Zoledronate treatment duration is linked to bisphosphonate‐related osteonecrosis of the jaw prevalence in rice rats with generalized periodontitis

ObjectivesTo determine the extent that zoledronate (ZOL) dose and duration is associated with bisphosphonate‐related osteonecrosis of the jaw (BRONJ) prevalence in rice rats with generalized periodontitis (PD), characterize structural and tissue‐level features of BRONJ‐like lesions in this model, and examine the specific anti‐resorptive role of ZOL in BRONJ.Materials and MethodsRice rats (n = 228) consumed high sucrose‐casein diet to enhance generalized PD. Groups of rats received 0, 8, 20, 50 or 125 µg/kg IV ZOL/4 weeks encompassing osteoporosis and oncology ZOL doses. Rats from each dose group (n = 9–16) were necropsied after 12, 18, 24 and 30 weeks of treatment. BRONJ‐like lesion prevalence and tissue‐level features were assessed grossly, histopathologically and by MicroCT. ZOL bone turnover effects were assessed by femoral peripheral quantitative computed tomography, serum bone turnover marker ELISAs and osteoclast immunolabelling.ResultsPrevalence of BRONJ‐like lesions was significantly associated with (a) ZOL treatment duration, but plateaued at the lowest oncologic dose, and (b) there was a similar dose‐related plateau in the systemic anti‐resorptive effect of ZOL. ZOL and BRONJ‐like lesions also altered the structural and tissue‐level features of the jaw.ConclusionThe relationship between BRONJ‐like lesion prevalence and ZOL dose and duration varies depending on the co‐ or pre‐existing oral risk factor. At clinically relevant doses of ZOL, BRONJ‐like lesions are associated with anti‐resorptive activity.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149302/1/odi13052.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149302/2/odi13052_am.pd

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury

<div><p>Sclerostin is a circulating osteocyte-derived glycoprotein that negatively regulates Wnt-signaling after binding the LRP5/LRP6 co-receptors. Pharmacologic sclerostin inhibition produces bone anabolic effects after spinal cord injury (SCI), however, the effects of sclerostin-antibody (Scl-Ab) on muscle morphology remain unknown. In comparison, androgen administration produces bone antiresorptive effects after SCI and some, but not all, studies have reported that testosterone treatment ameliorates skeletal muscle atrophy in this context. Our purposes were to determine whether Scl-Ab prevents hindlimb muscle loss after SCI and compare the effects of Scl-Ab to testosterone enanthate (TE), an agent with known myotrophic effects. Male Sprague-Dawley rats aged 5 months received: (A) SHAM surgery (T₈ laminectomy), (B) moderate-severe contusion SCI, (C) SCI+TE (7.0 mg/wk, im), or (D) SCI+Scl-Ab (25 mg/kg, twice weekly, sc). Twenty-one days post-injury, SCI animals exhibited a 31% lower soleus mass in comparison to SHAM, accompanied by >50% lower soleus muscle fiber cross-sectional area (fCSA) (p<0.01 for all fiber types). Scl-Ab did not prevent soleus atrophy, consistent with the relatively low circulating sclerostin concentrations and with the 91–99% lower LRP5/LRP6 gene expressions in soleus versus tibia (p<0.001), a tissue with known anabolic responsiveness to Scl-Ab. In comparison, TE partially prevented soleus atrophy and increased levator ani/bulbocavernosus (LABC) mass by 30–40% (p<0.001 vs all groups). The differing myotrophic responsiveness coincided with a 3-fold higher androgen receptor gene expression in LABC versus soleus (p<0.01). This study provides the first direct evidence that Scl-Ab does not prevent soleus muscle atrophy in rodents after SCI and suggests that variable myotrophic responses in rodent muscles after androgen administration are influenced by androgen receptor expression.</p></div

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury - Fig 2

<p>A-F. Soleus muscle fiber-type distribution and fiber cross-sectional area (fCSA) after sham surgery (T₈ laminectomy) or moderate-severe spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin-antibody (SCI+Scl-Ab). Panel A-D are representative images of serial cross-sections from soleus stained with monoclonal antibodies directed against (A) MHC-1 (stained green), (B) MHC-IIA (stained green), (C) MHC-IIX (unstained black, with all other MHC isoforms green), (D) MHC-IIB (green, none present). Panels E-F values are means ± SEM, n = 6-8/group. Letters a-d indicate differences from respectively labeled groups at p<0.05 or *p<0.01 (a = vs SHAM; b = vs SCI; c = vs SCI+TE; d = vs SCI+Scl-Ab).</p

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury - Fig 4

<p>A-H. Representative histologic images of hybrid type IIA/IIX fibers after sham surgery (T₈ laminectomy) or moderate-severe spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin-antibody (SCI+Scl-Ab). Panels in left and right columns are representative serial cross-sections from soleus stained with monoclonal antibodies directed against MHC-IIA (stained green) or MHC-IIX (unstained), respectively, for each group. +indicates hybrid IIA/IIX fibers. All images acquired at 20X magnification.</p

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury - Fig 5

<p>A-D. Pearson correlation coefficients for BBB score and muscle fiber cross-sectional area (fCSA) for animals that received spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin antibody (SCI+Scl-Ab). Values represent individual animals, n = 20-21/analysis.</p

Pearson correlation coefficients for BBB score and muscle fiber cross-sectional area (fCSA) within groups of animals receiving spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin antibody (SCI+Scl-Ab).

<p>Pearson correlation coefficients for BBB score and muscle fiber cross-sectional area (fCSA) within groups of animals receiving spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin antibody (SCI+Scl-Ab).</p

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury - Fig 3

<p>A-H. Representative histologic images of hybrid type I/IIA fibers after sham surgery (T₈ laminectomy) or moderate-severe spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin-antibody (SCI+Scl-Ab). Panels in left and right columns are representative serial cross-sections from soleus stained with monoclonal antibodies directed against MHC-1 (stained green) or MHC-IIA (stained green), respectively, for each group. +indicates hybrid I/IIA fibers. All images acquired at 20X magnification.</p

Muscle and prostate mass after sham surgery (T₈ laminectomy) or moderate-severe spinal cord injury (SCI) alone or in combination with testosterone-enanthate (SCI+TE) or sclerostin-antibody (SCI+Scl-Ab).

<p>Values are means ± SEM, n = 9-10/group. Letters a-d indicate differences from respectively labeled groups at p<0.05 or *p<0.01 (a = vs SHAM; b = vs SCI; c = vs SCI+TE; d = vs SCI+Scl-Ab).</p

Effects of pharmacologic sclerostin inhibition or testosterone administration on soleus muscle atrophy in rodents after spinal cord injury - Fig 6

<p>A-C. LDL receptor related protein 5 (LRP5) and 6 (LRP6), and androgen receptor (AR) gene expressions in tibia, levator ani/bulbocavernosus (LABC), and soleus from animals receiving sham surgery (T₈ laminectomy). Values are means ± SEM [corrected for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as the housekeeping gene] and expressed relative to the tibia, n = 6/tissue. Letters a-c indicate differences from respectively labeled groups at p<0.05 or *p<0.01 (a = vs Tibia; b = vs LABC; c = vs Soleus).</p