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Osteoporosis and Sarcopenia logoLink to Osteoporosis and Sarcopenia
. 2023 Dec 21;9(4):121–130. doi: 10.1016/j.afos.2023.11.002

Teriparatide and etelcalcetide improve bone, fibrosis, and fat parameters in chronic kidney disease model rats

Shun Igarashi a, Yuji Kasukawa b,∗, Koji Nozaka a, Hiroyuki Tsuchie a, Kazunobu Abe a, Hikaru Saito a, Ryo Shoji a, Fumihito Kasama a, Shuntaro Harata a, Kento Okamoto a, Keita Oya a, Naohisa Miyakoshi a
PMCID: PMC10874735  PMID: 38374820

Abstract

Objectives

Chronic kidney disease (CKD) complicated by secondary hyperparathyroidism (SHPT) is associated with an increased risk of fragility fractures. Etelcalcetide (EC) is a treatment for SHPT that reduces serum parathyroid hormone (PTH) levels. However, the effects of combined treatment with osteoporosis drugs such as teriparatide (TPTD) remain unclear. This study investigates the combined effects of EC and TPTD on bone in CKD model rats.

Methods

The CKD model was established in 8-week-old male Wistar rats by feeding them a 0.75% adenine diet for 4 weeks. At 20 weeks of age, the rats were divided into 4 groups (N = 9–10 in each group): CKD group (vehicle administration), TPTD group (30 μg/kg, 3 times/week), EC group (0.6 mg/kg, daily), and Comb group (TPTD and EC combined). EC was injected for 12 weeks starting at 20 weeks of age, and TPTD was injected for 8 weeks starting at 24 weeks of age. After treatment, the followings were evaluated: bone mineral density, bone strength, biochemical tests, bone and fat histomorphometry, and micro-computed tomography.

Results

In CKD model rats, the combination of EC and TPTD was more effective in increasing cortical bone thickness and bone strength and inhibiting porosity. In addition, the combined treatment decreased bone marrow adiposity and fibrosis, and it increased bone mass and improved bone microstructure in trabecular bone.

Conclusions

With the observed benefits such as improved bone mass, bone strength, structural properties, and bone marrow adiposity, combination therapy may be a potential way to improve bone fragility in CKD.

Keywords: Chronic kidney disease, Secondary hyperparathyroidism, Osteoporosis, Teriparatide, Etelcalcetide

1. Introduction

The number of patients with osteoporosis and chronic kidney disease (CKD) is increasing as the population ages, and there is a high rate of the 2 occurring together [1,2]. The risk of fragility fractures in patients with CKD has been reported to be considerably higher than in the general population, [3]. Since CKD patients have a higher incidence of fractures than predicted by bone mineral density (BMD), the increased risk of fracture in CKD patients is attributed to abnormalities in bone quality in addition to bone loss [4,5]. It has been reported that the incidence of fracture is higher when the disease progresses to stage 4 or higher compared to CKD stage 3 or lower [6]. Effective treatments of bone fragility associated with CKD are therefore essential to maintain activities of daily living (ADL) and quality of life (QoL), particularly in advanced-stage CKD and dialysis patients.

CKD-mineral bone disorder (CKD-MBD), one of the factors associated with bone fragility in CKD, is a clinical manifestation of the triad of biochemical abnormalities, bone loss, and vascular calcification due to prolonged and sustained decline in renal function [7]. In early stages (stages 2–3) of CKD, phosphodiesis by fibroblast growth factor 23 (FGF23) and suppression of 1, 25-hydroxylated vitamin D lead to stimulation of secondary hyperparathyroidism (SHPT) [8,9], which compensates for the phosphorus overload caused by CKD. When the compensatory mechanism fails in stage 4–5 CKD, serum phosphorus levels increase, and serum calcium (Ca) levels decrease to maintain the balance between Ca and phosphorus, both of which act to further promote SHPT. In addition, bone lesions in CKD include osteitis fibrosa due to SHPT, osteomalacia due to vitamin D deficiency, and a mixture of both, as well as aplastic osteopathy [7]. SHPT promotes bone resorption and bone formation by increasing the continuous secretion of PTH, with a higher degree of bone resorption, decreased bone mass, and increased fibrous components [10]. Particularly in cortical bone, increased bone resorption leads to deterioration of bone structure, such as porosity, leading to increased fracture risk in CKD [4,7].

Therefore, it is very important to improve SHPT in patients with CKD. Recently, peptide agonists of the calcium-sensing receptor (CaSR), known as calcimimetics, have been used to treat SHPT in dialysis patients [11,12]. The calcimimetics suppress PTH synthesis and secretion by acting on the CaSR, which becomes dysfunctional in SHPT. The calcimimetics have recently improved the outcome of CKD-MBD in patients treated with hemodialysis [13,14]. Etelcalcetide (EC) and cinacalcet are typical calcimimetics. EC suppresses PTH secretion more persistently than cinacalcet, and because it is administered intravenously, it is expected to improve compliance and gastrointestinal tolerability compared to cinacalcet [15]. However, because CKD patients often present with a variety of bone metabolic pathologies, there is no certainty regarding the effect of calcimimetics on fracture inhibition [16]. For these reasons, the need for combined treatment of osteoporosis in addition to CKD-MBD management has recently been identified for the appropriate management of bone lesions in advanced-stage CKD and dialysis patients [17].

However, there is insufficient evidence on the safety and efficacy of pharmacological treatment of osteoporosis in patients with advanced CKD. Although teriparatide (TPTD) treatment, involving intermittent administration of PTH, can increase trabecular bone mass and inhibit new vertebral fractures [18], further administration of PTH with TPTD is discouraged in the case of SHPT, in which endogenous PTH secretion is increased. Based on these background factors, there are few reports on the efficacy of TPTD in CKD and dialysis patients, and the detailed efficacy of TPTD for fracture suppression in advanced-stage CKD has not been clarified. In other words, the safety and efficacy of TPTD in SHPT patients, whose PTH secretion is controlled by EC, are not fully understood. In this study, the hypothesis is that TPTD for advanced-stage CKD, in which PTH secretion is suppressed by EC, has more positive effects on bone, such as increased bone mass and improved bone microstructure, in addition to improving bone metabolic abnormalities associated with CKD-MBD, without adversely affecting mineral metabolism or renal function. Therefore, the purpose of this study is to evaluate the safety and effects of EC in combination with TPTD on bone in a rat model of adenine-induced advanced-stage CKD.

2. Methods

2.1. Animal model and experimental design

Eight-week-old, male Wistar rats (N = 9–10) (Charles River Laboratories Inc., Tokyo, Japan) were housed in a controlled environment (temperature 23 ± 2°C, humidity 40 ± 20%) with a 12-hour light-dark cycle with free access to water and rat food. The details were described in previous studies and followed for the selection of rat species and sex [19]. Rats were treated with a 0.75% adenine diet (Oriental Yeast Co., Ltd., Tokyo Japan) for 4 weeks until 12 weeks of age, followed by a standard rodent chow (CE-7; Clea Japan, Tokyo, Japan) diet to generate CKD model rats (CKD group). The 4-week treatment with the adenine diet was decided based on previous studies [19,20], which reported that 4-week treatment with the adenine diet induced non-progressive, irreversible renal failure.

