Effects of teriparatide on morphology of aortic calcification in aged hyperlipidemic mice - PubMed (original) (raw)

. 2018 Jun 1;314(6):H1203-H1213.

doi: 10.1152/ajpheart.00718.2017. Epub 2018 Feb 16.

Jinxiu Lu 2, Soban Umar 3, Jason T Lee 4, Rajan P Kulkarni 1 5, Yichen Ding 1 5, Chih-Chiang Chang 5, Tzung K Hsiai 1 5, Akishige Hokugo 6, Ioannis Gkouveris 7, Sotirios Tetradis 7, Ichiro Nishimura 8, Linda L Demer 1 2 5, Yin Tintut 1 2 9

Affiliations

Effects of teriparatide on morphology of aortic calcification in aged hyperlipidemic mice

Jeffrey J Hsu et al. Am J Physiol Heart Circ Physiol. 2018.

Abstract

Calcific aortic vasculopathy correlates with bone loss in osteoporosis in an age-independent manner. Prior work suggests that teriparatide, the bone anabolic treatment for postmenopausal osteoporosis, may inhibit the onset of aortic calcification. Whether teriparatide affects the progression of preexisting aortic calcification, widespread among this patient population, is unknown. Female apolipoprotein E-deficient mice were aged for over 1 yr to induce aortic calcification, treated for 4.5 wk with daily injections of control vehicle (PBS), 40 µg/kg teriparatide (PTH40), or 400 µg/kg teriparatide (PTH400), and assayed for aortic calcification by microcomputed tomography (microCT) before and after treatment. In a followup cohort, aged female apolipoprotein E-deficient mice were treated with PBS or PTH400 and assayed for aortic calcification by serial microCT and micropositron emission tomography. In both cohorts, aortic calcification detected by microCT progressed similarly in all groups. Mean aortic 18F-NaF incorporation, detected by serial micropositron emission tomography, increased in the PBS-treated group (+14 ± 5%). In contrast, 18F-NaF incorporation decreased in the PTH400-treated group (-33 ± 20%, P = 0.03). Quantitative histochemical analysis by Alizarin red staining revealed a lower mineral surface area index in the PTH400-treated group compared with the PBS-treated group ( P = 0.04). Furthermore, Masson trichrome staining showed a significant increase in collagen deposition in the left ventricular myocardium of mice that received PTH400 [2.1 ± 0.6% vs. control mice (0.5 ± 0.1%), P = 0.02]. In summary, although teriparatide may not affect the calcium mineral content of aortic calcification, it reduces 18F-NaF uptake in calcified lesions, suggesting the possibility that it may reduce mineral surface area with potential impact on plaque stability. NEW & NOTEWORTHY Parathyroid hormone regulates bone mineralization and may also affect vascular calcification, which is an important issue, given that its active fragment, teriparatide, is widely used for the treatment of osteoporosis. To determine whether teriparatide alters vascular calcification, we imaged aortic calcification in mice treated with teriparatide and control mice. Although teriparatide did not affect the calcium content of cardiovascular deposits, it reduced their fluoride tracer uptake.

Keywords: aortic calcification; fibrosis; parathyroid hormone; teriparatide; vascular calcification.

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Figures

Fig. 1.

Fig. 1.

Effects of teriparatide on aortic calcification in the initial cohort. A: representative microcomputed tomography images with an intravenous contrast agent, Omnipaque 350, of transverse (left), coronal (middle), and sagittal (right) cardiac sections showing calcium mineral deposits in the regions of the aortic valve (closed arrow), aortic root (arrowhead), and aortic arch (dashed arrow). B: quantitative comparisons of volumetric calcium deposition (vHU) before and after treatment (Tx) with PBS (n = 5), 40 µg/kg teriparatide (PTH40; n = 6), and 400 µg/kg teriparatide (PTH400; n = 6) for 4.5 wk. The aortic calcium deposition (vHU), determined as the product of mean region of interest (ROI) density [Hounsfield units (HU)] and volume of the ROI, includes mineral in the aortic valves, aortic root, and aortic arch. A paired two-tailed _t_-test was used for before and after comparisons within the same treatment group, and one-way ANOVA was used for comparisons among the three groups.

Fig. 2.

Fig. 2.

Effects of teriparatide on aortic calcification by microcomputed tomography (microCT) and micropositron emission tomography (microPET) in the followup cohort. A: quantitative microCT analysis of aortic calcium content before and after treatment (Tx). vHU, volumetric calcium deposition; PTH40, 40 µg/kg teriparatide; PTH400, 400 µg/kg teriparatide. B: quantitative microPET analysis of fluoride uptake in the aortic region pre- and post-Tx. C: representative fused microPET/microCT images showing fluoride uptake (representing calcium mineral surface area) in 12-mo-old PBS-treated control mice and 16-mo-old PTH400-treated mice. Top left: transverse, coronal, and sagittal slices of the chest. Bottom left: corresponding views of maximum-intensity projections of the mediastinal regions of interest. Right: lateral view of the microPET maximum-intensity projection superimposed on the microCT image of the skeleton. A paired two-tailed _t_-test was used for the statistical analysis.

Fig. 3.

Fig. 3.

Effects of teriparatide on morphology of aortic calcium deposits. A and B: representative Alizarin red-stained aortic root sections from PBS-treated mice (A) and 400 µg/kg teriparatide (PTH400)-treated mice (B). The arrow in A denotes a region containing microcalcium deposits, whereas the arrowhead in B denotes a macrocalcium deposit. Scale bar = 500 µm. C_–_F: calcified deposits were computationally segmented, and their total perimeters (C and D) and areas (E and F) were drawn and measured in their respective groups. G_–_I: comparison of the total calcified area (G), mineral surface area index (total perimeter/total area; H), and percentage of calcified area present in macrocalcium deposits between groups (I). Statistical analysis was performed using a two-tailed Student’s _t_-test.

Fig. 4.

Fig. 4.

Location of calcium deposits and effect of baseline calcium mineral on progression. A: representative three-dimensional reconstruction of light-sheet fluorescence microscopic images showing calcium deposits in the aortic root and arch. The vertical dimension was ~1 cm. B and C: two-dimensional raw data of the distribution of calcium mineral in the aortic root (B) as well as the aortic valve, lesser curvature of the arch, and innominate artery (C). Aortic valve cusps are indicated by yellow arrows. Green pseudocolor indicates values >76% of background tissue autofluorescence. D: correlation between the baseline degree of calcification and progression over the 4.5-wk treatment (Tx) period in the aortic root, arch, and great vessels (Pre-Tx calcium) in mice from both initial and followup cohorts. MicroCT, microcomputed tomography; vHU, volumetric calcium deposition.

Fig. 5.

Fig. 5.

Effects of teriparatide on collagen deposition in the left ventricular (LV) myocardium. A: quantitative analysis of collagen deposition by trichrome-positive area (normalized to total tissue area) in the LV myocardium of mice (from both cohorts) treated with PBS (n = 9) or 400 µg/kg teriparatide (PTH400; n = 11). B: representative images of transverse sections stained for collagen (blue) by Masson trichrome stain showing interstitial fibrosis in the PTH400-treated group. Scale bar = 200 µm. C: representative images of transverse sections of a mouse in the PTH400-treated group. Scale bar = 200 µm. Statistical analysis was performed using a two-tailed Student’s _t_-test.

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