title: Osteocytic connexin 43 is not required for the increase in bone mass induced by intermittent PTH administration in male mice.
abstract: OBJECTIVE
  To investigate whether osteocytic connexin 43 (Cx43) is required for the bone response to intermittent PTH administration, and whether the connexin is involved in maintaining the bone matrix.
  
  
  METHODS
  Human PTH(1-34) was injected to adult male mice expressing (Cx43(fl/fl)) or not osteocytic Cx43 (Cx43(fl/fl);DMP1-8kb-Cre) daily (100 µg/kg/d) for 14 days.
  
  
  RESULTS
  Cx43(fl/fl);DMP1-8kb-Cre mice have no difference in body weight and BMD from 1 to 4 months of age. Intermittent PTH administration increased BMD and BV/TV and induced a similar increase in type I collagen, alkaline phosphatase, runx2, osteocalcin, and bone sialoprotein expression in mice from both genotypes. On the other hand, osteocytic deletion of Cx43 did not alter mRNA levels of glycosaminoglycans, proteoglycans, collagens and osteoblast-related genes. In addition, expression of collagens assessed by immunohistochemistry was not affected by deleting osteocytic Cx43. However, PTH administration increased type II collagen only in Cx43(fl/fl) control mice, whereas hormone increased type I collagen expression only in Cx43(fl/fl);DMP1-8kb-Cre mice. Furthermore, PTH increased maturity of collagen fibers in control, but not in Cx43-deficient mice.
  
  
  CONCLUSIONS
  Expression of Cx43 in osteocytes is dispensable for bone anabolism induced by intermittent PTH administration; but it can modulate, at least in part, the effect of PTH on the bone matrix environment.
authors.affiliation: Department of Morphology and Genetics, Federal University of São Paulo School of Medicine, São Paulo, SP 04023-900, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Pacheco-Costa
authors.forename: H M
authors.initials: HM
authors.lastname: Davis
authors.forename: E G
authors.initials: EG
authors.lastname: Atkinson
authors.forename: E
authors.initials: E
authors.lastname: Katchburian
authors.forename: L I
authors.initials: LI
authors.lastname: Plotkin
authors.forename: R D
authors.initials: RD
authors.lastname: Reginato
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D015519:Bone Density / Q000187:drug effects*; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D018031:Connexin 43 / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D010006:Osteoblasts / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055114:X-Ray Microtomography
chemical_list: D018031:Connexin 43; C543076:GJA1 protein, mouse; D010281:Parathyroid Hormone