At 20 weeks of age, the rats were divided into 4 groups: CKD group (vehicle administration), TPTD group (30 μg/kg subcutaneous injection of teriparatide (TPTD), 3 times/week), EC group (0.6 mg/kg subcutaneous injection of EC daily), and Comb group (TPTD and EC combined) (Fig. 1). Vehicle or EC was injected for 12 weeks from 20 weeks of age in the CKD group or the EC group, respectively, and TPTD was injected for 8 weeks from 24 weeks of age with prior administration of vehicle for 4 weeks from 20 weeks of age in the TPTD group. The Comb group was treated with EC for 4 weeks from 20 weeks of age and with EC and TPTD for 8 weeks from 24 weeks of age. The non-CKD control (Cont group) was also included without the adenine diet and treated with vehicle for 12 weeks from 20 weeks of age. The protocols for all animal experiments were approved in advance by the Animal Experimentation Committee of our institute (permit No. a-1-0271), and all subsequent animal experiments adhered to the Guidelines for Animal Experimentation of our institution.

Fig. 1.

Fig. 1

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Experimental protocol. Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide, Comb: CKD rats administered EC and TPTD.

2.2. Body weight measurement

Body weight (BW) was measured weekly from the beginning (20 weeks of age) until the end of the experiment.

2.3. Administration of TPTD and EC

TPTD (teriparatide acetate, LKT LABS, St. Paul, MN, USA) was dissolved in saline containing 0.1% rat serum albumin, and a dose of 30 μg/kg of BW was administered subcutaneously 3 times per week for 8 weeks according to a previously reported protocol [21,22]. EC (etelcalcetide hydrochloride) was provided by ONO Pharmaceutical, Co. Ltd. (Osaka, Japan). EC was dissolved in vehicle (1 mass/volume percent (m/v%) glycine, 1 m/v% d (+)-trehalose dihydrate, 0.27 m/v% disodium succinate hexahydrate, 2 m/v% d-mannitol, 0.9 m/v% benzyl alcohol, pH 4.5), and a dose of 0.6 mg/kg of BW was administered subcutaneously daily for 12 weeks based on a previously reported protocol [23].

2.4. Tissue preparation

After sacrifice, the right femur was fixed in 10% neutral-buffered formalin (Wako Chemical Industries, Osaka, Japan) until preparation for BMD measurement and micro-computed tomography (CT) measurements. The left femur was dissected free of soft tissue, wrapped in gauze moistened with saline, and frozen at −80°C until biomechanical testing. The bilateral proximal half of the tibia was decalcified with neutral 10% ethylene diamine tetraacetic acid for approximately 4 weeks and then embedded in paraffin. Subsequently, 3-μm-thick, mid-frontal slices were sectioned and stained with hematoxylin and eosin for bone histomorphometry.

2.5. Serum chemistry

At 32 weeks of age, blood samples were collected from the vena cava of rats 24–36 h after administration of EC. Blood samples were centrifuged at 3000 rpm for 30 minutes at 4°C to separate the serum, which was then stored in disposable aliquots at −80°C until analysis. Blood urea nitrogen (BUN), creatinine (CRE), calcium (Ca), and inorganic phosphorus (IP) levels were measured using a Hitachi Automatic Biochemical Analyzer 7180 (Hitachi Ltd., Tokyo, Japan). Intact-parathyroid hormone (I-PTH) levels were measured using an enzyme-linked immunosorbent assay (ELISA) kit (Rat Intact PTH ELISA Kit, Immutopics, Inc. San Clemente, CA, USA).

2.6. Bone histomorphometry

Bone histomorphometric analysis at the proximal tibia was performed at 200 × magnification using a semi-automated graphic system (Histometry RT CAMERA; System Supply, Nagano, Japan). Measurements were obtained 400 μm caudally from the lowest point of the growth plate and 100 μm medially from the endosteal surface. Bone histomorphometric parameters were calculated and expressed according to published methods [24]. The standard parameters evaluated were bone volume (BV/TV, %), osteoid surface (OS/BS, %), eroded surface (ES/BS, %), and fibrosis volume (Fb.V/TV, %).

2.7. Fat histomorphometry

Adipocyte volume per total bone marrow volume (Ad.V/Ma.V, %), number of adipocytes per unit area of marrow (N.Ad/Ma.V, number of cells/mm2), and volume of each adipocyte per number of adipocytes (Ad.V/N.Ad, μm2) were evaluated as parameters of fat histomorphometry in the bone marrow of the proximal tibia, as described previously [21,25,26]. The measurement range of the fat histomorphometry was the same as that of the bone histomorphometry.

2.8. Micro-computed tomography analysis

The excised right femur was secured in a specimen holder. Micro-CT was performed using the Cosmo Scan GX II (Rigaku Corporation, Tokyo, Japan) according to the manufacturer's instructions with an isotropic voxel size of 36 μm, energy of 90 kVp, and current of 88 μA. The acquired images were rendered using TRI/3D BON software (Ratoc System Engineering Co., Ltd., Tokyo, Japan). Osteoporosis assessment was performed based on total area (Tt.Ar, mm2), cortical area (Co.Ar, mm2), cortical volume (Ct.V, mm3), cortical area/total area (Ct.Ar/Tt.Ar, %), cortical thickness (Ct.Th, mm), and cortical porosity (Co.Po, %) at the mid femur and bone volume/tissue volume (BV/TV, %), trabecular thickness (Tb.Th, mm), trabecular number (Tb.N, 1/mm), trabecular separation (Tb.Sp, mm), structure model index (SMI), and degree of anisotropy (DA) at the distal femur. The measurement range of the mid femur was a 1000-μm-high region centered on the midpoint of the entire femur. The measurement range of the distal femur was 2000 μm cranially from 500 μm from the reference line connecting the two ends of the growth plate of the sagittal image.

2.9. BMD measurement

BMD of the femur was measured using dual-energy X-ray absorptiometry (Horizon® DXA System; Hologic, Bedford, MA, USA). Each region was scanned in “small animal” mode, with the “regional high resolution” scan option. Femoral BMD was measured at the proximal, middle, and distal thirds of the femur.

2.10. Biomechanical testing

Mechanical testing of the left femoral shaft was performed at room temperature using a material testing machine (MZ500S; Maruto, Tokyo, Japan). The mid-diaphysis of the femur was stabilized by placing it on 2 supports of the test apparatus placed 18 mm apart. The load of a three-point bending test was applied in the anteroposterior direction midway between the 2 supports. Load–displacement curves were recorded at a crosshead speed of 5 mm/minute. The maximum load (N), stiffness (N/mm), breaking energy (N mm), and breaking time (s) were calculated using software for measuring bone strength (CTR win. Version 1.05; System Supply, Nagano, Japan), as described previously [27]. In addition, the elastic modulus (GPa), as a tissue-level mechanical property, was calculated using the formula reported previously [28]. Following the 3-point bending test, the distal part of the femur was evaluated using a compression test, as previously described [29]. Load–displacement curves were recorded, and the maximum load (N), stiffness (N/mm), and breaking energy (N mm) were calculated using the same software.

