This Article Abstract Full Text (PDF) All Versions of this Article: 148/9/4466    most recent Author Manuscript (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Johnston, S. Articles by Iida-Klein, A. Search for Related Content PubMed PubMed Citation Articles by Johnston, S. Articles by Iida-Klein, A. Pubmed/NCBI databases Compound via MeSH Substance via MeSH

The Effects of Combination of Alendronate and Human Parathyroid Hormone(1–34) on Bone Strength Are Synergistic in the Lumbar Vertebra and Additive in the Femur of C57BL/6J Mice

The Regional Bone Center (S.J., S.A., D.W.D., A.I.-K.) and Clinical Research Center (F.C., R.L.), Helen Hayes Hospital, West Haverstraw, New York 10993; MDS Pharma Services Inc. (V.S.), Bothell, Washington 98021; and Departments of Medicine (F.C., R.L.) and Pathology (D.W.D., A.I.-K.), Columbia University, College of Physicians and Surgeons, New York, New York 10032

Address all correspondence and requests for reprints to: Akiko Iida-Klein, Ph.D., Helen Hayes Hospital, Regional Bone Center, 51 North Route 9W, West Haverstraw, New York 10993. E-mail: iida-kleina{at}helenhayeshosp.org.

	Abstract

Top Abstract Introduction Materials and Methods Materials Results Discussion References

 
A cyclic PTH regimen is as effective as a daily regimen on bone density gain in humans and in improving bone quality in mice. Our previous murine study evaluated the effects of a cyclic PTH regimen in the absence of a bisphosphonate, whereas our human study addressed the effects of a cyclic PTH regimen in the presence of ongoing alendronate (ALN) treatment. Accordingly, the current study examined the effects of cyclic or daily PTH regimens in combination with ALN on bone quality and bone density in mice. Twenty-week-old, female C57BL/6J mice were treated with the following sc injections (n = 10): 1) vehicle for 5 d/wk (control); 2) ALN (20 µg/kg·d) 3 d/wk (ALN); 3) human PTH(1–34) (40 µg/kg·d) 5 d/wk (daily PTH); 4) daily PTH in addition to ALN (daily PTH plus ALN); 5) PTH 5 d/wk and vehicle 5 d/wk alternating weekly (cyclic PTH); 6) cyclic PTH in addition to ALN (cyclic PTH plus ALN); and 7) PTH and ALN alternating weekly (alt PTH and ALN). Bone mineral density was measured weekly by dual-energy x-ray absorptiometry, and at 7 wk, bone markers, bone structure, and bone strength were evaluated by biochemical assays, peripheral quantitative computed tomography and mechanical testing, respectively. At 7 wk, all treatments significantly increased femoral and vertebral bone mineral density. ALN slightly decreased endosteal circumference, whereas PTH increased periosteal circumference, resulting in significant increases in femoral cortical thickness in all groups. PTH and ALN enhanced bone strength synergistically in the lumbar vertebrae and additively in the femur. Combined therapy, however, had no effects on bone markers. The results show that combinations of ALN and PTH, in both daily and cyclic regimens, produce more beneficial effects than treatment with either agent alone, suggesting that the mechanisms of actions of ALN and PTH on bone quality may be complementary.

	Introduction

Top Abstract Introduction Materials and Methods Materials Results Discussion References

 
TERIPARATIDE [HPTH(1–34), PTH] is currently the only Food and Drug Administration-approved anabolic agent for the treatment of osteoporosis (1, 2, 3). Patients who fail conventional therapy with bisphosphonates are among the potential candidates for treatment with PTH. Bisphosphonates, whose initial action is inhibition of osteoclast differentiation and function, ultimately suppress bone formation (4, 5, 6, 7, 8). On the other hand, PTH directly stimulates bone formation (9, 10, 11). PTH therapy, however, is currently limited to 2 yr and the anabolic effect of PTH plateaus over time, partly because it stimulates resorption as well as formation (12, 13, 14, 15). Therefore, a cyclic PTH regimen with repeated cycles of 3 months on and off PTH therapy was developed and its efficacy examined in patients who were established on and continued taking alendronate (ALN) (16). At 15 months, a cyclic PTH regimen increased vertebral bone mineral density (BMD) as effectively as a daily regimen in the presence of ALN (16). To support our clinical study, we developed a murine model (17, 18), which allowed us to follow bone density longitudinally and examine the effects of treatments on various bone quality indices, including bone structure, bone cell activity, and bone strength. Reminiscent of our clinical study (16), a regimen with repeated cycles of alternating 1 wk on and off daily injections with PTH (cyclic PTH) in female C57BL/6J mice was as effective as a daily PTH regimen in increasing vertebral BMD (17). In the femur, the cyclic PTH regimen produced significant anabolic effects that were 60–80% of those seen with daily PTH on most measures, including BMD, bone markers, bone structure, and bone strength (17). Moreover, histomorphometric analysis clearly showed that both cyclic and daily PTH regimens significantly and almost equally improved most variables of vertebral bone structure and cellular activity at both trabecular and cortical sites, indicating that PTH-stimulated increases in BMD may reflect improvement in bone microarchitecture in the murine lumbar vertebrae (18). Furthermore, because the cyclic regimens were as effective as daily PTH regimens with 40% less PTH administered, these protocols had economic advantages (17, 18).

