In Vivo Comparison of the Inflammatory Response Induced by Different Vascular Biomaterials

Predictors of long-term stenosis in bicuspid aortic valve repair

OBJECTIVES

The use of modern techniques for bicuspid aortic valve repair has been shown to provide safe and durable results against recurrent regurgitation. However, an emerging body of evidence is indicating that aortic stenosis might be an additional late complication of these procedures. To date, the pathogenesis and clinical impact of aortic stenosis after bicuspid aortic valve repair are poorly understood.

METHODS

A retrospective analysis of 367 patients with bicuspid aortic valve repair was performed to identify predictors of reoperation for stenosis. Bicuspid aortic valve repair was performed using a combination of procedures on the leaflet, annulus, and aortic root.

RESULTS

During a median follow-up of 8 years, reoperation for stenosis was required in 33 patients (9.0%). Freedom from reoperation for stenosis was 100%, 99.6%, 91.7%, and 74.9% at 1, 5, 10, and 15 years, respectively. The following factors were independently associated with reoperation for aortic stenosis: Leaflet or raphe resection with shaving was a protective factor (hazard ratio, 0.34; 95% confidence interval, 0.16-0.71; P = .004), whereas the use of expanded polytetrafluoroethylene for free-edge running suture (hazard ratio, 2.55; 95% confidence interval, 1.16-5.57; P = .019), supracoronary replacement of the ascending aorta in combination with valve repair (hazard ratio, 5.41; 95% confidence interval, 2.11-13.85; P = .001), and the need for a second aortic crossclamp (hazard ratio, 10.95; 95% confidence interval, 2.80-42.80; P = .001) were associated with increased risk of reoperation for aortic stenosis.

CONCLUSIONS

While confirming previous findings, our analysis suggests that the inability to restore leaflet mobility and polytetrafluoroethylene for free-edge running suture are risk factors for stenosis. The so-called ascending phenotypes are probably more prone to stenosis. If the first attempt to repair is unsuccessful, the risk of late reoperation for aortic stenosis is high.

Orbital Trauma

The orbit is contained within a complex bony architecture with overlying soft tissue that involves many important anatomical structures. Orbital trauma is a frequent cause of damage to these structures. The authors review the literature on reconstructive techniques focusing on fractures of the orbital rim, orbital roof, orbital floor, medial orbital wall, and naso-orbito-ethmoid complex. A thorough literature review was conducted using PubMed analyzing articles relevant to the subject matter. Various search terms were used to identify articles regarding orbital trauma presentation, diagnosis, management, as well as postoperative complications. Articles were examined by all authors and pertinent information was gleaned for the purpose of generating this review. Orbital trauma can result in a wide variety of complications in form and function. Not all orbital fractures require operative repair. However, bony disruption can cause enophthalmos, hypophthalmos, telecanthus, epiphora, cerebrospinal fluid leaks, orbital hematoma, and even blindness to name a few. Timing of operative repair as well as reconstructive method is dictated by the patient's individual presentation. Successful fracture management requires a detailed understanding of the anatomy and pathophysiology to ensure restoration of the patients' preoperative state. Orbital trauma encompasses a wide variety of mechanisms of injury and resulting fracture patterns. A variety of surgical approaches to the orbit exist as has been discussed allowing the surgeon access to all area of interest. Regardless of the fracture complexity, the principles of atraumatic technique, anatomic reduction, and stable fixation apply in all cases.

Systematic in vivo evaluation of the time-dependent inflammatory response to steel and Teflon insulin infusion catheters

Continuous subcutaneous insulin infusion (CSII) catheters are considered the weak link of insulin pump therapy. Wear-time considerably varies between patients and the choice of catheter material is based on personal preferences rather than scientific facts. Therefore, we systematically assessed and quantified the inflammatory tissue response to steel versus Teflon CSII catheters over a maximum wear-time of 7 days in swine. Tissue surrounding catheters was analysed using histopathology and quantitative real-time PCR. The area of inflammation increased significantly over time independent of material which was confirmed by an increase in CD68 expression and an increase in mononuclear and neutrophil cell infiltrate around the catheters. We observed substantially higher fibrin deposition (p < 0.05) around steel on day 4 of wear-time. IL-6 gene expression increased within 24 hours after insertion, returned to normal levels around Teflon (p < 0.05) but remained high around steel (p < 0.05). IL-10 and TGF-β levels did not resolve over time, indicating impaired wound healing. In conclusion, there was a major temporal effect in the acute inflammatory response to CSII catheters but we found little difference between materials. This study setup presents a robust tool for the systematic analysis of the tissue response to CSII catheters.