2.11. Statistical analysis

All data are expressed as means ± standard deviation (SD). A Kolmogorov-Smirnov test showed that all data were normally distributed. The sample size for each group is N = 9–10. Student's t test was used to compare data between the Cont and CKD groups. The differences between CKD groups such as CKD, EC, TPTD, and Comb groups were evaluated by one-way analysis of variance (ANOVA) and analyzed by Tukey's multiple comparison test as a post hoc test. All statistical analyses were performed with EZR [30], which is a modified version of R commander designed to add statistical functions frequently used in biostatistics. Values of P < 0.05 values were considered significant.

3. Results

3.1. Body weight and biochemistry

To evaluate the health status of the animals, BW and its changes during the experiment were measured. The results for BW are shown in Table 1. At the beginning of treatment, the CKD group weighed significantly less than the Cont group (P < 0.01), but there were no significant differences among the CKD, TPTD, EC, and Comb groups. At the end of the experiment, BW and weight gain were significantly lower in the EC and Comb groups than in the CKD and TPTD groups (P < 0.05 to P < 0.01).

Table 1.

Body weight and serum biochemical markers.

Cont
 CKD
 EC
 TPTD
 Comb
 ANOVA
N = 10 N = 10 N = 9 N = 9 N = 10 P-value
Body weight (g)
 Baseline 609.3 ± 34.8 513.9 ± 29.4a' 490.7 ± 19.8 514.1 ± 24.2 484.5 ± 33.4 < 0.001
 Endpoint 704.1 ± 34.8 603.9 ± 33.5a' 536.9 ± 33.2b' 594 ± 37.5c' 532.8 ± 34.8b'd < 0.001
Body weight change (%) 15.6 ± 2.9 17.5 ± 2.6 9.4 ± 3.6b' 16.1 ± 4.1c' 11.2 ± 2.1b'd' < 0.001
BUN (mg/dL) 20.7 ± 2.5 36.7 ± 8.2a' 30.6 ± 3.4 36.8 ± 9.5 35.7 ± 7.4 0.257
CRE (mg/dL) 0.33 ± 0.03 0.67 ± 0.16a' 0.60 ± 0.08 0.68 ± 0.20 0.56 ± 0.08 0.203
Ca (mg/dL) 11.4 ± 0.4 11.2 ± 0.4 10.5 ± 0.3b' 11.3 ± 0.4c' 10.8 ± 0.5 0.002
IP (mg/dL) 7.6 ± 1.2 7.4 ± 0.7 6.5 ± 0.7 6.9 ± 0.9 7.4 ± 1.3 0.143
I-PTH (pg/mL) 655.0 ± 294.9 1845.3 ± 587.4a' 1098.9 ± 254.9b 1420.3 ± 822.3 1129.6 ± 378.6b 0.002
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Values are presented as means ± standard deviation. N = 9–10 in each group.

Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide, Comb: CKD rats administered EC and TPTD, Bodyweight change: percentage change in body weight in each group from baseline, BUN: blood urea nitrogen, CRE: creatinine, Ca: calcium, IP: inorganic phosphorus, I-PTH: intact parathyroid hormone.

a' P < 0.01 vs Cont group (Student's t-test).

b P < 0.05, b' P < 0.01 vs CKD group, c' P < 0.01 vs EC group, d P < 0.05, d' P < 0.01 vs TPTD group (Tukey's multiple comparison test).

In addition, blood biochemical tests were performed to evaluate the effects of EC and TPTD at 32 weeks of age. The results for serum biochemical markers are shown in Table 1. Compared with Cont rats, serum BUN and CRE were significantly higher in the CKD group (P < 0.01), reflecting the deterioration of renal function, but EC and TPTD had no significant effect on serum BUN and CRE. EC decreased serum Ca compared to the CKD and TPTD groups (P < 0.01). Compared with Cont group rats, I-PTH levels were significantly higher in CKD group rats (P < 0.01). Serum I-PTH levels in EC group and Comb group rats were significantly lower compared with CKD group rats (P < 0.05).

3.2. Bone and fat histomorphometry

To evaluate the changes in trabecular bone and adipose tissue by the adenine-induced CKD model and treatment with EC and/or TPTD, bone and fat histomorphometry was performed on histologic sections of the proximal tibia. The histological sections are shown in Fig. 2. At lower magnification, trabecular bone volume was decreased in CKD rats compared to control rats (Cont group), and trabecular bone volume was restored in TPTD and Comb rats, but not in EC rats (Fig. 2A). At higher magnification, adipose tissue volume was increased in CKD and EC compared with Cont and decreased in TPTD and Comb groups, and fibrosis volume was increased in CKD and TPTD compared with Cont and decreased in EC and Comb groups (Fig. 2B).

Fig. 2.

Fig. 2

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Histological section of right proximal tibia stained with hematoxylin and eosin in the Cont, CKD, EC, TPTD, and Comb groups with 10 × magnification (A) and 200 × magnification (B). The black arrowheads in the images indicate peritrabecular fibrosis. (C) Bone volume (BV/TV), (D) osteoid surface (OS/BS), (E) eroded surface (ES/BS), (F) fibrosis volume (Fb.V/TV), (G) adipocyte volume per total bone marrow volume (Ad.V/Ma.V), (H) volume of each adipocyte per number of adipocytes (Ad.V/N.Ad), (I) number of adipocytes per unit area of marrow (N.Ad/Ma.V). Values represent the means ± SD (N = 9–10 in each group). ##: P < 0.01 vs Cont group (Student's t-test). *: P < 0.05, **: P < 0.01 (Tukey's multiple comparison test). Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide, Comb: CKD rats administered EC and TPTD.

CKD rats showed increased bone formation (OS/BS) (Fig. 2D), bone resorption (ES/BS) (Fig. 2E), and fibrous changes (Fb.V/TV) (Fig. 2F), as well as bone marrow lipogenesis (Ad.V/Ma.V and N.Ad/Ma.V) (Fig. 2G, I), compared with control rats (Cont group) (P < 0.05 to P < 0.01). In addition to the changes in bone turnover, the increased bone marrow adiposity and fibrosis resulted in decreased trabecular bone volume (BV/TV) (Fig. 2C) in CKD rats.

EC treatment significantly decreased bone formation (OS/BS) (Fig. 2D), bone resorption (ES/BS) (Fig. 2E), and fibrous change (Fb.V/TV) (Fig. 2F) parameters compared with those in CKD rats (P < 0.01). TPTD significantly decreased bone resorption parameters (ES/BS) (Fig. 2E) resulting in increased trabecular bone volume (BV/TV) (Fig. 2C) compared with CKD rats (P < 0.05 to P < 0.01). Although TPTD did not change the fibrous parameter (Fb.V/TV) (Fig. 2F), TPTD significantly decreased the adipose parameters (Ad.V/Ma.V and Ad.V/N.Ad) (Fig. 2G and H) compared with those in the CKD group (P < 0.01). Combination therapy with EC and TPTD significantly reduced bone marrow fibrosis (Fb.V/TV) (Fig. 2F) compared with CKD rats and TPTD alone (P < 0.05 to P < 0.01), significantly increased bone formation (OS/BS) (Fig. 2D) compared with EC alone (P < 0.01), and significantly increased bone volume (BV/TV) (Fig. 2C) compared with CKD rats and EC and TPTD alone (P < 0.05 to P < 0.01). In addition, the combination of EC and TPTD significantly suppressed bone marrow lipogenesis (Ad.V/Ma.V and Ad.V/N.Ad) (Fig. 2G and H) compared to CKD rats and EC alone, indicating a combined effect of these 2 treatments. Bone resorption parameters and fibrosis were significantly lower in the Comb group than in the CKD group, and bone formation parameters were preserved, suggesting that the metabolic abnormalities caused by fibrotic osteitis were improved.

