Restoration of Spermatogenesis by Adenoviral Gene Transfer into Injured Spinal Cords of Rats

Background: Spinal cord injury (SCI) has a significant impact on male reproductive functions which may lead to infertility. A large number of spinal cord injured men suffer from impaired spermatogenesis. Currently, in vivo gene transfer of molecules with potential therapeutic value has been recognized as a viable method for inducing functional recovery after SCI. This study characterized the role of adenovirus-mediated gene transfer into experimentally injured spinal cords of rats on possible restoration of spermatogenic cell lines.
Materials and Methods: Young adult Sprague-Dawley rats (200-250g) were assigned into one of the three different groups of control, SCI, and adenovirus transfer (Ad) (n=3/ group). Control rats received no injury, nor any surgery. For SCI rats, SCI was produced by a 10g brass rod with a tip diameter of 2 mm which was dropped from a height of 12.5 mm onto exposed spinal cord at level of T10 with NYU impactor. Animals were perfused transcardially 43 days post SCI. Both spinal cord and testicular tissues were cryo-sectioned and ultra thin-sectioned, respectively. Cellular morphology and morphometry were done for spinal cord tissues. The testicular samples were processed for both light and transmission electron microscopy (TEM). The third group of rats underwent SCI first, followed by microinjection of LacZ adenoviral vectors (5x10⁶ p.f.u./ μl) along the T6-T10 dorsal root entry zone bilaterally. The immune system of animals were suppressed before the Ad administration. Each Ad injection was done using a glass micropipet and a Nonoject injector. Rats were killed 43 days after Ad injections, and the tissues were studied as for other groups.
Results: The spinal cord lesion extents for SCI and Ad groups were 8.1±3 and 5.8±2.2 mm, respectively (p<0.05). The testicular tissue of controls revealed a normal arrangement of spermatogenesis cell types. However, impaired spermatogenesis including vacuolization of germ cells along with incomplete spermatogenesis were noted in the tubles of SCI group. Also, nuclei and cell membranes of spermatozoa were damaged. In Ad rats, relatively active spermatogenesis, ranging from reappearance of proliferating spermatogonia to the presence of mature spermatozoa were observed in some seminiferous tubles.
Conclusion: Bilateral adenovirus-mediated gene transfer into experimentally injured spinal cords of rats can restore the ultrastructure of spermatogenesis including mature spermatozoa.