Author ' s response to reviews Title : Interpositional Substitution of Free Vas Deferens Segment Autografts in Rat : Feasibility and

Abstract word count: 199) 25 26 Background: Insufficient vas length for performing a tension-free vasovasostomy is a 27 problem occasionally encountered by microsurgeons. Herein we evaluated utilization of a 28 non-vascularized vas deferens autograft in a rat model. 29 Methods: Segments of isolated vas deferens, 2.5 cm in length, were used as bilateral 30 autografts in 15 rats. Each autograft was implanted between the two transected ends of vas 31 deferens using end-to-end anastomosis. Fertility, sperm motility, and graft survival was 32 evaluated and compared with the control group. 33 Results: At the end of the 3 months, 9/15 (60%) rats were able to breed successfully and 24 34 (80%) vas grafts were patent and viable. Large granulomata developed at the proximal 35 anastomosis sites in 6 (20%) autografts that failed. Unilateral minimal fluid leakage was 36 observed in 6 (20%) of the proximal (testicular end) anastomosis sites in those rats that were 37 able to breed. Histological evaluations demonstrated that graft survival was associated with 38 mild to severe changes in the structure of the vas autograft. On semen analysis 76% of the 39 sperms in the experimental group had forward motility compared to 78% in the control group 40 (p>0.05). 41 Conclusions: Vas autograft can successfully be performed in a rat model with ultimate 42 breeding capability. 43