Targeted delivery of oligomannose-coated liposome to the omental micrometastasis by peritoneal macrophages from patients with gastric cancer.

We recently developed a novel drug delivery system (DDS) using oligomannose-coated liposomes (OMLs), which are effectively taken up by mouse peritoneal macrophages to carry anticancer drugs to omental milky spots known as initial metastatic sites in the peritoneal cavity in mice. However, the feasibility of the clinical application of this DDS to gastric cancer patients remains essentially unknown. In the present study, we investigated whether human peripheral blood monocytes (PBMs) and human peritoneal macrophages (PEMs) could successfully uptake OMLs and deliver them to the micrometastatic foci in the mouse omentum and resected omentum from cancer patients ex vivo. When OMLs were incubated with the PBMs from four healthy volunteers in vitro, an average 88% of CD14-positive PBMs, most of which also express CD206, took up OMLs, and this uptake was significantly inhibited by alpha-methylmannoside. In the experiment using PEMs obtained from peritoneal washes of five gastric cancer patients, the average uptake rate (63%) of OML by CD14-positive PEMs was somewhat lower than that of PBMs, but in three advanced gastric cancer patients the uptake rate of OMLs was 76% which was comparable to that of mouse PEMs. Oligomannose-coated liposome (OML)-incorporated PBMs and PEMs were successfully accumulated at the micrometastatic foci at the omentum formed after intraperitoneal injection of GFP-tagged gastric cancer cells into mice. Furthermore, OML-incorporated PBMs substantially accumulated to tumor foci in the surgically resected human omentum ex vivo. These results suggest that OMLs using human monocytes/macrophages as a cellular vehicle have the potential to target peritoneal micrometastasis in the omentum of gastric cancer patients.

A bio-inspired hybrid nanosack for graft vascularization at the omentum.

UNLABELLED: For three-dimensional tissue engineering scaffolds, the major challenges of hydrogels are poor mechanical integrity and difficulty in handling during implantation. In contrast, electrospun scaffolds provide tunable mechanical properties and high porosity; but, are limited in cell encapsulation. To overcome these limitations, we developed a "hybrid nanosack" by combination of a peptide amphiphile (PA) nanomatrix gel and an electrospun poly (ε-caprolactone) (ePCL) nanofiber sheet with porous crater-like structures. This hybrid nanosack design synergistically possessed the characteristics of both approaches. In this study, the hybrid nanosack was applied to enhance local angiogenesis in the omentum, which is required of tissue engineering scaffolds for graft survival. The ePCL sheet with porous crater-like structures improved cell and blood vessel penetration through the hybrid nanosack. The hybrid nanosack also provided multi-stage fibroblast growth factor-2 (FGF-2) release kinetics for stimulating local angiogenesis. The hybrid nanosack was implanted into rat omentum for 14days and vascularization was analyzed by micro-CT and immunohistochemistry; the data clearly demonstrated that both FGF-2 delivery and porous crater-like structures work synergistically to enhance blood vessel formation within the hybrid nanosack. Therefore, the hybrid nanosack will provide a new strategy for engineering scaffolds to achieve graft survival in the omentum by stimulating local vascularization, thus overcoming the limitations of current strategies. STATEMENT OF SIGNIFICANCE: For three-dimensional tissue engineering scaffolds, the major challenges of hydrogels are poor mechanical integrity and difficulty in handling during implantation. In contrast, electrospun scaffolds provide tunable mechanical properties and high porosity; but, are limited in cell encapsulation. To overcome these limitations, we developed a "hybrid nanosack" by combination of a peptide amphiphile (PA) nanomatrix gel and an electrospun poly (ε-caprolactone) (ePCL) nanofiber sheet with porous crater-like structures. This design synergistically possessed the characteristics of both approaches. In this study, the hybrid nanosack was applied to enhance local angiogenesis in the omentum, which is required of tissue engineering scaffolds for graft survival. The hybrid nanosack was implanted into rat omentum for 14days and vascularization was analyzed by micro-CT and immunohistochemistry. We demonstrate that both FGF-2 delivery and porous crater-like structures work synergistically to enhance blood vessel formation within the hybrid nanosack. Therefore, the hybrid nanosack will provide a new strategy for engineering scaffolds to achieve graft survival in the omentum by stimulating local vascularization, thus overcoming the limitations of current strategies.

Biocompatibility of a bicarbonate/lactate-buffered PD fluid tested with a double-chamber cell culture system.

