Development and characterization of a first-in-class adjustable-dose gene therapy system

INTRODUCTION

Despite significant potential, gene therapy has been relegated to the treatment of rare diseases, due in part to an inability to adjust dosage following initial administration. Other significant constraints include cost, specificity, antigenicity, and systemic toxicity of current generation technologies. To overcome these challenges, we developed a first-in-class adjustable-dose gene therapy system, with optimized biocompatibility, localization, durability, and cost.

METHODS

A lipid nanoparticle (LNP) delivery system was developed and characterized by dynamic light scattering for size, zeta potential, and polydispersity. Cytocompatibility and transfection efficiency were optimized in vitro using primary human adipocytes and preadipocytes. Durability, immunogenicity, and adjustment of expression were evaluated in C57BL/6 and B6 albino mice using in vivo bioluminescence imaging. Biodistribution was assessed by qPCR and immunohistochemistry; therapeutic protein expression was quantified by ELISA.

RESULTS

Following LNP optimization, in vitro transfection efficiency of primary human adipocytes reached 81.3 % ± 8.3 % without compromising cytocompatibility. Critical physico-chemical properties of the system (size, zeta potential, polydispersity) remained stable over a broad range of genetic cassette sizes (1,871-6,203 bp). Durable expression was observed in vivo over 6 months, localizing to subcutaneous adipose tissues at the injection site with no detectable transgene in the liver, heart, spleen, or kidney. Gene expression was adjustable using several physical and pharmacological approaches, including cryolipolysis, focused ultrasound, and pharmacologically inducible apoptosis. The ability of transfected adipocytes to express therapeutic transgenes ranging from peptides to antibodies, at potentially clinically relevant levels, was confirmed in vitro and in vivo.

CONCLUSION

We report the development of a novel, low-cost therapeutic platform, designed to enable the replacement of subcutaneously administered protein treatments with a single-injection, adjustable-dose gene therapy.

Partial skeletal muscle-specific Drp1 knockout enhances insulin sensitivity in diet-induced obese mice, but not in lean mice

OBJECTIVE

Dynamin-related protein 1 (Drp1) is the key regulator of mitochondrial fission. We and others have reported a strong correlation between enhanced Drp1 activity and impaired skeletal muscle insulin sensitivity. This study aimed to determine whether Drp1 directly regulates skeletal muscle insulin sensitivity and whole-body glucose homeostasis.

METHODS

We employed tamoxifen-inducible skeletal muscle-specific heterozygous Drp1 knockout mice (mDrp1+/-). Male mDrp1+/- and wildtype (WT) mice were fed with either a high-fat diet (HFD) or low-fat diet (LFD) for four weeks, followed by tamoxifen injections for five consecutive days, and remained on their respective diet for another four weeks. In addition, we used primary human skeletal muscle cells (HSkMC) from lean, insulin-sensitive, and severely obese, insulin-resistant humans and transfected the cells with either a Drp1 shRNA (shDrp1) or scramble shRNA construct. Skeletal muscle and whole-body insulin sensitivity, skeletal muscle insulin signaling, mitochondrial network morphology, respiration, and H2O2 production were measured.

RESULTS

Partial deletion of the Drp1 gene in skeletal muscle led to improved whole-body glucose tolerance and insulin sensitivity (P < 0.05) in diet-induced obese, insulin-resistant mice but not in lean mice. Analyses of mitochondrial structure and function revealed that the partial deletion of the Drp1 gene restored mitochondrial dynamics, improved mitochondrial morphology, and reduced mitochondrial Complex I- and II-derived H2O2 (P < 0.05) under the condition of diet-induced obesity. In addition, partial deletion of Drp1 in skeletal muscle resulted in elevated circulating FGF21 (P < 0.05) and in a trend towards increase of FGF21 expression in skeletal muscle tissue (P = 0.095). In primary myotubes derived from severely obese, insulin-resistant humans, ShRNA-induced-knockdown of Drp1 resulted in enhanced insulin signaling, insulin-stimulated glucose uptake and reduced cellular reactive oxygen species (ROS) content compared to the shScramble-treated myotubes from the same donors (P < 0.05).

CONCLUSION

These data demonstrate that partial loss of skeletal muscle-specific Drp1 expression is sufficient to improve whole-body glucose homeostasis and insulin sensitivity under obese, insulin-resistant conditions, which may be, at least in part, due to reduced mitochondrial H2O2 production. In addition, our findings revealed divergent effects of Drp1 on whole-body metabolism under lean healthy or obese insulin-resistant conditions in mice.

One in the eye for an orthopaedic surgeon

Despite many reports of injuries to surgeons during operative procedures, there is no record of an eye injury caused by a foreign body. Orthopaedic surgeons are particularly vulnerable to such injury. An instance in which a penetrating eye injury occurred while hammering a rasp into the femur during a hip replacement is described. There is a potential oblique trajectory for a foreign body to reach the eye from the operative field despite the use of a visor for eye protection.

Trace metals in the hair of habitants of the Ok Tedi region, Papua New Guinea

It has long been known that mining activity can markedly change the level and distribution of certain heavy metals in the adjacent environment. This pollution can be quite widespread and long lasting and often has deleterious effects on the health of local populations. In the present study scalp hair was used as the biopsy material because of its ease of collection and long history of use in this connection. Hair was collected from all the local villages in the vicinity of the mine site, as well as from Papua New Guinean nationals from other provinces, and European expatriates who were employed by the mining company and who were resident in the area. Hair from local people showed a remarkably high iron content by comparison with previously studied populations. The extreme variations in hair iron levels were reflected in the differential distribution of levels according to location, age and sex. Hair cadmium was also high in the population studied. Hair copper, lead, zinc and mercury all appeared to be within 'normal' limits by comparison with other general populations. These results are discussed in the context of the environmental and social impact of the mining operations on the local people.

Port Moresby road traffic accident survey

Road Traffic Accidents (RTA's) are an important cause of morbidity and mortality in Papua New Guinea today. A survey of casualties from RTA's attending Port Moresby General Hospital over a seven-month period from November 1982 to June 1983 showed that of 209 patients seen, one-third were in cars and one-quarter were in utilities. The most dangerous positions in vehicles were (1) in the open back of a utility or truck, and (2) in the front seat (driver or passenger) of a car or utility. Only 13% of injured front-seat occupants of cars or utilities were wearing a seat-belt; in one-third of vehicles no seat belts were fitted. A plea is made for the strengthening of legislation to ensure the safety of passengers travelling in the open back of trucks or utilities, and for the introduction of legislation for fitting and wearing of seat-belts by front-seat occupants.

Malaria and filariasis in the Ok Tedi Region of the Star Mountains, Papua New Guinea

Malaria and filariasis surveys were carried out as part of a broader general health survey between December, 1982 and May, 1983 in the Ok Tedi region of the Star Mountains, Western Province. Malaria, tropical splenomegaly syndrome (TSS) and anaemia were identified as significant health problems. Malaria slide positivity rates of 64.9% in children 2 to 9 years of age and 19.5% in adults 15 years and older indicate high levels of stable malaria transmission. Infections with Plasmodium falciparum were the most common (75.2%), but P. vivax (17.4%) and P. malariae (7.4%) were also encountered. Palpable splenomegaly occurred in 79.2% of adults and children over two years of age with more than 50% of the enlarged spleens grade III or greater (Hackett). Microfilariae (Wuchereria bancrofti) were present in 34.3% of night blood films, and estimated haemoglobin values were considerably below WHO standards. Data from the surveys provide a baseline against which to monitor changes in health status which might be expected to occur in conjunction with the development of a major mining project in the area.