H. P. Alizai

Comparison of Long-Term Biocompability of PVDF and PP Meshes

ABSTRACT Background: Abdominal hernia repair is the most frequently performed operation in surgery. Mesh repair in hernia surgery has become an integral component. Although meshes made of PVDF are already in clinical use, so far no data of long-term biocompability are available. Methods: In this study a PVDF mesh was compared to a polypropylene mesh with regard to its long-term biocompatibility. A total of 28 rats were randomized to two groups. Mesh material was implanted subcutaneously; animals were euthanized seven days and six months postoperatively. The quantity of inflammatory tissue response was characterized by measuring the diameter of the foreign body granuloma. Furthermore quality of cellular immune response (T-lymphocytes, macrophages, and neutrophils), and inflammation (COX-2) was analyzed by immunohistochemistry. Furthermore the collagen type I/III ratio was determined. Results: Macrophages, T-lymphocytes, neutrophiles, and COX-2 declined significantly up to six months postoperatively in comparison to day 7 for both PVDF and PP meshes, and in both groups the collagen ratio increased significantly in the course of time. PVDF meshes showed a foreign body granuloma size significantly reduced compared to PP (7 days: 20 ± 2 μm vs. 27 ± 2 μm; 6 months 15 ± 2 μm vs. 22 ± 3 μm; p < .001). However no significant differences were found analyzing cellular response six months postoperatively. Conclusions: Our current data suggest that even in the long-term course after six months and despite a higher effective surface of the PVDF samples it showed a smaller foreign body granuloma than with PP whereas the cellular response was similar.

In vitro and in vivo characteristics of gentamicin‐supplemented polyvinylidenfluoride mesh materials

To reduce infection rates after mesh implantation antibiotic-coated meshes were designed. The aim of the study was to analyze biocompatibility and in vitro efficiency of a modified gentamicin-supplemented polyvinylidenfluoride mesh. Twenty rats were randomized to two groups (PVDF group and Genta group). Mesh material was implanted subcutaneously. Blood samples were taken to determine the gentamicin serum concentration. Seven and 90 days after mesh implantation, animals were euthanized. The inflammatory tissue response was characterized by analyzing the foreign body granuloma. Cellular immune response was analyzed by immunohistochemical investigations. The collagen type I/III ratio was estimated by crosspolarization microscopy. In vitro agar diffusion test, suspension test, and gentamicin release were characterized. Agar diffusion and suspension test showed efficient antibiotic effects of the mesh in vitro. Serum concentrations of gentamicin showed a peak value 1 h postoperatively with a decline within the next day. The total size of the granuloma was significantly smaller in the Genta group compared to the PVDF group at both points of time. Except of a short period of increased expression of CD68 in the Genta group after 7 days, no further difference was found analyzing cellular immune response. The collagen type I/III ratio was widely constant analyzing the two mesh types without significant differences comparing both mesh materials. A significantly decreased foreign body granuloma formation compared to the pure PVDF mesh group was found. In vitro analysis showed efficient antibiotic effects of the Gentamicin supplementation compared to the pure PVDF mesh.

Influence of skin closure technique on surgical site infection after loop ileostomy reversal: Retrospective cohort study

BACKGROUND Intestinal stoma closure is associated with high risk of surgical site infection (SSI) at stoma reversal site. The aim of this retrospective cohort study was to determine the outcome of purse string approximation (PSA) compared to primary linear closure (PLC) of the skin after loop ileostomy reversal. METHODS Data of 140 patients operated between 2005 and 2012 were analyzed in this two-center-study to determine the outcome of patients with either PSA (n = 44) or PLC (n = 96) after loop ileostomy reversal. RESULTS Patients in the PSA group were significantly older than in the PLC group (64 ± 15 vs. 57 ± 18; p = 0.026). Cardiac diseases were significantly more present in the PSA group in comparison to the PLC group (59% vs. 38%; p = 0.017). Stoma creation was significantly more often due to malignancy in the PSA group in comparison to the PLC group (68% vs. 50%; p = 0.044). SSI occurred significantly more often in the PLC group in comparison to the PSA group (17% vs. 5%; p = 0.047). CONCLUSIONS The risk for SSI is lower in patients with PSA in comparison to patients with PLC. In order to diminish SSI we recommend performing a PSA in patients with loop ileostomy reversal.

