一种含双歧杆菌种属特异性复制子的新型大肠杆菌-双歧杆菌穿梭质粒的构建

目前,双歧杆菌的转化是一个技术难题,与大肠杆菌等宿主菌的高转化效率不同,采用普通的原核质粒无法转化双歧杆菌.为此,本文提出双歧杆菌转化对质粒复制子具有"种属特异性"要求,并通过构建含有双歧杆菌特异复制子的新型穿梭质粒,以求解决这一难题.首先从GenBank获取长双歧杆菌隐性质粒pMB1的序列信息,采用Overlap-PCR方法获得其全长DNA,作为拟构建质粒的复制子;继而采用重组技术,将其与pMK4质粒片段(含大肠杆菌复制子pUC和抗氯霉素基因Cat)重组,构建大肠杆菌-双歧杆菌穿梭质粒;用电穿孔法将重组质粒转化双歧杆菌,通过观察不同电转参数下的转化效率,选择双歧杆菌转化的最佳条件.结果,成功获得全长1899bp的pMB1复制子并构建成功含有pMB1和pUC双复制子的原核重组质粒,经酶切和测序鉴定正确,命名为pCMB1.以重组质粒成功转化了长双歧杆菌NCC2705和NQ1501,而其它3种野生型双歧杆菌(包括1株长双歧杆菌)未能转化成功.结论:质粒中含有双歧杆菌种属特异的复制子是实现双歧杆菌转化的必要条件;即使是含有特异复制子的质粒也只能转化有限数量种型甚至有限数量种株的双歧杆菌;选择最佳电转化条件能显著提高转化效率.     

四氧嘧啶诱导糖尿病小鼠的胰岛素原基因治疗

为了解决基因治疗中的安全性问题 ,和寻求一种简便而又经济的糖尿病基因治疗模式 ,采用腹腔注射四氧嘧啶的方法 ,以昆明小鼠为实验对象 ,成功地建立了糖尿病小鼠模型 .通过电穿孔的基因转移 ,将含有胰岛素原cDNA的质粒pCMV IN转移到这些小鼠的股四头肌 .反转录PCR的结果表明 ,转基因在转染部位有转录活性 ,而放射免疫分析结果却表明转基因的表达产物分泌进了小鼠的血循环系统之中 .血糖浓度的变化说明 ,这些产物具有明显的降血糖效果 .在电基因转移前对转移部位用透明质酸酶处理 ,使电激时的使用电压降低 ,增加了转移效果 ,也更加安全 .     

A thyrotoxic skeletal phenotype of advanced bone formation in mice with resistance to thyroid hormone

Thyroid hormone (T3) regulates bone turnover and mineralization in adults and is essential for skeletal development during childhood. Hyperthyroidism is an established risk factor for osteoporosis. Nevertheless, T3 actions in bone remain poorly understood. Patients with resistance to thyroid hormone, due to mutations of the T3-receptor beta (TRbeta) gene, display variable phenotypic abnormalities, particularly in the skeleton. To investigate the actions of T3 during bone development, we characterized the skeleton in TRbetaPV mutant mice. TRbetaPV mice harbor a targeted resistance to thyroid hormone mutation in TRbeta and recapitulate the human condition. A severe phenotype, which includes shortened body length, was evident in homozygous TRbetaPV/PV animals. Accelerated growth in utero was associated with advanced endochondral and intramembranous ossification. Advanced bone formation resulted in postnatal growth retardation, premature quiescence of the growth plates, and shortened bone length, together with increased bone mineralization and craniosynostosis. In situ hybridization demonstrated increased expression of fibroblast growth factor receptor-1, a T3-regulated gene in bone, in TRbetaPV/PV perichondrium, growth plate chondrocytes, and osteoblasts. Thus, the skeleton in TRbetaPV/PV mice is thyrotoxic and displays phenotypic features typical of juvenile hyperthyroidism.     

Gene therapy for diabetic rats by electroporational transfer of naked plasmid with human pre-pro-insulin gene into skeletal muscle

A naked plasmid with human pre-pro-insulin gene was transferred into skeletal muscle of diabetic rats by electric pulses and gene expression was detected. Blood glucose concentration was decreased from 24 mmol l^–1 to 8.5 mmol l^–1. Circulating insulin-like protein was increased significantly to 15–20 U ml^–1, while that of the control group injected with the empty vector remained at less than 10 U ml^–1. The low blood glucose concentration lasted for more than two months. These studies indicate that electroporational transfer of plasmid with human pre-pro-insulin gene into skeletal muscle could be a potential method of gene therapy for human diabetes mellitus.     

Influence of parathyroid hormone and heparin on tooth development in mice homozygous for the microphthalmia mutation]

In mice, homozygous by microphthalmia (mi/mi) gene the disturbance of dental development was due to defects in dental pulp and to the absence of bone resorpion. Administration of heparin or parathyroid hormone stimulated dental eruption in mi/mi mice. Following combined action of heparin and parathyroid hormone the number of erupted teeth was practically the same as after the action of heparin alone. Possibly the level of heparin is insufficient, but secretion of parathyroid hormone is unimpaired in mi/mi mice.     

