Delivery of Oligonucleotide Therapeutics: Chemical Modifications, Lipid Nanoparticles, and Extracellular Vesicles

Oligonucleotides (ONs) comprise a rapidly growing class of therapeutics. In recent years, the list of FDA-approved ON therapies has rapidly expanded. ONs are small (15-30 bp) nucleotide-based therapeutics which are capable of targeting DNA and RNA as well as other biomolecules. ONs can be subdivided into several classes based on their chemical modifications and on the mechanisms of their target interactions. Historically, the largest hindrance to the widespread usage of ON therapeutics has been their inability to effectively internalize into cells and escape from endosomes to reach their molecular targets in the cytosol or nucleus. While cell uptake has been improved, "endosomal escape" remains a significant problem. There are a range of approaches to overcome this, and in this review, we focus on three: altering the chemical structure of the ONs, formulating synthetic, lipid-based nanoparticles to encapsulate the ONs, or biologically loading the ONs into extracellular vesicles. This review provides a background to the design and mode of action of existing FDA-approved ONs. It presents the most common ON classifications and chemical modifications from a fundamental scientific perspective and provides a roadmap of the cellular uptake pathways by which ONs are trafficked. Finally, this review delves into each of the above-mentioned approaches to ON delivery, highlighting the scientific principles behind each and covering recent advances.

[Arterialization of the distal veins of the foot for limb salvage in arteritis. Techniques and results]

STUDY AIM

The aim of this retrospective study was to report the long term results with arterialisation of the veins of the foot as the final attempt to save an ischaemic limb when classical techniques have proved ineffective or impossible.

PATIENTS AND METHOD

From January 1974 to July 2000, 60 arterialisations of the distal veins of the foot were performed in 59 patients with arteritis, associated in 25 of them with diabetes mellitus. There were 41 men and 18 women, their mean age was 72 years (range from 49 to 95 years). There were 50 stage IV patients and 9 stage III patients. The arterialisation was performed by a reversed venous bypass between the femoral or popliteal artery and an internal vein of the foot, after destruction of the valvulas of the forefoot veins. The distal anastomosis was made termino lateral in order to provide tissular nutrition and to avoid blood congestion.

RESULTS

The result was considered good when a major amputation was avoided during one year at least, with a bypass permeability longer than one month. Among the 60 arterialisations, 36 were successful (60%), 7 in the short term (between one month and one year), 15 in the medium term (between one and five years), 14 in the long term (more than 5 years). Among the 15 medium-term good results, the mean time of bypass permeability was one year; three patients died, six were lost of follow-up, and six were still alive, four of them with a permeable bypass, at the time of the study. Among the 14 long term results, spontaneous bypass occlusion occurred after a 26-month mean time; despite this occlusion, the favourable result persisted till the death of the patient after a mean delay of 9 years (range from 5 to 15 years). The 24 other patients had a poor result followed by a major amputation. There were no deaths in relation with the reversed circulation.

CONCLUSION

These results suggest that the arterialisation of the distal veins of the foot may be considered a useful revascularization technique for limb salvage when all the classical methods have failed or are impossible.

[Splenic hydatidosis: report of 4 cases]

This report describes the clinical, diagnostic and treatment features of four patients with primary splenic hydatid disease who were treated between 1991 and 1993 in three hospitals of Lima where hydatid disease is often seen. Clinical features were not sufficient to reach a correct diagnosis in all cases. In two patients splenic cysts were found by accident. Abdominal ultrasound scanning gave erroneous or dubious results in three patients. Abdominal CAT scan was useful in locating a cyst in one of the cases. One patient harboured an infected cyst before surgery. Total splenectomy was performed in all cases with no complications up to discharge from the hospital. Splenic hydatidosis is rare but should be looked for in patients with cysts in other organs or with presumptive abdominal images suggestive of this disease.