Biocompatibility of PLGA/sP(EO-stat-PO)-Coated Mesh Surfaces under Constant Shearing Stress

Background: In order to allow inflammatory response modification and ultimately improvement in tissue remodeling, we developed a new surface modification for meshes that will serve as a carrier for other substances. Biocompatibility is tested in an animal model. Methods: The animal model for diaphragmatic hernia repair was established in prior studies. Meshes were surface modified with star-configured PEO (polyethylene oxide)-based molecules [sP(EO-stat-PO)]. An electrospun nanoweb of short-term absorbable PLGA (polylactide-co-glycolide) with integrated sP(EO-stat-PO) molecules was applied onto the modified meshes. This coating also served as aerial sealing of the diaphragm. A final layer of hydrogel was applied to the product. Adhesive properties, defect size and mesh shrinkage were determined, and histological and immunohistochemical investigations performed after 4 months. Results: The mean defect size decreased markedly in both modified mesh groups. Histologically and with regard to apoptosis and proliferation rate, smooth muscle cells, collagen I/III ratio and macrophage count, no statistically significant difference was seen between the 3 mesh groups. Conclusions: In this proof-of-principle investigation, we demonstrate good biocompatibility for this surface-modified mesh compared to a standard polypropylene-based mesh. This new coating represents a promising tool as a carrier for bioactive substances in the near future.

Colonic wall changes in patients with diverticular disease – Is there a predisposition for a complicated course?

BACKGROUND The aim of this study was to evaluate colonic wall changes and enteric neuropathy in patients with either uncomplicated (UDD) or complicated diverticular disease (CDD). Furthermore, we evaluated the presence of an anatomic sphincter at the rectosigmoid junction (RSJ). METHODS Samples of colonic tissue from fifteen patients with UDD, fifteen patients with CDD and fifteen patients as control were collected. Collagen quotient I/III was measured with the Sirius-red test, expression of MMP-1, MMP-13, innervation (S100), proliferation (Ki67) and apoptosis (TUNEL) in the colonic wall were investigated by immunohistochemical studies. Furthermore, measurements of the different layers were performed to investigate the RSJ. RESULTS Patients with either UDD or CDD had lower collagen I/III quotients compared to the control group, significant for CDD (p = 0.007). For MMP-1 and MMP-13 only a slight increase for patients with CDD was found. The percentage of proliferating (Ki67) and apoptotic (TUNEL) cells was significantly higher for patients with CDD than in the control group (p = 0.016; p = 0.037). Upon investigating the S100-expression a significant reduce in glial cells density was found in the myenteric and mucosal plexus for both groups (UDD and CDD) compared to the control group. Measurements of the different colon layers oral, aboral and at the RSJ revealed equal values. CONCLUSIONS This study has shown that colonic wall changes and enteric neuropathy seem to play a role in the pathogenesis of colonic diverticulosis. None of our results suggest a predisposition for a complicated diverticular disease. Furthermore, the presence of an anatomic sphincter at the rectosigmoid junction could not be detected.