Unlike our human study, however, our murine study evaluated the effects of cyclic and daily PTH regimens in the absence of ALN. Some clinical studies have reported that the concomitant use of a bisphosphonate blunts the anabolic action of PTH (19, 20, 21). In old female sheep, an animal model whose remodeling activity is as slow as that of elderly women, coadministration of the bisphosphonate tiludronate with hPTH (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34) blunted the stimulatory effects of PTH on both biochemical and histological indices (22). Similarly in rats, pretreatment with ALN significantly blunted the anabolic effects of PTH, although a beneficial effect of combination treatment on bone mass was still present (23). On the other hand, there are other reports showing that long-term pretreatment with antiresorptive agents including alendronate, did not reduce the anabolic action of PTH (24, 25). Moreover, Pettway et al. (26) have recently shown that the combination of PTH with zoledronic acid (ZA) produced a greater increase in bone mass than either agent alone. The authors concluded that ZA did not blunt the anabolic action of PTH and that PTH and ZA might act via different mechanisms to increase bone mass (26). Therefore, the current study addresses whether the concomitant use of ALN with both daily or cyclic PTH regimens, or alternating weekly cycles of PTH and ALN, produces more beneficial effects on BMD and bone quality than does PTH or ALN treatment alone.

	Materials and Methods

Top Abstract Introduction Materials and Methods Materials Results Discussion References

 
Animals
The experimental protocol was reviewed and approved by the Institutional Animal Care and Use Committee of Helen Hayes Hospital.

Seventy virgin, female C57BL/6J mice were purchased from the Jackson Laboratory (Bar Harbor, ME) and stabilized at the animal facility of Helen Hayes Hospital. At 20 wk, the animals were randomized into the following seven groups (n = 10) and sc injected with the following: 1) 10 mM acetic acid in PBS (pH 7.42) for 5 d/wk (control); 2) ALN (20 µg/kg·d) 3 d/wk (ALN); 3) hPTH(1–34) (40 µg/kg·d) 5 d/wk (daily PTH); 4) daily PTH in addition to ALN 3 d/wk (daily PTH plus ALN); 5) PTH 5 d/wk and vehicle 5 d/wk alternating weekly (cyclic PTH); 6) cyclic PTH in addition to ALN 3 d/wk (cyclic PTH plus ALN); and 7) PTH and ALN alternating weekly (alt PTH and ALN) (Table 1).

	Materials

Top Abstract Introduction Materials and Methods Materials Results Discussion References

 
Alendronate sodium salt was supplied by Merck & Co., Inc. (West Point, PA). Human PTH(1–34) fragment [hPTH(1–34)] was purchased from Bachem (Irvine, CA). All other chemicals used in the study including a mixture of ketamine 70 mg/xylazine 6 mg, calcein, and Dulbecco’s PBS (pH 7.42), were obtained from Sigma Chemical Co. Ltd. (St. Louis, MO). Mouse osteocalcin RIA kits and mouse intact PTH(1–84) ELISA kits were purchased from Immutopics (San Clemente, CA). Mouse tartrate-resistant acid phosphatase assay (mTRAP) kits and serum total calcium assay kits were obtained from Immunodiagnostic Systems (Fountain Hills, AZ) and Bioassay Systems (Hayward, CA), respectively.

BMD measurement
BMD was measured using dual-energy x-ray absorptiometry (GE Lunar PIXImus, Madison, WI) under anesthesia with ketamine 90 mg/kg and xylazine 7.7 mg/kg, ip, as previously described (27, 28). Measured scans were analyzed using mouse-specific software (version 2.2).

Collection of blood and bone specimens
Blood was collected by cardiac puncture at euthanasia, and serum was stored at –80 C until use for biochemical assays. The right femur and lumbar vertebrae 4–6 were excised, and connective tissues were removed, cleaned with PBS, wrapped in saline-soaked gauze, and stored at –20 C until mechanical testing (MDS Pharma Services Inc., Bothell, WA).

Mechanical loading and bone strength
Femoral strength.
Four-point bending assessment of femoral bone strength was performed as previously described (17). A defleshed whole femur was placed on a four-point bending fixture (mechanical testing machine; Instron, Norwood, MA). The bone was placed posterior side downward between two lower supports 7 mm apart. The upper loading device was aligned to the center of the femoral shaft, and load applied at 3 mm/min, until failure of the bone. Maximum load, stiffness, and energy absorbed were manually selected from the load and displacement curve and calculated by the machine software (Instron 4465, Merlin II; Instron).

