Regulation of differentiation of hard-tissue-constituting cells by pH regulating proteins. Clarification of the mechanism and its application for regenerative medicine.

我们发现碳酸氢酶-9(CA9)在小鼠软骨细胞中表达，单羧酸转运蛋白-1(MCT1)在成骨细胞中表达。因此，我们分别研究了CA9和MCT1在软骨细胞和成骨细胞分化中的作用。CA9在小鼠生长板的增殖期软骨细胞中表达，而在肥大的软骨细胞中不表达。通过其siRNA抑制CA9的表达，诱导小鼠原代软骨细胞肥大分化，提示CA9具有抑制软骨细胞肥大分化的作用。抑制小鼠成骨细胞中MCT1的表达导致碱性磷酸酶(ALP)表达降低，而MCT1底物乳酸增强成骨细胞中ALP的表达。我们还发现，在骨形态发生蛋白-2刺激后，MCT1正向调节成骨细胞中Smad1/5/8的磷酸化和核转位。

We found that carbonic anhydrase-9 (CA9) is expressed in mouse chondrocytes and monocarboxylate transporter-1 (MCT1) in osteoblasts, respectively. Hence we investigated the roles of CA9 and MCT1 in differentiation of chondrocytes and osteoblasts, respectively. CA9 was expressed in proliferating but not in hypertrophic chondrocytes in the growth plates of mice. Suppression of CA9 expression by its siRNA induced the hypertrophic differentiation in mouse primary chondrocytes, indicating that CA9 has a role to suppress hypertrophic differentiation of chondrocytes. Suppression of the expression of MCT1 in mouse osteoblasts induced lowered expression of alkaline phosphatase (ALP), while lactate, an MCT1 substrate, augmented the expression of ALP in osteoblasts. We also found that MCT1 positively regulates phosphorylation and nuclear translocation of Smad1/5/8 in osteoblasts after stimulation by bone morphogenetic protein-2.