Calvaria Derived Osteogenic Cells: Phenotypic Expression in Culture

The osteoblast phenotype is characterized by its ability to (a) synthesize a well defined mineralized collage nous matrix, (b) regulate the remodeling process by synthesizing local hormones (PGE₂) and specific molecules (osteocalcin) and enzymes (alkaline phosphatase and collagenase), (c) respond to a variety of hormones (PTH, PGs, vitamin-D metabolites, steroids and growth factors), (d) respond to mechanical stimulation. Most of osteoblast culture systems meet many of the above qualifications though most fail to show the PTH effect on DNA synthesis, (c), and mechanical stimulation, (d). Here we show that by using trypsin digestion and serum-containing low calcium medium (0.25 mM), all the above listed osteoblast phenotypic characteristics are demonstrated including their responsiveness to mechanical stimulation and the PTH effect on DNA synthesis.     

Psychopathology in individuals with post-traumatic headaches and other pain types

In this study, the psychological functioning of patients with chronic post-traumatic headache (PTH), chronic combination headache and chronic low back pain without headache, whose time of onset was similar, and a matched group of controls was investigated. The Symptom Checklist 90-Revised (SCL-90-R), State-Trait Anger Expression Inventory (STAXI), State-Trait Anxiety Inventory, Form Y (STAI-Y), and Beck Depression Inventory (BDI) were used to assess the degree of psychopathology. A MANOVA test indicated highly significant differences between groups. In general, the pain groups fell along a continuum with PTH subjects demonstrating the highest elevations, back pain subjects demonstrating the next highest elevations, and combination subjects demonstrating fewer elevations. A cluster analysis indicated that findings were best classified into four clusters, but no one pain diagnosis predominated in any cluster. Eighty-nine percent of controls were assigned to clusters 1 or 2, which revealed essentially normal scores on all tests. It is suggested that while chronic pain patients demonstrate more psychopathology than non-pain controls, a variety of coping styles exists within each pain group independent of diagnostic categorization.     

血液透析患者甲状旁腺激素水平与营养的关系研究

目的探讨血液透析患者甲状旁腺素与营养状况的关系,为提高患者透析充分而改善患者营养状况提供临床依据。方法①选择中山大学附属第一医院肾内科112例血液透析患者,测定患者透析前血清甲状旁腺(PTH)、血清白蛋白(ALB)、血红蛋白(Hb)、C-反应蛋(CRP)、转铁蛋白(TF);②人体指数学测量:肱二头肌皮褶(BSF)、肱三头肌皮褶(TSF)、上臂中部周径(MAC)、握力(HGS);③使用改良整体主观评估法(modifiedquantitativesubjectiveglobalassessment,MQSGA)评估患者营养状况;④测定患者透析前血清IGF-1、IGFBP3;⑤根据相关公式计算上臂中部肌肉周径(MAMC)、上臂中部肌肉面积(AMA);⑥统计分析PTH与各营养指标之间的直线相关和回归关系。结果PTH与MQSGA呈正相关(P<0.01),与ALB、MAC、MAMC、AMA呈负相关(P<0.05),与Hb呈显著负相关(P<0.001);PTH与MQSGA、Hb、MAMC、AMA之间存在回归关系(P<0.05)。结论PTH是影响血液透析患者营养状况的重要尿毒症毒素。     

Hydroxyapatite nanorods loaded with parathyroid hormone (PTH) synergistically enhance the net formative effect of PTH anabolic therapy

Parathyroid hormone (PTH) has been a major contributor to the anabolic therapy for osteoporosis, but its delivery to bone without losing activity and avoiding adverse local effects remain a challenge. Being the natural component of bone, use of hydroxyapatite for this purpose brings a major breakthrough in synergistic anabolism. This study focuses on synthesis, characterization and evaluation of in vitro and in vivo efficacy of PTH (1-34) adsorbed hydroxyapatite nanocarrier for synergistic enhancement in the anabolic activity of PTH for bone regeneration. The negative zeta potential of this nanocarrier facilitated its affinity to the Ca²⁺ rich bone tissue and solubilization at low pH enhanced specific delivery of PTH to the resorption pits in osteoporotic bone. In this process, PTH retained its anabolic effect and at the same time an increase in bone mineral content indicated enhancement of the net formative effect of the PTH anabolic therapy.     

