Fluctuation of Maternal and Fetal Free Extracellular Circulatory DNA in Maternal Plasma:

Increased concentrations of antibody-bound circulatory cell-free DNA in rheumatoid arthritis

BACKGROUND

Increased concentrations of cell-free DNA have been found in several disorders and have been interpreted as evidence of increased rates of cell death or turnover. Evidence from in vitro and animal experiments suggests that DNA may play a role in the pathogenesis of rheumatoid arthritis (RA).

METHODS

We measured cell-free DNA in plasma and serum from patients with RA and healthy controls by use of quantitative PCR for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) DNA. We used protein G Sepharosetrade mark bead adsorption of plasma and elution to isolate antibody-bound DNA.

RESULTS

In paired plasma and serum samples of 16 healthy controls the median GAPDH copies were 4500 genome equivalents (GE)/mL plasma (range 319-21 000) and in 26 RA patients 17 000 GE/mL plasma (2100-2 375 000, P = 0.0001). In the serum from normal controls the median GAPDH copies were 35 000 GE/mL (1700-239 000) and from RA patients 222 000 GE/mL (21 000-2 375 000, P = 0.004). A median of 81% of the cell-free DNA in RA was associated with antibody compared with 9% in healthy controls (P = 0.001). The concentrations of DNA did not vary with the type of therapy patients received.

CONCLUSIONS

These results provide new evidence for a role of cell-free DNA-antibody complexes in the etiology of RA, suggest new avenues for basic research, and may prove to be relevant to diagnosis and assessment of therapy.

Quantification of fetal microchimeric cells in clinically affected and unaffected skin of patients with systemic sclerosis

OBJECTIVE

Fetal microchimerism has been hypothesized as a potential pathogenic mechanism for systemic sclerosis (SSc). This hypothesis was based on the clinical similarities between SSc and graft-vs-host disease and the identification of microchimeric cells in affected SSc tissues. The aim of this study was to compare the quantity of microchimeric cells in clinically affected and non-affected skin of female patients with SSc.

METHODS

Fluorescence in situ hybridization (FISH) and real-time PCR were employed in paired skin biopsies obtained from clinically affected and unaffected areas from five female SSc patients with diffuse cutaneous SSc (dcSSC) and 10 healthy women. All women in the study had delivered a male fetus.

RESULTS

FISH analysis revealed the presence of male fetal cells in 1/5 SSc patients (20.0%) compared with 0/10 healthy women (P = 0.0037), whereas quantification by real-time PCR revealed that all SSc samples were positive for male DNA compared with none of the controls. In the five patients with dcSSc, there were similar numbers of microchimeric cells in both affected and unaffected skin (P = 0.4)

CONCLUSION

The presence of higher numbers of microchimeric cells in clinically unaffected SSc skin, before any clinically detectable evidence of sclerotic changes, suggests that an influx of microchimeric cells may precede the development of tissue fibrosis. This provides additional support to the hypothesis that fetal microchimerism may play a role in the pathogenesis of SSc.