3.3. Effects of combination therapy on micro-CT cortical bone parameters

Horizontal micro-CT images of the femoral diaphysis showed that rats in the CKD group had an enlarged medullary cavity and increased cortical porosity compared with normal rats in the Cont group. In addition, treatment with EC alone and the combination of EC and TPTD resulted in a decrease in cortical porosity, an increase in cortical bone thickness and an improvement in the shape of the medullary cavity in the CKD rats (Fig. 3A).

Fig. 3.

Fig. 3

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(A) Representative micro-CT images of cortical bone transverse sections from each group. (B) Total area (Tt.Ar), (C) cortical area (Ct.Ar), (D) cortical volume (Ct.V), (E) cortical area/total area (Ct.Ar/Tt.Ar), (F) cortical thickness (Ct.Th), and (G) cortical porosity (Ct.Po). The measurement range of the mid femur was a 1000-μm-high region centered on the midpoint of the entire femur. Values represent the means ± SD (N = 9–10 in each group). #: P < 0.05, ##: P < 0.01 vs Cont group (Student's t test). *: P < 0.05, **: P < 0.01 (Tukey's multiple comparison test). Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide, Comb: CKD rats administered EC and TPTD.

Analysis of the cortical bone of the femoral diaphysis by micro-CT showed a significant decrease in Ct.Ar/Tt.Ar (Fig. 3E) and a significant increase in Ct.Po (Fig. 3G) in rats in the CKD group compared with normal rats (Cont group). Ct.Ar/Tt.Ar was significantly increased (P < 0.05) (Fig. 3E), and Ct.Po was significantly decreased (P < 0.01) (Fig. 3G) in rats in the EC group compared with rats in the CKD group, indicating that increased bone resorption resulted in relative cortical bone thickness and porosity. Ct.Th in rats in the Comb group was significantly increased (P < 0.01) compared to rats in the CKD group (Fig. 3F), reflecting the finding that EC corrected PTH hypersecretion, thereby reducing the increase in bone resorption. Ct.Ar/Tt.Ar was significantly increased (P < 0.05 to P < 0.01), and Ct.Po was significantly decreased (P < 0.05 to P < 0.01) in Comb group rats compared to CKD and TPTD group rats, respectively (Fig. 3E, G), confirming an enhanced effect of the combination.

3.4. Effects of combination therapy on micro-CT trabecular bone parameters

Micro-CT horizontal section images of the distal femoral metaphysis showed that the trabecular bone microstructure was degraded in the CKD group compared with the Cont group, whereas the TPTD and Comb groups showed improved microstructure compared with the CKD group (Fig. 4A). Micro-CT analysis of the trabecular bone of the distal femur showed significantly reduced BV/TV (P < 0.05) (Fig. 4B) and Tb./N (P < 0.001) (Fig. 4D) and significantly increased Tb.Sp (P < 0.01) (Fig. 4E) and DA (P < 0.05) (Fig. 4G) in CKD group rats compared to normal rats (Cont group). Reduction in bone mass, rarefaction, and deterioration in structural properties were observed in the trabecular bone of CKD rats. BV/TV (Fig. 4B) and Tb.N (Fig. 4D) were significantly increased, and SMI (Fig. 4F) was significantly decreased in the TPTD and Comb groups compared to the CKD and EC groups (P < 0.05 to P < 0.01). Tb.Sp was significantly increased in the TPTD (P < 0.01) and Comb (P < 0.01) groups compared with the CKD group (Fig. 4E). Tb.Th was significantly increased in the Comb group compared with the CKD and EC groups (P < 0.01) (Fig. 4C). DA was significantly lower only in the Comb group than in the CKD group (P < 0.01) (Fig. 4G), confirming the enhanced effect of combined treatment on structural characteristics.

Fig. 4.

Fig. 4

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(A) Representative micro-CT images of trabecular bone transverse sections from each group. (B) Bone volume (BV/TV), (C) trabecular thickness (Tb.Th), (D) trabecular number (Tb.N), (E) trabecular separation (Tb.Sp), (F) structure model index (SMI), and (G) degree of anisotropy (DA). The measurement range of the distal femur was 2000 μm cranially from 500 μm from the reference line connecting the 2 ends of the growth plate of the sagittal image. Values represent the means ± SD (N = 9–10 in each group). #: P < 0.05, ##: P < 0.01 vs Cont group (Student's t-test). *: P < 0.05, **: P < 0.01 (Tukey's multiple comparison test). Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide, Comb: CKD rats administered EC and TPTD.

3.5. Effects of combination therapy on bone mineral density and bone strength

The results for femoral BMD are shown in Table 2. Compared with normal rats (Cont group), the BMDs of the whole femur and each region were significantly reduced in rats of the CKD group (P < 0.05 to P < 0.01). Compared with the CKD group, the TPTD and Cont groups showed significantly increased BMD of the whole femur, proximal and distal bone, but no significant changes in the cortical bone-dominated diaphysis.

Table 2.

Bone mineral density (mg/cm2).

Cont
 CKD
 EC
 TPTD
 Comb
 ANOVA
N = 10 N = 10 N = 9 N = 9 N = 10 P-value
Femur total 0.273 ± 0.009 0.259 ± 0.012a' 0.260 ± 0.006 0.277 ± 0.009bc 0.273 ± 0.013b < 0.001
Femur proximal 0.275 ± 0.008 0.258 ± 0.012a' 0.257 ± 0.008 0.278 ± 0.011b'c' 0.272 ± 0.011bc < 0.001
Femur middle 0.262 ± 0.010 0.250 ± 0.012a 0.255 ± 0.013 0.264 ± 0.007 0.257 ± 0.016 0.237
Femur distal 0.279 ± 0.010 0.265 ± 0.012a 0.266 ± 0.007 0.287 ± 0.011bc 0.286 ± 0.015bc < 0.001
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Values are presented as means ± standard deviation.N = 9–10 in each group.

Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide.

Comb: CKD rats administered EC and TPTD.

a P < 0.05, a' P < 0.01 vs Cont group (Student's t-test).

b P < 0.05, b' P < 0.01 vs CKD group, c P < 0.05, c' P < 0.01 vs EC group (Tukey's multiple comparison test).

Representative stress-strain curves from the three-point bending test are shown in Fig. 5A. In the 3-point bending test, the CKD group had significantly lower maximum load (Fig. 5B), breaking energy (Fig. 5D), and breaking time (Fig. 5E) compared to the Cont group (P < 0.05 to P < 0.01). The maximum load (Fig. 5B) was significantly higher in the TPTD and Comb groups than in the CKD group, and the breaking energy (Fig. 5D) and breaking time (Fig. 5E) were also significantly higher in the TPTD and Comb groups than in the CKD and EC groups, confirming an improved effect. Tissue-level osteomechanical properties assessed by the elastic modulus were significantly impaired in the CKD model rats (CKD group) compared to normal rats (P < 0.05) (Fig. 5F).

