AB1431 EPIDEMIOLOGICAL AND GENETIC FEATURES OF ANTI-3-HYDROXY-3-METHYLGLUTARYL-COA REDUCTASE NECROTIZING MYOPATHY IN NORTHERN SPAIN: SINGLE-CENTER EXPERIENCE

Background

Anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) immune-mediated necrotizing myopathy (IMNM) is an entity of growing interest. However, data on epidemiology and clinical spectrum are still scarce and there is a need for the identification of its potential risk factors.

Objectives

To characterize the demographic, genetic, clinical, and serological features of patients with anti-HMGCR IMNM in a region of northern Spain.

Methods

Study of all patients diagnosed with anti-HMGCR IMNM during a 5-year period at a reference hospital in Northern Spain. Besides clinical and laboratory data, we analyzed the genetic influence of HLA genes and the rs4149056 (c.521T>C) single nucleotide polymorphism (SNP) in the SLCO1B1 gene.

Results

8 patients (5 women, 3 men) with a mean ± SD age of 64.9±7.3 years, fulfilled the criteria for anti-HMGCR IMNM. The incidence rate was 0.6 per 100.000 person-years and the prevalence 3 per 100.000 population. All patients had dyslipidemia and had been exposed to statins. Seven of the 8 of cases complained of myalgia. All of them had predominant lower limb proximal and symmetric muscle weakness that was severe in 2 of them. None of the patients had extra-muscular involvement. No evidence of malignancy was found. All patients had elevated serum CK levels with a median [IQR] of 4488 [2538-9194] IU/L. Serum 25-hydroxy vitamin D levels were decreased in all patients in whom it was determined. The 3 patients with a previous diagnosis of hypothyroidism had abnormal levels of TSH at the time of diagnosis. All patients experienced improvement with different schemes of immunosuppressive therapy. Noteworthy, 7 of 8 patients carried the HLA-DRB1*11 allele. The frequency of the rs4149056 C allele in the SLCO1B1 gene (12.5%) was similar to that of the general population.

Conclusion

In northern Spain, the IMNM anti-HMGCR preferentially affects people over 50 years of age who are carriers of the HLA-DRB1*11 allele and take statins. Both low vitamin D levels and hypothyroidism may play a potential predisposing role in the development of this disease

Table 1.PatientAge/SexHLA DRB1*11rs4149056 genotypeMRC at the weakest muscle group*DysphagiaCK (IU/L) at diagnosisAnti-HMGCR titer (CU)Induction therapy*Maintenance therapyClinical improvement**CK (IU/L) at last follow-up visit156/MYesTT2No8963277.8GC. IVIG.MTXGC. IVIG. MTX. RTXMarked134269/FYesTT0Yes9271235.9GC iv bolus. IVIG.GC. MTX. RTX.Marked890364/FYesTT3No4000242.6IVIG.IVIG.RTXMarked1284479/MYesTT4No4977145.6GC. IVIG.GC. IVIG.Complete92562/FNoTT3No2116210.0GCGC.MTX.Marked236657/FYesTC4No2294259.3IGIVIGIVComplete235768/FYesTT3No3273236.0GC. IGIV. AZA.GC. AZAComplete249864/MYesTC4Yes11000179.0GC iv bolus. AZA.GC. AZAComplete161

AZA: azathioprine; CK: creatinine kinase; CU: chemiluminescence units; F: female; GC: glucocorticoids; IVIG: intravenous immunoglobulins; M: male; MRC: medical research council scale; MTX: methotrexate; RTX: rituximab; ** Induction therapy initiated within 3 months of diagnosis. **Clinical improvement: no improvement (no improvement in MRC grade), mild improvement (improvement of MRC grade but still requiring assistance for activities of daily living), marked improvement (persistence of mild weakness without functional limitation), and complete improvement (return to baseline with no symptoms or signs of weakness).

Disclosure of Interests

None declared

Osteogenic capacity of mesenchymal stem cells from patients with osteoporotic hip fractures in vivo

PURPOSE

Human mesenchymal stem cells (MSCs) have the ability to differentiate into bone-forming osteoblasts. The aim of this study was to elucidate if MSCs from patients with OP show a senescent phenotype and explore their bone-forming ability in vivo.

MATERIALS AND METHODS

MSCs from patients with OP and controls with osteoarthritis (OA) were implanted into the subcutaneous tissue of immunodeficient mice for histological analysis and expression of human genes by RT-PCR. The expression of senescence-associated phenotype (SASP) genes, as well as p16, p21, and galactosidase, was studied in cultures of MSCs.

