Dynamic observation on the bladder acellular matrix grafts for substituting albuginea penis in rabbits / 中国组织工程研究

ABSTRACT

BACKGROUND: At present, bladder acellular matrix grafts have been successfully used for substituting animal bladder and urinary canal, and for repairing hypospadia. However, reports on bladder acellular matrix grafts for substituting albuginea penis need to be investigated. OBJECTIVE: Allogeneic bladder acellular grafts were used for substituting albuginea penis of rabbits, in order to observe repairing results. DESIGN: A randomized controlled observation. SETTING: West China Medical Laboratory Animal Center and West China Laboratory of Tissue Engineering of Sichuan University as well as Laboratory of Tissue Engineering of Guiyang Medical College. MATERIALS: Fifty male healthy New Zealand Rabbits of grade 3, weighing 2.6-3.0 kg, without phimosis and penis dysplasia, and without presence of phallocampsis after normal saline being perfused, were provided by Huaxi Laboratory Animal Center of Sichuan University. METHODS: This study was performed at the West China Laboratory Animal Center and West China Laboratory of Tissue Engineering of Sichuan University as well as Laboratory of Tissue Engineering of Guiyang Medical College between December 2005 and June 2007. Bladders were taken from 10 experimental rabbits for preparing bladder acellular matrix grafts. The other 40 New Zealand rabbits were randomly divided into the control group, and the bladder acellular matrix grafts group, with 20 in each. An area of 10 mm×5 mm of albuginea penis was resected from dorsum penis of each rabbit. Suture in situ of albuginea penis and bladder acellular matrix grafting were conducted in rabbits of the control group and bladder acellular matrix grafts group, respectively. In the 2nd, 6th, 12th and 24th weeks postoperatively, each rabbit was intracavernously perfused normal saline for inducing penile erection, separately, in order to observe phallocampsis. At above-mentioned each time point, experimental animals were sacrificed. Sample was taken from surgical region for haematoxylin-eosin (HE) staining and Masson trichrome staining, in order to observe the changes of tissue and structure of surgical region. Types Ⅰand Ⅲ collagen fiber areas were detected by Stirus red staining, and the expressions of inducible nitric oxide synthase(iNOS) and transforming growth factor-β1 (TGF-β1) were detected by immunohistochemical staining. MAIN OUTCOME MEASURES: ①Phallocampsis status. ② Changes of tissue and structure of surgical region. ③iNOS and TGF-β1 expressions. ④TypeⅠand Ⅲ collagen fiber areas.RESULTS: Forty experimental rabbits were involved in the penile surgery, two of them died from overdose anesthesia, two died from chordapsus, so the remaining thirty-six rabbits were involved in the final analysis. In the 6th week postoperatively, phallocampsis reached its highest level, and 2 rabbits in the control group and 1 rabbit in the bladder acellular matrix grafts group presented phallocampsis. In the 12th week, every rabbit presented phallocampsis. In the 24th week, 1 rabbit in the control group but none in the bladder acellular matrix grafts group presented phallocampsis. In the 2nd week, the structure of surgical regions of each rabbit was poorly clear, with remarkable inflammatory infiltration. In the bladder acellular matrix grafts group, grafting regions presented cells ingrowing the bladder acellular matrix grafts. Masson trichrome staining results showed that in the surgical region, tunica albuginea fibers were thin and poorly arranged. In the 6th week, tunica albuginea recovered its integrity, and bladder acellular matrix grafts could not be distinguished. No significant difference existed between two groups. In the 24th week, tunica albuginea was even and complete in the sugical region, and fibers restored their arrangement of circular muscle in inner layer and longitudinal muscle in outer layer, without difference from normal tunica albuginea. iNOS and TGF-β1 expressions were the strongest in the 2nd week, and they were found in the fibrocytes and vascular endothelial cells in the 6th week, but a little in the 12th and 24th weeks postoperatively. There were no remarkable differences in iNOS and TGF-β1 expressions between two groups at the same time point. In the 2nd week, typesⅠand Ⅲ collagen fibers co-existed with equivalent proportion. Then, typeⅠcollagen fibers were gradually increased, while type Ⅲ collagen fibers were on the contrary. In the 24th week, typeⅠcollagen fibers took the main place and type Ⅲ collagen fibers were unremarkable. CONCLUSION: Bladder acellular matrix grafts have no remarkable inflammatory reactions and fibrosis in repairing tunica albuginea of New Zealand rabbits, so they are very ideal grafting materials for penile surgery.