Bone Status According to Neurofibromatosis Type 1 Phenotype: A Descriptive Study of 60 Women in France.

There is an increased risk of osteoporosis and an abnormal bone turn over in neurofibromatosis 1 (NF1). Our objective is to evaluate bone status in NF1 and to look for associations with cutaneous phenotype. We conducted a descriptive, monocentric study. We included 60 NF1 women, 18-51 years old, non-menopausal, divided in 2 groups: «at risk phenotype¼ (ARP) composed by 30 patients with at least 2 subcutaneous neurofibromas (SC-NF) and «classical phenotype¼ (CP) composed by 30 patients with none or 1 SC-NF. We evaluated low bone mineral density (BMD) risk factors and measured BMD, calcium and phosphorus homeostasis and bone turnover markers. Before 50 years old, Z-score has to be used to assess BMD. Z-score < - 2 is below expected range and represents 2.5% of the population. There was no difference between the two groups. Overall, Z-scores were low and 5 patients had a Z-score < - 2 (8.3%), which is 3 times general population low BMD frequency. 10 fragility fractures occurred in 8 patients, among which 2 were vertebral fractures. 85% had low calcium intake. 12 patients had hypophosphoremia, 25 elevated PTH. Vitamin D levels were low for 86.4%. 41 patients (69.5%) had at least one abnormal bone turnover markers. Low BMD is 3.3 times more frequent in NF1 than in general population, with high fracture risk, regardless of the skin phenotype, classical or at risk, because of high bone turn over and secondary hyperparathyroidism due to vitamin D deficiency and poor calcium intake.

Inflammatory Potential of Four Different Phases of Calcium Pyrophosphate Relies on NF-κB Activation and MAPK Pathways.

Background: Calcium pyrophosphate (CPP) microcrystal deposition is associated with wide clinical phenotypes, including acute and chronic arthritis, that are interleukin 1ß (IL-1ß)-driven. Two CPP microcrystals, namely monoclinic and triclinic CPP dihydrates (m- and t-CPPD), have been identified in human tissues in different proportions according to clinical features. m-CPP tetrahydrate beta (m-CPPTß) and amorphous CPP (a-CPP) phases are considered as m- and t-CPPD crystal precursors in vitro. Objectives: We aimed to decipher the inflammatory properties of the three crystalline phases and one amorphous CPP phase and the intracellular pathways involved. Methods: The four synthesized CPP phases and monosodium urate crystals (MSU, as a control) were used in vitro to stimulate the human monocytic leukemia THP-1 cell line or bone marrow-derived macrophages (BMDM) isolated from WT or NLRP3 KO mice. The gene expression of pro- and anti-inflammatory cytokines was evaluated by quantitative PCR; IL-1ß, IL-6 and IL-8 production by ELISA; and mitogen-activated protein kinase (MAPK) activation by immunoblot analysis. NF-κB activation was determined in THP-1 cells containing a reporter plasmid. In vivo, the inflammatory potential of CPP phases was assessed with the murine air pouch model via cell analysis and production of IL-1ß and CXCL1 in the exudate. The role of NF-κB was determined by a pharmacological approach, both in vivo and in vitro. Results:In vitro, IL-1ß production induced by m- and t-CPPD and m-CPPTß crystals was NLRP3 inflammasome dependent. m-CPPD crystals were the most inflammatory by inducing a faster and higher production and gene expression of IL-1ß, IL-6, and IL-8 than t-CPPD, m-CPPTß and MSU crystals. The a-CPP phase did not show an inflammatory property. Accordingly, m-CPPD crystals led to stronger activation of NF-κB, p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) MAPKs. Inhibition of NF-κB completely abrogated IL-1ß and IL-8 synthesis and secretion induced by all CPP crystals. Also, inhibition of JNK and ERK1/2 MAPKs decreased both IL-1ß secretion and NF-κB activation induced by CPP crystals. In vivo, IL-1ß and CXCL1 production and neutrophil infiltration induced by m-CPPD crystals were greatly decreased by NF-κB inhibitor treatment. Conclusion: Our results suggest that the inflammatory potential of different CPP crystals relies on their ability to activate the MAPK-dependent NF-κB pathway. Studies are ongoing to investigate the underlying mechanisms.