William R. Critchley

Altered Immunogenicity of Donor Lungs via Removal of Passenger Leukocytes Using Ex Vivo Lung Perfusion.

Passenger leukocyte transfer from the donor lung to the recipient is intrinsically involved in acute rejection. Direct presentation of alloantigen expressed on donor leukocytes is recognized by recipient T cells, promoting acute cellular rejection. We utilized ex vivo lung perfusion (EVLP) to study passenger leukocyte migration from donor lungs into the recipient and to evaluate the effects of donor leukocyte depletion prior to transplantation. For this purpose, female pigs received male left lungs either following 3 h of EVLP or retrieved using standard protocols. Recipients were monitored for 24 h and sequential samples were collected. EVLP‐reduced donor leukocyte transfer into the recipient and migration to recipient lymph nodes was markedly reduced. Recipient T cell infiltration of the donor lung was significantly diminished via EVLP. Donor leukocyte removal during EVLP reduces direct allorecognition and T cell priming, diminishing recipient T cell infiltration, the hallmark of acute rejection.

Altered immunogenicity of donor lungs via removal of passenger leukocytes using

Passenger leukocyte transfer from the donor lung to the recipient is intrinsically involved in acute rejection. Direct presentation of alloantigen expressed on donor leukocytes is recognized by recipient T cells, promoting acute cellular rejection. We utilized ex vivo lung perfusion (EVLP) to study passenger leukocyte migration from donor lungs into the recipient and to evaluate the effects of donor leukocyte depletion prior to transplantation. For this purpose, female pigs received male left lungs either following 3 h of EVLP or retrieved using standard protocols. Recipients were monitored for 24 h and sequential samples were collected. EVLP‐reduced donor leukocyte transfer into the recipient and migration to recipient lymph nodes was markedly reduced. Recipient T cell infiltration of the donor lung was significantly diminished via EVLP. Donor leukocyte removal during EVLP reduces direct allorecognition and T cell priming, diminishing recipient T cell infiltration, the hallmark of acute rejection.

A randomized study comparing three groups of vein harvesting methods for coronary artery bypass grafting: endoscopic harvest versus standard bridging and open techniques

OBJECTIVES The use of an open vein harvesting (OVH) technique for saphenous vein harvesting (SVH) is associated with wound complications and delayed patient mobilization. This has led to the development of minimally invasive vein harvesting (MIVH) techniques, such as standard bridging and endoscopic SVH (EVH). This randomized trial was established to assess immediate clinical outcome and patient satisfaction in our centre. METHODS A total of 150 consecutive patients were prospectively randomized into three groups. Group 1 consisted of 50 patients who underwent OVH, Group 2 consisted of 50 patients who underwent a standard bridging technique (SBT) and Group 3 consisted of 50 patients who underwent EVH. Each group was assessed for the incidence of wound infection, postoperative pain and satisfaction and the number of vein repairs using previously validated scoring systems. RESULTS The MIVH techniques reduced the pain at hospital (P < 0.001) and at 6 weeks (P < 0.001), and improved cosmesis (P < 0.001), compared with the OVH group. Patient satisfaction was greatest in the EVH group followed by the SBT and then the OVH group. The clinical markers of inflammation were reduced with an MIVHt. There were more vein repairs in the EVH compared with the OVH (P < 0.001) and the SBT (P = 0.04) groups. CONCLUSIONS This study demonstrates that MIVH reduces wound morbidity. We believe that each technique has advantages and disadvantages, which should be considered during the selection of a harvesting procedure by both the patient and the surgeon.

The effect of beta-blockers on the adaptive immune system in chronic heart failure.

It remains possible that the benefit from beta-blockers (BBs) in chronic heart failure (CHF) may not entirely be derived from a class-specific effect. Several experimental reports have alluded to the capability of immunomodulation by individual BBs. Given the increasingly recognized importance of the immune system in the pathogenesis of CHF, we studied the effects of BBs on the circulating immune system of these patients. Blood samples from CHF outpatients were prospectively analyzed using flow cytometry and gating software. Results were analyzed against comprehensive clinical details that were recorded during sample donation, including the type of BB administered. 273 blood samples were analyzed from 141 CHF patients, with an average ejection fraction of 31.9% and a mean age of 69.1 years. Patients taking carvedilol had a significantly lower expression of CD107a on cytotoxic T cells compared to bisoprolol (P= 0.001) and nebivolol (P= 0.008). They also had a significantly lower expression of HLA-DR on lymphocytes (P < 0.001 and P= 0.009 for bisoprolol and nebivolol, respectively). Cytotoxic T cells and lymphocytes expressing HLA-DR have been implicated in the pathogenesis of CHF. The fact that carvedilol, but not other commonly used beta-blockers, appears to modulate these important parameters, supports the concept that important differences exist between these agents, which may affect outcomes in CHF.