RESULTS

In vivo bone formation was evaluated in 103 implants (47 OP, 56 OA). New bone was observed in 45% of the implants with OP cells and 46% of those with OA cells (p = 0.99). The expression of several bone-related genes (collagen, osteocalcin, alkaline phosphatase, sialoprotein) was also similar in both groups. There were no differences between groups in SASP gene expression, p16, and p21 expression, or in senescence-associated galactosidase activity.

CONCLUSION

Senescence markers and the osteogenic capacity in vivo of MSCs from patients with OP are not inferior to that of cells from controls of similar age with OA. This supports the interest of future studies to evaluate the potential use of autologous MSCs from OP patients in bone regeneration procedures.

Association of LCT -13910C>T polymorphism and hip fracture in a cohort of older adult population from Northern Spain

Hip fracture is a common health problem very frequent in the older adult population and is associated with significant morbidity, mortality, and societal costs. There are several factors that increase the risk of suffering a hip fracture, however, the effect of genetic lactase non-persistence is not clear-cut yet. For this reason, we investigated if the LCT -13910C>T polymorphism is a potential risk factor for osteoporotic hip fractures in older adult people from the Northern Spain population. A total of 740 individuals were included in this study. Of them, 364 belonged to the group of patients whit osteoporotic hip fracture while the control group consisted of 376 individuals without hip fracture. The genotypes for the LCT -13910C>T polymorphism were analyzed by using polymerase chain reaction and high resolution melting. The prevalence of the CC genotype, which is related to lactase non-persistence, did not differ significantly in both groups. Likewise, no differences were observed between groups when they were compared with regard to the C or the T allele, or when they were analyzed considering gender. Additionally, our results were compared with those obtained in a control group of 207 nonagenarian individuals originally from Northern Spain and no differences were observed. In conclusion, no significant association was observed between the LCT -13910C>T polymorphism and the risk for suffering hip fracture in the older adult population of Northern Spain.

Methylation of the Sclerostin (SOST) Gene in Serum Free DNA: A New Bone Biomarker?

Introduction: Cell-free DNA (cfDNA) methylation is an important molecular biomarker, which provides information about the regulation of gene expression in the tissue of origin. There is an inverse correlation between SOST gene methylation and expression levels. Methods: We analyzed SOST promoter methylation in cfDNA from serum, and compared it with DNA from blood and bone cells from patients undergoing hip replacement surgery. We also measured cfDNA methylation in 28 osteoporotic patients at baseline and after 6 months of antiosteoporotic therapy (alendronate, teriparatide, or denosumab). Results: SOST gene promoter methylation levels in serum cfDNA were very similar to those of bone-derived DNA (79% ± 12% and 82% ± 7%, respectively), but lower than methylation levels in blood cell DNA (87% ± 10%). Furthermore, there was a positive correlation between an individual's SOST DNA methylation values in serum and bone. No differences in either serum sclerostin levels or SOST methylation were found after 6-months of therapy with antiosteoporotic drugs. Conclusions: Our results suggest that serum cfDNA does not originate from blood cells, but rather from bone. However, since we did not confirm changes in this marker after therapy with bone-active drugs, further studies examining the correlation between bone changes of SOST expression and SOST methylation in cfDNA are needed to confirm its potential role as a bone biomarker.

A genome-wide copy number association study of osteoporotic fractures points to the 6p25.1 locus

BACKGROUND

Osteoporosis is a systemic skeletal disease characterised by reduced bone mineral density and increased susceptibility to fracture; these traits are highly heritable. Both common and rare copy number variants (CNVs) potentially affect the function of genes and may influence disease risk.

AIM

To identify CNVs associated with osteoporotic bone fracture risk.

METHOD

We performed a genome-wide CNV association study in 5178 individuals from a prospective cohort in the Netherlands, including 809 osteoporotic fracture cases, and performed in silico lookups and de novo genotyping to replicate in several independent studies.

RESULTS

A rare (population prevalence 0.14%, 95% CI 0.03% to 0.24%) 210 kb deletion located on chromosome 6p25.1 was associated with the risk of fracture (OR 32.58, 95% CI 3.95 to 1488.89; p = 8.69 × 10(-5)). We performed an in silico meta-analysis in four studies with CNV microarray data and the association with fracture risk was replicated (OR 3.11, 95% CI 1.01 to 8.22; p = 0.02). The prevalence of this deletion showed geographic diversity, being absent in additional samples from Australia, Canada, Poland, Iceland, Denmark, and Sweden, but present in the Netherlands (0.34%), Spain (0.33%), USA (0.23%), England (0.15%), Scotland (0.10%), and Ireland (0.06%), with insufficient evidence for association with fracture risk.

CONCLUSIONS

These results suggest that deletions in the 6p25.1 locus may predispose to higher risk of fracture in a subset of populations of European origin; larger and geographically restricted studies will be needed to confirm this regional association. This is a first step towards the evaluation of the role of rare CNVs in osteoporosis.