Bone marrow transplantation as a therapy for autosomal dominant osteopetrosis type 2 in mice

Development and evaluation of siRNA-mediated gene silencing strategies for ADO2 therapy utilizing iPSCs model and DMPC-SPIONs delivery system

BACKGROUND

Autosomal dominant osteodystrophy type II (ADO2) is an inherited disease characterized by an abnormal increase in bone mineral density, and CLCN7 (R286W) is its most common causative mutation. The aim of this study was to explore the new idea of siRNA technology applied to the in vitro treatment of ADO2.

METHODS

Urinary-derived cells from ADO2 patients were collected to establish induced pluripotent stem cells (iPSCs) model. The siRNA targeting CLCN7 (R286W) mutant mRNA was designed. the cytotoxicity of the delivery vector DMPC-SPIONs was comprehensively evaluated by CCK-8 assay, flow cytometry and scratch assay. Finally, qPCR was utilized to verify the post-transcriptional silencing effect of siRNAs.

RESULTS

We found that DMPC-SPIONs had low cytotoxicity and were able to effectively deliver siRNAs into ADO2-iPSCs. qPCR confirmed that siRNA-DMPC-SPIONs were able to significantly reduce the expression level of mutant CLCN7 (66%), while there was no significant effect on the expression of wild-type CLCN7.

CONCLUSIONS

This study developed a gene silencing strategy based on siRNAs and DMPC-SPIONs, which provides a potential new approach for the treatment of ADO2 and demonstrates the potential application of siRNA technology in the treatment of autosomal dominant genetic diseases.

INNOVATIVE STATEMENTS

In this study, we used the established ADO2-iPSCs using patient's urine-derived cells to explore the safety and efficacy of siRNA technology based on the principle of RNA interference for ADO2 treatment for the first time. In addition, we chose DMPC-SPIONs as the delivery vehicle for siRNA, which cleverly exploits the advantages of nanoparticles such as superparamagnetism, low cytotoxicity, and good bio-histocompatibility.

Spectrum of Skeletal Imaging Features in Osteopetrosis: Inheritance Pattern and Radiological Associations

Osteopetrosis (from the Greek "osteo": bone; "petrosis": stone) is a clinically and genetically heterogeneous group of rare diseases of the skeleton, sharing the same main characteristic of an abnormally increased bone density. Dense bones in radiological studies are considered the hallmark of these diseases, and the reason for the common term used: "Marble bone disease". Interestingly, a radiologist, Dr. Albers-Schonberg, described this disease for the first time in Germany in 1904. Indeed, radiology has a key role in the clinical diagnosis of osteopetrosis and is fundamental in assessing the disease severity and complications, as well as in follow-up controls and the evaluation of the response to treatment. Osteopetrosis includes a broad spectrum of genetic mutations with very different clinical symptoms, age onset, and prognosis (from mild to severe). This diversity translates into different imaging patterns related to specific mutations, and different disease severity. The main recognized types of osteopetrosis are the infantile malignant forms with autosomal recessive transmission (ARO-including the rarer X-linked recessive form); the intermediate autosomal recessive form (IAO); and the autosomal dominant ones ADO, type I, and type II, the latter being called 'Albers-Schonberg' disease. Imaging features may change among those distinct types with different patterns, severities, skeletal segment involvement, and speeds of progression. There are several classical and well-recognized radiological features related to osteopetrosis: increased bone density (all types with different degrees of severity assuming a 'Marble Bone Appearance' especially in the ARO type), different metaphyseal alterations/enlargement including the so-called 'Erlenmeyer flask deformity' (particularly of femoral bones, more frequent in ADO type 2, and less frequent in ARO and IAO), 'bone in bone' appearance (more frequent in ADO type 2, less frequent in ARO and IAO), and 'rugger-jersey spine' appearance (typical of ADO type 2). After conducting an overview of the epidemiological and clinical characteristic of the disease, this review article aims at summarizing the main radiological features found in different forms of osteopetrosis together with their inheritance pattern.