Vertebral strength.
Compression testing of vertebral bone strength was performed as described below (17). The pedicle arch, spinous process, and cranial and caudal ends of each vertebral body were removed. Each vertebral body was cut with a diamond saw to produce parallel surfaces and a height of 2 mm. Each specimen was then placed between two platens and the load applied at a constant displacement rate of 0.6 mm/min until failure. Similar to the four-point bending test, maximum load, stiffness, and energy absorbed were determined as described above (Instron 4465, Merlin II; Instron).

Peripheral quantitative computed tomography (pQCT)
The bone structure of the midshaft femur was determined by pQCT before mechanical testing as previously described (17). A cross-section of the femoral midshaft was scanned at 50% of the total length from the distal end. The total, cortical, and trabecular bone mineral contents, endosteal and periosteal circumference, cortical thickness, and moment of inertia were measured.

Biochemical assays
Serum levels of osteocalcin and mTRAP were measured in duplicate according to the manufacturer’s instructions (17, 29). Serum intact PTH [mPTH(1–84)] and total calcium were also examined as previously described (17, 29). Average intraassay coefficients of variation for osteocalcin, mTRAP, mPTH(1–84), and total calcium assays were 10.45, 3.08, 9.10, and 2.92%, respectively.

Statistical analysis
Statistical analysis was performed using NCSS 2001 software (Kaysville, UT). All values are expressed as means ± SEM. The significance of differences among the groups was evaluated using one-way ANOVA followed by Duncan’s multiple comparison test with an value of 0.05 or lower.

	Results

Top Abstract Introduction Materials and Methods Materials Results Discussion References

 
Effects of PTH and ALN treatments on femoral BMD
Significant increases in femoral BMD were detected after 3 wk in the treatment groups and continued up to 7 wk (Fig. 1A). At 7 wk, all treatment groups had a significantly higher BMD than the control group (Fig. 1B). The greatest increase in femoral BMD was achieved with daily PTH plus ALN (18.5%), followed by cyclic PTH plus ALN (13.6%), daily PTH alone (11.2%), alt PTH and ALN (10.9%), cyclic PTH (6.7%), and ALN alone (6.4%) (all P < 0.001). The effect of daily PTH plus ALN on femoral BMD was significantly greater than that of all other treatments.

View larger version (48K): [in this window] [in a new window]   FIG. 1. Effects of PTH and ALN on femoral BMD. A, Time course. There were no significant differences among the groups at 0 wk. Data are means. B, BMD at 7 wk. Data are expressed as means ± SEM. Letters above each bar represent the groups that each bar is significantly different from at P < 0.001. SEM was too small to show.

View larger version (49K): [in this window] [in a new window]   FIG. 2. Effects of PTH and ALN on vertebral BMD. A, Time course. Similar to Fig. 1, data are means ± SEM. B, BMD at 7 wk. Letters above each bar represent the groups that each bar is significantly different from at P < 0.001. In some cases, SEM was too small to show.

View larger version (57K): [in this window] [in a new window]   FIG. 3. Effects of PTH and ALN on bone markers. A, Osteocalcin (n = 7–10). B, mTRAP (n = 7–10). C, Mouse PTH(1–84) (n = 7–10). D, Calcium (n = 9–10). Data are mean ± SEM. Letters above each bar represent the groups that each bar is significantly different from at P < 0.001.

There were no significant differences in mouse PTH(1–84) levels (Fig. 3C) or serum total calcium levels among the groups (Fig. 3D).

Femoral structure by pQCT
There were no significant effects on endosteal circumference in any treatment group (Fig. 4A). However, the presence of ALN tended to decrease endosteal circumference, whereas PTH alone, either daily or cyclic, produced slight but nonsignificant increases in endosteal circumference. Daily PTH alone significantly increased (3.7%, P < 0.001), whereas ALN slightly but not significantly decreased periosteal circumference (Fig. 4B). There were significant increases in cortical thickness in all treatment groups (P < 0.001, Fig. 4C). The greatest increase in cortical thickness was found in the daily PTH plus ALN group, followed by daily PTH, cyclic PTH plus ALN, alt PTH and ALN, cyclic PTH, and finally ALN.

View larger version (55K): [in this window] [in a new window]   FIG. 4. Effects of PTH and ALN on femoral bone structure. A, Endosteal circumference. B, Periosteal circumference. C, Cortical thickness. D, MOI. Data are mean ± SEM. Letters above each bar represent the groups that each bar is significantly different from at P < 0.001. In some cases, SEM was too small to show.

Femoral bone strength
Daily PTH plus ALN produced the greatest effects on femoral bone strength, as indicated by increases in maximum load (Fig. 5A), stiffness (Fig. 5B), and energy absorbed (Fig. 5C).

View larger version (53K): [in this window] [in a new window]   FIG. 5. Effects of PTH and ALN on femoral bone strength. A, Maximum load. B, Stiffness. C, Energy absorbed. Data are mean ± SEM. Letters above each bar represent the groups that each bar is significantly different from at P < 0.001 for maximum load and P < 0.01 for stiffness and energy absorbed.