Sost downregulation and local Wnt signaling are required for the osteogenic response to mechanical loading

Sclerostin, the Wnt signaling antagonist encoded by the Sost gene, is secreted by osteocytes and inhibits bone formation by osteoblasts. Mechanical stimulation reduces sclerostin expression, suggesting that osteocytes might coordinate the osteogenic response to mechanical force by locally unleashing Wnt signaling. To investigate whether sclerostin downregulation is a pre-requisite for load-induced bone formation, we conducted experiments in transgenic mice (TG) engineered to maintain high levels of SOST expression during mechanical loading. This was accomplished by introducing a human SOST transgene driven by the 8 kb fragment of the DMP1 promoter that also provided osteocyte specificity of the transgene. Right ulnae were subjected to in vivo cyclic axial loading at equivalent strains for 1 min/day at 2 Hz; left ulnae served as internal controls. Endogenous murine Sost mRNA expression measured 24 h after 1 loading bout was decreased by about 50% in TG and wild type (WT) littermates. In contrast, human SOST, only expressed in TG mice, remained high after loading. Mice were loaded on 3 consecutive days and bone formation was quantified 16 days after initiation of loading. Periosteal bone formation in control ulnae was similar in WT and TG mice. Loading induced the expected strain-dependent increase in bone formation in WT mice, resulting from increases in both mineralizing surface (MS/BS) and mineral apposition rate (MAR). In contrast, load-induced bone formation was reduced by 70-85% in TG mice, due to lower MS/BS and complete inhibition of MAR. Moreover, Wnt target gene expression induced by loading in WT mice was absent in TG mice. Thus, downregulation of Sost/sclerostin in osteocytes is an obligatory step in the mechanotransduction cascade that activates Wnt signaling and directs osteogenesis to where bone is structurally needed.     

Changes in 3-dimensional bone structure indices in hypoparathyroid patients treated with PTH(1-84): a randomized controlled study

Hypoparathyroidism (hypoPT) is characterized by a state of low bone turnover and high bone mineral density (BMD) despite conventional treatment with calcium supplements and active vitamin D analogues. To assess effects of PTH substitution therapy on 3‐dimensional bone structure, we randomized 62 patients with hypoPT into 24 weeks of treatment with either PTH(1‐84) 100 µg/day subcutaneously or similar placebo as an add‐on therapy. Micro‐computed tomography was performed on 44 iliac crest bone biopsies (23 on PTH treatment) obtained after 24 weeks of treatment. Compared with placebo, PTH caused a 27% lower trabecular thickness (p < 0.01) and 4% lower trabecular bone tissue density (p < 0.01), whereas connectivity density was 34% higher (p < 0.05). Trabecular tunneling was evident in 11 (48%) of the biopsies from the PTH group. Patients with tunneling had significantly higher levels of biochemical markers of bone resorption and formation. At cortical bone, number of Haversian canals per area was 139% higher (p = 0.01) in the PTH group, causing a tendency toward an increased cortical porosity (p = 0.09). At different subregions of the hip, areal BMD (aBMD) and volumetric BMD (vBMD), as assessed by dual‐energy X‐ray absorptiometry (DXA) and quantitative computed tomography (QCT), decreased significantly by 1% to 4% in the PTH group. However, at the lumbar spine, aBMD decreased by 1.8% (p < 0.05), whereas vBMD increased by 12.8% (p = 0.02) in the PTH compared with the placebo group. © 2012 American Society for Bone and Mineral Research.     

Proteoglycan 4: A dynamic regulator of skeletogenesis and parathyroid hormone skeletal anabolism

Proteoglycan 4 (Prg4), known for its lubricating and protective actions in joints, is a strong candidate regulator of skeletal homeostasis and parathyroid hormone (PTH) anabolism. Prg4 is a PTH‐responsive gene in bone and liver. Prg4 null mutant mice were used to investigate the impact of proteoglycan 4 on skeletal development, remodeling, and PTH anabolic actions. Young Prg4 mutant and wild‐type mice were administered intermittent PTH(1–34) or vehicle daily from 4 to 21 days. Young Prg4 mutant mice had decreased growth plate hypertrophic zones, trabecular bone, and serum bone formation markers versus wild‐type mice, but responded with a similar anabolic response to PTH. Adult Prg4 mutant and wild‐type mice were administered intermittent PTH(1–34) or vehicle daily from 16 to 22 weeks. Adult Prg4 mutant mice had decreased trabecular and cortical bone, and blunted PTH‐mediated increases in bone mass. Joint range of motion and animal mobility were lower in adult Prg4 mutant versus wild‐type mice. Adult Prg4 mutant mice had decreased marrow and liver fibroblast growth factor 2 (FGF‐2) mRNA and reduced serum FGF‐2, which were normalized by PTH. A single dose of PTH decreased the PTH/PTHrP receptor (PPR), and increased Prg4 and FGF‐2 to a similar extent in liver and bone. Proteoglycan 4 supports endochondral bone formation and the attainment of peak trabecular bone mass, and appears to support skeletal homeostasis indirectly by protecting joint function. Bone‐ and liver‐derived FGF‐2 likely regulate proteoglycan 4 actions supporting trabeculae formation. Blunted PTH anabolic responses in adult Prg4 mutant mice are associated with altered biomechanical impact secondary to joint failure. © 2012 American Society for Bone and Mineral Research