Towards a glioma model for surgical technique evaluation in the rat

Borneol increases blood-tumour barrier permeability by regulating the expression levels of tight junction-associated proteins

CONTEXT

Selectively opening the blood-tumour barrier (BTB) is critical to deliver antitumour drugs from blood to tumour tissues. The BTB problem is attributed to the tight junctions (TJs), which consist of several transmembrane proteins.

OBJECTIVE

To investigate whether borneol could open the BTB by affecting TJ-associated proteins ZO-1, occludin, claudin-5 and F-actin in the rat model of C6 glioma.

MATERIALS AND METHODS

The plasma and brain tissue of C6 glioma rats were collected at different points after rats were administered with 35 or 140 mg/kg borneol and 0.5% CMC-Na, respectively. The permeability of BTB was assessed by cisplatin extravasation. The mRNA and protein expression levels of TJ-associated proteins were determined by QPCR, ELISA and immunohistochemistry.

RESULTS

The cisplatin bioavailability in the brain tissue of C6 glioma rats administered either 35 or 140 mg/kg borneol and 0.5% CMC-Na were 415.07, 227.04 and 192.07 (mg/mL/h), respectively. The mRNA and protein expression levels of ZO-1 and F-actin began to decrease from the time point of 2 min; the lowest levels in the borneol high-dose (46.7% decrease for ZO-1 and 63.3% for F-actin compared with control) and low-dose groups (54.3% for ZO-1; 77.9% for F-actin) appeared at the time points of 30 and 45 min, respectively. Thereafter, the levels were gradually restored to the level of borneol at 0 h. Occludin and claudin-5 expression levels were not significantly modified.

CONCLUSION

Borneol could selectively open the BTB and consequently increase BTB permeability, and this mechanism is associated with the down-regulation of ZO-1 and F-actin.

Resection of C6 gliomas in rats with the aid of the waterjet technique

OBJECTIVES

While clinically the safety and efficacy of waterjet resection of brain tumors have been shown, evidence that waterjet dissection improves tumor resection radicality in comparison with conventional techniques is still missing. In the present study, resection radicality and tumor-free long-term survival of both techniques were evaluated in a C6-glioma model.

MATERIAL AND METHODS

Fifty-thousand C6-glioma cells were stereotactically transplanted in the left frontal lobe of 100 male Sprague-Dawley rats. After MRI-scanning for evaluation of tumor extension, microsurgical tumor resection was performed with conventional techniques (n=50) or with the waterjet dissector at pressures of 6bar (n=50). Twenty-five animals of each group were sacrificed after surgery for histological analysis. For analysis of survival after tumor resection, twenty-five animals of each group were followed-up to analyze tumor-free survival using the Kaplan Meier method.

RESULTS

In the waterjet group, the resection cavity was free of C6-tumor cells in 10/25 (40%) rats showing a trend (p=0.3) towards better resection radicality compared to the rats that were treated conventionally (7/10; 28%). R1-resection with up to 250C6 cells/object slice was found in 14/25 (56%) rats after waterjet dissection compared to 6/25 (24%) rats treated conventionally showing significance (p<0.01). Probability of survival was 38% after 2 weeks and 20% after 6 months in the waterjet group compared to 30% and 16% respectively in the conventional group. Diffuse tumor cell spreading with possible influence on survival was shown in 47/50 rats.

CONCLUSION

In this experimental model, waterjet tumor resection did reveal significantly better resection radicality compared to the conventional technique. Although a direct transfer of these results to human glioma surgery is prohibited, the waterjet technique might contribute to the best possible resection radicality in human gliomas. Nevertheless, tumor cell spreading remains a major problem. Further studies have to address that the surgical results - in deed - improve the postoperative outcome.