Fig. 5.

Fig. 5

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(A) Representative stress–strain curves of the three-point bending test at the mid-shaft of the femur. (B) Maximum load, (C) stiffness, (D) breaking energy, (E) breaking time, and (F) elastic modulus of the three-point bending test at the mid-shaft of the femur. (G) Maximum load, (H) stiffness, and (I) breaking energy of the compression test at the distal metaphysis of the femur. Values represent the means ± SD (N = 9–10 in each group). #: P < 0.05, ##: P < 0.01 vs Cont group (Student's t test). *: P < 0.05, **: P < 0.01 (Tukey's multiple comparison test). Cont: non-CKD control rats, CKD: CKD rats administered vehicle, EC: CKD rats administered etelcalcetide, TPTD: CKD rats administered teriparatide, Comb: CKD rats administered EC and TPTD.

In the compression test at the distal metaphysis of the femur, the CKD group did not have decreased bone strength as assessed by maximum load (Fig. 5G), stiffness (Fig. 5H), and breaking energy (Fig. 5I) compared with those in the Cont group. TPTD and Comb treatment, but not EC treatment, significantly increased the maximum load (Fig. 5G) and breaking energy (Fig. 5I) compared with those in the CKD and EC groups (P < 0.01).

4. Discussion

The combined effects of EC and TPTD on osteoporosis and CKD-MBD due to CKD have not been adequately studied. To the best of our knowledge, the present study is the first to report them in a rat model of adenine-induced CKD. The combination of EC and TPTD more effectively increased cortical bone thickness and cortical bone strength, decreased cortical porosity, and reduced bone marrow adiposity and trabecular bone fibrosis and deterioration of trabecular bone structural properties without apparent adverse effects on renal function or mineral metabolism.

We have previously reported that this CKD model presents with increased serum levels of intact-PTH (I-PTH) and renal fibrosis, as stage IV of CKD and SHPT, and decreased systemic BMD, cortical bone microstructure, and cortical and trabecular bone strength [19]. Similar results were observed in the CKD rats in the present study. In addition, further micro-CT analysis showed increased cortical porosity in cortical bone and decreased bone mass, progressive osteoporosis, and increased anisotropy in trabecular bone. In the present study, the endpoint was evaluated at 32 weeks of age, and the progression of bone lesions due to CKD may have been more strongly observed. In the trabecular bone of the proximal tibia, increased bone marrow adiposity and fibrosis and high bone-turnover were observed.

In the present study, EC administration significantly reduced bone formation parameters, bone resorption parameters, and bone marrow fibrosis. In cortical bone, the inhibition of bone resorption resulted in increased cortical bone thickness and decreased cortical bone porosity on micro-CT analysis. However, the bone strength of both cortical and trabecular bone was not restored by EC treatment in the adenine-induced CKD rats. This may be due to the fact that porosity still remained to some extent with EC treatment, and its effect was considered to be mainly inhibition of the development and progression of new porosity in CKD. It has also been reported that EC was effective in inhibiting the development and progression of cortical bone porosity, but it was not effective in replenishing the existing porosity [13]. In SHPT, the risk of fracture was reported to be higher in cases of severely elevated serum I-PTH levels above 900 pg/mL [31]. A strong correlation has been observed between the severity of SHPT and the degree of cortical bone deterioration [23], and cortical porosity and thinning progress rapidly in CKD rats between 30 and 35 weeks of age [32]. Therefore, SHPT should be treated by calcimimetics. It would be possible to prevent cortical bone loss if EC could be administered from the early stages of CKD when PTH secretion begins to increase, but calcimimetics including EC have not been approved for the treatment of SHPT in the early stages of CKD [33]. Furthermore, due to the wide variety of pathologies associated with fracture risk factors in CKD and hemodialysis patients, a clear fracture-preventive effect of EC treatment alone cannot be expected. Therefore, Parfrey et al [13] reported that EC should be used in combination with osteoporosis medications such as bone resorption inhibitors or bone formation stimulators to maintain bone mass and replenish porosity. For these reasons, combination therapy with drugs for osteoporosis is needed to improve cortical bone porosity and improve bone strength to prevent fractures in addition to the EC treatment for SHPT.

TPTD significantly improved bone strength in cortical bone and increased BMD, reduced bone marrow adiposity, improved structural properties, and improved bone strength in trabecular bone. Although previous clinical studies have reported that TPTD was effective in postmenopausal osteoporosis in patients with mild or moderate renal impairment (CKD stages 1–3) [34], the effect of TPTD therapy in CKD stage IV and SHPT was limited to animal studies. Ota et al [35] reported that TPTD has an anabolic effect on bone in CKD stage IV rats without adversely affecting mineral metabolism even under SHPT conditions. Similar results were generally obtained in the present study, except that OS/BS did not increase compared with the CKD group. On the other hand, a decrease in ES/BS was observed, resulting in an increase in trabecular bone volume. This may be due to differences in the type of teriparatide, the frequency, duration, and concentration of administration, and the timing of the evaluations. It seems that, in CKD model rats, even in the state of continuous hypersecretion of endogenous PTH, stimulation by intermittent administration of exogenous PTH has a predominant effect on bone formation.

Regarding the mechanisms of TPTD effects on bone in CKD with SHPT, basic and clinical studies have reported that PTH responsiveness to bone has been reduced due to decreased expression of the PTH-related peptide receptor (PTH1R) [36,37]. Furthermore, the relationship between increased serum PTH levels and decreased PTH1R expression in CKD model rats was not linear, and PTH1R expression remained decreased even when PTH was kept low by parathyroidectomy [38]. Since decreased PTH1R expression due to renal impairment was a contributing factor to abnormal bone metabolism in CKD, we hypothesized that PTH supplementation ameliorates bone dysplasia, which was one reason why TPTD was effective against SHPT in CKD rats. Based on these results, TPTD may be a useful treatment option. However, to date, the efficacy of TPTD in patients with advanced CKD, such as hemodialysis patients, has been limited to cases with reduced PTH secretion after parathyroidectomy and cases with a low metabolic turnover with reduced PTH secretion [39,40]. Furthermore, it is not practical to administer TPTD to untreated SHPT in clinical practice, and SHPT is a contraindication to the use of TPTD in Japan.