OBJECTIVE: In peritoneal dialysis (PD), neutrally buffered PD fluids with lower concentrations of glucose degradation products (GDP) have tested superior to conventional fluids in terms of biocompatibility. However, conventional in vitro studies provoke debate because, due to the lack of subsequent equilibration with the blood, they do not resemble the true intraperitoneal situation of PD. METHODS: We established a double-chamber cell culture system with peritoneal mesothelial cells seeded on top of a permeable membrane, with a physiological buffer below. Thus adequately reflecting the in vivo equilibration pattern, we compared a conventional fluid with a neutral bicarbonate/lactate-buffered PD solution. Using an exchange pattern adapted from an 8-hour continuous ambulatory PD regimen, cell viability was assessed with an MTT assay, and cell function via constitutive and stimulated interleukin (IL)-6 release. As an indicator of potential induction of fibrosis and as a parameter of mesothelial cell integrity, respectively, transforming growth factor-beta 1 (TGF-beta1) generation and cancer antigen 125 (CA125) release were measured. RESULTS: The conventional solution significantly compromised mesothelial cell viability and function in terms of mitochondrial activity (p < 0.05) and stimulated IL-6 release (p < 0.05). The bicarbonate/lactate fluid had no effect on cell viability or IL-6 release and turned out to be equivalent to the properties of the growth medium. Whereas lactate-incubated cells did not respond to IL-1beta stimulation, bicarbonate/lactate-treated cells adequately increased IL-6 release after stimulation (p < 0.0005). Release of TGF-beta1 and CA125 did not differ between the different fluids and the control. CONCLUSIONS: Due to the sustained equilibration process, the double-chamber cell culture model allows a more realistic insight into mesothelial cell viability and function in terms of PD. As in classic in vitro studies, an adverse effect of conventional PD solutions on mesothelial cells was overt in the present cell culture system. The neutral bicarbonate/lactate-buffered fluid with low GDP content, however, did not interfere with mesothelial cell vitality or function, indicating superior biocompatibility.

The relationship between five kinds of laparoscopic knots and five types of suture materials and histological findings in tissues: an experimental study on rabbits.

The aim of the current study was to examine the slipping and the tightening of laparoscopic knots with various kinds of sutures, as well as the histologic alterations in tissues. Fifty rabbits and five kinds of sutures were used-silk, polyglactine-910 (Vicryl), Polydioxanone (PDS), Polyglycol (Dexon), and cat-gut chromic-and five laparoscopic knots were used-Tayside, Roeder, Melzer, Cross, and Blood. The knots were performed extracorporeally and were used to ligate a part of the omentum. Sliding and tightening of the knots were evaluated. The omentum, the suture, and the knots were checked 10 days and 1 month after operation. Histologic examination was performed 1 month after surgery. Polyglactine-910 (Vicryl) and silk were the most qualitative sutures used in Tayside, Roeder, and Blood knots and the least harmful for the tissues. Catgut chromic and Polydioxanone (PDS) were the most defective sutures. The most efficient laparoscopic slipknots are Tayside, Roeder, and Blood, especially when constructed with silk and polyglactine-910 (Vicryl).

Improvement of a chronic rat model for peritoneal dialysis by using heparin-coated catheters.

The use of silicone peritoneal catheters, connected to implanted subcutaneous mini vascular access ports, was an essential step in the development of a widely used rat model for peritoneal dialysis (PD). Despite the model's many advantages, it has one major disadvantage: a high drop-out rate because of omental wrapping of the silicone catheter. To investigate whether heparinization of the peritoneal catheter reduces the high drop-out rate in the model, we infused rats with conventional PD fluid through either a regular silicone catheter (PDF, n = 14) or a heparin-coated catheter (PDF-h, n = 15) daily for 5 weeks. Untreated rats served as a control group (control, n = 7). We used various peritoneal tissues for cellular and morphologic analysis by light and electron microscopy. We found a statistically significant, lower rate of drop-out in rats implanted with heparin-coated catheters (20%) than in rats implanted with regular silicone catheters (57%, p < 0.05). No significant differences were seen between the two treated groups with regard to the PD fluid-induced angiogenic response in omentum and mesentery. Likewise, instillation of PD fluid resulted in a similar cellular response (increased numbers of mast cells and milky spots in the omentum and mesothelial regeneration on the liver) in both groups regardless of heparin coating. Based on our results, we recommend the use of heparin-coated catheters for instillation of dialysis solutions in the chronic PD model in the rat.

