Distinct developmental changes in the distribution of calcium, phosphorus and sulphur during fetal growth-plate development

High-fat diet and caffeine interact to modulate bone microstructure and biomechanics in mice

AIMS

Although excessive fat and caffeine intake are independent risk factors for bone microstructural and functional disturbances, their association remains overlooked. Thus, we investigated the impact of high-fat diet (HFD) and caffeine alone and combined on serum lipid profile, bone microstructure, micromineral distribution and biomechanical properties.

METHODS

Forty female C57BL/6 mice were randomized into 4 groups daily treated for seventeen weeks with standard diet (SD) or HFD (cafeteria diet) alone or combined with 50 mg/kg caffeine.

KEY FINDINGS

The association between HFD and caffeine reduced the weight gain compared to animals receiving HFD alone. Caffeine alone or combined with HFD increases total and HDL cholesterol circulating levels. HFD also reduced calcium, phosphorus and magnesium bone levels compared to the groups receiving SD, and this reduction was aggravated by caffeine coadministration. From biomechanical assays, HFD combined with caffeine increased bending strength and stiffness of tibia, a finding aligned with the marked microstructural remodeling of the cortical and cancellous bone in animals receiving this combination.

SIGNIFICANCE

Our findings indicated that HFD and caffeine interact to induce metabolic changes and bone microstructural remodeling, which are potentially related to bone biomechanical adaptations in response to HFD and caffeine coadministration.

Effect of Icariin on Tibial Dyschondroplasia Incidence and Tibial Characteristics by Regulating P2RX7 in Chickens

Tibial dyschondroplasia (TD) is a disease of rapid growing chickens that occurs in many avian species; it is characterized by nonvascular and nonmineralized growth plates, along with tibia bone deformation and lameness. Icariin is widely used to treat bone diseases in humans, but no report is available regarding the effectiveness of icariin against avian TD. Therefore, this study was designed to determine its effect against TD. For this purpose, a total of 180 broiler chicks were distributed into three groups including control, TD, and icariin group. Control group was given a standard normal diet, while TD and icariin groups received normal standard diet containing 50 mg/kg thiram to induce TD from days 3 to 7 after hatch. After the induction of TD, the chicks of icariin group were fed with standard normal diet by adding 10 mg/kg icariin in water. Then morphological and production parameters analysis of tibial bone indicators, physiological index changes, and gene expression were examined. The results showed that icariin administration not only decreased the mortality but also mitigated the lameness and promoted the angiogenesis, which diminished the TD lesion and significantly increased the expression of P2RX7 (P < 0.05) in TD affected thiram induced chicks. In conclusion, present findings suggest that icariin has a significant role in promoting the recovery of chicken growth plates affected by TD via regulating the P2RX7. Our findings reveal a new target for clinical treatment and prevention of TD in broiler chickens.

Multiplex analysis of serum hormone and cytokine in patients with cervical cOPLL: towards understanding the potential pathogenic mechanisms

Cervical ossification of the posterior longitudinal ligament (cOPLL) is one of the major causes of myelopathy. However, the mechanism underlying remains elusive. In the present study, using MILLIPLEX magnetic bead panel, we investigated four serum hormones and six serum cytokines in cOPLL patients and healthy subjects. The results showed that tumor necrosis factore-α (TNF-α) were significantly increased, and DDK-1 was significantly decreased in the serum from male and female cOPLL patients compared with those from healthy controls, respectively. Osteopontin (OPN) and fibroblast growth factor-23 (FGF-23) were significantly increased in male cOPLL patients compared with that in healthy male controls. Further analysis showed that FGF-23 and OPN significantly increased, dickkopf-1 (DKK-1) decreased in the extensive cOPLL group. In addition, a significant positive correlation between the OPN and FGF-23 was observed in male cOPLL patients. The results are useful for understanding the mechanism underlying cOPLL.

Submaximal suppression of parathyroid hormone ameliorates calcitriol-induced aortic calcification and remodeling and myocardial fibrosis in uremic rats

BACKGROUND AND OBJECTIVE

In subtotally nephrectomized rats, we studied to what extent high-dose calcitriol-induced cardiovascular disease can be modulated by almost complete suppression of parathyroid hormone (PTH), mediated by either cinacalcet (CINA) or parathyroidectomy (PTX).

METHODS

Five groups were studied: sham-operated controls, uremic (U), uremic with calcitriol (U+1,25D), uremic and calcitriol with CINA (U+1,25D+CINA) and uremic and calcitriol with PTX (U+1,25D+PTX). Treatments lasted 14 weeks.