Influence of MMP inhibitor GM6001 loading of fibre coated polypropylene meshes on wound healing: Implications for hernia repair

Polypropylene meshes are standard for hernia repair. Matrix metalloproteinases play a central role in inflammation. To reduce the inflammatory response and improve remodelling with an associated reduction of hernia recurrence, we modified polypropylene meshes by nanofibre coating and saturation with the broad-spectrum matrix metalloproteinase inhibitor GM6001. The aim was to modulate the inflammatory reaction, increase collagen deposition and improve mesh biointegration. Polypropylene meshes were surface-modified with star-configured NCO-sP(EO-stat-PO) and covered with electrospun nanofibres (polypropylene-nano) and GM6001 (polypropylene-nano-GM). In a hernia model, defects were reconstructed with one of the meshes. Inflammation, neovascularization, bio-integration, proliferation and apoptosis were assessed histologically, collagen content and gelatinases biochemically. Mesh surface modification resulted in higher inflammatory response compared to polypropylene. Pro-inflammatory matrix metalloproteinase-9 paralleled findings while GM6001 reduced matrix metalloproteinase-9 significantly. Significantly increased matrix metalloproteinase-2 beneficial for remodelling was noted with polypropylene-nano-meshes. Increased vascular endothelial growth factor, neo-vascularization and collagen content were measured in polypropylene-nano-meshes compared to polypropylene. GM6001 significantly reduced myofibroblasts. This effect ended after d14 due to engineering limitations with release of maximal GM6001 loading. Nanofibre-coating of polypropylene-meshes confers better tissue vascularization to the cost of increased inflammation. This phenomenon can be only partially compensated by GM6001. Future research will enable higher GM6001 uptake in nano-coated meshes and may alter mesh biointegration in a more pronounced way.

Influence of Telomere Length in Hepatocytes on Liver Regeneration after Partial Hepatectomy in Rats

Background: The aim of this study was to investigate telomere length in hepatocytes as a biomarker for liver regeneration after partial hepatectomy (PH) in rats. Materials and Methods: Sixty male Wistar rats underwent a 70% PH. One-month-old rats were assigned to group Y (n = 30) and 4-month-old rats were assigned to group O (n = 30). The rats were euthanized, and their livers were then harvested at postoperative day (POD) 1, 2, 3, 4, or 7. Telomere lengths and established parameters for liver regeneration (residual liver weight and levels of proliferating cell nuclear antigen [PCNA], Ki67, and interleukin [IL]-6) were measured. Results: We observed a significant increase in residual liver weight in group Y compared to that in group O (p = 0.001). The levels of Ki67 (p = 0.016), PCNA (p < 0.0001), and IL-6 (p < 0.001) were significantly higher in group Y. Furthermore, the rats in group Y had significantly earlier peak values of Ki67 and PCNA. Telomeres were significantly longer at the time of PH in group Y (p = 0.001). We showed a correlation between telomere length at the day of PH and liver regeneration. Animals with longer telomeres at the time of PH had better liver regeneration (p = 0.015). In group Y, animals with increased liver regeneration (median cut-off: > 122%) did not show any significant difference in telomere length (p = 0.587) compared to rats with regular regeneration (< 122%). However, in the older animals, rats with increased regeneration had significantly longer telomeres (p = 0.019) than rats with regular regeneration. Conclusion: Telomere length in rat hepatocytes depends on age, and animals with long telomeres had earlier and better regeneration of healthy liver tissue than rats with short telomeres. Our data confirms that telomere length in rat hepatocytes could be used as a possible predictive marker for liver regeneration, and could help to identify older individuals with a high capacity for hepatic regeneration.

Comparative study of the effects of terlipressin versus splenectomy on liver regeneration after partial hepatectomy in rats

