A biomechanical, histological and biochemical study in an experimental rabbit hypospadias repair model using scanning acoustic microscopy.

OBJECTIVE: To investigate the biomechanical, histological and biochemical properties of rabbit urethra at long-term follow up after hypospadias simulation and acute repair. MATERIALS AND METHODS: Thirty-eight white New Zealand male rabbits underwent experimental creation of a hypospadias-like defect and acute repair (mobilization and advancement, tubularized incised posterior urethral plate (TIP), modified TIP) and sham operation. After 23 weeks all groups + controls underwent biomechanical, histological and biochemical assessments. RESULTS: The mobilization and advancement group showed a higher stiffness compared to the TIP groups (P < 0.05) in the posterior urethra, whereas the TIP group was stiffer compared to the other two operative groups (P < 0.001) in the ventral urethra. In the dorsal urethra, the mobilization and advancement group and the modified TIP group had a higher collagen content compared to shams (P < 0.05). No differences in collagen content were found between groups in the ventral urethra. A correlation between acoustic and histological layers was found, partially related to collagen content. CONCLUSION: The urethras had different microelastic properties in different layers of the dorsal and ventral urethra, with higher stiffness in the connective tissue layers surrounding and within the urethra. The repaired urethras had partially recovered their elasticity at micrometer resolution at long-term follow up. Scanning acoustic microscopy elucidated structure-function relationships at microscopic level in normal and operated urethra.

Distribution of the microelastic properties within the human anterior mitral leaflet.

Knowledge of the biomechanical properties of the mitral valve leaflets and their relation to histologic structure is of importance for understanding the leaflet movement characteristics under normal and pathologic conditions, but such knowledge is not yet available. The aim of this study was to determine biomechanical properties of the human anterior mitral leaflet on a microscopic scale. We used scanning acoustic microscopy (SAM) to examine the human anterior mitral leaflet. Sections of fixed human anterior mitral leaflet tissue were obtained from postmortem human anterior mitral leaflets (n = 5). We measured the speed of sound (nu(L)) in each histologic layer in three regions-of-interest (ROIs): these were at the annular edge, at the valve midpoint and close to the free edge. nu(L) varied in the three histologic layers (p < 0.01). It was higher in the fibrous layer (1.76 km/s) compared with the atrial layer (1.75 km/s) and ventricular layer (1.73 km/s). Also, nu(L) differed between positions along the length of the annulus-free edge line (p < 0.01), showing a decline from the annular edge (1.76 km/s) to the free edge (1.73 km/s), both as a whole and also within the atrial and the fibrous layer. These results demonstrate that the fibrous layer is stiffer than the atrial and ventricular layer and that the leaflet as a whole and within the atrial and the fibrous layer is stiffer at the annulus part in comparison with those near the free edge. (E-mail: ).

A new method to correlate histology with biomechanical properties in urethral tissue. An in-vitro study using light microscopy and scanning acoustic microscopy.

When surveying the classical biomechanical theory of flow and resistance, the passive elastic properties of the urethra seems to be important for the transport of urine though the urethra. The aim of this study was to show that scanning acoustic microscopy (SAM) is a suitable methodology for investigating elastic properties of the urethra, and that it can be used to correlate elastic properties to histological areas. One 40 kg female pig and one 2 kg male rabbit comprised the material. A SAM2000 was used at a working frequency of 1000 MHz. Sections of nominal 3 micrometer thickness fixed urethral tissue were prepared for SAM and stained for light microscopy. The histological layers of the urethra were evident in the SAM image, and showed highly variable values of elastic properties. The layers seen with SAM correlated well with those seen with light microscopy. In conclusion, we have provided the first images of the microelastic properties of the urethra and correlated them to histology.