Histological and immunohistochemical evaluation of human saphenous vein harvested by endoscopic and open conventional methods

OBJECTIVES The introduction of endoscopic saphenous vein harvesting (ESVH) has been reported to decrease saphenectomy-associated wound pain and infection, compared with the traditional open conventional saphenous vein harvesting (OCSVH) technique. Despite all these benefits, the rate of adoption among surgeons has been variable. Criticism of this technique centres on the risk of injury at the time of vein harvest with its potential detrimental effect on structural viability and long-term patency. The aim of our study is to investigate the endothelial preservation of saphenous vein grafts harvested by various extraction methods. METHODS A prospective, observational study of 30 human saphenous vein grafts was performed to evaluate endothelial preservation by haematoxylin-eosin and CD 31 staining methods. The saphenous vein was harvested endoscopically either by an open tunnel (OT-ESVH), closed tunnel (CT-ESVH) or an OCSVH harvesting technique. Research samples were collected without distension to avoid intraluminal dilatation and endothelial disruption. Both haematoxylin-eosin and immunohistochemistry slides were imaged by a high-resolution slide-scanning system. RESULTS Haematoxylin-eosin staining of the CT-ESVH group showed mostly preserved endothelium (P = 0.398) with some endothelial stretching (P = 1.0) and no endothelial detachment (P = 0.197). The OT-ESVH group showed marked endothelial stretching (P = 0.053). However, the OCSVH group showed significantly more endothelial detachment than the endoscopic groups (P = 0.01). The mean grading score of immunohistochemistry using the CD 31 antibody was much lower in the OT-ESVH group (1.6 ± 0.84, P = 0.009), showing more poorly preserved endothelial cells than the CT-ESVH and OCSVH groups. CONCLUSIONS We observed more endothelial stretching in the OT-ESVH group, which in our opinion, was due to lack of subcutaneous tissue separation, poor visualization and traction stresses across the wall of the saphenous vein. However, the OCSVH method revealed poor endothelial protection with areas of endothelial detachment, not observed with both endoscopic techniques. Interestingly, most preserved endothelium was found in the CT-ESVH group, which was previously known to be associated with worse graft patency.

Brain natriuretic peptide induces CD8+ T cell death via a caspase 3 associated pathway--implications following heart transplantation.

BACKGROUND Brain natriuretic peptide (BNP) remains elevated after cardiac transplantation despite replacement of the failing ventricle. Serum peaks are also seen during acute rejection episodes independent of intracardiac hemodynamic disturbance. High BNP levels are also reported during bacterial sepsis, burns, stroke and myocardial infarction. Given all of these conditions are linked by immune activation processes, we hypothesised that BNP is an immunoactive agent. METHODS Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood of 40 cardiac transplant recipients. Cells were co-cultured for 72h in the presence or absence of BNP. Cells were then immunophenotyped using flow cytometry. Cell death pathways were determined using caspase 3 quantification and mitochondrial membrane assessment. Supernatants were analysed for cytokine, chemokine and growth factor production using luminex. RESULTS Co-culture of CD8+ T cells with BNP reduced cell number, and increased intracellular caspase 3. Supernatant analysis revealed that BNP reduced the expression of inflammatory cytokines including TNF-α, IL-1α and IL-6. However it preserved the production of anti-inflammatory and regulatory cytokines such as IL-4, 5 and 13. CONCLUSION Our findings provide evidence that BNP directly induces CD8+ T cell apoptosis via a caspase 3 associated mechanism from cardiac transplant patients. This may impart significant consequences on immune mediated disease processes, such as allograft rejection.