Long-term follow-up of childhood-onset hypopituitarism in patients with the PROP-1 gene mutation

OBJECTIVE: The PROP-1 gene mutation is a rare disorder leading to combined pituitary hormone deficiencies over time. The aim was to analyze the clinical picture of 40 years of an almost untreated PROP-1 gene mutation. METHODS: We describe the clinical and hormonal data of 2 brothers from childhood to adulthood as well as imaging procedures (MRI of the pituitary gland, bone mineral density by QCT and DPX). The PROP-1 gene mutation (301-302delAG) was confirmed by DNA sequencing. RESULTS: Although long-standing untreated hypopituitarism was present, there was normal physical and professional activity. Bone mineral density was low only in 1 patient. Adrenocortical deficiency occurred late at 45 and 39 years. CONCLUSIONS: The biological evolution of the PROP-1 gene mutation illustrates the importance of continuous care for these patients. Hormonal deficiencies do not necessarily lead to the same phenotype as is obvious in differences of bone age and bone mineral density.     

甲状腺素及维甲酸对成骨样细胞甲状旁腺素受体的调节作用

研究了甲状腺素（T3／T4）及维甲酸（RA）对大鼠成骨样细胞ROS17／2．8细胞林甲状旁腺素（PTH）受体的调节作用．实验结果表明：细胞经T3／T4处理后,可显著增高PTH受体结合率及碱性磷酸酶活性,以及PTH受体mRNA的表达．细胞经RA处理后,则相反地降低PTH受体结合率及碱性磷酸酶活性．     

IL-6 is not required for parathyroid hormone stimulation of RANKL expression, osteoclast formation, and bone loss in mice

Continuous elevation of parathyroid hormone (PTH) increases osteoclast precursors, the number of osteoclasts on cancellous bone, and bone turnover. The essential molecular mediators of these effects are controversial, however, and both increased receptor activator of NF-kappaB ligand (RANKL) and IL-6 have been implicated. The goal of these studies was to determine whether continuous elevation of endogenous PTH alters IL-6 gene expression in vivo and whether IL-6 is required for PTH-induced bone loss. To accomplish this, we generated transgenic mice harboring a luciferase reporter gene under the control of IL-6 gene regulatory regions to allow accurate quantification of IL-6 gene activity in vivo. In these mice, induction of secondary hyperparathyroidism using a calcium-deficient diet did not alter IL-6-luciferase transgene expression, whereas RANKL mRNA expression was elevated in bone tissue. Moreover, secondary hyperparathyroidism induced an equivalent amount of bone loss in wild-type and IL-6-deficient mice, and PTH elevated RANKL mRNA and osteoclast formation to the same extent in bone marrow cultures derived from wild-type and IL-6-deficient mice. These results demonstrate that IL-6 is not required for the osteoclast formation and bone loss that accompanies continuous elevation of PTH.     

Disproportional skeletal growth and markedly decreased bone mineral content in growth hormone receptor -/- mice

Growth hormone (GH) is important for skeletal growth as well as for a normal bone metabolism in adults. The skeletal growth and adult bone metabolism was studied in mice with an inactivated growth hormone receptor (GHR) gene. The lengths of femur, tibia, and crown-rump were, as expected, decreased in GHR-/- mice. Unexpectedly, GHR-/- mice displayed disproportional skeletal growth reflected by decreased femur/crown-rump and femur/tibia ratios. GHR-/- mice demonstrated decreased width of the growth plates in the long bones and disturbed ossification of the proximal tibial epiphysis. Furthermore, the area bone mineral density (BMD) as well as the bone mineral content (BMC)/body weight were markedly decreased in GHR-/- mice. The decrease in BMC in GHR-/- mice was not due to decreased trabecular volumetric BMD but to a decreased cross-sectional cortical bone area In conclusion, GHR-/- mice demonstrate disproportional skeletal growth and markedly decreased bone mineral content.     