A new prosthetic implant for inguinal hernia repair: its features in a porcine experimental model

Even after more than 100 years of inguinal hernia repair, the rate of complications and recurrence remains unacceptably high. In the last decades, few effective advances in surgical technique and materials have been made. The authors see them as minor adjustments in the shape and materials of the prosthetic implants. Still, the underlying genesis of inguinal hernia remains undefined. Based upon this, it seems the surgical repair of inguinal protrusions cannot be based upon the pathogenesis because the etiology to date has not been addressed. Most hernia repairs are performed with some degree of point fixation (sutures/tacks) to stop the mesh from migrating and creating high recurrence rates. This should be a priority for our considerations, as fixating mesh puts it in stark contrast to the physiology and dynamics of the myotendineal structures of the groin. Following years of surgical practice, implant fixation, mesh shrinkage, and poor quality of tissue ingrowth still represent an unresolved issue in modern hernia repair. Conventional prosthetics used for inguinal hernia repair are static and passive. They do not move in harmony with the dynamic elements of the groin structure and, as a result, induce the ingrowth of thin scar plates or shrinking regressive tissue that colonizes the implants. The authors strongly believe that these characteristics may be a contributing factor for recurrences and patient discomfort. Other complications are reported in the literature to be a direct result of fixation of the implants, such as bleeding, nerve entrapment, hematoma, pain, discomfort, and testicular complications. To improve results by respecting the physiology and kinetics of the inguinal region, we felt that a new type of prosthesis should be designed that induces a more structured tissue ingrowth similar to the natural biologic components of the abdominal wall. This prosthetic device was specifically designed to be placed with no point fixation. This was achieved by using inherent radial recoil, vertical buffering, friction, and delivering the device in a constrained state. A secondary benefit of this "dynamic" design is that the implant moves in a three-dimensional way in unison with the movements of the myotendineal structures of the groin. The results appear to show that the three-dimensional structure not only acts as a suitable scaffold for a full thickness ingrowth of a tissue barrier but also seems to induce an ordered, supple, elastic tissue, which allows for neorevascularization and neoneural growth. The outcomes indicate a reduced impact of fibrotic shrinkage on the implant/scar tissue when compared with shrinkage of polypropylene meshes reported in the literature. This pilot study shows the features of such an implant in a porcine experimental model.

Polymeric implant materials for the reconstruction of tracheal and pharyngeal mucosal defects in head and neck surgery

The existing therapeutical options for the tracheal and pharyngeal reconstruction by use of implant materials are described. Inspite of a multitude of options and the availability of very different materials none of these methods applied for tracheal reconstruction were successfully introduced into the clinical routine. Essential problems are insufficiencies of anastomoses, stenoses, lack of mucociliary clearance and vascularisation. The advances in Tissue Engineering (TE) offer new therapeutical options also in the field of the reconstructive surgery of the trachea. In pharyngeal reconstruction far reaching developments cannot be recognized at the moment which would allow to give a prognosis of their success in clinical application. A new polymeric implant material consisting of multiblock copolymers was applied in our own work which was regarded as a promising material for the reconstruction of the upper aerodigestive tract (ADT) due to its physicochemical characteristics. In order to test this material for applications in the ADT under extreme chemical, enzymatical, bacterial and mechanical conditions we applied it for the reconstruction of a complete defect of the gastric wall in an animal model. In none of the animals tested either gastrointestinal complications or negative systemic events occurred, however, there was a multilayered regeneration of the gastric wall implying a regular structured mucosa.

In future the advanced stem cell technology will allow further progress in the reconstruction of different kind of tissues also in the field of head and neck surgery following the principles of Tissue Engineering.

Effect of steel and teflon infusion catheters on subcutaneous adipose tissue blood flow and infusion counter pressure in humans

BACKGROUND

Subcutaneous tissue is an important target for drug deposition or infusion. A local trauma may induce alterations in local microcirculation and diffusion barriers with consequences for drug bioavailability. We examined the influence of infusion catheters' wear time on local microcirculation and infusion counter pressure.