View larger version (48K): [in this window] [in a new window]   FIG. 6. Effects of PTH and ALN on vertebral bone strength. A, Maximum load. B, Stiffness. C, Energy absorbed. Data are mean ± SEM. Letters above each bar represent the groups that each bar is significantly different from at P < 0.05 for maximum load and P < 0.001 for stiffness and energy absorbed.

	Discussion

Top Abstract Introduction Materials and Methods Materials Results Discussion References

Confirming our previous observation (17), the effects of PTH on most variables of cortical bone structure and bone strength were proportional to the effects of PTH on BMD in the femur. Moreover, at this site, the combined use of any PTH regimen with ALN produced additive effects on BMD, bone structure, and bone strength. This is consistent with the recent report by Samadfam et al. (30), who demonstrated that neither ALN nor osteoprotegerin impeded the anabolic effects of PTH on BMD and femoral bone strength in ovariectomized mice and that the combined effects of PTH with ALN were additive at this site.

One notable finding in the current study was the site specificity of the murine skeleton in response to both PTH and ALN in terms of bone strength. The combination of PTH with ALN synergistically increased vertebral bone strength, although its effect on BMD was additive only at this site. The effects on vertebral BMD in our current study were slightly different from those of Samadfam et al. (30), who showed that the combination of PTH and ALN supraadditively or almost synergistically increased BMD in the lumbar vertebrae. This may be in part due to substantial differences in the protocols between the two studies, e.g. age of mice used, estrogen status, doses of PTH and ALN, and duration of the treatment, etc. In addition, it should be noted that daily PTH in our current study is actually a modified cyclical PTH regimen with 5 d on and 2 d off PTH. Nevertheless, it is clear that there is synergism between the effects of PTH and ALN on bone strength in the lumbar vertebrae, in which trabecular bones are enriched, regardless of whether daily or cyclic PTH regimens are used.

Our data on femoral cortical structure showed that PTH significantly increased periosteal circumference, whereas ALN tended to decrease endosteal circumference, and any combination of these two agents produced significant increases in cortical thickness as a result. This suggests that these two agents may act on the different skeletal envelopes through different mechanisms, leading to complementary effects on bone. Envelope specificity was reported by Gardiner et al. (31) in mice overexpressing vitamin D receptor genes in the mature osteoblast lineage. Moreover, in the rat femur, Iwata et al. (32) showed that ALN decreased mineral apposition rate (MAR) without any significant changes in labeled perimeter at the periosteal surface but decreased both labeled perimeter and MAR at the endocortical surface. This suggests that ALN suppresses periosteal osteoblast cell activity without changing osteoblast number, whereas it reduces both endocortical osteoblast number and activity (33). In contrast to Iwata’s report, Allen et al. (33) demonstrated that in the canine ribs, ALN significantly suppressed both labeled surface and MAR on the endocortical/trabecular envelope but had no effects on the periosteal or intracortical envelope. Similar to the canine study (33), a human transilial biopsy study revealed that ALN reduced endocortical and trabecular bone formation but had no effect at the periosteal surface in postmenopausal women (34).

Although firm conclusions cannot be made in the absence of histomorphometric data in the present study, the results from the canine and human studies are consistent with our current study, which showed that the effects of ALN on femoral cortical structure were more marked at the endocortical surface than at the periosteal surface. In addition, it is well known that PTH activates Haversian remodeling in humans (35) and primates (36), resulting in a decreased BMD at appendicular skeletal sites (37). Although mice do not display Haversian remodeling, they exhibit a similar response to PTH at the endocortical surface (increased turnover, Fig. 4A), particularly in the cyclical regimen as shown by the slight increase in endocortical circumference. Addition of ALN reverses this effect of PTH, thus lending additional support for combination treatment regimens. Moreover, our group has recently demonstrated PTH-stimulated periosteal bone formation in humans (38), consistent with our current and previous (17, 18) data in mice. Thus, based on our recent finding that PTH (both cyclic and daily) increased periosteal expansion as well as endocortical and trabecular bone formation (17, 18, 38), it is likely that the combination of PTH and ALN may produce complementary effects to increase cortical thickness and bone strength. Further investigations using dynamic histomorphometry are currently ongoing and may provide better insight in this regard.

In our previous study, we found that PTH failed to produce any significant effects on vertebral bone strength, and we speculated that technical difficulties in excision and measurement of the vertebral bone specimens might account for the lack of observed effects (17). In the current study, however, vertebral bone strength was significantly improved in the daily PTH plus ALN group, whereas all other treatment groups exhibited trends toward increased strength, but the differences were not statistically significant. This suggests that factors associated with structural differences in trabecular and cortical bone rather than technical difficulties may contribute to the observed lack of effects. Envelope specificity could be one of these factors (38). Another possible explanation is that in the lumbar vertebrae, the PTH-induced increase in trabecular BMD exceeds its effects on cortical BMD, mitigating overall effects on bone strength. This may support the established concept that changes in BMD do not always precisely reflect changes in fracture risk reduction in humans (2, 39, 40). Moreover, whereas bone strength testing in animal models uses simplified force systems (41, 42, 43), the types of mechanical stress in humans can be more complicated, including compressive, bending, shearing, and torsion forces or a combination of these. In this regard, moment of inertia (MOI) in the femur was significantly increased by daily PTH alone and just tended to be increased by the other treatments, including daily PTH plus ALN. One explanation for this is that PTH alone increased periosteal circumference to the greatest extent, and MOI is proportional to the outer radius.

