Date Published: June 3, 2008
Publisher: BioMed Central
Author(s): Monika Martiniaková, Radoslav Omelka, Birgit Grosskopf, Alexander V Sirotkin, Peter Chrenek.
While gross morphological changes in the skeleton between males and females are well know, differences between sexes in the histomorphology are less known. It is important to have knowledge on the bone structure of rabbits, as this is a widely used species in biomedical research. A study was performed to evaluate the association between sex and the compact bone morphology of the femoral diaphysis in juvenile rabbits.
Seventeen clinically healthy 2–3 month-old rabbits (9 females, 8 males) were included in the study. The rabbits were euthanized and the right femur was sampled for analysis. 70–80 microns thick bone sections of the femoral diaphysis were prepared using standard histological equipment. The qualitative histological characteristics were determined according to internationally accepted classification systems while the quantitative parameters were assessed using the software Scion Image. Areas, perimeters, minimum and maximum diameters of primary osteons’ vascular canals, Haversian canals and secondary osteons were measured. Additionally, blood plasma concentrations of progesterone, corticosterone, IGF-I, testosterone and estradiol were analyzed.
Qualitative histological characteristics were similar for both sexes. However, variations of certain quantitative histological characteristics were identified. Measured parameters of the primary osteons’ vascular canals were higher in males than for females. On the other hand, females had significant higher values of secondary osteons parameters. Differences in Haversian canals parameters were only significant for minimum diameter.
The study demonstrated that quantitative histological characteristics of compact bone tissue of the femoral diaphysis in juvenile rabbits were sex dependent. The variations may be associated with different growth and modeling of the femur through influence by sex-specific steroids, mechanical loads, genetic factors and a multitude of other sources. The results can be applied in experimental studies focusing on comparison of the skeletal biology of the sexes.
Animal models are commonly used in the study of skeletal biology. The rabbit is one of the most commonly used animals for biomedical research, being used in approximately 35% of musculoskeletal research studies . This is in part due to ease of handling and size, but the rabbit is also convenient as it reaches skeletal maturity shortly after sexual maturity at around 6 months of age [2,3].
In general, our qualitative histological results correspond with those previously reported [19,20]. The basic structural pattern of compact bone tissue was primary vascular longitudinal in both sexes of juvenile rabbits. In addition, dense Haversian bone tissue and/or primary vascular radial bone tissue were found in the middle part of the compacta. In humans, qualitative characteristics of compact bone tissue are independent of sex [7-9]. This demonstrates that qualitative bone morphology expresses a low sex-related variation. Together with a strong genetic component of the qualitative traits, it allows them to be used for taxonomic identification of various species [5,19].
The study demonstrated that quantitative histological characteristics of compact bone tissue of the femoral diaphysis in juvenile rabbits were sex dependent. Specifically, area, perimeter and maximum diameter of the vascular canals of primary osteons were higher in males. Females had significant higher values of the secondary osteons parameters. Differences in Haversian canals parameters were only significant for minimum diameter. We believe that the variations may be associated with different growth and modeling of the femur through influence by sex-specific steroids, mechanical loads, genetic factors and a multitude of other sources. The effect of sex-specific hormones on sex-related variation in compact bone tissue seems to be important also in juvenile rabbits. Our study seems to be the first reporting differences in compact bone tissue between juvenile females and males rabbits. The results can be applied in experimental studies focusing on comparison of the skeletal biology of the sexes.
The authors declare that they have no competing interests.
MM carried out the histological analysis of examined bones, RO performed the statistical analysis of presented data, BG prepared thin sections for histological analysis, AS carried out the hormonal analysis, PCh supported animal care and femora taking. All authors read and approved the final manuscript.