The mouse tibia is a common site to investigate bone adaptation. Strain gauges, digital image correlation (DIC) and digital volume correlation (DVC) can elastic and yield properties of human femoral trabecular and cortical bone tissue. If genetic control impacted femur-tibia correlation, a variety of A total of mice long bones were collected ( femurs and tibias) and. Twin studies as well as inbred mouse studies have confirmed that bone The correlation between body weight and skeletal measures such as cortical The femur and tibia were cleaned and stored at −20°C until mechanically tested.
As the correlation of X1 to X2 and X3 to X2 was increased to 0. The model of Atchley et al. The larger the CV of the denominator relative to the numerator, the greater will be the induced correlation. Attempting to remove the covariant body size from muscle and bone measures could actually produce an increase in the size effect, an increase in correlation of muscle to bone, and an increase in the correlation of muscle to body size and bone to body size. The issue of removing size effects is particularly germane to skeletal studies aimed at defining genetic regulation of the skeleton and pathways through which specific genes function.
Twin studies 10 as well as inbred mouse studies 11 — 13 have confirmed that bone properties are under significant genetic influence. Many factors are known to influence bone mass acquisition, including diet, sex, endocrine factors, mechanical loading, and genetics. Previous studies have also shown that muscle mass is associated with increased bone mass.
Murine Hind Limb Long Bone Dissection and Bone Marrow Isolation | Protocol
The mechanical strength of bone is not based solely on density bone tissue per unit volume but rather is the result of complex interactions among size, shape, cross-sectional tissue distribution, and mechanical integrity of the matrix itself.
By way of example, it has long been known that the cortical expansion of long bones that occurs with age acts partially to offset the effects of age-related bone loss because the redistribution of cortical bone away from the axis of bending increases bending strength, thus a geometric change in bone distribution compensates for a volumetric change in bone mass. The highest loads normally experienced by bone are from muscle forces used to resist or produce movement.
As muscle mass increases the potential load applied to bone increases, with concurrent increases in bone strain.
Muscle-bone relationships in mice selected for different body conformations.
A study by Zanchetta et al. Whereas muscles are thought to provide the largest source of bone strain, body weight is the second biggest intrinsic contributor. The effect of body size, both length and mass, is complex and can interact with physical activity, which also plays a role in the skeletal loading environment. The correlation between body weight and skeletal measures such as cortical thickness or BMD by DXA could also be a result of a simple scaling effect where larger individuals have larger bones, resulting in increased cortical thickness and increased BMD.
QTL analysis is one method that can be used to identify genetic influence of continuously distributed traits. The genome of the F2 generation will vary across each chromosome with three possible allelic states.
At each marker, one-quarter of the mice will be homozygous with a B6-B6 allelic state, one-quarter of the mice will be homozygous with a D2-D2 allelic state, and one-half of the mice will be heterozygous with a B6-D2 allelic state. For each individual mouse, the genotype is determined for several markers on each chromosome in the mouse genome, and the genotype of each marker can be in any of the three allelic states because of recombination during meiosis.
This variation allows for the isolation of chromosomal intervals that are associated with differences in a phenotypic trait among the individual F2 mice.
Muscle-bone relationships in mice selected for different body conformations.
Recently, there have been many studies in the literature reporting QTLs for skeletal measures, such as BMD, bone strength, or cortical thickness, that have co-localized with QTLs for nonskeletal phenotypes such as body weight, body length, and adipose mass. Adjusting data to body size allows for the investigation of QTLs that influence skeletal measures independently of body size.
This paper explores statistical issues associated with adjusting skeletal measures to body size in an attempt to remove simple scaling effects. The effects that specific adjustment procedures have on the results of QTL analyses of skeletal data are examined and discussed. Animal breeding and maintenance were conducted in a specific pathogen-free barrier facility maintained by The Center for Developmental and Health Genetics at The Pennsylvania State University.
Mice were weaned into like-sex sibling groups at about 25 days of age with four animals per cage. They were fed a diet of autoclaved Purina Mouse Chow content: Genotyping All animals were genotyped using 96 microsatellite markers distributed throughout the genome with an average spacing of 15—20 cM.
Marker analyses were conducted on purified DNA samples procured from tail snips using an automated, fluorescence-based detection system described in detail in Vandenbergh et al. Nose-to-anus length was recorded immediately after death. Epididymal fat pads in males and uterine fat pads in females were dissected and weighed to 0. The right hind limb was harvested, and the gastrocnemius, soleus, tibialis anterior, and extensor digitorum longus muscles were dissected and weighed to the nearest hundredth of a milligram.
