Regulation of the gene that encodes the peptide core of heparin proteoglycan and other proteoglycans that are stored in the secretory granules of hematopoietic cells

Proteoglycans in Normal and Healing Skin

Significance: Proteoglycans have a distinct spatial localization in normal skin and are essential for the correct structural development, organization, hydration, and functional properties of this tissue. The extracellular matrix (ECM) is no longer considered to be just an inert supportive material but is a source of directive, spatial and temporal, contextual information to the cells via components such as the proteoglycans. There is a pressing need to improve our understanding of how these important molecules functionally interact with other matrix structures, cells and cellular mediators in normal skin and during wound healing. Recent Advances: New antibodies to glycosaminoglycan side chain components of skin proteoglycans have facilitated the elucidation of detailed localization patterns within skin. Other studies have revealed important proliferative activities of proteinase-generated fragments of proteoglycans and other ECM components (matricryptins). Knockout mice have further established the functional importance of skin proteoglycans in the assembly and homeostasis of the normal skin ECM. Critical Issues: Our comprehension of the molecular and structural complexity of skin as a complex, dynamic, constantly renewing, layered connective tissue is incomplete. The impact of changes in proteoglycans on skin pathology and the wound healing process is recognized as an important area of pathobiology and is an area of intense investigation. Future Directions: Advanced technology is allowing the development of new artificial skins. Recent knowledge on skin proteoglycans can be used to incorporate these molecules into useful adjunct therapies for wound healing and for maintenance of optimal tissue homeostasis in aging skin.

DNase I hypersensitivity patterns of the serglycin proteoglycan gene in resting and phorbol 12-myristate 13-acetate-stimulated human erythroleukemia (HEL), CHRF 288-11, and HL-60 cells compared with neutrophils and human umbilical vein endothelial cells

We mapped the DNase I-hypersensitive sites (DHSS) of the serglycin gene in resting and phorbol 12-myristate 13-acetate (PMA)-stimulated human erythroleukemia (HEL) and CHRF 288-11 cells, which have megakaryocytic characteristics, and HL-60 promyelocytic leukemia cells. We compared these DHSS with those of normal primary neutrophils and human umbilical vein endothelial cells. Several DHSS appear to be involved in regulating the level of endogenous expression and in the PMA response of hematopoietic cell lines. A DHSS unique to resting HL-60 cells and induced in CHRF 288-11 by PMA may explain the high degree of endogenous expression in HL-60 relative to HEL and CHRF (Schick, B. P., Petrushina, I., Brodbeck, K. C., and Castronuevo, P. (2001) J. Biol. Chem. 276, 24726-24735). A total of 4 DHSS in intron 1 and 6 in intron 2 are associated with the PMA response in a cell-specific manner. A DHSS in the 5'-flanking region and another in intron 1 lie in areas that have high homology with the orthologous murine serglycin locus and are rich in potential transcription factor binding sites. One DHSS in intron 1 and one in intron 2 are located within Alu repeats. Two DHSS found in DNA of normal primary neutrophils were different from those of the cell lines. One DHSS in exon 2 unique to neutrophils correlated with a previously unrecognized alternative splicing that removes exon 2. Human umbilical vein endothelial cells had a DHSS in intron 1 that was common with the cell lines. The different patterns of DHSS exhibited by the cells studied suggest that cell- and differentiation-specific alterations in chromatin structure may control serglycin gene expression.

Regulation of osteoblast, chondrocyte, and osteoclast functions by fibroblast growth factor (FGF)-18 in comparison with FGF-2 and FGF-10

This study investigated the actions of fibroblast growth factor (FGF)-18, a novel member of the FGF family, on osteoblasts, chondrocytes, and osteoclasts and compared them with those of FGF-2 and FGF-10. FGF-18 stimulated the proliferation of cultured mouse primary osteoblasts, osteoblastic MC3T3-E1 cells, primary chondrocytes, and prechondrocytic ATDC5 cells, although it inhibited the differentiation and matrix synthesis of these cells. FGF-18 up-regulated the phosphorylation of extracellular signal-regulated kinase in both osteoblasts and chondrocytes and up-regulated the phosphorylation of p38 mitogen-activated protein kinase only in chondrocytes. FGF-18 mitogenic actions were blocked by a specific inhibitor of extracellular signal-regulated kinase in both osteoblasts and chondrocytes and by a specific inhibitor of p38 mitogen-activated protein kinase in chondrocytes. With regard to the action of FGF-18 on bone resorption, FGF-18 not only induced osteoclast formation through receptor activator of nuclear factor-kappaB ligand and cyclooxygenase-2 but also stimulated osteoclast function to form resorbed pits on a dentine slice in the mouse coculture system. All these effects of FGF-18 bore a close resemblance to those of FGF-2, whereas FGF-10 affects none of these cells. FGF-18 may therefore compensate for the action of FGF-2 on bone and cartilage.

FGF-18, a novel member of the fibroblast growth factor family, stimulates hepatic and intestinal proliferation

The fibroblast growth factors (FGFs) play key roles in controlling tissue growth, morphogenesis, and repair in animals. We have cloned a novel member of the FGF family, designated FGF-18, that is expressed primarily in the lungs and kidneys and at lower levels in the heart, testes, spleen, skeletal muscle, and brain. Sequence comparison indicates that FGF-18 is highly conserved between humans and mice and is most homologous to FGF-8 among the FGF family members. FGF-18 has a typical signal sequence and was glycosylated and secreted when it was transfected into 293-EBNA cells. Recombinant murine FGF-18 protein (rMuFGF-18) stimulated proliferation in the fibroblast cell line NIH 3T3 in vitro in a heparan sulfate-dependent manner. To examine its biological activity in vivo, rMuFGF-18 was injected into normal mice and ectopically overexpressed in transgenic mice by using a liver-specific promoter. Injection of rMuFGF-18 induced proliferation in a wide variety of tissues, including tissues of both epithelial and mesenchymal origin. The two tissues which appeared to be the primary targets of FGF-18 were the liver and small intestine, both of which exhibited histologic evidence of proliferation and showed significant gains in organ weight following 7 (sometimes 3) days of FGF-18 treatment. Transgenic mice that overexpressed FGF-18 in the liver also exhibited an increase in liver weight and hepatocellular proliferation. These results suggest that FGF-18 is a pleiotropic growth factor that stimulates proliferation in a number of tissues, most notably the liver and small intestine.

Physiological degradation converts the soluble syndecan-1 ectodomain from an inhibitor to a potent activator of FGF-2

The activity of fibroblast growth factor 2 (FGF-2) is stringently controlled. Inactive in undisturbed tissues, it is activated during injury and is critical for tissue repair. We find that this control can be imposed by the soluble syndecan-1 ectodomain, a heparan sulfate proteoglycan shed from cell surfaces into wound fluids. The ectodomain potently inhibits heparin-mediated FGF-2 mitogenicity because of the poorly sulfated domains in its heparin sulfate chains. Degradation of these regions by platelet heparanase produces heparin-like heparin sulfate fragments that markedly activate FGF-2 mitogenicity and are found in wound fluids. These results establish a novel physiological control for FGF-2 and suggest new ways to modulate FGF activity.