Striated muscle gene therapy for the treatment of lipoprotein lipase deficiency

Excessive circulating triglycerides due to reduction or loss of lipoprotein lipase activity contribute to hypertriglyceridemia and increased risk for pancreatitis. The only gene therapy treatment for lipoprotein lipase deficiency decreases pancreatitis but minimally reduces hypertriglyceridemia. Synthesized in multiple tissues including striated muscle and adipose tissue, lipoprotein lipase is trafficked to blood vessel endothelial cells where it is anchored at the plasma membrane and hydrolyzes triglycerides into free fatty acids. We conditionally knocked out lipoprotein lipase in differentiated striated muscle tissue lowering striated muscle lipoprotein lipase activity causing hypertriglyceridemia. We then crossed lipoprotein lipase striated muscle knockout mice with mice possessing a conditional avian retroviral receptor gene and injected mice with either a human lipoprotein lipase retrovirus or an mCherry control retrovirus. Post-heparin plasma lipoprotein lipase activity increased for three weeks following human lipoprotein lipase retroviral infection compared to mCherry infected mice. Human lipoprotein lipase infected mice had significantly lower blood triglycerides compared to mCherry controls and were comparable to wild-type blood triglyceride levels. Thus, targeted delivery of human lipoprotein lipase into striated muscle tissue identifies a potential therapeutic target for lipoprotein lipase deficiency

Muscle stem cell dysfunction impairs muscle regeneration in a mouse model of Down syndrome

Abstract Down syndrome, caused by trisomy 21, is characterized by a variety of medical conditions including intellectual impairments, cardiovascular defects, blood cell disorders and pre-mature aging phenotypes. Several somatic stem cell populations are dysfunctional in Down syndrome and their deficiencies may contribute to multiple Down syndrome phenotypes. Down syndrome is associated with muscle weakness but skeletal muscle stem cells or satellite cells in Down syndrome have not been investigated. We find that a failure in satellite cell expansion impairs muscle regeneration in the Ts65Dn mouse model of Down syndrome. Ts65Dn satellite cells accumulate DNA damage and over express Usp16, a histone de-ubiquitinating enzyme that regulates the DNA damage response. Impairment of satellite cell function, which further declines as Ts65Dn mice age, underscores stem cell deficiencies as an important contributor to Down syndrome pathologies

RNA-based therapy for osteogenesis

International audienceNucleic acid-based therapy has shown great promise in accelerating bone regeneration as well as other diseases. Nucleic acids used in gene therapy mainly are either plasmid DNA (pDNA) or RNAs. Although pDNA therapy has been extensively studied for decades with encouraging preclinical and clinical results, side effects, and low efficiency associated with nuclear trafficking are hard to bypass. Unlike pDNA, RNAs (mRNA, siRNA, miRNA) exert their function in the cytoplasm, thereby being more efficient in hard-to-transfect cells such as primary osteoblasts. RNA interference-based gene silencing represents a negative regulation which knockdown the expression of antagonists that impair osteogenesis process. In contrary, mRNA therapy for osteogenesis represents a positive regulation which delivers mRNA encoding growth factors to accelerate bone regeneration. This review presents a comprehensive summary of the mRNA and siRNA-based therapies and the targets for bone re-generation in case of bone defect and osteoporosis