METHODS

One steel catheter and one Teflon (Dupont, Wilmington, DE) catheter were inserted in subcutaneous, abdominal adipose tissue (SCAAT) in 10 healthy, lean men. The catheters were infused with isotonic saline at a rate of 10 microL/h for 48 h. Another steel catheter and a Teflon catheter were inserted contralateral to the previous catheters after 48 h. The infusion counter pressure was measured during a basal infusion rate followed by a bolus infusion. The measurements during a basal rate infusion were repeated after the bolus infusion. Adipose tissue blood flow (ATBF) was measured in SCAAT continuously.

RESULTS

A significant increase in ATBF was observed with wear time for Teflon but not for steel catheters. Mean infusion pressure during the bolus phase increased significantly from 0 to 48 h for Teflon but not for steel catheters. ATBF and infusion counter pressure was similar between Teflon and steel catheters after acute catheter implantation and after wear time of 48 h. The maximum value of pressure during the bolus phase increased with wear time of a catheter.

CONCLUSIONS

ATBF and bolus mean infusion pressure increased significantly with a wear time of 48 h in Teflon but not in steel catheters. The maximal pressure required to deliver a bolus infusion increased with wear time of a catheter. A higher maximal pressure was required to deliver a bolus infusion through a Teflon than through a steel catheter. We propose that the difference in infusion counter pressure and ATBF between Teflon and steel catheters with wear time may be explained by better biocompatibility of steel than Teflon.

Cellular immunity impaired among patients on left ventricular assist device for 6 months

BACKGROUND

Sustained maintenance on left ventricular assist device (LVAD) is associated with an increased frequency of severe infections. Although temporary changes in cellular immunity are seen immediately after implantation, the consequence of sustained LVAD treatment on immunity is unknown.

METHODS

In vitro functional and phenotypic markers of T cell activation and 6 month clinical outcome were compared between patients with > or = 6-month LVAD therapy and heart failure control patients.

RESULTS

Recipients of LVADs had more infections (45.5% versus 0%; p < 0.05) and mortality (54% versus 16%; p < 0.05) than control patients. T-cell proliferative responses were lower among LVAD recipients than control patients when challenged with phytohemagglutinin (3.4 +/- 4.7 versus 28.5 +/- 19.6; p < 0.01), anti-CD3 (4.3 +/- 4.5 versus 16.4 +/- 17; p < 0.01), and staphylococcal enterotoxin B (7.2 +/- 6.3 versus 26.1 +/- 15.6; p = 0.002). Proliferative hyporesponsiveness among LVAD recipients was not caused by apoptosis (2.6% +/- 2.7% versus 2.7% +/- 2.1%; p = 0.94) or insufficient CD4+ cells (42.1% +/- 11.3% versus 40.2% +/- 7.5%; p = 0.71) relative to control patients. Instead, CD3+ cells from LVAD patients expressed less interleukin 2 (2.5% +/- 1.5% versus 5.2% +/- 3.1%; p = 0.03) and tumor necrosis factor-alpha (6.0% +/- 3.5% versus 25.8% +/- 8.7%; p < 0.001) and more interleukin 10 (5.8% +/- 6.1% versus 2.6% +/- 2.1%; p < 0.05). In addition, suppressive T-regulatory cells were more prevalent in LVAD patients than control patients (12.9% +/- 3.2% versus 1.2% +/- 1.1%; p < 0.001).

CONCLUSIONS

Cellular immunity is compromised among long-term LVAD recipients because of a downregulatory cytokine imbalance and emergence of suppressive T-regulatory cells.

Prosthetic material in inguinal hernia repair: how do I choose?

With numerous prosthetic options and a changing landscape of prosthetic development, a systematic approach to choosing a prosthetic is more sensible than trying to memorize all the details of each prosthetic. The surgeon should hone a single technique for the vast majority of inguinal hernia repairs to maximize proficiency. This limits the number of prosthetics to those suitable for that technique. Narrowing the choice further should be based on the likelihood that a given prosthetic will achieve the preoperative goals of the hernia repair. For alternative clinical scenarios, the surgeon should know one to two additional techniques, which may require a different prosthetic. The surgeon should use existing experimental and clinical data to estimate long-term benefits of any new prosthetic.

