Background: Disc degeneration is characterized by elevated levels of cytokines, TNF-␣ and IL-1␤ and an increase in aggrecan-rich matrix degradation. Results: Cytokine-dependent syndecan-4 expression regulate ADAMTS-5/aggrecanse2 activation in disc cells. Conclusion: Syndecan-4 may play a key role in pathogenesis of degenerative disc disease. Significance: Syndecan-4 may offer a potential therapeutic target for controlling progression of degenerative disc disease.

Fibulins are a family of five extracellular matrix proteins characterized by tandem arrays of epidermal growth factor-like domains and a C-terminal fibulin-type module. They are widely distributed and often associated with vasculature and elastic tissues. In this study, we expressed the three more recently identified family members, fibulin-3, fibulin-4, and fibulin-5, as recombinant proteins in mammalian cells. The purified proteins showed short rod structures of ϳ20 nm with a globule at one end, after rotary shadowing and electron microscopy. Two forms of mouse fibulin-3 were purified, and the O-glycan profiles of the larger form were characterized. Polyclonal antibodies raised against the purified proteins did not show any crossreactivity with other family members and were used to assess the levels and localization of the fibulins in mouse tissues. Their binding interactions, cell adhesive properties, and tissue localization were analyzed in parallel with the previously characterized fibulin-1 and -2. Binding to tropoelastin was strong for fibulin-2 and -5, moderate for fibulin-4 and -1, and relatively weak for fibulin-3. Fibulin-4, but not fibulin-3 and -5, exhibited distinct interactions with collagen IV and nidogen-2 and moderate binding to the endostatin domain from collagen XV. Cell adhesive activities were not observed for all fibulins, except mouse fibulin-2, with various cell lines tested. All five fibulins were found in perichondrium and various regions of the lungs. Immunoelectron microscopy localized fibulin-4 and -5 to fibrillin microfibrils at distinct locations. Our studies suggest there are unique and redundant functions shared by these structurally related proteins.Fibulins are a family of extracellular glycoproteins with distinctive features of a fibulin-type C-terminal domain preceded by tandem calcium-binding (cb) 4 epidermal growth factor (EGF)-like modules (1-3). The five-member family can be further classified into two subgroups. Fibulin-1 and -2, the first subgroup, are substantially larger than the other three members of the family because of the presence of an extra domain with three anaphylatoxin modules and higher numbers of cbEGF modules (see Fig. 1). Fibuin-1 at 90 -100 kDa has variable C-terminal domains. Two major splice variants, fibulin-1C and -1D, are present in approximately equal amounts in most tissues of all animal species studied to date. Fibulin-2 at 200 kDa is the largest of all the fibulins, because it possesses an additional N-terminal domain of ϳ400 amino acids not found in other fibulins. Members of the second subgroup, fibulin-3, -4, and -5, are similarly small in size (50 -60 kDa) and highly homologous to one another in modular structure. They consist of a modified cbEGF domain at the N terminus followed by five tandem cbEGF modules and the fibulin-type C-terminal region (Fig. 1).Fibulin-1 and -2, the first subgroup, have been characterized extensively and shown to display distinct yet overlapping molecular interactions and expression patterns. Both proteins ar...

RANTES and IL-1β expression was significantly elevated in painful IVDs after careful selection of painless versus painful IVD tissue. RANTES expression was found to correlate significantly with expression of IL-1β. RANTES was upregulated by IL-1β/TNF-α/1% fetal bovine serum an in vitro treatment to induce a degenerative phenotype.

Background: Regulation of PHD expression and their function in hypoxia is unknown in nucleus pulposus. Results: Expression of PHD1-3 is regulated differentially by HIF-1/2. Under hypoxia, PHD2 degrades HIF-1␣, whereas PHD3 promotes its activity. Conclusion:In hypoxic nucleus pulposus, HIFs and PHDs constitute a regulatory network. Significance: PHD2 and 3 may serve as oxygen sensors in the intervertebral disc.

Inherited cutis laxa is a connective tissue disorder characterized by loose skin and variable internal organ involvement, resulting from paucity of elastic fibers. Elsewhere, frameshift mutations in the elastin gene have been reported in three families with autosomal dominant inheritance, and a family with autosomal recessive cutis laxa was recently reported to have a homozygous missense mutation in the fibulin-5 gene. In the present study, we analyzed the gene expression of elastin and fibulins 1-5 in fibroblasts from five patients with cutis laxa. One patient was found to express both normal (2.2 kb) and mutant (2.7 kb) fibulin-5 mRNA transcripts. The larger transcript contains an internal duplication of 483 nucleotides, which resulted in the synthesis and secretion of a mutant fibulin-5 protein with four additional tandem calcium-binding epidermal growth factor-like motifs. The mutation arose from a 22-kb tandem gene duplication, encompassing the sequence from intron 4 to exon 9. No fibulin-5 or elastin mutations were detected in the other patients. The results demonstrate that a heterozygous mutation in fibulin-5 can cause cutis laxa and also suggest that fibulin-5 and elastin gene mutations are not the exclusive cause of the disease.