Growth factor induced by high phosphate in cultured human parathyroid gland : gene analysis using cDNA microarray

1例低磷酸盐血症性骨软化症患者接受高磷酸盐治疗后，发生了第三性甲状旁腺功能亢进。四种甲状旁腺肥大的基因分析揭示了几种基因突变，表明高磷酸盐浓度刺激甲状旁腺生长，伴随着癌基因和肿瘤抑制基因的突变（I. d.为了阐明磷酸盐诱导的甲状旁腺细胞增殖，我们建立了从原发性或继发性甲状旁腺机能亢进患者获得的甲状旁腺组织的器官培养。在该器官培养物中，完整的PTH活跃分泌超过1个月。在生理上可达到的Ca^<++>水平下，高钙浓度会抑制完整的PTH分泌。当甲状旁腺组织与高磷酸盐培养基培养时，完整的PTH分泌增加，细胞增殖也受到刺激。基因芯片分析显示，IGF-1、AIF 1、FIGF等生长因子和细胞因子表达增加。我们正在分析高磷酸盐诱导的4800个基因，因为目前可获得更大量的总RNA（>30μg）。我们希望这些新发现将有助于阐明甲状旁腺细胞增殖的机制，并开发继发性甲状旁腺功能亢进的新治疗方法。在早期的一系列实验中，仅从甲状旁腺细胞培养中获得少量总RNA，我们分析了甲状腺滤泡中的2400个基因，其中很容易获得大量总RNA，并发现几种基因（包括朊病毒）由TSH诱导（参考文献2和3）。

A patient with hypophosphatemic osteomalacia, who was treated with high phosphate, developed tertiary hyperparathyroidism. Gene analysis of the four hyperparathyroid glands revealed several gene mutations, suggesting that high phosphate concentration stimulated parathyroid growth, accompanied with mutations of oncogenes and tumor suppressor genes (I.d. MEN1) (Reference 1).To clarify phosphate-induced cell proliferation of parathyroid gland, we established organ culture of parathyroid tissue obtained from patient with primary or secondary hyperparathyroidism. In this organ culture, intact PTH was actively secreted for more than 1 month. Intact PTH secretion was inhibited at high calcium concentration at physiologically attainable Ca^<++> levels. When parathyroid tissue were cultured with high phosphate medium, intact PTH secretion was increased and cell proliferation was also stimulated. Gene analyses of DNA microarray revealed that several growth factors (IGF-1, AIF1, FIGF) and cytokines were increased. We are analyzing 4800 genes induced by high phosphate since a greater amount of total RNA (>30μg) is available at the present time. We expect that these new findings will contribute to elucidate the mechanism of parathyroid cell proliferation, and to develop new treatments for secondary hyperparathyroidism.In early series of this experiments in which only a small amount of total RNA was obtained from parathyroid cell culture, we analyzed 2400 genes in thyroid follicles in which a large amount of total RNA was easily obtained, and found that several genes (including prion) are induced by TSH (reference 2 & 3).