Training a sophisticated microsurgical technique: interposition of external jugular vein graft in the common carotid artery in rats

Experimental study of histological changes in vascular loops according to the duration of the postoperative period: Application in reconstructive microsurgery

OBJECTIVES

To analyze the histological changes observed in venous grafts subjected to arterial blood flow as a function of the duration of the postoperative period to optimize their use in free flap reconstructions.

METHOD

Twenty-five rats (7 females and 18 males) underwent surgery. Surgeries were performed on one animal per week. Five weeks after the first surgery, the same five animals were subjected to an additional surgery to assess the presence or absence of blood flow through the vascular loop, and samples were collected for histological analysis. This cycle was performed five times.

RESULTS

Of the rats euthanized four to five weeks after the first surgery, no blood flow was observed through the graft in 80% of the cases. In the group euthanized three weeks after the first surgery, no blood flow was observed in 20% of the cases. In the groups euthanized one to two weeks after the first surgery, blood flow through the vascular loop was observed in all animals. Moreover, intimal proliferation tended to increase with the duration of the postoperative period. Two weeks after surgery, intimal proliferation increased slightly, whereas strong intimal proliferation was observed in all rats evaluated five weeks after surgery.

CONCLUSION

Intimal proliferation was the most significant change noted in venous grafts as a function of the duration of the postoperative period and was directly correlated with graft occlusion. In cases in which vascular loops are required during free flap reconstruction, both procedures should preferably be performed during the same surgery.

MicroRNA-26a targets MAPK6 to inhibit smooth muscle cell proliferation and vein graft neointimal hyperplasia

Neointima formation is the major reason for vein graft failure. However, the underlying mechanism is unclear. The aim of this study was to determine the role of miR-26a in the development of neointimal hyperplasia of autogenous vein grafts. Using autologous jugular vein grafts in the rat carotid artery as a model, we found that miR-26a was significantly downregulated in grafted veins as well as proliferating vascular smooth muscle cells (VSMCs) stimulated with platelet-derived growth factor-BB (PDGF-BB). Overexpression of miR-26a reduced the proliferation and migration of VSMCs. Further analysis revealed that the effects of miR-26a in VSMCs were mediated by targeting MAPK6 at the mRNA and protein levels. Luciferase assays showed that miR-26a repressed wild type (WT) MAPK6-3′-UTR-luciferase activity but not mutant MAPK6-3′-UTR-luciferease reporter. MAPK6 deficiency reduced proliferation and migration; in contrast, overexpression of MAPK6 enhanced the proliferation and migration of VSMCs. This study confirmed that neointimal hyperplasia in vein grafts was reduced in vivo by up-regulated miR-26a expression. In conclusion, our results showed that miR-26a is an important regulator of VSMC functions and neointimal hyperplasia, suggesting that miR-26a may be a potential therapeutic target for autologous vein graft diseases.

COMPARATIVE STUDY OF MICROANASTOMOSIS WITH DISTINCT 10-0 NYLON SUTURES IN RATS

Objective:

The aim of this study is to compare micro-sutures commonly used in our midst.

Methods:

In this double-blind study, 30 Wistar rats were operated randomly divided into three groups matched according to the suture used (Nylon 10-0, 75micron, brands Microsuture^(r), Polysuture^(r) and Ethicon^(r)). We analyzed the number of surgical nodes required, bleeding, surgical time and histological evaluation.

Results:

There was no significant difference between the amount of stitches of arterial suture per anastomosis. Surgical time was longer in Microsuture^(r) group as compared to Polysuture^(r) (p ≤ 0.05). Bleeding in Microsuture^(r) group was higher when compared to the others (p <0.01). In the histological analysis, the Microsuture^(r) group showed a greater tendency to develop fibrosis and aneurysm in surgical site than the others (p <0.01 and p≤0,05, respectively). Similarly, the Ethicon^(r) group showed less tendency to myointimal proliferation than the rest. (p = 0.025).

Conclusion:

The results confirm the relevance of the choice of surgical thread as an independent determining factor for the success of the procedure, besides serving as a rational subsidy for a better cost-benefit analysis. Level of Evidence I, Experimental Study, Controlled Animal Study.