Cardiovascular disease activity in lupus -- even during remission?
- Haematopoietic and endothelial progenitor cells are deficient in quiescent systemic lupus erythematosus
- Annals of the Rheumatic Diseases, Volume 66, Number 7, July 2007, pp. 865-870
What is the topic?
Lupus is a disease that has periods of obvious activity and apparent remission. However, even during what seems like quiet periods when there are no clearcut symptoms, it is possible that changes are occurring below the surface that can cause complications later.
What did the researchers hope to learn?
Lupus patients are at increased risk for cardiovascular disease (CVD), which involves hardening of the arteries and can lead to heart attacks or strokes later in life. The bone marrow makes special cells that help repair damaged blood vessels (endothelial progenitor cells, EPCs); people with CVD may have fewer of these repair cells in their blood stream, and this may contribute to the damage of the blood vessel walls, increasing the risk for cardiovascular disease. This group of researchers wanted to learn if lupus patients had lower levels of these helper cells, even when they were in remission.
Who was studied?
Fifteen women with lupus and 15 healthy women of the same age and similar smoking histories were recruited for this study. The lupus patients all were in remission for at least one year, and used low doses of prednisone or hydroxychloroquine alone or in combination with other lupus medications.
How was the study conducted?
The researchers took blood samples from all of the study participants and measured the EPCs and other cells that help produce them, called hematopoetic stem cells (HSCs). They compared the levels of EPCs and HSCs in the lupus patients and the healthy controls, and they also looked for relationships between the levels of these repair cells and other factors. To see whether the patients were developing CVD, the researchers measured the "stiffness" of the patients’ arteries with tests for blood pressure and blood flow.
What did the researchers find?
The levels of the EPC and HSC repair cells were lower in the lupus patients than in the controls. There was no correlation between the levels of these cells and measures of active lupus such as anti-dsDNA antibodies or antiphospholipid antibodies. Prednisone use did not appear to affect the number of the EPCs or HSCs, but hydroxychloroquine use did -- higher doses of this medication were associated with increased numbers of EPCs. Also, lupus patients who used hydroxychloroquine tended to have lower stiffness scores for their arteries than other lupus patients, which the researchers took as a sign that their blood vessels were staying healthier than others. All of these findings led the researchers to conclude that for some lupus patients, the ability to repair damaged blood vessels may be impaired, even if the patients are in remission and on medication, and it might be that continuing to take hydroxychloroquine even when otherwise well could help to protect the arteries from future risk.
What were the limitations of the study?
The size of the study population was very small, which makes it difficult for these preliminary findings to be thought of as proven. The researchers didn’t examine past use of medications, which may have had an impact on the lupus patients’ status when the study was conducted. Also, the lupus patients as a group had more traditional CVD risk factors than the controls, such as higher cholesterol, and it is possible that these other risk factors could have been affecting the levels of EPCs rather than lupus -- as could other things going on in the blood vessels and elsewhere they didn’t account for.
What do the results mean for you?
This study suggests the possibility that lupus might be contributing to future blood vessel damage even when there is no visible sign of the disease. At the same time, it suggests that finding a way to boost levels of EPCs and the HSCs might help prevent CVD from occurring in some lupus patients. It also offered further evidence suggesting that hydroxychloroquine might be useful in preventing CVD in lupus patients. It would be helpful to have a "before and after" study to see whether hydroxychloroquine raises EPCs in patients after it is given, compared to what is found in the same patients before it is given.