Development of a detection method for antisense oligonucleotides in mouse kidneys by matrix-assisted laser desorption/ionization imaging mass spectrometry

RATIONALE

Oligonucleotide therapeutics have recently gained much attention, but its pharmacokinetic evaluation methods are still not sufficient, and, in particular, more tools are needed to evaluate their tissue distribution and metabolites. We developed a matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS)-based method to evaluate the tissue distribution of oligonucleotide therapeutics.

METHODS

We used an antisense oligonucleotide containing locked nucleic acids (LNA-A). Various washing protocols were examined using mouse kidney homogenate sections. Next, we applied a two-step matrix preparation strategy. As a first step, 3-hydroxypicolinic acid (3-HPA) matrix containing citrate and amines was sprayed using an airbrush and subsequently 3-HPA matrix containing citrate only was sprayed using the ImagePrep. Finally, kidney sections prepared from LNA-A-dosed mice were treated with our optimized method and analyzed with MALDI-IMS.

RESULTS

The selected washing method made it possible to detect LNA-A with MALDI-IMS and, furthermore, our developed matrix pretreatment method enhanced signal intensity approximately two-fold. MALDI-IMS revealed that LNA-A localized in a portion presumed to be the renal cortex. We also obtained information on LNA-A metabolites, which showed the same distribution profile as LNA-A in kidneys.

CONCLUSIONS

This study shows that MALDI-IMS can be applied to evaluate the tissue distribution of oligonucleotide therapeutics. Our method can evaluate the tissue distribution along with metabolites and has the potential to help the development of novel oligonucleotide therapeutics.

Automatic DPC Code Selection from Electronic Medical Records

Objectives: We extracted index terms related to diseases recorded in hospital discharge summaries and examined the capability of the vector space model to select a suitable diagnosis with these terms.

Methods: By morphological analysis, we extracted index terms and constructed an original dictionary for the discharge summary analysis. We chose 125 different DPC (Japanese DRG system) codes for the diseases, each of which had more than 20 cases. We divided them into two groups. One group consisted of 5927 cases from 2004 fiscal year and was used to generate the document vector space according to the DPC. The other group of 3187 cases was collected to verify the automatic DPC selection by using data from 2005 fiscal year. The top 200 extracted index terms for each disease were used to calculate the weight of each disease.

Results: The DPC code obtained by the calculated similarity was compared with the original codes of patients for 125 DPCs of 3187 cases. Eighty percent of the cases matched the diagnosis of the DPC (first six digits) and 56% of the cases completely matched all 14 digits of the DPC.

Conclusions: We demonstrated that we could extract suitable terms for each disease and obtain characteristics, such as the diagnosis, from the calculated vectors. This technique can be used to measure the qualification of discharge summaries and to integrate discharge summaries among different facilities. By the text mining technique, we can characterize the contents of electronic discharge summaries and deduce diagnoses with the data.

Novel flat and wide meniscal repair material improves the ultimate load of knot breakage in a porcine trans-capsular meniscal repair model

Background

In the meniscal repair procedures, a high ultimate load capacity and low cyclic creep at the repair site are favorable and lead to good biological incorporation of the tear site after surgery. Previous biomechanical tensile tests of the meniscal sutures have identified the suture knot as the weakest point. We hypothesized that the strength of a suture knot depends on the suture shape, and therefore, we compared three differently shaped suture materials composed of the same material and quantity per length. The purpose of this study was to determine whether a novel flat and wide repair material (FWRM), which consists of braided multi-threads that are cross-sectionally flat and wide, improves the ultimate load of knot breakage in a biomechanical experiment using a porcine trans-capsular meniscal repair model.

