Lee S K, Lorenzo J A
V.A. Connecticut Healthcare System, Newington 06111, USA.
Endocrinology. 1999 Aug;140(8):3552-61. doi: 10.1210/endo.140.8.6887.
We studied the effects of PTH on the expression of tumor necrosis factor-related activation-induced cytokine (TRANCE), osteoprotegerin (OPG), and receptor activator of NF kappaB (RANK) messenger RNA (mRNA) in cultured murine bone marrow, calvaria, and osteoblasts. TRANCE, OPG, and RANK are recently identified regulators of osteoclast formation. Bone marrow cells were cultured with or without PTH(1-34) for 6 days. TRANCE, OPG, and RANK mRNA were measured by RT-PCR. In 6-day cultures, PTH stimulated the number of OCL/well in a dose-dependent manner. A time course showed significant (P < 0.01) increases in OCL/well after 24 h of PTH (100 ng/ml). TRANCE mRNA expression, like OCL formation, increased dose dependently and was maximal, with 10-100 ng/ml PTH. In contrast, OPG mRNA expression was decreased by 0.1 ng/ml PTH (40%) and completely abolished by 1 ng/ml. TRANCE mRNA expression was rapidly stimulated by PTH (maximal response at 1 h, 8.1-fold over control). Expression declined by 40% at 24 h but was still much greater than control at 6 days (4.6-fold) in a time-course study. PTH caused a transient stimulation of OPG mRNA at 1 h (2-fold), which returned to basal levels by 2 h. After 6 h, PTH completely inhibited OPG mRNA. There were only minor effects of PTH on RANK mRNA expression. PTH had less potent effects on TRANCE and OPG mRNA expression in calvaria organ cultures and osteoblasts. In mouse calvaria cultures, TRANCE expression was detectable in controls and was increased 2.9-fold by PTH at 24 h. PTH treatment of calvaria decreased OPG expression by 30% at 6 h. MC3T3 E-1 osteoblastic cells expressed minimal levels of TRANCE mRNA either before or after PTH treatment. OPG mRNA was present in MC3T3 E-1 cells, but levels were not modulated by PTH. In primary osteoblastic cells, PTH stimulated TRANCE mRNA expression 4-fold at 2 h and inhibited OPG mRNA expression by 46%. These results demonstrate a tight correlation between the ability of PTH to stimulate OCL formation in marrow culture and expression of TRANCE (r = 0.87, P < or = 0.05) and OPG mRNA (r = -0.88, P < or = 0.05). Reciprocal regulation of TRANCE and OPG mRNA by PTH preceded its effects on OCL formation by 18-23 h. Hence, it is likely that PTH regulates bone resorption, at least in part, via its effects on TRANCE and OPG expression.
我们研究了甲状旁腺激素（PTH）对培养的小鼠骨髓、颅骨和成骨细胞中肿瘤坏死因子相关激活诱导细胞因子（TRANCE）、骨保护素（OPG）以及核因子κB受体激活剂（RANK）信使核糖核酸（mRNA）表达的影响。TRANCE、OPG和RANK是最近确定的破骨细胞形成调节因子。将骨髓细胞在有或无PTH(1 - 34)的条件下培养6天。通过逆转录聚合酶链反应（RT-PCR）检测TRANCE、OPG和RANK mRNA。在6天的培养中，PTH以剂量依赖的方式刺激每个孔中破骨细胞（OCL）的数量。时间进程显示，在加入PTH（100 ng/ml）24小时后，每个孔中的OCL数量显著增加（P < 0.01）。TRANCE mRNA表达与OCL形成一样，呈剂量依赖性增加，在PTH浓度为10 - 100 ng/ml时达到最大值。相比之下，0.1 ng/ml的PTH使OPG mRNA表达降低40%，而1 ng/ml的PTH则使其完全消失。PTH能迅速刺激TRANCE mRNA表达（1小时时达到最大反应，比对照高8.1倍）。在一项时间进程研究中，24小时时表达下降40%，但在6天时仍比对照高得多（4.6倍）。PTH在1小时时对OPG mRNA有短暂刺激作用（2倍），2小时时恢复到基础水平。6小时后PTH完全抑制OPG mRNA。PTH对RANK mRNA表达的影响较小。PTH对颅骨器官培养物和成骨细胞中TRANCE和OPG mRNA表达的作用较弱。在小鼠颅骨培养物中，对照中可检测到TRANCE表达，24小时时PTH使其增加2.9倍。PTH处理颅骨6小时后使OPG表达降低30%。MC3T3 E - 1成骨细胞在PTH处理前后TRANCE mRNA表达水平极低。MC3T3 E - 1细胞中有OPG mRNA，但PTH对其水平无调节作用。在原代成骨细胞中，PTH在2小时时刺激TRANCE mRNA表达4倍，并使OPG mRNA表达降低46%。这些结果表明，PTH在骨髓培养物中刺激OCL形成的能力与TRANCE（r = 0.87，P ≤ 0.05）和OPG mRNA（r = -0.88，P ≤ 0.05）的表达之间存在紧密相关性。PTH对TRANCE和OPG mRNA的相互调节作用比其对OCL形成的影响提前18 - 23小时。因此，PTH可能至少部分通过其对TRANCE和OPG表达的影响来调节骨吸收。
