Dietary betaine reduces plasma homocysteine concentrations and improves bone strength in laying hens

1. This study tested the hypothesis that the methyl-donor properties of betaine could reduce homocysteine concentrations, which has been recognised in a previous genetics study to be linked to bone quality. This was combined with phytase treatment, as phosphorus is critical for bone mineralisation.2. Using a 2 × 2 factorial arrangement, a total of 1920 Lohmann LSL-lite chickens housed as 24 replicates of 20 chickens were fed one of four diets containing dietary betaine (0 or 1000 mg/kg) and phytase (300 or 1000 FTU/kg) from one day old until end-of-lay. Blood and bone samples were collected at 45 and 70 weeks of age.3. Hens fed betaine had lower plasma homocysteine level (P < 0.05), higher tibia breaking strength (P < 0.05) and higher tibia bone density (P < 0.05).4. Egg production and quality was excellent throughout the study and were not affected by the dietary treatments.5. The addition of dietary betaine was successful at reducing plasma homocysteine concentrations and improving bone strength in laying hens, which could be used as an intervention to alleviate welfare concerns.

Apparent elastic modulus of ex vivo trabecular bovine bone increases with dynamic loading

Although it is widely known that bone tissue responds to mechanical stimuli, the underlying biological control is still not completely understood. The purpose of this study was to validate required methods necessary to maintain active osteocytes and minimize bone tissue injury in an ex vivo three-dimensional model that could mimic in vivo cellular function. The response of 22 bovine trabecular bone cores to uniaxial compressive load was investigated by using the ZETOS bone loading and bioreactor system while perfused with culture medium for 21 days. Two groups were formed, the "treatment" group (n = 12) was stimulated with a physiological compressive strain (4000 µε) in the form of a "jump" wave, while the "control" group (n = 10) was loaded only during three measurements for apparent elastic modulus on days 3, 10, and 21. At the end of the experiment, apoptosis and active osteocytes were quantified with histological analysis, and bone formation was identified by means of the calcium-binding dye, calcein. It was demonstrated that the treatment group increased the elastic modulus by 61%, whereas the control group increased by 28% (p<0.05). Of the total osteocytes observed at the end of 21 days, 1.7% (±0.3%) stained positive for apoptosis in the loaded group, whereas 2.7% (±0.4%) stained positive in the control group. Apoptosis in the center of the bone cores of both groups at the end of 21 days was similar to that observed in vivo. Therefore, the three-dimensional model used in this research permitted the investigation of physiological responses to mechanical loads on morphology adaptation of trabecular bone in a controlled defined load and chemical environment.

Osteocyte apoptosis and osteoclast presence in chicken radii 0-4 days following osteotomy

Osteocyte apoptosis caused by load-induced microdamage is followed by osteoclastic bone remodeling, and a causal link between apoptosis and repair has been suggested. The objectives of the present study were to use a chick model to examine the incidence of osteocyte apoptosis and the presence of osteoclasts during the first 96 hours following an osteotomy, prior to extensive callus mineralization. Osteotomies were performed on the right radii of 24 chicks at 23-24 days of age. The left radii served as controls. Radii were collected and processed at six time points following surgery (0, 12, 24, 48, 72, and 96 hours). Decalcified bone tissue sections were stained either for apoptosis using a modified TUNEL procedure or for tartrate-resistant acid phosphatase to identify osteoclasts in the intracortical and periosteal envelopes. The percentage of apoptotic osteocytes, as well as osteoclast counts (n/mm or n/mm2) were quantified in four regions (0-1, 1-2, 2-4, and 4-8 mm from the site of the osteotomy; regions 1-4, respectively) in the osteotomized radii and in the same measured areas in the control radii. Data for osteocyte apoptosis and osteoclasts in the control limb were subtracted from the osteotomized limb data to identify differences due to surgical influence. The incidence of osteocyte apoptosis was significantly higher at 12, 24, 48, and 72 hours versus 0 hours following osteotomy, and the response was highest in region 1; however, there was no interaction between time and region. Intracortical osteoclast counts (n/mm2) were elevated after 48 hours, and the response was similar in all regions. The data demonstrate that osteocyte apoptosis occurs within 24 hours in response to an osteotomy and temporally precedes an increase in osteoclast presence. Hence, osteocyte apoptosis may play a role in signaling during the bone healing process.