BACKGROUND Post-hepatectomy liver failure as a result of insufficient liver remnant is a feared complication in liver surgery. Efforts have been made to find new strategies to support liver regeneration. The aim of this study was to investigate the effects of terlipressin versus splenectomy on postoperative liver function and liver regeneration in rats undergoing 70% partial hepatectomy. METHODS Seventy-two male Wistar rats were randomly assigned into three groups (n=24 in each group): 70% partial hepatectomy as control (PHC), 70% partial hepatectomy with splenectomy (PHS) or 70% partial hepatectomy with a micropump for terlipressin administration (PHT). Eight rats in each group were sacrificed on postoperative day (POD) 1, 3 and 7. To assess liver regeneration, immunohistochemical analysis of liver tissue using bromodeoxyuridine (BrdU) and Ki-67 labeling was performed. Portal venous pressure, serum concentrations of creatinine, urea, albumin, bilirubin and prothrombin time as well as liver-, body-weight and their ratio were determined on POD 1, 3 and 7. RESULTS The liver-, body-weight and their ratio were not statistically different among the groups. On POD 1, 3 and 7 portal venous pressure in the intervention groups (PHT: 8.13±1.55, 10.38±1.30, 6.25±0.89 cmH2O and PHS: 7.50±0.93, 8.88±2.42, 5.75±1.04 cmH2O) was lower compared to the control group (PHC: 8.63±2.06, 10.50±2.45, 6.50±2.67 cmH2O). Hepatocyte proliferation in the intervention groups was delayed, especially after splenectomy on POD 1 (BrdU: PHS vs PHC, 20.85%±13.05% vs 28.11%±10.10%; Ki-67, 20.14%±14.10% vs 23.96%±11.69%). However, none of the differences were statistically significant. CONCLUSIONS Neither the administration of terlipressin nor splenectomy improved liver regeneration after 70% partial hepatectomy in rats. Further studies assessing the regulation of portal venous pressure as well as extended hepatectomy animal models and liver function tests will help to further investigate mechanisms of liver regeneration.

Argon Delays Initiation of Liver Regeneration after Partial Hepatectomy in Rats

Background: The liver can heal up to restitutio ad integrum following damage resulting from various causes. Different studies have demonstrated the protective effect of argon on various cells and organs. To the best of our knowledge, the organ-protective effects of the noble gas argon on the liver have not yet been investigated, although argon appears to influence signal paths that are well-known mediators of liver regeneration. We hypothesized that argon inhalation prior to partial hepatectomy (70%) has a positive effect on the initiation of liver regeneration in rats. Methods: Partial hepatectomy (70%) with or without inhaled argon (50 vol%) was performed for 1 h. Liver tissue was harvested after 3, 36, and 96 h to analyze the mRNA and protein expression of hepatocyte growth factor (HGF), interleukin-6 (IL-6), tumor necrosis factor-α, and extracellular signal-regulated kinase 1/2. Histological tissue samples were prepared for immunohistochemistry (bromodeoxyuridine [BrdU], Ki-67, and TUNEL) and blood was analyzed regarding the effects of argon on liver function. Statistical analyses were performed using 1-way ANOVA followed by the post hoc Tukey-Kramer test. Results: After 3 h, the primary outcome parameter of hepatocyte proliferation was significantly reduced with argon 50 vol% inhalation in comparison to nitrogen inhalation (BrdU: 15.7 ± 9.7 vs. 7.7 ± 3.1 positive cells/1,000 hepatocytes, p = 0.013; Ki-67: 17.6 ± 13.3 vs. 4.7 ± 5.4 positive cells/1,000 hepatocytes, p = 0.006). This was most likely mediated by significant downregulation of HGF (after 3 h: 5.2 ± 3.2 vs. 2.3 ± 1.0 fold, p = 0.032; after 96 h: 2.1 ± 0.5 vs. 1.3 ± 0.3 fold, p = 0.029) and IL-6 (after 3 h: 43.7 ± 39.6 vs. 8.5 ± 9.2 fold, p = 0.032). Nevertheless, we could detect no significant effect on the weight of the residual liver, liver-body weight ratio, or liver blood test results after argon inhalation. Conclusion: Impairment of liver regeneration was apparent after argon 50 vol% inhalation that was most probably mediated by downregulation of HGF and IL-6 in the initial phase. However, the present study was not adequately powered to prove that argon has detrimental effects on the liver. Further studies are needed to evaluate the effects of argon on livers with preexisting conditions as well as on ischemia-reperfusion models.