RESULTS

Compared with U group animals, PTH was significantly lower with calcitriol treatment and almost completely suppressed in animals treated with either PTX or CINA. Serum calcium and phosphorus levels were similarly elevated in all groups receiving calcitriol. Renal function in uremic animals was significantly more impaired in the U+1,25D group. Aortic calcifications were pronounced in U+1,25D animals and reduced by more than 50% by concomittant treatment with CINA or PTX. Chondrocytes were observed near areas of calcification (>90%) and endochondral bone formation was confirmed by positive immunofluorescence for chondrocytic transcription factor sox9 and matrix protein collagen X. Altered arterial (aneurysmatic) geometry with a significant increase in wall/lumen and lumen/body weight ratio was found only in the U+1,25D group. Myocardial fibrosis was present in all uremic groups with a significant increase in the U+1,25D group. Connective tissue growth factor messenger RNA was significantly upregulated only in the U+1,25D group.

CONCLUSION

Submaximal suppression of PTH by either CINA or PTX reduced vascular calcifications, arterial remodeling and myocardial fibrosis to a similar degree and independent of the serum calcium and phosphorus levels. These data do not indicate vasculotropic effects of calcimimetics independent of PTH suppression.

Involvement of SOX-9 and FGF-23 in RUNX-2 regulation in osteoarthritic chondrocytes

Chondrocytes’ hypertrophy includes metabolic changes, matrix remodelling, proliferation and apoptosis, characteristics associated with the progression of osteoarthritis. We investigated a possible association among Runt-related transcription factor 2 (RUNX-2), SOX-9 and fibroblast growth factor (FGF)-23 mRNA expressions in articular chondrocytes in order to elucidate their contribution in the osteoarthritic hypertrophic cartilage. SOX-9, FGF-23, RUNX-2 and matrix metalloproteinase (MMP)-13 mRNA expressions were evaluated in osteoarthritic and normal chondrocytes by real-time PCR whereas MMP-13 protein expression by immunofluorescense. RUNX-2, FGF-23 and SOX-9 were down-regulated using small interfering RNA technology and transfection with liposomes. The effect of human recombinant FGF-23 (hrFGF-23) on SOX-9 and RUNX-2 expression was tested in normal chondrocytes. We found higher expression of RUNX-2 and FGF-23 and a decreased expression of SOX-9 mRNA in osteoarthritic chondrocytes compared to normal (P < 0.0001). RUNX-2 down-regulation resulted in reduced MMP-13 expression in osteoarthritic chondrocytes and inhibition of SOX-9 in increased RUNX-2 and MMP-13 mRNA expression in normal chondrocytes, whereas inhibition of FGF-23 resulted in reduced RUNX-2 mRNA expression in osteoarthritic chondrocytes (all P < 0.0001). Silencing of RUNX-2 or FGF-23 did not affect SOX-9 mRNA levels in osteoarthritic chondrocytes. Moreover simultaneous down-regulation of SOX-9 and up-regulation of FGF-23 mRNA expressions in normal chondrocytes resulted in additive up-regulation of RUNX-2 mRNA expression. Treatment of normal chondrocytes with hrFGF-23 resulted in increased RUNX-2 mRNA expression, whereas it had no effect on SOX-9 mRNA expression. We demonstrated convincing associations among RUNX-2, SOX-9 and FGF-23 in relation to MMP-13 expression in osteoarthritic chondrocytes, contributing to a better understanding of the abnormal gene expression and cartilage degeneration processes associated with osteoarthritis.

The epidermal Ca(2+) gradient: Measurement using the phasor representation of fluorescent lifetime imaging