In humans, efficacy of antiosteoporotic agents can be assessed by biomarkers of bone turnover. In the current study, however, bone markers were not changed significantly by the combined treatments, despite the fact that the effects of the combined treatment of ALN and PTH on bone density and quality were remarkable. This is consistent with the recent report by Samadfam et al. (30), who demonstrated in ovariectomized mice that a 60-d treatment with a combination of PTH (80 µg/kg·d) and ALN (100 µg/kg·wk) did not alter serum osteocalcin levels, despite significant increases in BMD and bone strength in the femur and lumbar spine (30). In a second study, Samadfam et al. further demonstrated that a 30-d pretreatment of ALN blunted the effects of PTH monotherapy on bone markers and BMD but did not completely eliminate the anabolic response to PTH in ovariectomized mice (44). The authors concluded that antiresorptive agents may reduce the efficacy of PTH, but PTH treatment after antiresorptive therapy still provides some skeletal benefit. However, pretreatment with ALN did not blunt the effects of combined treatment with PTH and ALN (44).

In human studies, there was no synergy between PTH and ALN, and concurrent use of ALN reduced the anabolic effects of PTH (2, 19, 20, 21, 39, 40). The dose of PTH used in mice is generally 50–100 times higher than that used in humans based on body weight, whereas the dose of ALN is equivalent to or less than that used in humans. Therefore, the apparent discrepancy that ALN suppresses the anabolic effect of PTH in humans but synergistically enhances it in rodents may be in part due to the differences in doses of the two drugs. Unfortunately, there are very few reports indicating that the human dose of PTH exerts any significant effects on BMD or bone quality in animals in vivo, specifically in mice, and significant effects on bone mass or serum calcium levels are generally found at higher doses (45, 46). Quite recently, Turner et al. (10) demonstrated that the dose of PTH used in humans (1 µg/kg·d) prevented disuse-induced trabecular thinning in hindlimb-unloaded rats, whereas a pharmacological dose of PTH (80 µg/kg·d) stimulated bone formation and increased trabecular thickness.

Unlike our previous study, in which the effects of cyclic PTH were found to be almost equal to those of daily PTH on vertebral BMD and other histomorphometric measures, the effects of cyclic PTH in the current study were clearly less than those produced by daily PTH (17, 18). One reason for this inconsistency could be that animals in the current study were treated with 5 d on and 2 d off PTH cycles in the daily PTH group, whereas animals were treated with PTH 7 d/wk in the previous study (17, 18). Moreover, in the current cyclic PTH group, animals were treated with 3 d on, 2 d off, and 2 d on PTH, followed by 7 d off PTH, and this cycle was repeated. Thus, it appears that the anabolic effects of cyclic PTH on bone may be better when the PTH "on" period is longer and uninterrupted. However, this disadvantage was clearly overcome in the presence of ALN, as shown in the combined groups, suggesting that addition of ALN may compensate for the effects of interrupting PTH during the on period. We are also aware that the total amount of PTH given in the current study was less than that in the previous study (17, 18). For example, PTH was given for a total of 35 and 49 d in the current and previous (17, 18) studies, respectively, in the daily groups, whereas PTH was administered for 20 and 28 d, respectively, in the cyclic groups. However, in the daily groups, there were no statistically significant differences in BMD and bone strength at 7 wk between the two studies. In the cyclic PTH groups, there was a slightly lower gain in BMD in the current study, compared with the previous study, although there were no statistically significant differences in bone strength increments. Thus, although we have introduced new variables by using the 5 d on and 2 d off protocol, it appeared that both daily regimens produced similar results in terms of BMD and bone strength despite the fact that 30% less PTH was delivered in the current study. In the alt PTH and ALN group, the effects on both femoral and vertebral BMD were significantly greater than those seen with either ALN alone or PTH alone. In addition, the effects of alt PTH and ALN on other measures including femoral cortical structure and bone strength were similar to those of cyclic PTH plus ALN. Thus, a protocol with alternating PTH and a bisphosphonate may be worth exploring in a clinical setting.

Caution must always be exercised when extrapolating from animal models to humans because there always exist substantial differences in life span, body size, skeletal growth rate, growth period, posture, and reproductive systems, etc. between humans and any other species including mice. Furthermore, mice do not exhibit Haversian remodeling. Despite these limitations, animal models have been useful in determining the effects of bone active agents and offer the significant advantage that bone strength can be measured.