Bone loss induced by ovariectomy in rats is prevented by gene transfer of parathyroid hormone or an Arg-Gly-Asp-containing peptide

Osteoporosis is a major and growing healthcare concern as the population ages. The genes of both a Arg-Gly-Asp (RGD)-containing peptide and parathyroid hormone (PTH) were used to reduce bone loss induced by ovariectomy (OVX) in rats. Plasmids with either RGD or PTH gene were delivered into the quadriceps of OVX rats. The expression of the genes was detected by RT-PCR and radioimmunoassay. Analysis of bone mineral density, bone mechanical testing and bone mineral content indicated an improvement in bone properties in both RGD-transferred and PTH-transferred rats compared to OVX rats. Gene transfer of either RGD or PTH is therefore a possible approach to prevent bone loss in OVX rats thus providing a potential method to prevent osteoporosis in clinical situations.These authors contributed equally to this work     

Thyroid hormone excess rather than thyrotropin deficiency induces osteoporosis in hyperthyroidism

Thyrotoxicosis is an important but under recognized cause of osteoporosis. Recently, TSH deficiency, rather than thyroid hormone excess, has been suggested as the underlying cause. To investigate the molecular mechanism of osteoporosis in thyroid disease, we characterized the skeleton in mice lacking either thyroid hormone receptor alpha or beta (TRalpha(0/0), TRbeta-/-). Remarkably, in the presence of normal circulating thyroid hormone and TSH concentrations, adult TRalpha(0/0) mice had osteosclerosis accompanied by reduced osteoclastic bone resorption, whereas juveniles had delayed endochondral ossification with reduced bone mineral deposition. By contrast, adult TRbeta-/- mice with elevated TSH and thyroid hormone levels were osteoporotic with evidence of increased bone resorption, whereas juveniles had advanced ossification with increased bone mineral deposition. Analysis of T3 target gene expression revealed skeletal hypothyroidism in TRalpha(0/0) mice, but skeletal thyrotoxicosis in TRbeta-/- mice. These studies demonstrate that bone loss in thyrotoxicosis is independent of circulating TSH levels and mediated predominantly by TRalpha, thus identifying TRalpha as a novel drug target in the prevention and treatment of osteoporosis.     

Thyroid hormone treatment of cultured chondrocytes mimics in vivo stimulation of collagen X mRNA by increasing BMP 4 expression

During endochondral bone formation, chondrocytes undergo terminal differentiation, during which the rate of proliferation decreases, cells become hypertrophic, and the extracellular matrix is altered by production of collagen X, as well as proteins required for matrix mineralization. This maturation process is responsible for most longitudinal bone growth, both during embryonic development and in postnatal long bone growth plates. Among the major signaling molecules implicated in regulation of this process are the positive regulators thyroid hormone (T3) and bone morphogenetic proteins (BMPs). Both T3 and BMPs are essential for endochondral bone formation and cannot compensate for each other, suggesting interaction of the two signaling pathways. We have analyzed the temporal and spatial expression patterns of numerous genes believed to play a role in chondrocyte maturation. Our results show that T3 stimulates collagen X gene expression in cultured chondrocytres with kinetics and magnitude similar to those observed in vivo. Stimulation of collagen X gene expression by T3 occurs only after a significant delay, implying that this hormone may act indirectly. We show further that T3 rapidly stimulates production of BMP 4, concomitant with a decrease in the BMP inhibitor Noggin, potentially resulting in a net increase in BMP signaling. Finally, inhibition of BMP signaling with exogenous Noggin prevents T3 stimulation of collagen X expression, indicating that BMP signaling is essential for this process. These data position thyroid hormone at the top of a T3/BMP cascade, potentially explaining why both pathways are essential for chondrocyte maturation. J. Cell. Physiol. 219: 595–605, 2009. © 2009 Wiley‐Liss, Inc.     

Leptin is a potent stimulator of bone growth in ob/ob mice

Leptin, the product of the obese gene, is a circulating hormone secreted primarily from adipocytes. The lack of leptin in ob/ob mice, who are homozygous for the obese gene, results in hyperglycemia, hyperinsulinemia, hyperphagia, obesity, infertility, decreased brain size and decreased stature. To this end, we investigated the role of leptin as a hormonal regulator of bone growth. Leptin administration led to a significant increase in femoral length, total body bone area, bone mineral content and bone density in ob/ob mice as compared to vehicle treated controls. The increase in total body bone mass was a result of an increase in both trabecular and cortical bone mass. These results suggest that the decreased stature of the ob/ob mouse is due to a developmental defect that is readily reversible upon leptin administration. Our demonstration that the signalling or long form (Ob-Rb) of the leptin receptor is present in both primary adult osteoblasts and chondrocytes suggests that the growth promoting effects of leptin could be direct. In summary, these results indicate a novel role for leptin in skeletal bone growth and development.     

Direct transcriptional targets of sex steroid hormones in bone

The sex steroid hormones, androgens and estrogens, via their respective nuclear receptors, regulate bone mineral density in humans and mice. Very little is known about the direct targets of the androgen and estrogen receptors in bone cells. First, models of hormone and receptor deficiency in mouse and human bone are discussed. This review then focuses on the direct targets of the receptors in osteoblasts and osteoclasts. A direct target of a NR is defined here as a gene that is regulated by NR binding to the DNA (either through DNA binding or association with a DNA binding protein) at an enhancer or promoter of that gene. The experimental evidence that illustrates androgen and estrogen gene regulation in osteoblasts and osteoclasts will be summarized and compared with the phenotype of the hormones in vivo.