Therefore, the most important aspect of this study was to examine the effects of TPTD on bone microstructure and bone strength of cortical and trabecular bone in a CKD rat model in which SHPT was controlled by EC, which has not been investigated before. The results in the present study indicate that EC administration corrects the high metabolic turnover state caused by continuous PTH hypersecretion, and that TPTD can maintain the metabolic turnover from a state of bone resorption dominance to a state of bone formation dominance. Interestingly, in adipocyte metabolism, the effect of reducing adipocyte volume was also enhanced in the combined group. High concentrations of PTH have been found to promote adipocyte differentiation from mesenchymal stem cells [41]. On the other hand, intermittent administration of TPTD inhibits differentiation of mesenchymal stem cells into adipocytes and promotes differentiation into osteoblasts [42]. EC has been reported to enhance osteoblast activity in a non-PTH-dependent pathway [43]. In other words, the combination of EC and TPTD may be more effective in simultaneously inhibiting adipocyte differentiation and promoting bone formation. From the viewpoint of bone fracture prevention, it is important to note that the combination of EC and TPTD enhanced the improvement of bone strength of cortical bone. This may reflect the effect of improved porosity and thickness confirmed by micro-CT. However, parameters such as elastic modulus and stiffness, which are tissue-level mechanical properties, were not improved. In addition, the effect on BMD in the combination group was observed only in the trabecular bone area, suggesting that this effect may be mainly due to TPTD. Although no apparent adverse effects were observed with combination therapy in the present study, further research is needed to address issues that are expected to occur in humans, such as increased gastrointestinal side effects and fluctuations in serum calcium levels and blood pressure after administration.

In recent years, basic experiments have suggested that uremic toxin is involved in the impairment of bone quality in renal failure. In a rat model of renal failure, femoral BMD was only slightly decreased, but bone dynamic viscoelasticity was significantly decreased with renal dysfunction [44,45]. Although TPTD has been reported to improve bone quality by restoring bone remodeling, significantly increasing collagen content and enzyme-dependent cross-links, and decreasing AGE cross-linked pentosidine [46], its effect on uremia-induced bone quality loss in CKD is unknown. Regarding the effects of EC on bone quality, EC improved material and mechanical properties at the tissue level in CKD rats (Cy/+) [47], and EC improved bone strength in a nephrectomized CKD rat model [23]. In the present study, there was no significant improvement effect of EC on material properties or mechanical properties. The decrease in material properties, mechanical properties, and bone strength in CKD cannot be explained by abnormal bone mineral metabolism alone, but it may be due to other related factors, such as uremic toxin, and may warrant further investigation.

This study has several limitations. First, it was not possible to measure or evaluate FGF23 or vitamin D, which are important in CKD-MBD; investigation of their blood kinetics, which have interactions with PTH, should be investigated in future studies. Second, bone metabolism markers in serum were not measured. The status of bone metabolism was determined by bone morphometry, but changes over time in bone formation and resorption markers due to administration of EC and TPTD need to be investigated in future studies.

5. Conclusions

In conclusion, this study shows that combination therapy provides a beneficial effect in improving bone deterioration in CKD that cannot be achieved with monotherapy; the cortical bone retention and bone metabolism turnover-improving effects of EC and the trabecular bone osteogenesis-promoting effects of TPTD go hand in hand, affecting both trabecular and cortical bone in CKD. Because they effectively improve health, they may represent a new option to combat skeletal fragility. To optimize the treatment and bone health of CKD patients, combination therapies should be considered as a future treatment modality.

CRediT author statement

Shun Igarashi: Investigation, Validation, Visualization, Writing - Original Draft. Yuji Kasukawa: Conceptualization, Methodology, Project administration, Writing - Review & Editing. Koji Nozaka: Conceptualization, Methodology, Writing - Review & Editing. Hiroyuki Tsuchie: Investigation, Formal analysis. Kazunobu Abe: Investigation. Hikaru Saito: Investigation. Ryo Shoji: Investigation. Fumihito Kasama: Investigation. Shuntaro Harata: Investigation. Kento Okamoto: Investigation. Keita Oya: Investigation. Naohisa Miyakoshi: Conceptualization, Funding acquisition, Supervision, Writing - Review & Editing.

Conflicts of interest

The authors declare no competing interests.

Acknowledgments

This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant No. 20K09450), Japan. The authors would like to thank ONO Pharmaceutical Co., Ltd. for providing EC and Ms. Kudo for support of our experiments. ORCID Shun Igarashi: 0009-0008-8075-8319. Yuji Kasukawa: 0000-0001-7008-675X. Koji Nozaka: 0000-0003-0238-8929. Hiroyuki Tsuchie: 0000-0001-5011-7184. Kazunobu Abe: 0000-0002-4991-4239. Hikaru Saito: 0000-0002-8901-3232. Ryo Shoji: 0000-0003-1255-6308. Fumihito Kasama: 0009-0003-2539-2741. Shuntaro Harata: 0009-0005-2922-9292. Kento Okamoto: 0009-0007-7062-466X. Keita Oya: 0009-0006-6163-421X. Naohisa Miyakoshi: 0000-0001-5175-3350.

Footnotes

Peer review under responsibility of The Korean Society of Osteoporosis.

