The study, “Soluble CD163 as a Potential Biomarker in Systemic Sclerosis,” was published in the journal Disease Markers.
Systemic sclerosis (SSc) — a severe connective tissue disorder — is associated with a high mortality risk. While the processes leading to the disease are currently unknown, there is increasing evidence for the role of white blood cells, such as monocytes and macrophages, in the development of SSc.
There are two types of macrophages: the classically M1-activated type that secretes high levels of pro-inflammatory cytokines, and an alternatively activated M2 type that exhibits an anti-inflammatory function.
While both M1 and M2 types are known to be involved in the disease development of systemic sclerosis, there is a strong M2 signature in the skin, blood, and lungs of SSc patients.
CD163 is a protein that is expressed on the surface of most macrophages, and is a well-accepted marker for activated M2 macrophages. Also, a soluble form of CD163 (sCD163) is released from the macrophage cell surface and found in the serum, a protein-rich liquid in blood that doesn’t include red or white blood cells.
High levels of CD163 on skin macrophages, as well as increased sCD163 serum levels, have been reported in patients with SSc when compared to the general population.
But there have been no studies that examined the significance of urinary sCD163 levels in SSc, despite the fact that urine concentrations are promising markers in other connective tissue diseases.
In the current study, researchers from Cochin Hospital at Paris Descartes University aimed to determine the serum and urinary sCD163 levels in a large population of SSc patients, and to assess any possible association with clinical and laboratory characteristics.
The study included 203 systemic sclerosis patients and 47 age- and sex-matched people with non-inflammatory diseases, mainly osteoporosis (used as controls).
Results showed that serum sCD163 levels were significantly higher in SSc patients (mean value of 529 ng/mL) compared to the controls (mean value of 385 ng/mL).
Urinary sCD163 concentrations were also higher in SSc patients than in controls, but the difference was not statistically significant.
The differing levels of soluble CD163 concentrations were not associated with any clinical or laboratory characteristics of systemic sclerosis patients.
“Our results show higher urinary sCD163 concentrations in SSc patients as compared to controls, but the difference did not reach significance, suggesting that evaluation of serum sCD163 levels should be prioritized for further studies as compared to urinary concentrations,” the researchers wrote.
“Our results further support that the M2 macrophages/CD163 signaling system may play a role in the pathogenesis of SSc,” the team added.
Researchers emphasized that additional studies are needed to determine the exact role of CD163 in the development of systemic sclerosis, and to assess whether it can indeed be used as a biomarker of the disease.