At the time of testing, the bones were thawed at ambient temperature. A digital caliper accurate to 0. Femoral head and neck diameter were also measured. The tibia was measured similarly, except that the proximal, rather than distal, epiphyseal width was measured. Femurs were consistently oriented so that the nosepiece was posteriorly directed in respect to the diaphysis. A small section of the anterior flare of the proximal tibia was carefully removed to stabilize the bone on the support span where it was loaded with the anterior cortex in tension.
All testing was executed with the bones wet and at ambient temperature. Yield load, yield displacement, energy absorbed at yield, failure load, failure displacement, energy absorbed at failure, and stiffness were determined.
Percentage water, organic, ash, and mineralization were obtained based on the wet, dry, and ash mass of the tibia.
Tissue processing and histomorphometry The proximal tibia and previously ashed distal femur were embedded in methyl methacrylate using a three-step three-solution approach. Total area within the periosteal surface, medullary area within the endosteal surface, cortical area, centroid of the cross-section, cross-sectional moment of inertia CSMIaverage cortical thickness, and distance from the centroid to the tensile periosteal surface were calculated using a MATLAB program version 6.
Equations used to calculate material properties were derived from standard beam theory. Analyses All phenotypic data were tested for normality, and natural log or square root transformations were used when necessary. More importantly, positive and negative femur-tibia associations indicated that genetic makeup had an influence on skeletal integrity. We conclude that a femur-tibia association in bone morphological properties significantly varies from strain to strain, which may be caused by genetic differences among strains, and b strainwise variations were seen in bone mass, bone morphology, and bone microarchitecture along with bone structural property.
Introduction Osteoporosis is recognized as the most common bone disease in the world. It is characterized with a reduction in bone mass and an alternation of bone microarchitecture, which have been proved to be the major determinants of bone strength. Patients who have osteoporosis are likely to have bone fractures in vertebrae, distal arm, or femoral neck and risk of fracture at many other sites is also increased when bone density is reduced and bone structures are deteriorated, such as tibia [ 1 ].
While inbred strains of mice have proven to be useful models for studies of genetic effects on bone structure [ 23 ], Turner et al.
For example, although C3H mice have significantly stronger femurs compared with B6, their lumbar vertebrae are not stronger, but instead they are more brittle.
This result indicated that the genes contributing to improved femoral strength have no effect or even negative effect on trabecular bone structure in the spine.
However, there has been no study demonstrating the predictability between long bones. Comparison using mice in F2 population seems exceedingly complex because of the genomic heterozygosity of the F2 population. In the current study, we evaluated the bone mass and microstructure of femurs and tibias in BXD RI mouse strains.
Recombinant inbred RI strains were created by intercrossing two inbred lines often classical lines and then breeding them to homozygosity through more than 20 generations of sibling mating, meaning mating brothers and sisters from the same strain.
The resulting F1 generation was inbred to produce F2 and subsequent generations.
Then, brother and sister pairs in F5 were used to produce offspring BXD strains by inbreeding over 20 generations to ensure that BXD strains were all homozygous. Some BXD strains became distinct and thus were not included in the study e. We hypothesized that associations between long bone morphologies are affected by heritable components.
To test this hypothesis, we quantified femoral and tibial bone structure and density in 46 BXD RI strains and the progenitor B6 and D2 strains. If genetic control impacted femur-tibia correlation, a variety of associations could be revealed across strains. Materials and Methods 2. Strict breeding environment provides a means to circumvent complicating environmental factors. There were 46 BXD recombinant inbred strains that had sufficient number of animals for each strain for testing.
There were 41 strains with male and female animals, 5 strains only with males, and 1 strain only with females. In total, mice were collected for sacrifice.
After all, one femur and one tibia were collected free of soft tissue observed by naked eye from each mouse. A total of mice long bones were collected femurs and tibias and of them were included in the study femurs and tibias to ensure a sufficient number of samples for each strain. The femoral heads and necks are retained on the femurs, while the fibulas were removed from tibia.
Specimens Handling Bone specimens that underwent X-ray imaging were required to be preserved and stored with special care. Ethanol preserves protein bone marrowbone mineralization, and hydration. The bone samples were placed in a Morphometric and architectural parameters of bones were assessed and realistic 3D visual models were constructed for the object by selecting the volumes of interest VOI.
Whole Bone Analysis For whole bone analysis, three parameters were measured: Cortical Bone Analysis For cortical bone analysis, a cross-sectional region of transverse slices a total length of 0.