Omental flap for hepatic artery coverage during liver transplantation

The effect of omentoplasty in various surgical operations: Systematic review and meta-analysis

BACKGROUND

Omentoplasty is commonly used in various surgeries. However, its effectiveness is unsure due to lack of convincing data and research. To clarify the impact of omentoplasty on postoperative complications of various procedures, this systematic review and meta-analysis was performed.

METHODS

A systematic review of published literatures from four databases: PubMed, Web of Science, Cochrane Library, and Embase before July 14, 2022. We primarily included publications on five major surgical operations performed in conjunction with omentoplasty: thoracic surgery, esophageal surgery, gastrointestinal surgery, pelvi-perineal surgery, and liver surgery. The protocol was registered in PROSPERO.

RESULTS

This review included 25 273 patients from 91 studies (n=9 670 underwent omentoplasty). Omentoplasty was associated with a lower risk of overall complications particularly in gastrointestinal (RR 0.53; 95%CI 0.39-0.72) and liver surgery (RR 0.54; 95%CI 0.39-0.74). Omentoplasty reduced the risk of postoperative infection in thoracic (RR 0.38; 95%CI 0.18-0.78) and liver surgery (RR 0.39; 95%CI 0.29-0.52). In patients undergoing esophageal (RR 0.89; 95%CI 0.80-0.99) and gastrointestinal (RR 0.28; 95%CI 0.23-0.34) surgery with a BMI greater than 25, omentoplasty is significantly associated with a reduced risk of overall complications compared to patients with normal BMI. No significant differences were found in pelvi-perineal surgery, except infection in patients whose BMI ranged from 25 kg/m2 to 29.9 kg/m2 (RR 1.25; 95%CI 1.04-1.50) and anastomotic leakage in patients aged over 60 (RR 0.59; 95%CI-0.39-0.91).

CONCLUSION

Omentoplasty can effectively prevent postoperative infection. It is associated with a lower incidence of multiple postoperative complications in gastrointestinal and liver surgery.

Promoting vascularization for tissue engineering constructs: current strategies focusing on HIF-regulating scaffolds

INTRODUCTION

Vascularization remains one of the greatest yet unmet challenges in tissue engineering. When engineered tissues are scaled up to therapeutically relevant dimensions, their demand of oxygen and nutrients can no longer be met by diffusion. Thus, there is a need for perfusable vascular structures. Hypoxia-inducible factors (HIF) act as transcriptional oxygen sensors and regulate a multitude of genes involved in adaptive processes to hypoxia, including angiogenesis. Thus, targeting HIFs is a promising strategy to induce vascularization of engineered tissues.

AREAS COVERED

Here we review current vascularization strategies and summarize the present knowledge regarding activation of HIF signaling by ions, iron chelating agents, α-Ketoglutarate (αKG) analogues, and the lipid-lowering drug simvastatin to induce angiogenesis. Specifically, we focus on the incorporation of HIF-activating agents into biomaterials and scaffolds for controlled release.

EXPERT OPINION

Vascularization of tissue constructs through activation of upstream regulators of angiogenesis offers advantages but also suffers from drawbacks. HIFs can induce a complete angiogenic program; however, this program appears to be too slow to vascularize larger constructs before cell death occurs. It is therefore crucial that HIF-activation is combined with cell protective strategies and prevascularization techniques to obtain fully vascularized, vital tissues of therapeutically relevant dimensions.

Vascularisation for cardiac tissue engineering: the extracellular matrix

Cardiovascular diseases present a major socio-economic burden. One major problem underlying most cardiovascular and congenital heart diseases is the irreversible loss of contractile heart muscle cells, the cardiomyocytes. To reverse damage incurred by myocardial infarction or by surgical correction of cardiac malformations, the loss of cardiac tissue with a thickness of a few millimetres needs to be compensated. A promising approach to this issue is cardiac tissue engineering. In this review we focus on the problem of in vitro vascularisation as implantation of cardiac patches consisting of more than three layers of cardiomyocytes (> 100 μm thick) already results in necrosis. We explain the need for vascularisation and elaborate on the importance to include non-myocytes in order to generate functional vascularised cardiac tissue. We discuss the potential of extracellular matrix molecules in promoting vascularisation and introduce nephronectin as an example of a new promising candidate. Finally, we discuss current biomaterial- based approaches including micropatterning, electrospinning, 3D micro-manufacturing technology and porogens. Collectively, the current literature supports the notion that cardiac tissue engineering is a realistic option for future treatment of paediatric and adult patients with cardiac disease.