title: Conditional deletion of Pkd1 in osteocytes disrupts skeletal mechanosensing in mice.
abstract: We investigated whether polycystin-1 is a bone mechanosensor. We conditionally deleted Pkd1 in mature osteoblasts/osteocytes by crossing Dmp1-Cre with Pkd1(flox/m1Bei) mice, in which the m1Bei allele is nonfunctional. We assessed in wild-type and Pkd1-deficient mice the response to mechanical loading in vivo by ulna loading and ex vivo by measuring the response of isolated osteoblasts to fluid shear stress. We found that conditional Pkd1 heterozygotes (Dmp1-Cre;Pkd1(flox/+)) and null mice (Pkd1(Dmp1-cKO)) exhibited a ∼ 40 and ∼ 90% decrease, respectively, in functional Pkd1 transcripts in bone. Femoral bone mineral density (12 vs. 27%), trabecular bone volume (32 vs. 48%), and cortical thickness (6 vs. 17%) were reduced proportionate to the reduction of Pkd1 gene dose, as were mineral apposition rate (MAR) and expression of Runx2-II, Osteocalcin, Dmp1, and Phex. Anabolic load-induced periosteal lamellar MAR (0.58 ± 0.14; Pkd1(Dmp1-cKO) vs. 1.68 ± 0.34 μm/d; control) and increases in Cox-2, c-Jun, Wnt10b, Axin2, and Runx2-II gene expression were significantly attenuated in Pkd1(Dmp1-cKO) mice compared with controls. Application of fluid shear stress to immortalized osteoblasts from Pkd1(null/null) and Pkd1(m1Bei/m1Bei)-derived osteoblasts failed to elicit the increments in cytosolic calcium observed in wild-type controls. These data indicate that polycystin-1 is essential for the anabolic response to skeletal loading in osteoblasts/osteocytes.
authors: Department of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38165, USA. zxiao2@uthsc.edu
authors: Zhousheng
authors: Z
authors: Xiao
authors: Mark
authors: M
authors: Dallas
authors: Ni
authors: N
authors: Qiu
authors: Daniel
authors: D
authors: Nicolella
authors: Li
authors: L
authors: Cao
authors: Mark
authors: M
authors: Johnson
authors: Lynda
authors: L
authors: Bonewald
authors: L Darryl
authors: LD
authors: Quarles
mesh_terms: D000818:Animals; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000235:genetics / Q000503:physiopathology; D001842:Bone and Bones / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics; D016326:Extracellular Matrix Proteins / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D020869:Gene Expression Profiling; D008297:Male; D040542:Mechanotransduction, Cellular / Q000235:genetics* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics; D010011:Osteocytes / Q000166:cytology / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D016474:Weight-Bearing
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; C493716:Runx2 protein, mouse; D015675:Osteocalcin; C089212:protein kinase D; D011493:Protein Kinase C