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URETHRAL RECONSTRUCTION
WITH HOMOLOGOUS ACELLULAR URETHRAL MATRIX (AUM)
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Authors:
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Karl-Dietrich Sievert1,
2), Jörg Wefer1), Michael Muscheck1), Lora Nunes1), Rajvir Dahiya1)
and Emil A. Tanagho1)
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Institution:
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1) University of California,
San Francisco, School of Medicine Department of Urology 2) Westfälische
Wilhelms-Universität Münster Klinik und Poliklinik für Urologie
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Aims of Study
To evaluate urethral replacement by a free homologous urethral graft of acellular
matrix in a rabbit model.
Methods
In 24 male New Zealand rabbits, a 0.8- to 1.1-cm segment of the urethra was
resected, replaced with an acellular matrix graft of 1.0 to 1.5 cm (mean 1.3
cm), and placed on an 8-F feeding tube. Before sacrifice the animals underwent
retrograde urethrography. At the time of explantation the implants were measured.
The grafted specimens were prepared for electron and light microscopy as well
for rt-PCR.
Results
The acellular matrix graft remained in its original position. The production
related length increase of the matrix ("11%) was almost kept ("5.8%) over 8
months postoperative time. Histologic examination showed complete epithelialization
and progressive vessel infiltration. At 3 months, smooth muscle bundles were
first observed infiltrating the matrix at the end-to-end anastomosis; after
6 months, the smooth muscle bundles had grown into 1/3 of the matrix. Urodynamics
did not detect any difference between the control and matrix-grafted animals.
Rt-PCR detected an increase in IGF and HB-EGF in the graft from day 10 through
month 6. After 6 months, it was difficult to differentiate host from implant
by urethrography.
Conclusions
The acellular urethral matrix allows single-stage urethral reconstruction without
sign of matrix shrinking or strictures. All tissue components are seen in the
grafted matrix after 3 months, with further improvement over time. However,
the smooth muscle in the matrix is less than in normal rabbit urethra and is
not well oriented.