In conclusion, the present study demonstrated that the addition of ALN to daily or cyclic PTH regimens synergistically strengthens vertebral bones and additively enhances femoral bone strength, with marked improvement of BMD at both sites. Combination of PTH with different antiresorptive agents in appropriate protocols (e.g. coadministration or alternating administration) may be beneficial in terms of its effects on bone quality and bone density, as well as providing a more economical treatment regimen than daily PTH administration.

	Acknowledgments

 
We are grateful to Ms. Annette Moreno, Ms. Christine Hughes, and Mrs. Elizabeth Vasquez for their assistance in biochemical assays, excision of bone specimens, and statistical analyses, respectively.

	Footnotes

 
This work was supported by Merck-Investigator-Initiated Studies Program of Merck & Co., Inc. The opinions expressed in this paper are those of the authors and do not necessarily represent those of Merck & Co., Inc.

Disclosure Statement: S.J., S.A., and A.I.-K. have nothing to declare. V.S. is an employee of MDS Pharma Inc. F.C. consults for Pfizer, Merck, and Novartis and received lecture fees from Eli Lilly, Merck, and Roche. R.L. consults for Wyeth and P&G and received lecture fees from Wyeth, P&G, Sanofi Avantis, Eli Lilly, and GSK. D.W.D. consults for Eli Lilly and Merck and received lecture fees from Eli Lilly, Merck, GSK, Roche, P&G, and Safoni Avantis.

First Published Online June 14, 2007

Abbreviations: ALN, Alendronate; BMD, bone mineral density; hPTH, human PTH; MAR, mineral apposition rate; MOI, moment of inertia; mTRAP, mouse tartrate-resistant acid phosphatase assay; pQCT, peripheral quantitative computed tomography; ZA, zoledronic acid.

Received February 16, 2007.

Accepted for publication June 5, 2007.

	References

Top Abstract Introduction Materials and Methods Materials Results Discussion References

 

