Background/Purpose:

SLE patients are especially vulnerable to corticosteroid induced avascular necrosis. While it is appreciated that multiple factors contribute to AVN, the bone-fat axis in bone marrow is critical. The goals of this project are to examine the mechanisms by which MSC differention was affected in SLE and to develop targeted therapies to mitigate this risk. In SLE, type I interferons are key drivers of chronic inflammation, and thus might be a predisposing factor for avascular necrosis. Our recently published data demonstrate that SLE bone marrow MSC produce increased quantities of IFNβ. Moreover, SLE BMSC production of IFNβ is based on a positive feedback loop involving the innate signaling molecule Mitochondrial Antiviral Signaling (MAVS) protein and that this pathway contributes to human SLE BMSCs senescence associated secretory phenotype (SASP). Here we set out to investigate the differentiation defects of SLE BM-MSCs and the potential intervention approaches.

Methods:

The SLE patients recruited in this proposal satisfy the ACR classification criteria for SLE. BM MSCs were isolated with Ficoll centrifugation (1.073 g/ml) and phenotyped using flow cytometry. In vitro studies included real-time PCR, western blotting.

Results:

Our data suggested heterogeneity in SLE patients based on IFNβ level in blood serum. About 3/4 SLE patients had increased levels of IFNβ (mean= 2.30pg/ml) compared to healthy controls (mean=0.11pg/ml). Moreover, serum levels of IFNβ protein correlated with IFNβ mRNA in BM-MSCs (R² = 0.8, p<0.05). We compared 6 age paired BM aspirates from healthy controls and SLE patients. BM-MSCs from SLE patients and healthy controls were isolated and cultured. The MSC surface markers are positive for CD73, CD90 and CD105, but negative for CD34 and CD45 in both healthy and SLE BM-MSCs culture. SLE BM-MSCs display significantly decreased osteogenesis markers, such as ALP (6 folds, p<0.05), RUNX2 (8 folds, p<0.05), OCN (4 folds, p<0.05) and BSP (4 folds, p<0.05). However, when adipogenesis markers were evaluated, increased C/EBP delta (7 fold, p<0.05), PPARG (4 fold, p<0.05), Fabp4 (5 fold, p<0.05) and Adiponectin (5 fold, p<0.05) were found. Because transcription factor Runx2 is a critical regulator for osteogenesis and C/EBP delta is required for early adipogenesis, we then investigated the correlation between IFNβ gene expression and these two transcription factors. The results suggested that Runx2 is negatively correlated with IFNβ (R² = 0.78, p<0.05); while C/EBP delta positively correated with IFNβ (R² = 0.89, p<0.05). When BM-MSCs from healthy controls were treated with IFNβ, reduced ALP (12 folds, p<0.05), RUNX2 (11 folds, p<0.05), OCN (8 folds, p<0.05) and BSP (7 folds, p<0.05) were observed. In contrast to osteogenesis markers, IFNβ up-regulated adipogenesis markers C/EBP delta (6 folds, p<0.05). Taken together, our data indicate a role of IFNβ in osteogenesis-adipogenesis axis in SLE.

Conclusion:

IFN-I signature is an important feature of SLE. Our present work suggests that IFNβ affects osteogenesis-adipogenesis axis. By revealing the essential role of IFNβ on SLE BM-MSC differentiation, our study shed light on SLE pathogenesis and provides a new potential therapeutic target for SLE treatment.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/ifn%ce%b2-affects-osteogenesis-adipogenesis-axis-in-sle-bone-marrow/