gms | German Medical Science

Objective: For the prevention of stroke in chronic cerebral ischemia, myoblast-mediated gene transfer via an encephalomyosynangiosis (EMS) may represent an innovative approach to augment therapeutic angiogenesis in the brain. The aim of the present study was to test the effect of an EMS with and without implantation of VEGF-transfected myoblasts in a mouse model of chronic cerebral hypoperfusion.

Methods: Male C57/BL6 mice, aged 4 to 6 weeks were randomized into four groups (1) ICAO/EMS, (2) ICAO/VEGF, (3) ICAO and (4) Sham (n=16 each). To simulate chronic cerebral hypoperfusion, the right-sided ICA was permanently ligated before performing an EMS with or without implantation of 4x10⁵ VEGF-transfected myoblasts into the temporal muscle of the EMS. In the ICAO and Sham groups, no EMS was performed. Functional outcome was assessed by cerebrovascular reserve capacity (CVRC) measurements with laser speckle contrast analysis on day 3, 7, 14 and 21 over the ipsilateral and contralateral hemisphere. On day 21, a 60-minute middle cerebral artery occlusion (MCAO) was performed. The infarct volume was determined after 24 hours by MRI. Vascular morphology at the muscle-brain interface was assessed on day 21 by fluorescence- and confocal microscopy (CD31/Desmin staining and FITC-lectin perfusion).

Results: On day 3, 7 and 14, the CVRC did not differ between groups. On day 21, the CVRC was significantly lower in the ICAO group than in groups receiving an EMS, with or without VEGF-treatment (mean CRVC; ipsilateral: VEGF 46 ± 12%, EMS 41 ± 9%, ICAO 28 ± 17%, Sham 45 ± 12%; contralateral: VEGF 53 ± 12%, EMS 49 ± 9%, ICAO 36 ± 7%, Sham 43 ± 14%; p<0.05, one-way ANOVA). 24 hours after MCAO, the mortality rate in the ICAO and Sham groups was 30% and 29%, respectively and both EMS and VEGF groups showed a trend towards lower stroke volumes than animals treated with ICAO or Sham (mean stroke volume: VEGF 52 ± 23mm³, EMS 52 ± 21mm³, ICAO 68 ± 30mm³, Sham 72 ± 36mm³). In the VEGF group, immunofluorescence revealed a higher number of CD31/Desmin positive cells at the muscle-brain interface with transpial vessel bridges across the muscle-brain border after FITC-lectin perfusion.

Conclusions: An EMS with VEGF resulted in augmentation of collateral CBF and potential ischemic tolerance after 21 days of chronic cerebral hypoperfusion with indications of transpial vessel bridging and increased neovascularization at the muscle brain interface of the EMS.