Seamless vascularized large-diameter tubular collagen scaffolds reinforced with polymer knittings for esophageal regenerative medicine.

A clinical demand exists for alternatives to repair the esophagus in case of congenital defects, cancer, or trauma. A seamless biocompatible off-the-shelf large-diameter tubular scaffold, which is accessible for vascularization, could set the stage for regenerative medicine of the esophagus. The use of seamless scaffolds eliminates the error-prone tubularization step, which is necessary when emanating from flat scaffolds. In this study, we developed and characterized three different types of seamless tubular scaffolds, and evaluated in vivo tissue compatibility, including vascularization by omental wrapping. Scaffolds (luminal Ø âˆ¼ 1.5 cm) were constructed using freezing, lyophilizing, and cross-linking techniques and included (1) single-layered porous collagen scaffold, (2) dual-layered (porous+dense) collagen scaffold, and (3) hybrid scaffold (collagen+incorporated polycaprolacton knitting). The latter had an ultimate tensile strength comparable to a porcine esophagus. To induce rapid vascularization, scaffolds were implanted in the omentum of sheep using a wrapping technique. After 6 weeks of biocompatibility, vascularization, calcification, and hypoxia were evaluated using immunohistochemistry. Scaffolds were biocompatible, and cellular influx and ingrowth of blood vessels were observed throughout the whole scaffold. No calcification was observed, and slight hypoxic conditions were detected only in the direct vicinity of the polymer knitting. It is concluded that seamless large-diameter tubular collagen-based scaffolds can be constructed and vascularized in vivo. Such scaffolds provide novel tools for esophageal reconstruction.

HSP induction in mesothelial cells by peritoneal dialysis fluid depends on biocompatibility test system.

BACKGROUND: We have previously shown that exposure of mesothelial cells (MC) to peritoneal dialysis fluids (PDF) not only caused toxic injury, but also induced cytoprotective heat shock proteins (HSP). This study was performed in order to compare HSP expression in MC upon PDF exposure in three currently used biocompatibility test systems. METHODS: Omentum-derived human peritoneal MC underwent 3 modalities of exposure to heat- or filter-sterilized PDF: (A) pure PDF for 60 minutes followed by a recovery-period in pure culture medium for 24 hours; (B) 1:1 mixture of PDF and culture medium for 24 hours or (C) pure PDF for 60 minutes followed by a recovery-period in a 1:1 mixture of PDF and culture medium for 24 hours. Biocompatibility was assessed by LDH-release into the supernatant and HSP-72 expression in MC lysates. RESULTS: Short-term exposure of MC to pure PDF (Modality A) resulted in concordant LDH release and upregulation of HSP-72, regardless of heat or filter sterilization. In contrast, both test systems that exposed MC to heat-sterilized PDF during the recovery period (Modalities B and C) resulted in severe cellular lethality but low HSP-72 expression. CONCLUSIONS: This study clearly shows that HSP expression in MC upon PDF exposure depends on the biocompatibility test system. The presence of heat-sterilized PDF during recovery resulted in significant downregulation of Hsp-72 despite severe cell injury. Therefore, Hsp-72 expression reflects adequate cellular stress responses rather than PDF cytotoxicity.

Rat models in peritoneal dialysis.

BACKGROUND: It is widely accepted that the currently used dialysis solutions are not biocompatible with the peritoneal membrane. Therefore, animal studies have been performed to study different aspects of peritoneal dialysis. However, representative models mimicking the human situation are not yet available. METHODS: The effect of a single injection of peritoneal dialysis (PD) fluid on the cellular composition was studied. Thereafter, the effect of a single injection of PD fluid on bacterial clearing was tested over time. Finally, an in vivo rat model was established to study the effects of long-term exposure to PD fluid on the peritoneal membrane and the local host defence (peritoneal cells). RESULTS: In the rat model, long-term daily exposure is possible. The 'drop-out' after 9-10 weeks on the most commonly used PD fluid Dianeal 3.86%, however, is approximately 50% due to omental wrapping. In the remaining study group, large differences were observed (as compared with controls), especially with respect to morphological parameters. CONCLUSIONS: The rat peritoneal continuous exposure model seems to have potential for intervention studies, since it uses no additions, no antibiotics and no omentomectomy, and gives continuous long-term exposure to PD fluid. However, problems still remain: 'drop-out' is quite often seen and this non-uraemic exposure model does not totally mimic the situation present in continuous ambulatory PD patients.