1. Lindsay R, Nieves J, Formica C, Henneman E, Woelfert L, Shen V, Dempster D, Cosman F 1997 Randomised controlled study of effect of parathyroid hormone on vertebral-bone mass and fracture incidence among postmenopausal women on oestrogen with osteoporosis. Lancet 350:550–555[CrossRef][Medline]
2. Neer RM, Arnaud CD, Zanchetta JR, Prince R, Gaich GA, Reginster JY, Hodsman AB, Eriksen EF, Ish-Shalom S, Genant HK, Wang O, Mitlak BH 2001 Effect of parathyroid hormone (1–34) on fractures and bone mineral density in postmenopausal women with osteoporosis. N Engl J Med 344:1434–1441[Abstract/Free Full Text]
3. Martin TJ, Seeman E 2007 New mechanisms and targets in the treatment of bone fragility. Clin Sci (Lond) 112:77–91[Medline]
4. Rogers MJ 2003 New insights into the molecular mechanisms of actions of bisphosphonates. Curr Pharm Des 9:2643–2658[CrossRef][Medline]
5. Porras AG, Holland SD, Gertz BJ 1999 Pharmacokinetics of alendronate. Clin Pharmacokinet 36:316–328
6. Chapurlat RD, Delmas PD 2006 Drug insights: bisphosphonates for postmenopausal osteoporosis. Nat Clin Pract Endocrinol Metab 2:211–219[CrossRef][Medline]
7. Fisher JE, Rodan GA, Reszka AA 2000 In vivo effects of bisphosphonates on the osteoclast mevalonate pathway. Endocrinology 141:4793–4796[Abstract/Free Full Text]
8. Kim YH, Kim G-S, Baek J-H 2002 Inhibitory action of bisphosphonates on bone resorption does not involve the regulation of RANKL and OPG expression. Exp Mol Med 34:145–151[Medline]
9. Hodsman AB, Steer BM 1993 Early histomorphometric changes in response to parathyroid hormone therapy in osteoporosis: evidence for de novo bone formation on quiescent cancellous surfaces. Bone 523–527
10. Dobnig H, Turner RT 1995 Evidence that intermittent treatment with parathyroid hormone increases bone formation in adult rats by activation of bone lining cells. Endocrinology 136:3632–3638[Abstract]
11. Lindsay R, Cosman F, Zhou H, Bostrom MP, Shen VW, Cruz JD, Nieves JW, Dempster DW 2006 A novel tetracycline labeling schedule for longitudinal evaluation of the short-term effects of anabolic therapy with a single iliac crest bone biopsy: early actions of teriparatide. J Bone Miner Res 21:366–373[CrossRef][Medline]
12. Girotra M, Rubin MR, Bilezikian JP 2006 The use of parathyroid hormone in the treatment of osteoporosis. Rev Endocr Metab Disord 7:113–121[CrossRef][Medline]
13. Turner RT, Evans GL, Lotinun S, Lapke PD, Iwaniec UT, Morey-Holton E 2007 Dose-response effects of intermittent PTH on cancellous bone in hindlimb unloaded rats. J Bone Miner Res 22:64–71[CrossRef][Medline]
14. Ishizuya T, Yokose S, Hori M, Noda T, Suda T, Yoshiki S 1997 Parathyroid hormone exerts disparate effects on osteoblast differentiation depending on exposure time in rat osteoblastic cells. J Clin Invest 99:2961–2970[Medline]
15. Cosman F, Nieves J, Woelfert L, Formica C, Gordon S, Shen V, Lindsay R 2001 Parathyroid hormone added to established hormone therapy: effects on vertebral fracture and maintenance of bone mass after PTH withdrawal. J Bone Miner Res 16:925–931[CrossRef][Medline]
16. Cosman F, Nieves JW, Lucky MM, Zion M, Woelfert L, Lindsay R 2005 Daily and cyclic parathyroid hormone in women receiving alendronate alone for treatment. N Engl J Med 353:566–575[Abstract/Free Full Text]
17. Iida-Klein A, Hughes C, Shen V, Moreno A, Lu SS, Dempster DW, Cosman F, Lindsay R 2006 Effects of cyclic vs. daily PTH regimens on bone strength in association with bone density, biochemical markers and bone structure in mice. J Bone Miner Res 21:274–282[CrossRef][Medline]
18. Iida-Klein A, Lu SS, Dempster DW, Cosman F, Lindsay R 2007 Effects of cyclic vs. daily PTH on murine bone structure and cellular activity. Bone 40:391–398[Medline]
19. Black DM, Greenspan SL, Ensrud KE, Palermo L, McGowan JA, Lang TF, Garnero P, Bouxsein ML, Bilezikian JP, Rosen CJ; PaTH Study Investigators 2003 The effects of parathyroid hormone and alendronate alone or in combination in postmenopausal osteoporosis. N Engl J Med 349:1207–1215[Abstract/Free Full Text]
20. Finkelstein JS, Hayes A, Hunzelman JL, Wyland JJ, Lee H, Neer RM 2003 The effects of parathyroid hormone, alendronate, or both in men with osteoporosis. N Engl J Med 349:1216–1226[Abstract/Free Full Text]
21. Ettinger B, San Martin J, Crans G, Pavo I 2004 Differential effects of teriparatide on BMD after treatment with raloxifene or alendronate. J Bone Miner Res 19:745–751[CrossRef][Medline]
22. Delmas PD, Vergnaud P, Arlot ME, Pastoureau P, Meunier PJ, Nilssen MH 1995 The anabolic effect of human PTH(1–34) on bone formation is blunted when bone resorption is inhibited by the bisphosphonate—is activated resorption a prerequisite for the in vivo effect of PTH on formation in a remodeling system? Bone 16:603–610[Medline]
23. Gasser JA, Kneissel M, Thomsen JS, Mosedilde L 2000 PTH and interactions with bisphosphonates. J Musculoskelet Neuronal Interact 1:53–56[Medline]
24. Li M, Jiao J, Meng XW, Xing XP, Xia WB, Zhou XY, Liu HC, Jiang Y, Wang O, Hu YY, Zhan ZW 2005 Effects of teriparatide and alendronate on bone mineral density of osteoporotic rats. Zhonghua Yi Xue Za Zhi 85:335–338[Medline]
25. Ma YL, Bryant HU, Zeng Q, Schmidt A, Hoover J, Cole HW, Yao W, Jee WS, Sato M 2003 New bone formation with teriparatide [human parathyroid hormone(1–34)] is not retarded by long-term pretreatment with alendronate, estrogen, or raloxifene in ovariectomized rats. Endocrinology 144:2008–2015[Abstract/Free Full Text]
