human skin. (Molecular Endocrinology 4: 1377-1385, 1990)
We investigated the regulation of mRNAs coding for acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), and transforming growth factor-a (TGFa) in cultures of human neonatal foreskin fibroblasts, keratinocytes, and melanocytes. Each cell type was propagated in an optimized serum-free medium. In rapidly growing fibroblasts, the addition of fetal bovine serum caused a modest induction of aFGF message within 2 h in conjunction with a concomitant elevation of bFGF transcripts. In these same cells, TGFa mRNA could not be detected in any experimental condition. In contrast, keratinocytes rapidly growing in the presence of epidermal growth factor (EGF) contained transcripts for TGFa that increased substantially when these cells were treated with serum. This observation suggests that factors present in serum can elevate the levels of TGFa mRNA beyond the levels already present in keratinocyte cultures growing in the presence of EGF. These same keratinocyte cultures had low to undetectable levels of bFGF or aFGF message, and the levels of these mRNAs were not affected by serum treatment. Treatment of keratinocytes proliferating in the presence of EGF with TGF/3 for 48 h caused expression of bFGF mRNA in four of six independent cell strains. TGF/9-enhanced expression of bFGF mRNA occurred as early as 12-24 h after TGF0 exposure. TGF0 did not enhance the expression of mRNA for aFGF or TGFa in keratinocytes. Melanocytes failed to express detectable levels of mRNA coding for any of these growth factors
INTRODUCTION It has been suggested that production of growth factors by cells may regulate the growth and/or differentiation of the producer cell (autocrine activity) or neighboring cells (paracrine activity) (1). Importantly, altered production of or responsiveness to specific growth factors may be important events that result in pathological states. Elucidation of the underlying mechanisms that regulate the synthesis of growth factors in specific cell types will be crucial to the eventual development of novel strategies for the treatment of disease. Transforming growth factora (TGFa) (2) was first isolated from the conditioned medium of virus-transformed cells. The mature form of TGFa is a single chain polypeptide with structural homology to epidermal growth factor (EGF). TGFa is synthesized as an integral membrane protein that can be released via proteolytic cleavage as multiple mol wt forms into the extracellular environment (2). The actions of TGFa and EGF are thought to be mediated by their binding to the same receptor, and both polypeptides elicit similar biological responses. However, TGFa has been reported to be a more potent angiogenic factor than EGF (3). Although TGFa was originally thought to be an oncofetal form of EGF, it has been shown to be expressed in normal as
0888-8809/90/1377-1385S02.00/0 Molecular Endocrinology Copyright
Paul W. Cook, Robert J. Coffey, Jr., Bruce E. Magun, Mark R. Pittelkow, and Gary D. Shipley Department of Cell Biology and Anatomy Oregon Health Sciences University Portland, Oregon 97201 Department of Dermatology Mayo Clinic/Foundation (M.R.P.) Rochester, Minnesota 55905 Departments of Cell Biology and Medicine Vanderbilt University School of Medicine (R.J.C.) Nashville, Tennessee 37232
in the presence or absence of TGF/3 or serum. Collectively, our results demonstrate thaf distinct patterns of growth factor gene expression occur in different normal cell types isolated from human skin. (Molecular Endocrinology 4: 1377-1385, 1990)
We investigated the regulation of mRNAs coding for acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), and transforming growth factor-a (TGFa) in cultures of human neonatal foreskin fibroblasts, keratinocytes, and melanocytes. Each cell type was propagated in an optimized serum-free medium. In rapidly growing fibroblasts, the addition of fetal bovine serum caused a modest induction of aFGF message within 2 h in conjunction with a concomitant elevation of bFGF transcripts. In these same cells, TGFa mRNA could not be detected in any experimental condition. In contrast, keratinocytes rapidly growing in the presence of epidermal growth factor (EGF) contained transcripts for TGFa that increased substantially when these cells were treated with serum. This observation suggests that factors present in serum can elevate the levels of TGFa mRNA beyond the levels already present in keratinocyte cultures growing in the presence of EGF. These same keratinocyte cultures had low to undetectable levels of bFGF or aFGF message, and the levels of these mRNAs were not affected by serum treatment. Treatment of keratinocytes proliferating in the presence of EGF with TGF/3 for 48 h caused expression of bFGF mRNA in four of six independent cell strains. TGF/9-enhanced expression of bFGF mRNA occurred as early as 12-24 h after TGF0 exposure. TGF0 did not enhance the expression of mRNA for aFGF or TGFa in keratinocytes. Melanocytes failed to express detectable levels of mRNA coding for any of these growth factors
INTRODUCTION It has been suggested that production of growth factors by cells may regulate the growth and/or differentiation of the producer cell (autocrine activity) or neighboring cells (paracrine activity) (1). Importantly, altered production of or responsiveness to specific growth factors may be important events that result in pathological states. Elucidation of the underlying mechanisms that regulate the synthesis of growth factors in specific cell types will be crucial to the eventual development of novel strategies for the treatment of disease. Transforming growth factora (TGFa) (2) was first isolated from the conditioned medium of virus-transformed cells. The mature form of TGFa is a single chain polypeptide with structural homology to epidermal growth factor (EGF). TGFa is synthesized as an integral membrane protein that can be released via proteolytic cleavage as multiple mol wt forms into the extracellular environment (2). The actions of TGFa and EGF are thought to be mediated by their binding to the same receptor, and both polypeptides elicit similar biological responses. However, TGFa has been reported to be a more potent angiogenic factor than EGF (3). Although TGFa was originally thought to be an oncofetal form of EGF, it has been shown to be expressed in normal as
0888-8809/90/1377-1385S02.00/0 Molecular Endocrinology Copyright
