Application of AAV2-mediated bFGF gene therapy on survival of ischemic flaps: effects of timing of gene transfer

VEGF and Other Gene Therapies Improve Flap Survival-A Systematic Review and Meta-Analysis of Preclinical Studies

Surgical flaps are basic tools in reconstructive surgery. Their use may be limited by ischemia and necrosis. Few therapies address or prevent them. Genetic therapy could improve flap outcomes, but primary studies in this field present conflicting results. This systematic review and meta-analysis aimed to appraise the efficacy of external gene delivery to the flap for its survival in preclinical models. This review was registered with PROSPERO (CRD42022359982). PubMed, Embase, Web of Science, and Scopus were searched to identify studies using animal models reporting flap survival outcomes following any genetic modifications. Random-effects meta-analysis was used to calculate mean differences in flap survival with accompanying 95% CI. The risk of bias was assessed using the SYRCLE tool. Subgroup and sensitivity analyses were performed to ascertain the robustness of primary analyses, and the evidence was assessed using the GRADE approach. The initial search yielded 690 articles; 51 were eventually included, 36 of which with 1576 rats were meta-analyzed. VEGF gene delivery to different flap types significantly improved flap survival area by 15.66% (95% CI 11.80-19.52). Other interventions had smaller or less precise effects: PDGF-13.44% (95% CI 3.53-23.35); VEGF + FGF-8.64% (95% CI 6.94-10.34); HGF-5.61% (95% CI 0.43-10.78); FGF 3.84% (95% CI 1.13-6.55). Despite considerable heterogeneity, moderate risk of bias, and low quality of evidence, the efficacy of VEGF gene therapy remained significant in all sensitivity analyses. Preclinical data indicate that gene therapy is effective for increasing flap survival, but further animal studies are required for successful clinical translation.

High cut-off microdialysis catheters to clinically investigate cytokine changes following flap transfer

Background

‘Choke vessels’ are thought to dilate in the first 72 h when blood flow to an area is disrupted. This study used ‘high cut-off’ microdialysis catheters in clinical research to investigate factors mediating circulatory change within free flaps.

Methods

Six patients undergoing DIEP flap breast reconstruction each had three ‘high cut-off’ microdialysis catheters, with a membrane modification allowing molecules as large as 100 kDa to pass, inserted into Hartrampf zones 1, 2 and 4 to assess multiple vascular territories. Microdialysis continued for 72 h post-operatively. Samples were analysed for interleukin-6 (IL-6), tumour necrosis factor alpha (TNFα) and fibroblast growth factor basic (FGFβ).

Results

Three hundred and twenty-four samples were analysed for IL-6, FGFβ and TNFα totalling 915 analyses. IL-6 showed an increasing trend until 36 h post-operatively before remaining relatively constant. Overall, there was an increase (p < 0.001) over the time period from 4 to 72 h, fitting a linear trend. TNFα had a peak around 20–24 h before a gradual decrease. There was a significant linear time trend (p = 0.029) between 4 and 76 h, decreasing over the time period. FGFβ concentrations did not appear to have any overall difference in concentration with time. The concentration however appeared to oscillate about a horizontal trend line. There were no differences between the DIEP zones in concentrations of cytokines collected.

Conclusion

This study uses high-cut off microdialysis catheters to evaluate changes in cytokines, and requires further research to be undertaken to add to our knowledge of choke vessels and flap physiology.

Level of evidence:

Level IV, diagnostic study.