A randomized study comparing traditional monofilament knotted sutures with barbed knotless sutures for donor leg wound closure in coronary artery bypass surgery

OBJECTIVES Surgical knots on the suture line provide an anchoring function, but also represent a potential source of infection and irritation on the donor leg after coronary artery bypass surgery. Knotless barbed sutures were designed to prevent knot-related complications. This study compared knot-related wound complication rates between patients receiving traditional monofilament sutures and those receiving barbed knotless sutures for closure of the donor leg. METHODS One hundred and forty-two patients were randomized into two groups. Group 1 (n = 70) received traditional monofilament sutures and Group 2 (n = 72) received barbed knotless sutures. All wounds were assessed on postoperative days 3 and 5 and weeks 2, 4 and 6 using a validated wound scoring system. Antibiotics usage and general practitioner and district nurse visits were recorded. RESULTS No demographic differences were observed between groups. Leg wound skin closure times were significantly shorter in Group 2 compared with Group 1 (P < 0.001). Group 1 demonstrated a greater incidence of excessive scarring (P < 0.001), itching (P < 0.001), irritation (P < 0.001) and adverse skin tissue reactions (P < 0.001) than Group 2. Fewer general practitioner visits were recorded in Group 1 compared with Group 2 (P = 0.051). CONCLUSION Knotless barbed suture usage significantly reduces the incidence of knot-related leg wound complications compared with traditional monofilament knotted sutures. This may be related to differences in the rate of absorption of the suture material or an associated decrease in the incidence of adverse skin tissue reactions that may delay postoperative wound healing.

Does the introduction of a comprehensive structured training programme for endoscopic vein harvesting improve conduit quality? A multicentre pilot study

OBJECTIVES Endoscopic vein harvesting is one of the most popular minimally invasive vein-harvesting techniques for coronary artery bypass graft surgery. It is associated with improved cosmetic outcome and fewer wound-related problems compared with the conventional open technique. However, its efficacy with regard to conduit damage and long-term patency has recently been questioned. Learning curve-associated trauma to the vein has a major impact on vein quality and the incidence of graft failure post-surgery. In an attempt to address this problem, we have devised and tested a learning tool termed Manchester Endoscopic Learning Tool (MELT). In this study, we compare vein quality following MELT training with standard recommended training. METHODS Fourteen practitioners across seven UK centres were enrolled into the study. Practitioners were categorized into two groups receiving MELT or standard training. Data were collected prospectively from the first eight vein retrievals per operator following training. A total of n = 112 vein-harvesting procedures were included in the study. RESULTS Veins harvested by MELT practitioners had fewer small avulsions (P <0.001), required fewer repairs (P <0.001) and experienced a lower incidence of bruising (P <0.001) than veins obtained by practitioners receiving standard training. The incidence of very short side branches requiring repair was also significantly reduced (P <0.001) in the MELT group compared with standard training. CONCLUSIONS Our formalized training programme consistently minimizes vein trauma resulting in better-quality conduits when compared with the current standard training. Exposure of surgical practitioners to the structured curriculum during their endoscopic vein harvesting training will enhance their learning and lead to better-quality conduits. This is likely to impart clinical benefit post-surgery.

Should we consider heart rate reduction in cardiac transplant recipients

Increased resting heart rate is an independent modifiable risk factor for the development of cardiovascular disease. Numerous studies have demonstrated improved clinical outcomes with heart rate reduction in patients with coronary artery disease and heart failure, but its role in transplanted hearts is not yet established. Sinus tachycardia is more common in heart transplant recipients due to graft denervation. Although a large number of studies have recognized increased heart rate as a predictor of native coronary artery atherosclerosis and overall cardiac mortality, contradicting results have been observed in heart transplant recipients. There is no clear consensus about what the normal range of heart rate should be following heart transplantation. The aim of this article was to review the literature to evaluate whether heart rate reduction should be considered in heart transplant recipients.

Graft rejection – endogenous or allogeneic?

The presence and persistence of alloantigen is necessary for graft‐specific T‐cell‐mediated immunity. However, specificity comprises only a single facet of an extremely complex process. Evidence is accruing to suggest that immunogenicity could be manipulated by endogenous ligands released during tissue injury. Stress molecules are significantly up‐regulated following transplantation and stimulate conserved receptors on a range of leucocytes, including dendritic cells (DCs). The DCs are essential for co‐stimulation and the induction of adaptive immunity. Stress signals can act as an adjuvant leading to DC maturation and activation. DCs stimulated by endogens exhibit enhanced alloantigen presentation, co‐stimulation and production of pro‐inflammatory cytokines, such as interleukin‐1β (IL‐1β) and IL‐18. Inflammasomes have a major role in IL‐1β/IL‐18 production and secretion, and can be stimulated by endogens. Importantly, the polarization toward inflammatory T helper type 17 cells as opposed to regulatory T cells is dependent upon, among other factors, IL‐1β. This highlights an important differentiation pathway that may be influenced by endogenous signals. Minimizing graft damage and stress expression should hypothetically be advantageous, and we feel that this area warrants further research, and may provide novel treatment modalities with potential clinical benefit.