Effects of cavernous nerve reconstruction on expression of nitric oxide synthase isoforms in rats.
OBJECTIVE
To evaluate the expression of nitric oxide synthase (NOS) isoforms after various reconstruction techniques in rats, to improve the understanding of neuronal repair mechanisms after radical prostatectomy, as Schwann cell-seeded guidance tubes have been shown to promote cavernous nerve regeneration, and glial cell-line-derived neurotrophic factor (GDNF)-overexpressing Schwann cells enhance nerve regenerative capacity.


METHODS
Segments (5 mm) of the cavernous nerve were excised bilaterally, followed by immediate bilateral microsurgical reconstruction. In four rats per group, the eight nerves were reconstructed by autologous nerve grafting (A), interposition of Schwann cell-seeded silicon tubes (B), or silicon tubes seeded with GDNF-hypersecreting Schwann cells (C). Further rats were either sham-operated (D) or had nerve excision without repair (E). Erectile function was evaluated after 6 weeks by re-laparotomy, electrical nerve stimulation and morphological evaluation of reconstructed nerves. NOS isoform mRNA expression was analysed by reverse transcription-polymerase chain reaction in tissue specimens taken from the corpora cavernosa.


RESULTS
GDNF-transduced Schwann cell grafts restored erectile function better than untransduced Schwann cell and autologous nerve grafts (88% vs 75% vs 38%; not significant). Tissue specimens in group C had the highest expression of neuronal NOS mRNA in relation to the neuronal marker PGP9.5 among all treatment groups (not significant). Compared to nerve grafts (A) and negative controls (E) nNOS/PGP9.5 expression was significantly higher (P < 0.05). Both inducible NOS and endothelial NOS expression did not differ significantly among the various groups. Morphological evaluation showed significantly larger cross-sectional areas and a higher percentage of neural tissue than in untransduced Schwann cell grafts (P < 0.05).


CONCLUSIONS
Restoration of erectile function is paralleled by an increase of neuronal NOS expression in rats. Further experiments will determine the physiological role of neuronal NOS in erectile nerve repair processes.
Schlenker
Boris
B
Department of Urology, Ludwig-Maximilians-University, Munchen, Germany. Boris.Schlenker@med.unimuenchen.de
Matiasek
Kaspar
K
Saur
Dieter
D
Gratzke
Christian
C
Bauer
Ricarda M
RM
Herouy
Yared
Y
Arndt
Christian
C
Blesch
Armin
A
Hartung
Rudolf
R
Stief
Christian G
CG
Weidner
Norbert
N
May
Florian
F
D000818:Animals; D017690:Cell Transplantation / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism; D018783:Impotence, Vasculogenic / Q000601:surgery*; D008297:Male; D009416:Nerve Regeneration / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010410:Penile Erection / Q000502:physiology; D010413:Penis / Q000201:enzymology / Q000294:innervation* / Q000601:surgery; D051381:Rats; D011916:Rats, Inbred F344; D020127:Recovery of Function; D012583:Schwann Cells / Q000378:metabolism / Q000637:transplantation*
D051100:Glial Cell Line-Derived Neurotrophic Factor; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III