Ji Hoon Shin, M.D, is an associate professor with the radiology department, Asan Medical Center, University of Ulsan College of Medicine in Seoul, South Korea.
Benign esophageal stricture is a common complication in cases of caustic ingestion, esophageal surgery, and radiotherapy. Stenting technique is a valid alternative when other local therapies are not effective. Although the short-term effect of stenting is good, the long-term effect is limited by complications like tissue hyperplasia (TH) secondary to stent placement.Recently, RNA interference (RNAi) technique has been popular to down-regulate protein expression at the level of RNA transcription. RNAi is an RNA-dependent gene silencing process that is controlled by the RNA-induced silencing complex and is initiated by short double-stranded RNA molecule. Combination of RNAi technique to prevent TH is limited.To establish character, level, and expression of MMP-9 in TH and to evaluate the efficacy of RNAi therapy using Chol-R9 delivered siRNA targeting MMP-9 to prevent TH after bare stent insertion in a rat esophageal model. After 3 weeks following esophageal stent placement (5㎜ diameter & 15㎜ length) in 10 rats, esophageal samples were subjected to histological examination and quantification of MMP-9 by zymography, western blotting and quantitative real-time polymerase chain reaction (qRT-PCR). Chol-R9 was used to deliver MMP-9 targeted siRNA into rat esophagus. Ten rats underwent Chol-R9 delivered siRNA targeting MMP-9 at 1 week and 2 weeks after stenting and were sacrificed at 3 weeks. To assess the relationship between the therapeutic effect of Chol-R9/siRNA complex and MMP-9 over-expression in tissue hyperplasia, degree of TH and change of MMP-9 level were evaluated in esophagus samples (rat’s esophagus of Chol-R9/siRNA treatment group).\r\n\r\n\r\n
Elena O Nasakina, the authors work is aimed at developing materials for the production of non-invasive implants of medical appointment, such as stent and kava filter, of a self-expandable design aimed at treating cancer and cardiovascular, respiratory, excretory and digestive systems, with an improved complex of operational characteristics, including maximally extended service life, biological inertness, improved mechanical performance, providing the possibility of implants work in the human body under increased loads, better coincidence in geometric parameters with curved parts of the prosthetic organ and minimization of the traumatic effect of the operation due to a reduction in the dimensions in the transport position, a reduction in the cross-section of the mechanism of their delivery to the organ to be restored, the possibility of local therapeutic effect on the damaged site, elimination/reduction of the probability of renewal of the problem being solved.\r\n\r\n
NiTi alloys possessing a shape memory effect and mechanical characteristics similar to the behavior of living tissues have been already used for years as the material for production of medical devices, including implants, for example-stents, without the need for additional devices except catheter-carrier. However, nitinol contains nickel (including on its surface) which is toxic for organism. Different authors give completely different durations and magnitudes of the nickel ion release from microstructural nitinol into the medium, as well as level of biocompatibility and electro-chemical corrosion characteristics. As is well-known that formation of nanostructures is able to afford to give to materials special, controlled characteristics. On the other hand, the high density of inter-granular surface defects could lead to a poor corrosion performance. The purpose of this study is to investigate the composition, structure and properties of polycrystalline nitinol with nano-grains. Nano-structural NiTi (55.91 weight % Ni, 44.03 weight % Ti) wires for production of non-invasive implants (stents) was tested for corrosion resistance under static conditions by dipping into solutions with various acidities (pH from 1.68 to 9.18) for two years, for static mechanical properties and biocompatibility. The structure was determined with the use of the transmission electron microscope (TEM), X-ray diffractometer, scanning electron microscope (SEM) and on the Auger spectrometer. The nickel release is less in comparison with data for microstructural nitinol in a solution of any acidity. A significant retardation of the nickel ion release and the absence of titanium ion release in the weakly acidic and neutral solutions with polished samples are observed. A simultaneous 7–11% increase in strength and plasticity in comparison with microstructural nitinol was attained. Toxicity of samples hasn\'t been revealed.\r\n\r\n