26. Pettway GJ, Meganck JA, Wei CL, Goldstein SA, McCauley, LK 2006 Anabolic actions of PTH in bone: role of osteoblast proliferation, differentiation, and combinatorial treatment with bisphosphonates. J Bone Miner Res 21(Suppl 1):S114
27. Iida-Klein A, Lu SS, Yokoyama K, Dempster DW, Nieves J, Lindsay R 2003 Precision, accuracy, and reproducibility of dual x-ray absorptiometry measurements in mice in vivo. J Clin Densitom 6:25–33[CrossRef][Medline]
28. Iida-Klein A, Zhou H, Lu SS, Levine L, Ducayen-Knowles M, Dempster DW, Nieves J, Lindsay R 2002 Anabolic action of human parathyroid hormone is skeletal site specific at the tissue and cellular levels in mice. J Bone Miner Res 17:808–816[CrossRef][Medline]
29. Iida-Klein A, Lu SS, Kapadia R, Burkhart M, Moreno A, Dempster DW, Lindsay R 2005 Short-term continuous infusion of human parathyroid 1–34 fragment is catabolic with decreased trabecular connectivity density accompanied by hypercalcemia in C57BL/J6 mice. J Endocrinol 186:549–557[Abstract/Free Full Text]
30. Samadfam R, Xia Q, Goltzman D 2006 Co-treatment of PTH with osteoprotegerin or alendronate increases its anabolic effect on the skeleton of oophorectomized mice. J Bone Miner Res 22:55–63
31. Gardiner EM, Baldock PA, Thomas GP, Sims NA, Henderson NK, Hollis B, White CP, Sunn KL, Morrison NA, Walsh WR, Eisman JA 2000 Increased formation and decreased resorption of bone in mice with elevated vitamin D receptor in mature cells of the osteoblastic lineage. FASEB J 14:1908–1916[Abstract/Free Full Text]
32. Iwata K, Li J, Follet H, Phipps RJ, Burr DB 2006 Bisphosphonates suppress periosteal osteoblast activity independently of resorption in rat femur and tibia. Bone 39:1053–1058[Medline]
33. Allen MR, Follet H, Khurana M, Sato M, Burr DB 2006 Antiremodeling agents influence osteoblast activity differently in modeling and remodeling sites of canine rib. Calcif Tissue Int 79:255–261[CrossRef][Medline]
34. Bare S, Recker S, Recker R, Kimmel D 2005 Bone formation in the periosteal, endocortical, and trabecular envelopes of the ilium of adult women. J Bone Miner Res 20(Suppl 1):S274
35. Ma YL, Zeng Q, Donley DW, Ste-Marie L, Gallagher JC, Dalsky GP, Marcus R Eriksen EF 2006 Teriparatide increases bone formation in modeling and remodeling osteons and enhances IGF-II immunoreactivity in postmenopausal women with osteoporosis. J Bone Miner Res 21:855–864[CrossRef][Medline]
36. Jerome CP, Johnson CS, Vafai HT, Kaplan KC, Bailey J, Capwell B, Fraser F, Hansen L, Ramsay H, Shadoan M, Lees CJ, Thomsen JS, Mosekilde L 1999 Effects of treatment for 6 months with human parathyroid hormone 1–34 peptide in ovariectomized cynomolgus monkeys (Macaca fascicularis). Bone 25:301–309[Medline]
37. Reeves J, Davies UM, Hesp R, McNally E, Katz D 1990 Treatment of osteoporosis with human parathyroid peptide and observations on effect of sodium fluoride. Br Med J 301:314–318[Medline]
38. Lindsay R, Zhou H, Cosman F, Nieves J, Dempster DW, Hodsman A 2007 Effects of a one-month treatment with PTH(1–34) on bone formation on cancellous, endocortical and periosteal surfaces of the human ilium. J Bone Miner Res 22:495–502[CrossRef][Medline]
39. Cummings SR, Black DM, Thompson DE, Applegate WB, Barrett-Connor E, Musliner TA, Palermo L, Prineas R, Rubin SM, Scott JC, Vogt T, Wallace R, Yates AJ, LaCroix AZ 1998 Effect of alendronate on risk of fracture in women with low bone density but without vertebral fractures. JAMA 280:2077–2082[Abstract/Free Full Text]
40. Finkelstein JS, Leder BZ, Burnett SM, Wyland JJ, Lee H, de la Paz AV, Gibson K, Neer RM 2006 Effects of teriparatide, alendronate, or both on bone turnover in osteoporotic men. J Clin Endocrinol Metab 91:2882–2887[Abstract/Free Full Text]
41. Borg U Compressive strength of fiber composite with porosity. Proc 21st International Congress of Theoretical and Applied Mechanics, Warsaw, Poland, August 15–21, 2004 (Abstract SM13L-12214)
42. Aultman CD, Drake JD, Callaghan JP, McGill SM 2004 The effect of static torsion on the compressive strength of the spine: an in vitro analysis using a porcine spine model. Spine 29: E304–E309
43. Bono CM, Einhorn TA 2005 Overview of osteoporosis: pathophysiology and determinants of bone strength. In: Aebi M, Gunzburg R, Szpalski MP, eds. The aging spine. Heidelberg: Springer-Berlin; 8–14
44. Samadfam R, Xia Q, Golzman D 2007 Pretreatment with anticatabolic agents blunts but does not eliminate the skeletal anabolic response to parathyroid hormone in oophorectomized mice. Endocrinology 148:2778–2787[Abstract/Free Full Text]
45. Yates AJP, Gutierrez GE, Smolens P, Travis PS, Katz MS, Aufdemorte TB, Boyce BF, Hymer TK, Poser JW, Mundy GR 1988 Effects of a synthetic peptide of a parathyroid hormone-related protein on calcium homeostasis, renal tubular calcium reabsorption, and bone metabolism in vivo and in vitro rodents. J Clin Invest 88:932–938
46. Mitlak BH, Burdette-Miller P, Schoenfeld D, Neer RM 1996 Sequential effects of chronic human PTH (1–84) treatment of estrogen deficiency osteopenia in the rat. J Bone Miner Res 11:430–439[Medline]

This Article Abstract Full Text (PDF) All Versions of this Article: 148/9/4466    most recent Author Manuscript (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Johnston, S. Articles by Iida-Klein, A. Search for Related Content PubMed PubMed Citation Articles by Johnston, S. Articles by Iida-Klein, A. Pubmed/NCBI databases Compound via MeSH Substance via MeSH