Qian Guofeng, Fan Wei, Ahlemeyer Barbara, Karnati Srikanth, Baumgart-Vogt Eveline
Institute for Anatomy and Cell Biology, Medical Cell Biology, Justus-Liebig-University, Aulweg 123, 35385 Giessen, Germany.
PLoS One. 2015 Dec 2;10(12):e0143439. doi: 10.1371/journal.pone.0143439. eCollection 2015.
Ossification defects leading to craniofacial dysmorphism or rhizomelia are typical phenotypes in patients and corresponding knockout mouse models with distinct peroxisomal disorders. Despite these obvious skeletal pathologies, to date no careful analysis exists on the distribution and function of peroxisomes in skeletal tissues and their alterations during ossification. Therefore, we analyzed the peroxisomal compartment in different cell types of mouse cartilage and bone as well as in primary cultures of calvarial osteoblasts. The peroxisome number and metabolism strongly increased in chondrocytes during endochondral ossification from the reserve to the hypertrophic zone, whereas in bone, metabolically active osteoblasts contained a higher numerical abundance of this organelle than osteocytes. The high abundance of peroxisomes in these skeletal cell types is reflected by high levels of Pex11β gene expression. During culture, calvarial pre-osteoblasts differentiated into secretory osteoblasts accompanied by peroxisome proliferation and increased levels of peroxisomal genes and proteins. Since many peroxisomal genes contain a PPAR-responsive element, we analyzed the gene expression of PPARɑ/ß/ɣ in calvarial osteoblasts and MC3T3-E1 cells, revealing higher levels for PPARß than for PPARɑ and PPARɣ. Treatment with different PPAR agonists and antagonists not only changed the peroxisomal compartment and associated gene expression, but also induced complex alterations of the gene expression patterns of the other PPAR family members. Studies in M3CT3-E1 cells showed that the PPARß agonist GW0742 activated the PPRE-mediated luciferase expression and up-regulated peroxisomal gene transcription (Pex11, Pex13, Pex14, Acox1 and Cat), whereas the PPARß antagonist GSK0660 led to repression of the PPRE and a decrease of the corresponding mRNA levels. In the same way, treatment of calvarial osteoblasts with GW0742 increased in peroxisome number and related gene expression and accelerated osteoblast differentiation. Taken together, our results suggest that PPARß regulates the numerical abundance and metabolic function of peroxisomes via Pex11ß in parallel to osteoblast differentiation.
导致颅面畸形或肢根短小的骨化缺陷是患有不同过氧化物酶体疾病的患者及相应基因敲除小鼠模型的典型表型。尽管存在这些明显的骨骼病变，但迄今为止，尚未对过氧化物酶体在骨骼组织中的分布和功能及其在骨化过程中的变化进行仔细分析。因此，我们分析了小鼠软骨和骨的不同细胞类型以及颅盖成骨细胞原代培养物中的过氧化物酶体区室。在软骨内骨化过程中，从储备区到肥大区，软骨细胞中的过氧化物酶体数量和代谢显著增加，而在骨中，代谢活跃的成骨细胞比骨细胞含有更高数量的这种细胞器。这些骨骼细胞类型中过氧化物酶体的高丰度通过Pex11β基因的高水平表达得以体现。在培养过程中，颅盖前成骨细胞分化为分泌性成骨细胞，同时伴随着过氧化物酶体增殖以及过氧化物酶体基因和蛋白质水平的增加。由于许多过氧化物酶体基因含有PPAR反应元件，我们分析了颅盖成骨细胞和MC3T3-E1细胞中PPARɑ/ß/ɣ的基因表达，结果显示PPARß的水平高于PPARɑ和PPARɣ。用不同的PPAR激动剂和拮抗剂处理不仅改变了过氧化物酶体区室和相关基因表达，还诱导了其他PPAR家族成员基因表达模式的复杂变化。在M3CT3-E1细胞中的研究表明，PPARß激动剂GW0742激活了PPRE介导的荧光素酶表达并上调了过氧化物酶体基因转录（Pex11、Pex13、Pex14、Acox1和Cat），而PPARß拮抗剂GSK0660导致PPRE的抑制和相应mRNA水平的降低。同样，用GW0742处理颅盖成骨细胞增加了过氧化物酶体数量和相关基因表达，并加速了成骨细胞分化。综上所述，我们的结果表明，PPARß通过Pex11ß在平行于成骨细胞分化的过程中调节过氧化物酶体的数量丰度和代谢功能。
