An established abdominal wall multidisciplinary team improves patient care and aids surgical decision making with complex ventral hernia patients.

INTRODUCTION: Abdominal wall reconstruction (AWR) is an emerging subspecialty within general surgery. The practice of multidisciplinary team (MDT) meetings to aid decision making and improve patient care has been demonstrated, with widespread acceptance. This study presents our initial experience of over 150 cases of complex hernia patients discussed in a newly established MDT setting. METHODS: From February 2020 to July 2022 (30-month period), abdominal wall MDTs were held bimonthly. Key stakeholders included upper and lower gastrointestinal surgeons, a gastrointestinal specialist radiologist, a plastic surgeon, a high-risk anaesthetist and two junior doctors integrated into the AWR clinical team. Meetings were held online, where patient history, past medical and surgical history, hernia characteristics and up-to-date computed tomography scans were discussed. RESULTS: Some 156 patients were discussed over 18 meetings within the above period. Ninety-five (61%) patients were recommended for surgery, and 61 (39%) patients were recommended for conservative management or referred elsewhere. Seventy-eight (82%) patients were directly waitlisted, whereas seventeen (18%) required preoperative optimisation: three (18%) for smoking cessation, eleven (65%) for weight-loss management and three (18%) for specialist diabetic assessment and management. In total, 92 (59%) patients (including operative and nonoperative management) have been discharged to primary care. DISCUSSION: A multidisciplinary forum for complex abdominal wall patients is a safe process that facilitates decision making, promotes education and improves patient care. As the AWR subspecialty evolves, our view is that the "complex hernia MDT" will become commonplace. We present our experience and share advice for others planning to establish an AWR centre.

The expression of P-glycoprotein does influence the distribution of novel fluorescent compounds in solid tumour models.

Solid tumours display a complex drug resistance phenotype that involves inherent and acquired mechanisms. Multicellular resistance is an inherent feature of solid tumours and is known to present significant barriers to drug permeation in tumours. Given this barrier, do acquired resistance mechanisms such as P-glycoprotein (P-gp) contribute significantly to resistance? To address this question, the multicellular tumour spheroid (MCTS) model was used to examine the influence of P-gp on drug distribution in solid tissue. Tumour spheroids (TS) were generated from either drug-sensitive MCF7(WT) cells or a drug-resistant, P-gp-expressing derivative MCF7(Adr). Confocal microscopy was used to measure time courses and distribution patterns of three fluorescent compounds; calcein-AM, rhodamine123 and BODIPY-taxol. These compounds were chosen because they are all substrates for P-gp-mediated transport, exhibit high fluorescence and are chemically dissimilar. For example, BODIPY-taxol and rhodamine 123 showed high accumulation and distributed extensively throughout the TS(WT), whereas calcein-AM accumulation was restricted to the outermost layers. The presence of P-gp in TS(Adr) resulted in negligible accumulation, regardless of the compound. Moreover, the inhibition of P-gp by nicardipine restored intracellular accumulation and distribution patterns to levels observed in TS(WT). The results demonstrate the effectiveness of P-gp in modulating drug distribution in solid tumour models. However, the penetration of agents throughout the tissue is strongly determined by the physico-chemical properties of the individual compounds.

The importance of cholesterol in maintenance of P-glycoprotein activity and its membrane perturbing influence.

In tumour cell lines that display multidrug resistance, expression of P-glycoprotein (P-gp) alters many aspects of biomembrane organization in addition to its well-characterized drug transport activity. We have developed a reconstitution system to directly investigate the effect of purified P-gp on the biophysical properties of lipid bilayers. Using a mixed detergent system it was possible to efficiently reconstitute P-gp at lipid:protein ratios as low as 2.5 (w/w) by removal of detergent using adsorption to SM-2 BioBeads. P-gp was able to alter many biophysical parameters associated with lipid organization within bilayers. For example, the changes in overall fluidity and excimer formation by lipid analogues indicate modified packing organization of bilayer constituents. Surprisingly, given its role in conferring drug resistance, P-gp insertion into bilayers also caused significantly increased permeability to aqueous compounds, also reflecting a modified phospholipid environment. Translocation of various phospholipid species between leaflets of the bilayer was increased in the presence of P-gp; however, the effect was not dependent on ATP hydrolysis by the protein. Physiological concentrations of cholesterol modified P-gp function and the degree to which it perturbed bilayer organization. The basal ATPase activity of P-gp was increased in a dose-dependent fashion by the incorporation of cholesterol in PC:PE liposomes. In addition, the degree to which the modulator verapamil was able to stimulate this basal ATPase activity was reduced by the presence of cholesterol in proteoliposomes. However, the potency of verapamil was unaltered, suggesting a specific effect, not simply caused by lower drug penetration into the cholesterol containing bilayers. In summary, P-gp is able to cause perturbation in the organization of bilayer constituents. Cholesterol imparted "stability" to this perturbation of bilayer organization by P-gp and moreover this led to altered protein function.