title: Polycystin-1 mediates mechanical strain-induced osteoblastic mechanoresponses via potentiation of intracellular calcium and Akt/β-catenin pathway.
abstract: Mechanical regulation of bone formation involves a complex biophysical process, yet the underlying mechanisms remain poorly understood. Polycystin-1 (PC1) is postulated to function as a mechanosensory molecule mediating mechanical signal transduction in renal epithelial cells. To investigate the involvement of PC1 in mechanical strain-induced signaling cascades controlling osteogenesis, PKD1 gene was stably silenced in osteoblastic cell line MC3T3-E1 by using lentivirus-mediated shRNA technology. Here, our findings showed that mechanical tensile strain sufficiently enhanced osteogenic gene expressions and osteoblastic proliferation. However, PC1 deficiency resulted in the loss of the ability to sense external mechanical stimuli thereby promoting osteoblastic osteogenesis and proliferation. The signal pathways implicated in this process were intracellular calcium and Akt/β-catenin pathway. The basal levels of intracellular calcium, phospho-Akt, phospho-GSK-3β and nuclear accumulation of active β-catenin were significantly attenuated in PC1 deficient osteoblasts. In addition, PC1 deficiency impaired mechanical strain-induced potentiation of intracellular calcium, and activation of Akt-dependent and Wnt/β-catenin pathways, which was able to be partially reversed by calcium ionophore A23187 treatment. Furthermore, applications of LiCl or A23187 in PC1 deficient osteoblasts could promote osteoblastic differentiation and proliferation under mechanical strain conditions. Therefore, our results demonstrated that osteoblasts require mechanosensory molecule PC1 to adapt to external mechanical tensile strain thereby inducing osteoblastic mechanoresponse, partially through the potentiation of intracellular calcium and downstream Akt/β-catenin signaling pathway.
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: The Research Center for Bone and Stem Cells, Department of Anatomy, Histology and Embryology, Nanjing Medical University, Nanjing, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Sun
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing, China.
authors.forename: Junqing
authors.initials: J
authors.lastname: Ma
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing, China.
authors.forename: Yongchu
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Institute of Stomatology, Nanjing Medical University, Nanjing, China.
authors.forename: Weibing
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction; D050396:TRPP Cation Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D002118:Calcium; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D050396:TRPP Cation Channels; D051176:beta Catenin; C000605507:Gsk3b protein, mouse