References

  • 1.Levey AS, Atkins R, Coresh J, Cohen EP, Collins AJ, Eckardt KU, et al. Chronic kidney disease as a global public health problem: approaches and initiatives - a position statement from Kidney Disease Improving Global Outcomes. Kidney Int. 2007;72:247–249. doi: 10.1038/sj.ki.5002343. [DOI] [PubMed] [Google Scholar]
  • 2.Klawansky S, Komaroff E, Cavanaugh PF, Mitchell DY, Gordon MJ, Connelly JE, et al. Relationship between age, renal function and bone mineral density in the US population. Osteoporos Int. 2003;14:570–576. doi: 10.1007/s00198-003-1435-y. [DOI] [PubMed] [Google Scholar]
  • 3.Alem AM, Sherrard DJ, Gillen DL, Weiss NS, Beresford SA, Heckbert SR, et al. Increased risk of hip fracture among patients with end-stage renal disease. Kidney Int. 2000;58:396–399. doi: 10.1046/j.1523-1755.2000.00178.x. [DOI] [PubMed] [Google Scholar]
  • 4.Nickolas TL, Stein EM, Dworakowski E, Nishiyama KK, Komandah-Kosseh M, Zhang CA, et al. Rapid cortical bone loss in patients with chronic kidney disease. J Bone Miner Res. 2013;28:1811–1820. doi: 10.1002/jbmr.1916. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Metzger CE, Swallow EA, Stacy AJ, Allen MR. Strain-specific alterations in the skeletal response to adenine-induced chronic kidney disease are associated with differences in parathyroid hormone levels. Bone. 2021;148 doi: 10.1016/j.bone.2021.115963. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Ensrud KE, Lui LY, Taylor BC, Ishani A, Shlipak MG, Stone KL, et al. Osteoporotic Fractures Research Group. Renal function and risk of hip and vertebral fractures in older women. Arch Intern Med. 2007;167:133–139. doi: 10.1001/archinte.167.2.133. [DOI] [PubMed] [Google Scholar]
  • 7.Moe S, Drüeke T, Cunningham J, Goodman W, Martin K, Olgaard K, et al. Kidney disease: improving global outcomes (KDIGO). Definition, evaluation, and classification of renal osteodystrophy: a position statement from kidney disease: improving global outcomes (KDIGO) Kidney Int. 2006;69:1945–1953. doi: 10.1038/sj.ki.5000414. [DOI] [PubMed] [Google Scholar]
  • 8.Komaba H, Kakuta T, Fukagawa M. Diseases of the parathyroid gland in chronic kidney disease. Clin Exp Nephrol. 2011;15:797–809. doi: 10.1007/s10157-011-0502-5. [DOI] [PubMed] [Google Scholar]
  • 9.Isakova T, Wahl P, Vargas GS, Gutiérrez OM, Scialla J, Xie H, et al. Fibroblast growth factor 23 is elevated before parathyroid hormone and phosphate in chronic kidney disease. Kidney Int. 2011;79:1370–1378. doi: 10.1038/ki.2011.47. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Sherrard DJ, Hercz G, Pei Y, Maloney NA, Greenwood C, Manuel A, et al. The spectrum of bone disease in end-stage renal failure--an evolving disorder. Kidney Int. 1993;43:436–442. doi: 10.1038/ki.1993.64. [DOI] [PubMed] [Google Scholar]
  • 11.Alexander ST, Hunter T, Walter S, Dong J, Maclean D, Baruch A, et al. Critical cysteine residues in both the calcium-sensing receptor and the allosteric activator AMG 416 underlie the mechanism of action. Mol Pharmacol. 2015;88:853–865. doi: 10.1124/mol.115.098392. [DOI] [PubMed] [Google Scholar]
  • 12.Martin KJ, Pickthorn K, Huang S, Block GA, Vick A, Mount PF, et al. AMG 416 (velcalcetide) is a novel peptide for the treatment of secondary hyperparathyroidism in a single-dose study in hemodialysis patients. Kidney Int. 2014;85:191–197. doi: 10.1038/ki.2013.289. [DOI] [PubMed] [Google Scholar]
  • 13.Parfrey PS, Drüeke TB, Block GA, Correa-Rotter R, Floege J, Herzog CA, et al. Evaluation of cinacalcet HCl therapy to lower cardiovascular events (EVOLVE) trial investigators. The effects of cinacalcet in older and younger patients on hemodialysis: the evaluation of cinacalcet HCl therapy to lower cardiovascular events (EVOLVE) trial. Clin J Am Soc Nephrol. 2015;10:791–799. doi: 10.2215/CJN.07730814. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Moe SM, Chertow GM, Parfrey PS, Kubo Y, Block GA, Correa-Rotter R, et al. Evaluation of cinacalcet HCl therapy to lower cardiovascular events (EVOLVE) trial investigators. Cinacalcet, fibroblast growth factor-23, and cardiovascular disease in hemodialysis: the evaluation of cinacalcet HCl therapy to lower cardiovascular events (EVOLVE) trial. Circulation. 2015;32:27–39. doi: 10.1161/CIRCULATIONAHA.114.013876. [DOI] [PubMed] [Google Scholar]
  • 15.Walter S, Baruch A, Alexander ST, Janes J, Sho E, Dong J, et al. Comparison of AMG 416 and cinacalcet in rodent models of uremia. BMC Nephrol. 2014;15:81. doi: 10.1186/1471-2369-15-81. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Jadoul M, Albert JM, Akiba T, Akizawa T, Arab L, Bragg-Gresham JL, et al. Incidence and risk factors for hip or other bone fractures among hemodialysis patients in the Dialysis Outcomes and Practice Patterns Study. Kidney Int. 2006;70:1358–1366. doi: 10.1038/sj.ki.5001754. [DOI] [PubMed] [Google Scholar]
  • 17.Swallow EA, Metzger CE, Newman CL, Chen NX, Moe SM, Allen MR. Cortical porosity development and progression is mitigated after etelcalcetide treatment in an animal model of chronic kidney disease. Bone. 2022;157 doi: 10.1016/j.bone.2022.116340. [DOI] [PubMed] [Google Scholar]
  • 18.Nakamura T, Sugimoto T, Nakano T, Kishimoto H, Ito M, Fukunaga M, et al. Randomized Teriparatide [human parathyroid hormone (PTH) 1-34] Once-Weekly Efficacy Research (TOWER) trial for examining the reduction in new vertebral fractures in subjects with primary osteoporosis and high fracture risk. J Clin Endocrinol Metab. 2012;97:3097–3106. doi: 10.1210/jc.2011-3479. [DOI] [PubMed] [Google Scholar]
  • 19.Saito H, Miyakoshi N, Kasukawa Y, Nozaka K, Tsuchie H, Sato C, et al. Analysis of bone in adenine-induced chronic kidney disease model rats. Osteoporos Sarcopenia. 2021;7:121–126. doi: 10.1016/j.afos.2021.11.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Yokozawa T, Zheng PD, Oura H, Koizumi F. Animal model of adenine-induced chronic renal failure in rats. Nephron. 1986;44:230–234. doi: 10.1159/000183992. [DOI] [PubMed] [Google Scholar]
  • 21.Sato C, Miyakoshi N, Kasukawa Y, Nozaka K, Tsuchie H, Nagahata I, et al. Teriparatide and exercise improve bone, skeletal muscle, and fat parameters in ovariectomized and tail-suspended rats. J Bone Miner Metab. 2021;39:385–395. doi: 10.1007/s00774-020-01184-0. [DOI] [PubMed] [Google Scholar]
  • 22.Abe K, Miyakoshi N, Kasukawa Y, Nozaka K, Tsuchie H, Sato C, et al. Effects of teriparatide and low-intensity aerobic exercise on osteopenia in type 2 diabetes mellitus rats. J Bone Miner Metab. 2022;40:229–239. doi: 10.1007/s00774-021-01289-0. [DOI] [PubMed] [Google Scholar]
  • 23.Li X, Yu L, Asuncion F, Grisanti M, Alexander S, Hensley K, et al. Etelcalcetide (AMG 416), a peptide agonist of the calcium-sensing receptor, preserved cortical bone structure and bone strength in subtotal nephrectomized rats with established secondary hyperparathyroidism. Bone. 2017;105:163–172. doi: 10.1016/j.bone.2017.08.026. [DOI] [PubMed] [Google Scholar]
