Cervical masses in dogs and cats 1. Investigation and management

Abnormalities in the cervical region can be challenging to investigate and manage; however, the area is a common location for disease processes in dogs and cats. The anatomy of this region can make investigations and treatment difficult and a thorough understanding of this is essential before embarking on management and treatment of conditions in this location. Due to the various anatomical structures in the cervical area, there is often a long potential differential diagnoses list for mass lesions in this region. It is important to perform a thorough and logical investigative process in order to manage these masses appropriately. This article discusses investigation and management of cervical masses, while a second article, to be published in a subsequent issue of In Practice, will focus on differential diagnoses

Anti-Sclerostin Antibody Treatment in a Rat Model of Progressive Renal Osteodystrophy

Chronic Kidney Disease (CKD) is associated with abnormalities in bone quantity and quality leading to increased fractures. Recent studies suggest abnormalities of Wnt signaling in animal models of CKD and elevated sclerostin levels in patients with CKD. The goal of this study was to evaluate the effectiveness of anti-sclerostin antibody treatment in an animal model of progressive CKD with low and high parathyroid hormone (PTH) levels. Cy/+ male rats (CKD) were treated without or with calcium in the drinking water at 25 weeks of age to stratify the animals into high PTH and low PTH groups, respectively, by 30 weeks. Animals were then treated with anti-sclerostin antibody at 100 mg/kg IV weekly for 5 doses, a single 20 ug/kg subcutaneous dose of zoledronic acid, or no treatment and sacrificed at 35 weeks. As a positive control, the efficacy of anti-sclerostin antibody treatment was also evaluated in normal littermates. The results demonstrated that the CKD animals with high PTH had lower calcium, higher phosphorus, and lower FGF23 compared to the CKD animals with low PTH. Treatment with anti-sclerostin Ab had no effect on any of the biochemistries, while zoledronic acid lowered dkk-1 levels. The anti-sclerostin antibody increased trabecular BV/TV., trabecular mineralization surface, in animals with low, but not high, PTH. Neither anti-sclerostin antibody nor zoledronic acid improved biomechanical properties in the animals. Cortical porosity was severe in high PTH animals and unaffected by either treatment. In contrast, in normal animals treated with anti-sclerostin antibody, there was an improvement in bone volume, cortical geometry, and biomechanical properties. In summary, this is the first study to test the efficacy of anti-sclerostin Ab treatment on animals with advanced CKD. We found efficacy in improving bone properties only when the PTH levels were low.NIH AR 058005 and Novartis

Anabolic Therapies

The striking clinical benefits of intermittent parathyroid hormone in osteoporosis have begun a new era of skeletal anabolic agents. Recombinant human parathyroid hormone (rhPTH) (1–34) is the first US Food and Drug Administration–approved anabolic therapy. Its use has been limited by the need for subcutaneous injection. Newer delivery systems include transdermal and oral preparations. Newer anabolic therapies include monoclonal antibody to sclerostin, a potent inhibitor of osteoblastogenesis; and use of bone morphogenetic proteins and parathyroid hormone–related protein PTHrP, a calcium-regulating hormone similar to PTH

The Appearance and Modulation of Osteocyte Marker Expression during Calcification of Vascular Smooth Muscle Cells

Vascular calcification is an indicator of elevated cardiovascular risk. Vascular smooth muscle cells (VSMCs), the predominant cell type involved in medial vascular calcification, can undergo phenotypic transition to both osteoblastic and chondrocytic cells within a calcifying environment.In the present study, using in vitro VSMC calcification studies in conjunction with ex vivo analyses of a mouse model of medial calcification, we show that vascular calcification is also associated with the expression of osteocyte phenotype markers. As controls, the terminal differentiation of murine calvarial osteoblasts into osteocytes was induced in vitro in the presence of calcifying medium (containing ß-glycerophosphate and ascorbic acid), as determined by increased expression of the osteocyte markers DMP-1, E11 and sclerostin. Culture of murine aortic VSMCs under identical conditions confirmed that the calcification of these cells can also be induced in similar calcifying medium. Calcified VSMCs had increased alkaline phosphatase activity and PiT-1 expression, which are recognized markers of vascular calcification. Expression of DMP-1, E11 and sclerostin was up-regulated during VSMC calcification in vitro. Increased protein expression of E11, an early osteocyte marker, and sclerostin, expressed by more mature osteocytes was also observed in the calcified media of Enpp1(-/-) mouse aortic tissue.This study has demonstrated the up-regulation of key osteocytic molecules during the vascular calcification process. A fuller understanding of the functional role of osteocyte formation and specifically sclerostin and E11 expression in the vascular calcification process may identify novel potential therapeutic strategies for clinical intervention

Rapamycin and the transcription factor C/EBPβ as a switch in osteoclast differentiation: implications for lytic bone diseases

Lytic bone diseases and in particular osteoporosis are common age-related diseases characterized by enhanced bone fragility due to loss of bone density. Increasingly, osteoporosis poses a major global health-care problem due to the growth of the elderly population. Recently, it was found that the gene regulatory transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) is involved in bone metabolism. C/EBPβ occurs as different protein isoforms of variable amino terminal length, and regulation of the C/EBPβ isoform ratio balance was found to represent an important factor in osteoclast differentiation and bone homeostasis. Interestingly, adjustment of the C/EBPβ isoform ratio by the process of translational control is downstream of the mammalian target of rapamycin kinase (mTOR), a sensor of the nutritional status and a target of immunosuppressive and anticancer drugs. The findings imply that modulating the process of translational control of C/EBPβ isoform expression could represent a novel therapeutic approach in osteolytic bone diseases, including cancer and infection-induced bone loss