Biocompatibility evaluation of surface-treated AISI 316L austenitic stainless steel in human cell cultures

The effects of AISI 316L austenitic stainless steel, tested in untreated state or subjected to glow-discharge nitriding (at 10 or 20 hPa) and nitriding + post-oxidizing treatments, on human umbilical vein endothelial cells (HUVEC) and on peripheral blood mononuclear cells (PBMC) were evaluated. All the treated samples showed a better corrosion resistance in PBS and higher surface hardness in comparison with the untreated alloy. In HUVEC put in contact for 72 h with the sample types, proliferation and apoptosis decreased and increased, respectively, in the presence of the nitrided + post-oxidized samples, while only slight differences in cytokine (TNF-alpha, IL-6, and TGF-beta1) release were registered. Intercellular adhesion molecule-1 (ICAM-1) increased in HUVEC incubated with all the treated samples, while vascular cell adhesion molecule-1 (VCAM-1) and E-selectin increased in the presence of all the sample types. PBMC incubated for 48 h with the samples showed a decrease in proliferation and an increase in apoptosis in the presence of the untreated samples and the nitrided + post-oxidized ones. All the sample types induced a remarkable increase in TNF-alpha and IL-6 release in PBMC culture medium, while only the untreated sample and the nitrided at 10 hPa induced an increase in ICAM-1 expression. In HUVEC cocultured with PBMC, previously put in contact with the treated AISI 316L samples, increased levels of ICAM-1 were detected. In HUVEC coincubated with the culture medium of PBMC, previously put in contact with the samples under study, a noteworthy increase in ICAM-1, VCAM-1, and E-selectin levels was always registered, with the exception of VCAM-1, which was not affected by the untreated sample. In conclusion, even if the treated samples do not show a marked increase in biocompatibility in comparison with the untreated alloy, their higher corrosion resistance may suggest a better performance as the contact with physiological environment becomes longer.

Host response to sponge implants differs between subcutaneous and intraperitoneal sites in mice

Synthetic matrices have been used widely to repair and/or to replace biological tissues. However, there is relatively little information on the effect of different anatomical compartments on the host response to foreign implants. We have analyzed such responses to sponge implants in subcutaneous and in intraperitoneal sites in mice at days 3, 5, and 8 postimplantation by measuring inflammation, angiogenesis, and production of proangiogenic/inflammatory cytokines. The angiogenic response, assessed by hemoglobin content and by morphometric analysis of the number of vessels, was higher in intraperitoneal implants. Levels of vascular endothelial growth factor in intraperitoneal implants were 14-fold higher than in subcutaneous implants at day 3 and remained high for the next 5 days. Neutrophil accumulation as determined by myeloperoxidase activity was the same in both types of implants. Macrophage accumulation (N-acetylglucosaminidase activity) was also similar on days 3 and 8 in both implants. Levels of the chemokine CXCL2/KC were always higher, but those of CCL2/JE lower, in the intraperitoneal implant. These results demonstrate that the anatomical site of the implant markedly influenced the host response to synthetic matrices. Our results provide a greater understanding of factors affecting the biocompatibility of exogenous materials placed at different anatomical sites.

Digital image analysis for morphometric evaluation of tissue response after implanting alloplastic vascular prostheses

The aim of this study was to examine the suitability of digital image analysis, using the KS400 software system, for the morphometric evaluation of the tissue response after prosthesis implantation in an animal model. Twenty-four female pigs aged 10 weeks were implanted with infrarenal Dacron(R) prostheses for 14, 21, 28, and 116 days. Following the explantation and investigation of the neointima region, the expression of beta-1-integrin, the proliferation rate by means of Ki-67 positive cells, and the intima thickness were evaluated as exemplary parameters of the tissue response after implantation. Frozen tissue sections were immunohistochemically stained and subsequently examined using computer-aided image analysis. A maximum expression of 32.9% was observed for beta-1-integrin 14 days after implantation, gradually declining over time to 9.8% after 116 days. The proliferation rate was found to be 19% on day 14, increasing to 39% on day 21 with a subsequent gradual decline to 5% after 116 days. The intima thickness increased from 189.9 microm on day 14 to 1228.0 microm on day 116. In conclusion, digital image analysis was found to be an efficient and reproducible method for the morphometric evaluation of a peri-prosthetic tissue response.