Analysis of collateral tortuosity development and impact of aging, genetics, and occlusive disease. (2009)

Undergraduates: Pranay Prabhakar, Mary Susan Burnett, Stephen E. Epstein, James E. Faber

Faculty Advisor: James Faber
Department: Health Policy & Management

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Presence of a collateral circulation improves tissue oxygenation, especially in occlusive disease. Unique features of collaterals include their significant tortuosity (TY), which increases in ischemic disease causing decreased conductance. When native collaterals acquire TY and whether it changes with aging, genetic background or disease are unknown, nor has increased TY in ischemia been quantified. Therefore, we measured collateral diameter, number, length, (l), span (L, scalar distance between collateral “stem and rentry” points between adjacent trees) and TY index (TYI=l/L) in the cerebral pial circulation of C57BL/6 and BALB/c mice. Conductance was estimated using Poiseuille’s equation. Conclusions: Collaterals acquire TY shortly after birth (between E15.5 and postnatal day 21). TY, and thus resistance, continue to increase with aging (upto 30 mos of age). BALB/c mice have a genetic defect in overall collateral growth (Physiol Genomics 2007), which we show also includes TY. TY intensifies following artery obstruction (up to 6 days following middle cerebral artery occlusion (MCAO)) during enlargement of collateral diameter, but subsequently lessens in association with induction of tortuosity into the tips of the adjacent arterial trees (by 14 days following MCAO). These findings suggest that genetics, risk factors and environment affect tortuosity of collaterals, and either promote or impair their conductance function.