Deletion of the Transcription Factor PGC-1α in Mice Negatively Regulates Bone Mass
Peroxisome proliferator-activated receptor-gamma coactivator (PGC1α) is a transcription coactivator that interacts with a broad range of transcription factors involved in several biological responses. Here, we show that PGC1α plays a role in skeletal homeostasis since aged PGC1α-deficient mice (PGC1α−/−) display impaired bone structure. Micro-CT of the tibial mid-shaft showed a marked decrease of cortical thickness in PGC1α−/− (− 11.9%, p < 0.05) mice compared to wild-type littermate. Trabecular bone was also impaired in knock out mice which displayed lower trabecular thickness (Tb.Th) (− 5.9% vs PGC1α+/+, p < 0.05), whereas trabecular number (Tb.N) was higher than wild-type mice (+ 72% vs PGC1α+/+, p < 0.05), thus resulting in increased (+ 31.7% vs PGC1α+/+, p < 0.05) degree of anisotropy (DA), despite unchanged bone volume fraction (BV/TV). Notably, these impairments of cortical and trabecular bone led to a dramatic ~ 48.4% decrease in bending strength (p < 0.01). These changes in PGC1α−/− mice were paralleled by a significant increase in osteoclast number at the cortical bone surface and in serum level of the bone resorption marker, namely, C-terminal cross-linked telopeptides of type I collagen (CTX-I). We also found that in cortical bone, there was lower expression of mRNA codifying for the key bone-building protein Osteocalcin (Ocn). Interestingly, Collagen I mRNA expression was reduced in mesenchymal stem cells from bone marrow of PGC1α−/−, thus indicating that differentiation of osteoblast lineage is downregulated. Overall, results presented herein suggest that PGC1α may play a key role in bone metabolism.
KeywordsPeroxisome proliferator-activated receptor-gamma coactivator Bone Osteocalcin Osteoclast Osteoblast Mitochondria
We thank Dr. Antonio Moschetta (Department of Interdisciplinary Medicine, “Aldo Moro” University of Bari, 70124 Bari, Italy) for the generous gift of PGC1α heterozygous mice to generate the colony. This work was supported in part by MIUR Grant ex60% (to M.G.), by SIOMMMS Grant (to G.C.) and by ERISTO (ESA) Grant (to M.G.).
GC, LL, UT, SC, MG designed research; LL, LS, MC, NC performed research; GC, LL, GB, GP, JR, ES, MFF, UT, SC, MG analyzed, interpreted and discussed the data; and GC, LL, MG wrote the paper.
Compliance with Ethical Standards
Conflict of interest
Graziana Colaianni, Luciana Lippo, Lorenzo Sanesi, Giacomina Brunetti, Monica Celi, Nunzio Cirulli, Giovanni Passeri, Janne Reseland, Ernestina Schipani, Maria Felicia Faienza, Umberto Tarantino, Silvia Colucci, and Maria Grano declare that there is no conflict of interest regarding the publication of this paper.
Human and Animal Rights and Informed Consent
This study is in accordance with the European Law Implementation of Directive 2010/63/EU and all experimental protocols were reviewed and approved by the Veterinary Department of the Italian Ministry of Health (Project 522-2016PR). Experimental procedures have been carried out following the standard biosecurity and the institutional safety procedures. For this type of study formal consent is not required.
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