Regulation of synovial cell growth by polypeptide growth factors

Macrophage-like synoviocytes display phenotypic polymorphisms in a serum-free tissue-culture medium

Synovial macrophages play an outstanding role in many rheumatic diseases. However, traditional serum-containing tissue-culture techniques hamper in vitro studies due to fibroblast activation not found in vivo. The objective of this study was to examine dissociated synovial cells in a macrophage-selective, serum-free tissue-culture medium. Osteoarthritis synovial tissue (n=11) was cultured in Iscove's Modified Dulbecco's Medium (IMDM) with 10% fetal bovine serum (FBS) and compared to a serum-free, insulin-supplemented medium. After 9-11 and 19-21 days in vitro, immunohistochemistry was performed for macrophage/lymphocyte markers and cell division. Cytokine profiles were determined by RT-PCR. In serum, cells with a bipolar morphology rapidly proliferated. Respectively, 14.34+/-12.94% and 13.25+/-12.66% expressed CD68 and HLA-DR. These markers further decreased after one passage. In serum-free medium, proliferation was infrequent, and cells with diverse morphologies expressed 83.10+/-6.80% and 55.03+/-6.88% CD68 and HLA-DR respectively. CD14 was rare, and lymphocytes were missing. Both cultures expressed interleukin-6 and interleukin-8. This novel serum-free method permits the culture of distinct CD68/HLA-DR associated phenotypes.

Transcriptional regulation of the HOX4C gene by basic fibroblast growth factor on rheumatoid synovial fibroblasts

OBJECTIVE

To examine the expression of genes of the HOX D cluster in the synovial tissue of patients with rheumatoid arthritis (RA), and to determine whether basic fibroblast growth factor (bFGF) influences the expression and transcriptional regulation of the gene.

METHODS

The expression of genes of the HOX D cluster, including HOX4C, HOX4D, HOX4H, and HOX4I, was determined in the synovium of 4 patients with RA and 4 with osteoarthritis (OA) by in situ reverse transcription (RT) and RT-polymerase chain reaction (RT-PCR). The induction of HOX4C messenger RNA (mRNA) by bFGF was determined by RT-PCR. The binding activity of a transcriptional regulator of the HOX4C gene, C2, was analyzed by the mobility shift assay. NIH-3T3 cells transfected with a construct containing C2 binding sequence were incubated with bFGF, and the activity of the reporter was measured by luciferase assay.

RESULTS

Using an in situ RT assay, specific expression of HOX4C mRNA was detected in 3 of 4 RA synovial samples, whereas none of the OA synovia expressed HOX4C. HOX4D, HOX4H, and HOX4I genes were expressed in all synovial samples from RA and OA patients. The presence of HOX4C mRNA was also confirmed by RT-PCR and Southern blotting. Treatment with bFGF increased the expression of HOX4C mRNA in RA fibroblasts. The mobility shift assay and luciferase assay showed that bFGF enhanced C2 binding activity and significantly increased the transcriptional activity on RA fibroblasts.

CONCLUSION

Our findings suggest that HOX4C is involved in synovial hyperplasia, and that the transcriptional regulation of HOX4C genes by bFGF may play a crucial role in the pathogenesis of RA.

Anchorage-independent colony growth of pulmonary fibroblasts derived from fibrotic human lung tissue

Fibroblast heterogeneity is known to exist in chronically inflamed tissue such as pulmonary fibrosis (IPF) and scleroderma. We have previously shown differences in proliferation rates in primary lines and cloned lines of fibroblasts derived from IPF tissue compared with normal lung. In this study, we report that cell lines derived from fibrotic tissue demonstrate anchorage-independent growth in soft agarose culture whereas normal lung fibroblast lines do not. We also show that fibroblast lines derived from neonatal lung tissue form colonies at about the same frequency as the fibrotic cells. Colonies from both fibrotic and neonatal lines were shown to be positive for vimentin, laminin, fibronectin, fibronectin receptor, beta-actin, and tropomyosin by immunohistochemistry but were negative for desmin, keratin, Factor VIII, alpha-smooth muscle cell actin, and tenascin. Treatment with cytokines TGF-beta and PDGF or with corticosteroid modified the colony-forming capacity of fibrotic and neonatal cell lines, however, none of these treatments induced normal lung cell lines to form colonies. The presence of cells in adult fibrotic tissue with growth characteristics similar to those exhibited by neonatal cells is further evidence of fibroblast heterogeneity and suggests newly differentiated fibroblasts may be prevalent in fibrotic tissue and contribute directly to the matrix disorder seen in this disease.

T cell receptor analysis in rheumatoid arthritis: what have we learnt?

Many clues point to a role for T lymphocytes in the pathogenesis of rheumatoid arthritis (RA), although the importance of these cells and their position within the rheumatoid pathogenic scheme remain unknown. Encouraged by data from animal models of T-lymphocyte-mediated autoimmunity, a major focus of research into the role of T lymphocytes in RA has been the usage of T cell receptor V genes in rheumatoid synovitis. Despite many methodologic problems, involving choice of patients and controls, choice of specimens, and technical factors, several conclusions can be drawn from the published research. In particular, synovial T lymphocyte populations, as a whole, frequently show biased V gene usage and restricted clonality within those T lymphocyte subsets that utilize over-represented V gene families. Continued research into these synovial T lymphocyte subsets should provide important insights into the pathogenesis of RA, particularly if solutions to the identified methodologic problems are implemented.

Characterization of the immunophenotype and functional properties of fibroblast-like synoviocytes in comparison to skin fibroblasts and umbilical vein endothelial cells

We characterized the immunophenotype as well as functional properties--phagocytosis, the uptake of acetylated LDL, and the expression of HLA class II antigens, adhesion molecules, and cytokine mRNA--of fibroblast-like synoviocytes from rheumatoid arthritis synovium. Skin fibroblasts (FB) and umbilical vein endothelial cells (HUVEC) were studied in parallel. Cytofluorometric immunophenotyping by use of 84 mAb and 2 lectins and immunofluorescence microscopy indicated a high degree of homology between the three cell types. Only staining with mAb to von Willebrand factor (vWF) and CD31 and the lectin UEA-I appeared specific to HUVEC, whereas the mAb 5B5 to prolyl 4-hydroxylase that has been reported to be specific to FB stained HUVEC as well as synoviocytes and FB. All of the cells phagocytosed fluorescent latex beads of 1.7 and 2.6 microns in size. The uptake of acetylated LDL could be shown by HUVEC and, surprisingly, by synoviocytes, but not by FB. The induction of HLA-DR, -DP, and -DQ by IFN-gamma on the three cell types showed a similar dose-dependence. The upregulation of ICAM-1 by IL-1 alpha, TNF-alpha, and IFN-gamma appeared similar, whereas the induction of VCAM-1 by IL-1 alpha, IL-4, TNF-alpha, and IFN-gamma showed differences between the three cell types. ELAM-1 was expressed only on HUVEC after treatment with IL-1 alpha and TNF-alpha. The capacity of the cells to produce cytokines was studied at the level of mRNA by reverse transcription and PCR. All three cell types expressed the mRNA of IL-1 alpha, IL-6, IL-8, GM-CSF, and TGF-beta 1 spontaneously or after LPS stimulation, but never TNF-alpha mRNA. Our results indicate a high degree of relationship between the three cell types. In contrast to HUVEC, none of the markers and functional properties investigated appear specific to FB. Therefore, the issue of the origin of fibroblast-like synoviocytes and the role of vascular endothelial cells in the inflamed synovium is discussed.