Methods

Eighteen fresh-frozen porcine knees (n = 6 in each group) were used. A longitudinal tear in the middle segment of the medial meniscus was created and repaired with a trans-capsular inside-out method using the following suture materials: No. 2–0 braided polyester conventional suture, hollow suture, and FWRM. After the separation of the inner segment of the meniscus with leaving, the suture stability of the repaired menisci was biomechanically analyzed with a video camera system for widening after a cyclic load between 5 and 20 N was applied 300 times. Ultimate failure load and stiffness at 5 mm/ min were also analyzed.

Results

We found no significant difference in suture widening after cyclic load tests [conventional suture, mean 0.51 mm (S.D. 0.39 mm); hollow suture, mean 0.23 mm (S.D. 0.11 mm); and FWRM, mean 0.54 mm (S.D. 0.08 mm)]. The failure mode in all specimens was knot breakage. Compared with those of the other groups, the ultimate failure load of FWRM was statistically significantly higher in the load-to-failure tests (conventional suture, mean 58.8 N [S.D. 8.25 N]; hollow suture, mean 79.4 N [S.D. 10.2 N]; and FWRM, mean 97.4 N [S.D. 3.65 N]; p < 0.05).

Conclusion

FWRM improves the ultimate load of knot breakage without altering stability. This material may contribute to safe and stable meniscus repair.

Vibration acceleration promotes bone formation in rodent models

All living tissues and cells on Earth are subject to gravitational acceleration, but no reports have verified whether acceleration mode influences bone formation and healing. Therefore, this study was to compare the effects of two acceleration modes, vibration and constant (centrifugal) accelerations, on bone formation and healing in the trunk using BMP 2-induced ectopic bone formation (EBF) mouse model and a rib fracture healing (RFH) rat model. Additionally, we tried to verify the difference in mechanism of effect on bone formation by accelerations between these two models. Three groups (low- and high-magnitude vibration and control-VA groups) were evaluated in the vibration acceleration study, and two groups (centrifuge acceleration and control-CA groups) were used in the constant acceleration study. In each model, the intervention was applied for ten minutes per day from three days after surgery for eleven days (EBF model) or nine days (RFH model). All animals were sacrificed the day after the intervention ended. In the EBF model, ectopic bone was evaluated by macroscopic and histological observations, wet weight, radiography and microfocus computed tomography (micro-CT). In the RFH model, whole fracture-repaired ribs were excised with removal of soft tissue, and evaluated radiologically and histologically. Ectopic bones in the low-magnitude group (EBF model) had significantly greater wet weight and were significantly larger (macroscopically and radiographically) than those in the other two groups, whereas the size and wet weight of ectopic bones in the centrifuge acceleration group showed no significant difference compared those in control-CA group. All ectopic bones showed calcified trabeculae and maturated bone marrow. Micro-CT showed that bone volume (BV) in the low-magnitude group of EBF model was significantly higher than those in the other two groups (3.1±1.2mm³ v.s. 1.8±1.2mm³ in high-magnitude group and 1.3±0.9mm³ in control-VA group), but BV in the centrifuge acceleration group had no significant difference compared those in control-CA group. Union rate and BV in the low-magnitude group of RFH model were also significantly higher than those in the other groups (Union rate: 60% v.s. 0% in the high-magnitude group and 10% in the control-VA group, BV: 0.69±0.30mm³ v.s. 0.15±0.09mm³ in high-magnitude group and 0.22±0.17mm³ in control-VA group). BV/TV in the low-magnitude group of RFH model was significantly higher than that in control-VA group (59.4±14.9% v.s. 35.8±13.5%). On the other hand, radiographic union rate (10% in centrifuge acceleration group v.s. 20% in control-CA group) and micro-CT parameters in RFH model were not significantly different between two groups in the constant acceleration studies. Radiographic images of non-union rib fractures showed cartilage at the fracture site and poor new bone formation, whereas union samples showed only new bone. In conclusion, low-magnitude vibration acceleration promoted bone formation at the trunk in both BMP-induced ectopic bone formation and rib fracture healing models. However, the micro-CT parameters were not similar between two models, which suggested that there might be difference in the mechanism of effect by vibration between two models.

