Targeted Reduction of Vascular Msx1 And Msx2 Mitigates Arteriosclerotic Calcification And Aortic Stiffness In LDLR-Deficient Mice Fed Diabetogenic Diets

  1. Dwight A. Towler5,*
  1. 1Sanford-Burnham Medical Research Institute, Orlando, FL (S.L.C., A.B., B.R., K.K., Y.B.A., D.A.T.)
  2. 2MD Anderson Cancer Center, Houston, TX (J.S.S.)
  3. 3Washington University in St. Louis, St. Louis, MO (A.K.)
  4. 4Norris Cancer Center, University of Southern California, Los Angeles, CA. (R.M.)
  5. 5Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, FL (D.A.T.)
  1. *Corresponding Author: Dwight A. Towler, Email: dtowler{at}sanfordburnham.org

Abstract

When fed high fat diets, male LDLR-/- mice develop obesity, hyperlipidemia, hyperglycemia, and arteriosclerotic calcification. An osteogenic Msx-Wnt regulatory program is concomitantly upregulated in the vasculature. To better understand the mechanisms of diabetic arteriosclerosis, we generated SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- mice, assessing the impact of Msx1+Msx2 gene deletion in vascular myofibroblast and smooth muscle cells. