An animal model to study microcirculatory changes associated with vasculardelay

Vascular delay is a surgical procedure that renders a flap partially ischae mic several days prior to its transfer in order to increase its viability a fter its transfer. Though much debate exists regarding the actual mechanism of vascular delay, most theories agree that changes in the microcirculatio n play a key role. In this paper, we describe four experiments that establi sh the ear of the homozygous (hr/hr) hairless mouse as an effective model f or directly viewing and measuring delay-induced changes in microcirculation . In our first experiment, we compared mouse ears that were delayed (n = 18 ) with ones that were not (control) (n = 13) and showed that vascular delay significantly (P < 0.05) reduced ear flap necrosis. In a second experiment , we delayed mouse ears for 2 (n = 9), 4 (n = 14), 6 (n = 10), 8 (n = 10), 10 (n = 10), 20 (n = 18), 40 (n = 10) and 80 (n = 11)days and found that th e reduction in necrosis becomes statistically significant (P < 0.05) over n on-delayed controls (n = 12) after a minimum delay period of 6 days. In a t hird experiment, we delayed mouse ears by ligating only the vein (n = 14), only the artery (n = 11), only the nerve (sympathectomy) (n = 14), and vein , artery and nerve (n = 14) of the main neurovascular pedicle and found sig nificant (P < 0.05) reductions in flap necrosis in all groups compared to n on-delayed controls (n = 12). Finally, in a fourth experiment, we measured vessel directionality changes in mouse ears that were delayed for 6 (n = 4) , 10 (n = 4), 20 (n = 4), 40 (n = 4) and 80 (n = 4) days, and found that di rectionality changes became significant (P < 0.05) at 6 days of delay and r emained so for all the days studied when compared with non-delayed controls (n = 4).