ABSTRACT
Objective To observe the expression of matrix gla protein(MGP) mRNA in primary osteoblasts of Sprague-Dawley (SD) rat in vitro after treatment with anti-osteoporosis agents [vitamin K2,PTH,1,25 (OH)2D3,and alendronate],and to investigate the potential role of MGP in the pathogenesis of osteoporosis.Methods Primary osteoblasts(OBs) were derived from sequential trypsin/collagenase-digested calvaria isolated from newborn SD rat (postnastal day 1-3).OBs of the second generation were identified by Van Gieson collagen staining,alkaline phosphatase(ALP) staining and calcified nodules staining.OBs of the fourth generation were selected to interfere with vitamin K2,PTH,1,25 (OH)2D3,and alendronate,then cultured for 24 h in mediums which contained various concentrations of vitamin K2 (10-7,10-6,and 10-5 mol/L),PTH (10-9,10-8,and 10-7 mol/L),1,25 (OH) 2D3(10-10,10-9,and 10-8mol/L),alendronate(10-6,10-5,and 10-4mol/L).After being cultured for 24 h,total RNA was extracted and examined by real-time quantitative RT-PCR.Results The primary cultured cells had typical morphological characters of osteoblast.van Gieson collagen staining,ALP staining,and calcified nodules staining were all positive.Vitamin K2,PTH,1,25 (OH)2D3,and alendronate could modulate the expression of MGP mRNA in osteoblasts in a dose-dependent fashion.MGP mRNA expressions were 2.56-fold,2.12-fold,and 1.57-fold with 10-5,10-6,and 10-7 mol/L of vitamin K2 treatment,respectively.The expressions were 6.78-fold,5.31-fold,and 2.23-fold with 10-7,10-8,and 10-9mol/L of PTH(1-34) treatment,8.93-fold,6.95-fold,and 3.47-fold with 10-8 10-9,and 10-10mol/L of 1,25 (OH)2D3 treatment,and 3.47-fold,2.49-fold,and 1.98-fold with 10-4,10-5,and 10-6mol/L of alendronate treatment.Conclusion Vitamin K2,PTH,1,25 (OH)2D3,and alendronate all canregulate MGP mRNA expression in calvarial osteoblasts in a dose-dependent manner.MGP seems to be a potent target of anti-osteoporosis agents,and involved in the pathogenesis of osteoporosis.
ABSTRACT
Objective To investigate the effect of estrogen on expression of matrix GLA protein (MGP)in ovariectomized Sprague-Dawley(SD)rats and the role of estrogen in improving postmenopausal osteoporosis.Methods Thirty-six SD female rats were allocated into 3 groups randomly,every 12 rats in ovariectomized group(OVX group),estrogen group(E group)and control group(sham group).Rats in OVX and E group all underwent bilateral ovariectomy,those rats in E group were given by estradiol benzoate intramuscularly after 3 weeks of ovariectomy.Rats in sham group underwent bilateral lipectomy near the ovary.All rats were kept the urine and the serum every three weeks and were sacrificed after 15 weeks.The pathology changes of uterus,lumbar vertebral bones were observed by immunohistochemistry.Bone mineral density(BMD)of lumbar vertebra of rats was determined by dual energy X ray absorptiometry(DEXA).The content of MGP in serum and urine was determined by ELISA.Expression of underearboxylated matrix GLA Protein(MGP)was detected by immunohistochemistry.Relative quantification of MGP mRNA expression in lumbar vertebra bone was detected by Fluorescent real-time quantitative polymerase chain reaction.Results(1)After 15 weeks of ovariectomized,the endometrium of uterus and lumbar vertebra exhibit remarkable pathologic changes in OVX group.The serum estrogen of(454±66)pmol/L in OVX group were lower than in(527 ±77)pmol/L in sham group and(556 ±80)pmol/L in E group significantly (P ＜ 0.05).The BMD of lumbar vertebra of(0.263 ± 0.030)g/cm2 in OVX group were lower than (0.295 ±0.024)g/cm2 in sham group and(0.279 ±0.024)g/cm2 in E group significantly(P ＜0.01).(2)The serum MPG protein in OVX group and E group showed decreased trends after ovariectomized,which were(104 ±64)ng/L in OVX group and(134 ±6)ng/L in E group at 9 weeks,which reached statistical difference(P ＜ 0.05).However,MGP in urine in sham group did not exhibit significant difference after 15 weeks of surgery(P ＞0.05).The MGP in urine of E group showed increased trends after 12 weeks of surgery,which reached(110.0 ±3.4)ng/L at 15 weeks,in the mean time,it was found that(86.5 ±2.5)ng/L of MGP in urine in OVX group,which showed significant difference(P ＜ 0.05).(3)MGP could be observed in lumbar vertebra in OVX group by immunochemistry staining.In the other two groups,the expression of MGP was not dominant.(4)Relative quantification of MGP mRNA expression in lumbar vertebra was defined as 1 in OVX group,when compared with 0.289 ±0.260 in E group and 0.103 ±0.098 in sham group,the difference showed statistically significant(P ＜ 0.01).Conclusion Estrogen could increase the expression of MGP mRNA and protein in ovariectomized rats and might play an important role in improving postmenopausal osteoporosis.
ABSTRACT
ObjectiveTo observe the effect of parathyroid hormone on expression of matrix GLA protein (MGP) in ovariectomized SD rats and primary osteoblast,and to study the role of MGP on the possible mechanism of postmenopausal osteoporosis.MethodsThirty-six Sprague-Dawley female rats were allocated into 3 groups,12 in each:sham operation group,ovariectomized group( OVX group),ovariectomized and parathyroid hormone treatment group.Animals in the parathyroid hormone group were injected parathyroid hormone (20 μg/kg,three times a week for 12 weeks) three weeks after ovariectomy.All rats were sacrificed after 18 weeks.Urine and serum were collected every three weeks.Lumbar vertebral bones were observed by immunohistochemistry.Bone mineral density (BMD) of lumbar vertebra of rats was determined.The content of MGP in serum and urine was determined by enzyme-linked immunosorbent assay (ELISA).Expression of undercarboxylated Matrix GLA Protein (ucMGP) was detected by immunochistochemistry.Relative quantification of MGP mRNA expression in lumbar vertebra bone was detected by Fluorescent real-time quantitative polymerause chain reaction.Results ( 1 ) 18 weeks after ovariectomy,BMD of lumbar vertebra in OVX group was lower than those in sham group and parathyroid hormone group significantly ( P＜0.05 ).(2) The content of MGP in serum and urine was dynamic variation after treatment hy parathyroid hormone,and it was significant compared with OVX group ( P＜0.05 ).( 3 ) Immunohistochemical localization of ucMGP was seen in lumbar vertebra in OVX group.(4) Relative quantification of MGP mRNA expression in lumbar vertebra in OVX group was increased significantly compared with other groups ( P＜0.01 ).( 5 ) parathyroid hormone ( 1-34 ) in 10-7mol/L,10-8mol/L,10-9 mol/L up-regulated MGP mRNA expression in primary osteoblasts about 6.78,5.31,and 2.23 times than control respectively.It was in a dose-dependent manner.ConclusionThe effect of parathyroid hormone on the expression of matrix gla protein may play an important role in mechanism of postmenopausal osteoporosis