Ilsong Institute of Life Science, Hallym University, Anyang, Gyeonggi-do 14066, Republic of Korea.
Department of Biomedical Gerontology, Graduate School of Hallym University, Chuncheon, Gangwon-do 24252, Republic of Korea.
Int J Med Sci. 2021 Feb 4;18(7):1580-1591. doi: 10.7150/ijms.53650. eCollection 2021.
Melanotransferrin (CD228), firstly reported as a melanoma-associated antigen, is a membrane-bound glycoprotein of an iron-binding transferrin homolog. CD228 was found to be expressed significantly higher in human bone marrow-derived mesenchymal stem cells (hBM-MSC) than in human embryonic fibroblasts (FB) by RT-PCR, western blotting and flow cytometry. The expression of CD228 declined in aged hBM-MSC as osteogenesis-related genes did. We examined a possible role for CD228 in the regulation of osteogenesis and adipogenesis of hBM-MSC. Surprisingly, siRNA-mediated CD228 knockdown increased the expression of the transcription factor DLX5 and enhanced osteogenesis of hBM-MSC evidenced by an increased expression of the runt-related transcription factor 2 (RUNX2), osterix (Osx), and osteocalcin (OC), as well as higher alkaline phosphatase (ALP) activity and extracellular calcium deposition. Interestingly, hBM-MSC transfected with CD228 siRNA also showed an increase in intracellular lipid level during adipogenesis, indicated by oil red O staining of differentiated adipocytes. Overall, our study unveils CD228 as a cell surface molecule expressed by young hBM-MSC, but not by FB. It also provides evidence to suggest a role for CD228 as a negative regulator of osteogenesis and of lipid accumulation during adipogenesis in hBM-MSC
黑素转铁蛋白（CD228）最初被报道为一种黑色素瘤相关抗原，是一种铁结合转铁蛋白同源物的膜结合糖蛋白。通过 RT-PCR、western blot 和流式细胞术发现，CD228 在人骨髓间充质干细胞（hBM-MSC）中的表达明显高于人胚胎成纤维细胞（FB）。CD228 的表达随着成骨相关基因的表达而在衰老的 hBM-MSC 中下降。我们研究了 CD228 对 hBM-MSC 成骨和脂肪生成的调节作用。令人惊讶的是，siRNA 介导的 CD228 敲低增加了转录因子 DLX5 的表达，并增强了 hBM-MSC 的成骨作用，表现为 runt 相关转录因子 2（RUNX2）、osterix（Osx）和骨钙素（OC）的表达增加，以及碱性磷酸酶（ALP）活性和细胞外钙沉积增加。有趣的是，转染 CD228 siRNA 的 hBM-MSC 在脂肪生成过程中也表现出细胞内脂质水平的增加，这可以通过分化的脂肪细胞的油红 O 染色来证实。总的来说，我们的研究揭示了 CD228 作为一种年轻的 hBM-MSC 表面分子表达，但不表达于 FB。它还提供了证据表明 CD228 作为 hBM-MSC 成骨和脂肪生成过程中脂质积累的负调节剂的作用。