Retinoic Acid Increases Proliferation of Human Osteoclast Progenitors and Inhibits RANKL-Stimulated Osteoclast Differentiation by Suppressing RANK

It has been shown that high vitamin A intake is associated with bone fragility and fractures in both animals and humans. However, the mechanism by which vitamin A affects bones is unclear. In the present study, the direct effects of retinoic acid (RA) on human and murine osteoclastogenesis were evaluated using cultured peripheral blood CD14+ monocytes and RAW264.7 cells. Both the activity of the osteoclast marker tartrate resistant acid phosphatase (TRAP) in culture supernatant and the expression of the genes involved in osteoclast differentiation together with bone resorption were measured. To our knowledge, this is the first time that the effects of RA on human osteoclast progenitors and mature osteoclasts have been studied in vitro. RA stimulated proliferation of osteoclast progenitors both from humans and mice. In contrast, RA inhibited differentiation of the receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclastogenesis of human and murine osteoclast progenitors via retinoic acid receptors (RARs). We also show that the mRNA levels of receptor activator of nuclear factor κB (RANK), the key initiating factor and osteoclast associated receptor for RANKL, were potently suppressed by RA in osteoclast progenitors. More importantly, RA abolished the RANK protein in osteoclast progenitors. This inhibition could be partially reversed by a RAR pan-antagonist. Furthermore, RA treatment suppressed the expression of the transcription factor nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) and increased the expression of interferon regulatory factor-8 (IRF-8) in osteoclast progenitors via RARs. Also, RA demonstrated differential effects depending on the material supporting the cell culture. RA did not affect TRAP activity in the culture supernatant in the bone slice culture system, but inhibited the release of TRAP activity if cells were cultured on plastic. In conclusion, our results suggest that retinoic acid increases proliferation of human osteoclast progenitors and that it inhibits RANK-stimulated osteoclast differentiation by suppressing RANK

Osseointegration of biochemically modified implants in an osteoporosis rodent model

The present study examined the impact of implant surface modifications on osseointegration in an osteoporotic rodent model. Sandblasted, acid-etched titanium implants were either used directly (control) or were further modified by surface conditioning with NaOH or by coating with one of the following active agents: collagen/chondroitin sulphate, simvastatin, or zoledronic acid. Control and modified implants were inserted into the proximal tibia of aged ovariectomised (OVX) osteoporotic rats (n = 32/group). In addition, aged oestrogen competent animals received either control or NaOH conditioned implants. Animals were sacrificed 2 and 4 weeks post-implantation. The excised tibiae were utilised for biomechanical and morphometric readouts (n = 8/group/readout). Biomechanical testing revealed at both time points dramatically reduced osseointegration in the tibia of oestrogen deprived osteoporotic animals compared to intact controls irrespective of NaOH exposure. Consistently, histomorphometric and microCT analyses demonstrated diminished bone-implant contact (BIC), peri-implant bone area (BA), bone volume/tissue volume (BV/TV) and bone-mineral density (BMD) in OVX animals. Surface coating with collagen/chondroitin sulphate had no detectable impact on osseointegration. Interestingly, statin coating resulted in a transient increase in BIC 2 weeks post-implantation; which, however, did not correspond to improvement of biomechanical readouts. Local exposure to zoledronic acid increased BIC, BA, BV/TV and BMD at 4 weeks. Yet this translated only into a non-significant improvement of biomechanical properties. In conclusion, this study presents a rodent model mimicking severely osteoporotic bone. Contrary to the other bioactive agents, locally released zoledronic acid had a positive impact on osseointegration albeit to a lesser extent than reported in less challenging models

Cortical and cancellous bone in the human femoral neck: Evaluation of an interactive image analysis system

An interactive image analysis package was developed to examine whole cross-sections from the femoral neck. The package quantifies cortical width (Ct.Wi), cortical porosity (Ct.Po), and proportions of cortical, cancellous bone as a percentage of bone plus marrow area. Segmental analysis was used to quantify circumferential variations in bone distribution within the femoral cross-section. To evaluate reproducibility of data four independent operators analyzed previously prepared femoral neck sections from a 2000 BC population. Differences in total and circumferential distributions of cortical and cancellous bone with respect to gender and age of samples were demonstrated. Reproducibility was assessed using coefficients of variation (CV). Analysis of sections using a variable magnification, giving largest possible image size, rather than a set magnification reduced variation between operators for all measurements. Use of a calculated threshold significantly decreased variation between operators for the proportions of cortical and cancellous bone (p ≤ 0.026). Dividing the image into 8 rather than 16 segments also improved reproducibility. There was little agreement between operators in the determination of cortical porosity. The mean CV for the other quantitative indices such as cortical width and proportions of cortical and cancellous bone ranged from 4.87% to 13.52%. The genders showed similar patterns in circumferential distribution of bone. Cortical width was significantly greater in the inferior region compared to the other areas, whereas percent cortical bone was lowest at the superior region. The center of mass (COM) for the younger age group was located anteriorly, whereas in the older samples the COM was located posteriorly of the center of area (p = 0.041). Basic data relating to cortical and cancellous bone of acceptable reproducibility in comparison with current standards in iliac histomorphometry can now be pro-vided at modest cost in operator time and resources. © 1996 by Elsevier Science Inc