Search

Summary: Shwachman–Diamond syndrome (SDS) is characterized by neutropenia, exocrine pancreatic insufficiency and skeletal abnormalities. SDS bone marrow haematopoietic progenitors show increased apoptosis and impairment in granulocytic differentiation. Loss of Shwachman–Bodian–Diamond syndrome (SBDS) expression results in reduced eukaryotic 80S ribosome maturation. Biallelic mutations in the SBDS gene are found in ~90% of SDS patients, ~55% of whom carry the c.183‐184TA>CT nonsense mutation. Several translational readthrough‐inducing drugs aimed at suppressing nonsense mutations have been developed. One of these, ataluren, has received approval in Europe for the treatment of Duchenne muscular dystrophy. We previously showed that ataluren can restore full‐length SBDS protein synthesis in SDS‐derived bone marrow cells. Here, we extend our preclinical study to assess the functional restoration of SBDS capabilities in vitro and ex vivo. Ataluren improved 80S ribosome assembly and total protein synthesis in SDS‐derived cells, restored myelopoiesis in myeloid progenitors, improved neutrophil chemotaxis in vitro and reduced neutrophil dysplastic markers ex vivo. Ataluren also restored full‐length SBDS synthesis in primary osteoblasts, suggesting that its beneficial role may go beyond the myeloid compartment. Altogether, our results strengthened the rationale for a Phase I/II clinical trial of ataluren in SDS patients who harbour the nonsense mutation. [ABSTRACT FROM AUTHOR]

Bone fragility and associated fracture risk are major problems in aging. Oxidative stress and mitochondrial dysfunction play a key role in the development of bone fragility. Mitochondrial dysfunction is closely associated with excessive production of reactive oxygen species (ROS). L-Carnitine (L-C), a fundamental cofactor in lipid metabolism, has an important antioxidant property. Several studies have shown how L-C enhances osteoblastic proliferation and activity. In the current study, we investigated the potential effects of L-C on mitochondrial activity, ROS production, and gene expression involved in osteoblastic differentiation using osteoblast-like cells (hOBs) derived from elderly patients. The effect of 5mM L-C treatment on mitochondrial activity and L-C antioxidant activity was studied by ROS production evaluation and cell-based antioxidant activity assay. The possible effects of L-C on hOBs differentiation were assessed by analyzing gene and protein expression by Real Time PCR and western blotting, respectively. L-C enhanced mitochondrial activity and improved antioxidant defense of hOBs. Furthermore, L-C increased the phosphorylation of Ca2+/calmodulin-dependent protein kinase II. Additionally, L-C induced the phosphorylation of ERK1/2 and AKT and the main kinases involved in osteoblastic differentiation and upregulated the expression of osteogenic related genes, RUNX2, osterix (OSX), bone sialoprotein (BSP), and osteopontin (OPN) as well as OPN protein synthesis, suggesting that L-C exerts a positive modulation of key osteogenic factors. In conclusion, L-C supplementation could represent a possible adjuvant in the treatment of bone fragility, counteracting oxidative phenomena and promoting bone quality maintenance. [ABSTRACT FROM AUTHOR]

Wnt signaling, a major regulator of bone formation and homeostasis, might be involved in the bone loss of osteoporotic patients and the consequent impaired response to fracture. Therefore we analyzed Wnt-related, osteogenic, and adipogenic genes in bone tissue of elderly postmenopausal women undergoing hip replacement for either femoral fracture or osteoarthritis. Bone specimens derived from the intertrochanteric region of the femurs of 25 women with fracture (F) and 29 with osteoarthritis without fracture (OA) were analyzed. Specific miRNAs were analyzed in bone and in matched blood samples. RUNX2, BGP, and OPG showed lower expression in F than in OA samples, while OSX, OPN, BSP, and RANKL were not different. Inhibitory genes of Wnt pathway were lower in F versus OA. 𝛽-Catenin protein levels were higher in F versus OA, whereas its cotranscriptional regulator (Lef1) was lower in F group. miR-204, which targets RUNX2, and miR-130a, which inhibits PPAR𝛾, were lower and higher, respectively, in F versus OA serum samples. The present study showed an inefficient Wnt signal transduction in F group despite higher 𝛽-catenin protein levels, consistent with the expected overall postfracture systemic activation towards osteogenesis. This transcriptional inefficiency could contribute to the osteoporotic bone fragility. [ABSTRACT FROM AUTHOR]