Ionic gradients are found across a variety of tissues and organs. In this report, we apply the phasor representation of fluorescence lifetime imaging data to the quantitative study of ionic concentrations in tissues, overcoming technical problems of tissue thickness, concentration artifacts of ion-sensitive dyes, and calibration across inhomogeneous tissue. We used epidermis as a model system, as Ca(2+) gradients in this organ have been shown previously to control essential biologic processes of differentiation and formation of the epidermal permeability barrier. The approach described here allowed much better localization of Ca(2+) stores than those used in previous studies, and revealed that the bulk of free Ca(2+) measured in the epidermis comes from intracellular Ca(2+) stores such as the Golgi and the endoplasmic reticulum, with extracellular Ca(2+) making a relatively small contribution to the epidermal Ca(2+) gradient. Due to the high spatial resolution of two-photon microscopy, we were able to measure a marked heterogeneity in average calcium concentrations from cell to cell in the basal keratinocytes. This finding, not reported in previous studies, calls into question the long-held hypothesis that keratinocytes increase intracellular Ca(2+), cease proliferation, and differentiate passively in response to changes in extracellular Ca(2+). The experimental results obtained using this approach illustrate the power of the experimental and analytical techniques outlined in this report. Our approach can be used in mechanistic studies to address the formation, maintenance, and function of the epidermal Ca(2+) gradient, and it should be broadly applicable to the study of other tissues with ionic gradients.

Temporal and spatial changes in element distribution in bone and cartilage

BACKGROUND

Bone and cartilage act as reservoirs for a number of elements, and the perturbation of these elements is suggested to contribute to various diseases. Even so, little is known about their respective temporal and spatial distribution.

METHODS

Three knee joints of three mice on the first day after birth, three knee joints of 3-week-old mice, and three knee joints of 20-week-old mice were prepared. We performed element mapping in the bone and cartilage of normal mouse knee joints. We measured element distribution in articular cartilage, trabecular bone, cortical bone, joint cartilage, growth plates, and joint cavities using energy dispersive X-ray spectrometry.

RESULTS

The analysis revealed the following: (1) The main elements in articular cartilage of 1-day-old mice were Na, O, P, S, and Ca; and those in bone were Na, O, P, S, K, Ca, and Mg. (2) The main elements in the growth plate of 3-week-old mice were Na, N, O, P, S, Cl, K, and Ca; those in joint cartilage were Na, O, P, S, Cl, and K; and those in bone were Na, O, P, Ca, and Mg. (3) The main elements in the growth plate of 20-week-old mice were Na, O, P, S, Cl, K, and Ca; and those in bone were Na, O, P, S, K, Ca, and Mg. After corrections were made for the Na ratios of these elements, we investigated the temporal and spatial changes in the distribution of each element. On the first day after birth, a spatial change was seen in the growth plate cartilage: the more the cartilage matured toward hypertrophy, the more S and Ca it contained. Temporal changes in element distribution in the growth plate cartilage, articular cartilage, and bone were observed. Growth plate cartilage of the older mice contained more S and Ca than that of the younger mice. Bone of the older mice contained more Ca and Mg than that of the younger mice. Spatial changes in element distribution in the cortical bone were also seen; that is, the more the cortical bone matured toward diaphysis, the more Mg and the less S it contained. In contrast, no temporal or spatial changes in element distribution were observed in the joint space. No significant temporal or spatial changes in the distribution of P, Cl, or K were seen.

CONCLUSIONS

These results suggest that element mapping may be useful for identifying the age and maturity of different skeletal tissues. In particular, it may help distinguish between immature cartilage and mature cartilage based on the Ca and S contents.

Bone growth during daily or intermittent calcitriol treatment during renal failure with advanced secondary hyperparathyroidism

Calcitriol is a standard therapy for secondary hyperparathyroidism in chronic renal failure. We evaluated whether the effect of daily or intermittent calcitriol administration is more efficient in enhancing bone growth in renal failure with advanced secondary hyperparathyroidism in weanling 5/6 nephrectomized rats loaded with phosphorus to induce severe secondary hyperparathyroidism. The animals were treated daily or three times weekly with calcitriol for 4 weeks but the total weekly dose of calcitriol was the same. Although calcitriol increased the serum calcium, it did not lower parathyroid hormone (PTH) or improve tibia and body length. Animals with renal failure and advanced secondary hyperparathyroidism had decreased PTH/PTHrP, which was accompanied by an increase in the cyclin kinase inhibitor p57(Kip2). Calcitriol treatment upregulated the PTH/PTHrP receptor but also increased inhibitors of cell proliferation such as p21(Waf1/Cip1), IGFBP3, and FGFR3. Calcitriol also enhanced markers of chondrocyte differentiation, such as IGF1, Vitamin D receptor, FGF23, and bone morphogenetic protein-7. Receptor activator of nuclear factor-kappabeta ligand levels improved with calcitriol treatment but without changes in osteoprotegerin suggesting an enhancement of osteo/chondroclastogenesis and mineralization. Overall, both daily and intermittent calcitriol had similar effects on endochondral bone growth in phosphorus-loaded rats with renal failure.