Search

A number of osteoporotic patients under bisphosphonate treatment present persistent fragility fractures and bone loss despite good compliance. The objective of this 18-month prospective study was to investigate the effect of teriparatide [rhPTH(1-34)] in 25 female osteoporotics who were inadequate responders to oral bisphosphonates and to correlate microarchitectural changes in three consecutive iliac crest biopsies measured by micro-computed tomography (μCT) with bone mineral density (BMD) and bone serum markers. Scanned biopsies at baseline (M0), 6 months (M6), and 18 months (M18) demonstrated early significant (P < 0.01) increases in bone volume per tissue volume (+34%) and trabecular number (+14%) at M6 with only moderate changes in most μCT structural parameters between M6 and M18. μCT-measured bone tissue density was significantly decreased at M18, expressing an overall lower degree of tissue mineralization characteristic for new bone formation despite unchanged trabecular thickness due to increased intratrabecular tunneling at M18. μCT results were consistent with serum bone turnover markers, reaching maximal levels of bone alkaline phosphatase and serum β-crosslaps at M6, with subsequent decline until M18. BMD assessed by DXA demonstrated persistent increases at the lumbar spine until M12, whereas no significant change was observed at the hip. Type (alendronate/risedronate) and duration (3.5 ± 4 years) of prior bisphosphonate treatment did not influence outcome on μCT, BMD, or bone marker results. The overall results indicate a positive ceiling effect of teriparatide on bone microarchitecture and bone markers after 6 and 12 months for lumbar spine BMD, with no additional gain until M18 in bisphosphonate nonresponders.

Background: Several agents are available to treat osteoporosis while addressing patient-specific medical needs. Individuals' residual risk to severe fracture may require changes in treatment strategy. Data at osseous cellular and microstructural levels due to a therapy switch between agents with different modes of action are rare. Our study on a series of five consecutively taken bone biopsies from an osteoporotic individual over a six-year period analyzes changes in cellular characteristics, bone microstructure and mineralization caused by a therapy switch from an antiresorptive (bisphosphonate) to a dual action bone agent (strontium ranelate)., Methodology/principal Findings: Biopsies were progressively taken from the iliac crest of a female patient. Four biopsies were taken during bisphosphonate therapy and one biopsy was taken after one year of strontium ranelate (SR) treatment. Furthermore, serum bone markers and dual x-ray absorptiometry measurements were acquired. Undecalcified histology was used to assess osteoid parameters and bone turnover. Structural indices and degree of mineralization were determined using microcomputed tomography, quantitative backscattered electron imaging, and combined energy dispersive x-ray/µ-x-ray-fluorescence microanalysis., Conclusions/significance: Microstructural data revealed a notable increase in bone volume fraction after one year of SR treatment compared to the bisphosphonate treatment period. Indices of connectivity density, structure model index and trabecular bone pattern factor were predominantly enhanced indicating that the architectural transformation from trabecular rods to plates was responsible for the bone volume increase and less due to changes in trabecular thickness and number. Administration of SR following bisphosphonates led to a maintained mineralization profile with an uptake of strontium on the bone surface level. Reactivated osteoclasts designed tunneling, hook-like intratrabecular resorption sites. The appearance of tunneling resorption lacunae and the formation of both mini-modeling units and osteon-like structures within increased plate-like cancellous bone mass provides additional information on the mechanisms of strontium ranelate following bisphosphonate treatment, which may deserve special attention when monitoring a treatment switch.

Strontium ranelate (SR) is one therapeutic option for reducing risk of fracture in osteoporosis. The effects of SR treatment on hydroxyapatite (HA) previously altered by bisphosphonate (BP) administration remain to be established. Patients who have received long-term BP treatment and present with persistent high fracture risk are of particular interest. Paired iliac crest biopsies from 15 patients post-BP therapy were subjected to a baseline biopsy and a follow-up biopsy after treatment with 2g SR day⁻¹ after either 6 months (n=5) or 12 months (n=10). Dual energy X-ray absorptiometry scans, serum parameters and biochemical markers were obtained. Quantitative backscattered electron imaging and energy-dispersive X-ray analyses combined with micro-X-ray fluorescence determinations were performed to observe any mineralization changes. Static 2-D histomorphometry was carried out to evaluate cellular and structural indices. After 6 months of SR treatment, increases in osteoid surface and strontium content were observed, but no other indices showed significant change. After 12 months of SR treatment, there was a significant increase in bone volume and trabecular thickness, and further increases in strontium content and backscattered signal intensity. These structural changes were accompanied by increased numbers of osteoblasts and increased osteoid surface and volume. Additionally, low bone resorption, as measured by beta-cross-laps, and a low number of osteoclasts were observed. SR treatment led to increased strontium content within the BP-HA nanocomposites and to increased osteoid indices and bone volume, which is indicative of newly formed bone, while osteoclasts were still suppressed. These data points suggest that SR might be considered as a therapeutic option for patients following long-term BP treatment., (Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)