  • 24.Dempster DW, Compston JE, Drezner MK, Glorieux FH, Kanis JA, Malluche H, et al. Standardized nomenclature, symbols, and units for bone histomorphometry: a 2012 update of the report of the ASBMR Histomorphometry Nomenclature Committee. J Bone Miner Res. 2013;28:2–17. doi: 10.1002/jbmr.1805. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Nozaka K, Miyakoshi N, Kasukawa Y, Maekawa S, Noguchi H, Shimada Y. Intermittent administration of human parathyroid hormone enhances bone formation and union at the site of cancellous bone osteotomy in normal and ovariectomized rats. Bone. 2008;42:90–97. doi: 10.1016/j.bone.2007.08.041. [DOI] [PubMed] [Google Scholar]
  • 26.Yuasa Y, Miyakoshi N, Kasukawa Y, Nagahata I, Akagawa M, Ono Y, et al. Effects of bazedoxifene and low-intensity aerobic exercise on bone and fat parameters in ovariectomized rats. J Bone Miner Metab. 2020;38:179–187. doi: 10.1007/s00774-019-01045-5. [DOI] [PubMed] [Google Scholar]
  • 27.Miyakoshi N, Fujii M, Kasukawa Y, Shimada Y. Impact of vitamin C on teriparatide treatment in the improvement of bone mineral density, strength, and quality in vitamin C-deficient rats. J Bone Miner Metab. 2019;37:411–418. doi: 10.1007/s00774-018-0941-0. [DOI] [PubMed] [Google Scholar]
  • 28.Jepsen KJ, Silva MJ, Vashishth D, Guo XE, van der Meulen MC. Establishing biomechanical mechanisms in mouse models: practical guidelines for systematically evaluating phenotypic changes in the diaphyses of long bones. J Bone Miner Res. 2015;30:951–966. doi: 10.1002/jbmr.2539. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29.Kasukawa Y, Miyakoshi N, Itoi E, Tsuchida T, Tamura Y, Kudo T, et al. Effects of h-PTH on cancellous bone mass, connectivity, and bone strength in ovariectomized rats with and without sciatic-neurectomy. J Orthop Res. 2004;22:457–464. doi: 10.1016/j.orthres.2003.08.017. [DOI] [PubMed] [Google Scholar]
  • 30.Kanda Y. Investigation of the freely available easy-to-use software 'EZR' for medical statistics. Bone Marrow Transplant. 2013;48:452–458. doi: 10.1038/bmt.2012.244. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31.Jadoul M, Albert JM, Akiba T, Akizawa T, Arab L, Bragg-Gresham JL, et al. Incidence and risk factors for hip or other bone fractures among hemodialysis patients in the Dialysis Outcomes and Practice Patterns Study. Kidney Int. 2006;70:1358–1366. doi: 10.1038/sj.ki.5001754. [DOI] [PubMed] [Google Scholar]
  • 32.McNerny EMB, Buening DT, Aref MW, Chen NX, Moe SM, Allen MR. Time course of rapid bone loss and cortical porosity formation observed by longitudinal μCT in a rat model of CKD. Bone. 2019;125:16–24. doi: 10.1016/j.bone.2019.05.002. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33.Bolasco P. Treatment options of secondary hyperparathyroidism (SHPT) in patients with chronic kidney disease stages 3 and 4: an historic review. Clin Cases Miner Bone Metab. 2009;6:210–219. [PMC free article] [PubMed] [Google Scholar]
  • 34.Miller PD, Schwartz EN, Chen P, Misurski DA, Krege JH. Teriparatide in postmenopausal women with osteoporosis and mild or moderate renal impairment. Osteoporos Int. 2007;18:59–68. doi: 10.1007/s00198-006-0189-8. [DOI] [PubMed] [Google Scholar]
  • 35.Ota M, Takahata M, Shimizu T, Kanehira Y, Kimura-Suda H, Kameda Y, et al. Efficacy and safety of osteoporosis medications in a rat model of late-stage chronic kidney disease accompanied by secondary hyperparathyroidism and hyperphosphatemia. Osteoporos Int. 2017;28:1481–1490. doi: 10.1007/s00198-016-3861-7. [DOI] [PubMed] [Google Scholar]
  • 36.Fukagawa M, Iwasaki Y, Kazama JJ. Skeletal resistance to parathyroid hormone as a background abnormality in uremia. Nephrology. 2003;8(Suppl):S50–S52. doi: 10.1046/j.1440-1797.8.s.7.x. [DOI] [PubMed] [Google Scholar]
  • 37.Iwasaki Y, Yamato H, Nii-Kono T, Fujieda A, Uchida M, Hosokawa A, et al. Insufficiency of PTH action on bone in uremia. Kidney Int Suppl. 2006;102:S34–S36. doi: 10.1038/sj.ki.5001600. [DOI] [PubMed] [Google Scholar]
  • 38.Ureña P, Mannstadt M, Hruby M, Ferreira A, Schmitt F, Silve C, et al. Parathyroidectomy does not prevent the renal PTH/PTHrP receptor down-regulation in uremic rats. Kidney Int. 1995;47:1797–1805. doi: 10.1038/ki.1995.248. [DOI] [PubMed] [Google Scholar]
  • 39.Palcu P, Dion N, Ste-Marie LG, Goltzman D, Radziunas I, Miller PD, et al. Teriparatide and bone turnover and formation in a hemodialysis patient with low-turnover bone disease: a case report. Am J Kidney Dis. 2015;65:933–936. doi: 10.1053/j.ajkd.2015.01.025. [DOI] [PubMed] [Google Scholar]
  • 40.Cejka D, Kodras K, Bader T, Haas M. Treatment of hemodialysis-associated adynamic bone disease with teriparatide (PTH1-34): a pilot study. Kidney Blood Press Res. 2010;33:221–226. doi: 10.1159/000316708. [DOI] [PubMed] [Google Scholar]
  • 41.Ni LH, Tang RN, Yuan C, Song KY, Wang LT, Zhang XL, et al. Cinacalcet attenuated bone loss via inhibiting parathyroid hormone-induced endothelial-to-adipocyte transition in chronic kidney disease rats. Ann Transl Med. 2019;7:312. doi: 10.21037/atm.2019.06.44. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Rickard DJ, Wang FL, Rodriguez-Rojas AM, Wu Z, Trice WJ, Hoffman SJ, et al. Intermittent treatment with parathyroid hormone (PTH) as well as a non-peptide small molecule agonist of the PTH1 receptor inhibits adipocyte differentiation in human bone marrow stromal cells. Bone. 2006;39:1361–1372. doi: 10.1016/j.bone.2006.06.010. [DOI] [PubMed] [Google Scholar]
  • 43.Díaz-Tocados JM, Rodríguez-Ortiz ME, Almadén Y, Pineda C, Martínez-Moreno JM, Herencia C, et al. Calcimimetics maintain bone turnover in uremic rats despite the concomitant decrease in parathyroid hormone concentration. Kidney Int. 2019;95:1064–1078. doi: 10.1016/j.kint.2018.12.015. [DOI] [PubMed] [Google Scholar]
  • 44.Iwasaki Y, Kazama JJ, Yamato H, Fukagawa M. Changes in chemical composition of cortical bone associated with bone fragility in rat model with chronic kidney disease. Bone. 2011;48:1260–1267. doi: 10.1016/j.bone.2011.03.672. [DOI] [PubMed] [Google Scholar]
  • 45.Iwasaki Y, Kazama JJ, Yamato H, Shimoda H, Fukagawa M. Accumulated uremic toxins attenuate bone mechanical properties in rats with chronic kidney disease. Bone. 2013;57:477–483. doi: 10.1016/j.bone.2013.07.037. [DOI] [PubMed] [Google Scholar]
  • 46.Saito M, Marumo K, Kida Y, Ushiku C, Kato S, Takao-Kawabata R, et al. Changes in the contents of enzymatic immature, mature, and non-enzymatic senescent cross-links of collagen after once-weekly treatment with human parathyroid hormone (1-34) for 18 months contribute to improvement of bone strength in ovariectomized monkeys. Osteoporos Int. 2011;22:2373–2383. doi: 10.1007/s00198-010-1454-4. [DOI] [PubMed] [Google Scholar]
  • 47.Damrath JG, Moe SM, Wallace JM. Calcimimetics alter periosteal and perilacunar bone matrix composition and material properties in early chronic kidney disease. J Bone Miner Res. 2022;37:1297–1306. doi: 10.1002/jbmr.4574. [DOI] [PMC free article] [PubMed] [Google Scholar]

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