Schwannoma of the nasal septum presenting as a multicentric neuronal tumour

PROBLEM

Schwannomas (neurilemmomas) are benign primary tumours that arise from Schwann cells. Schwannomas arising from the nasal septum are exceptionally rare. Here, we report a unique case of schwannoma of the nasal septum presenting as a multicentric neuronal tumour.

RESULTS

A 40-year old male sustained intermittent left tinnitus. Magnetic resonance imaging revealed masses near the nasal septum and upper cervical cord in addition to a tumour in the left cerebellopontine (CP) angle. The tumour in the nasal septum was completely resected by endoscopic endonasal surgery and diagnosed as a typical schwannoma. The CP angle tumour was treated with stereotactic radiosurgery, while the asymptomatic cord lesion showed no significant growth and remains under observation.

CONCLUSION

Endoscopic endonasal surgery is useful for the resection of schwannomas of the nasal septum. Schwannomas of the nasal septum may present as multiple neuronal tumours.

Visualization Analysis of Asymmetric Fountain Flow Phenomenon in Injection Molding of Filler-reinforced Resins by Rotary Runner Exchange System

In this study, we attempted to visualize the flow patterns inside molded samples of glass-fibers or talc reinforced GPPS and PP especially in the vicinity of the flow front, using a rotary runner exchange system which instantaneously switches melt flowing into the cavity. From the visualization results, an extremely characteristic flow behavior was seen at the flow front area for resins with fillers which was not observed for those without fillers. Especially in the case of resins with 40 wt.% talc or 30 wt.% GF, a-symmetric zigzag fountain flows were generated alternately upward and downward along the cavity width direction. Moreover along the outer layer of the flow front, one observed a large amount of residual resin remaining for a long time during the cavity filling process, in the case of 40 wt.% GF, primarily due to the increase of viscosity which restricts the occurrence of diverging flow. Based on the above visualization results, we proposed a generic model of zigzag fountain flow; an a-symmetric upward flow in a certain area starts preventing the fountain flow in the upper side of the adjacent area, causing the diverging center to sink. This phenomenon subsequently causes an a-symmetric flow in the opposite direction in the next adjacent area, which continuously propagates along the cavity width direction.

Visualization Analysis of a Multilayer Foam Development Process in Microcellular Injection Molding

In this study, cross-sectional analyses were performed on microcellular injection-molded high-impact polystyrene products. The results confirm that the following five types of layers were formed: Skin layers I (the silver streak layer) and II (a nonfoamed layer), Core layers I (cell diameter, d > 150 μm), II (d < 50 μm), and III (d > 100 μm). As the maximum in-mold pressure (Pmax) was increased from 5 to 30 MPa, the thickness of Skin layer II remained nearly constant. However, the foam types in the core layers changed from I and II to II and III or III only, resulting in an increase in cell diameter and a decrease in cell density. The process of cellular structure formation was observed using a glass-inserted mold, which revealed that this process consists of a flow (with a burst of cells at the melt front and the subsequent flow of the melt containing the cells), an end of the filling (involving elastic compression or the dissolution and disappearance of cells formed in the flow stage), and a cooling (new cell generation and growth and cooling solidification). Based on these cross-sectional observations, in concert with melt-pressure measurements and visualizations, we developed a model describing the formation process of Skin layer II and the core layers including a new concept that considers the melt pressure inside the cavity. The following layers are incorporated into the model: Skin layer II: A nonfoamed layer is formed in the area of the melt front where gases diffuse out from within the melt during the filling stage, and this nonfoamed layer moves to from melt front to the surface of the product due to fountain flow. Core layers I and II: A multilayer is formed containing a distribution of cells preserved from the flow stage due to the low compression forces, Core layer III: cells are dissolved in the melt due to strong compression forces at the end of the filling stage and then reform and grow in the cooling stage.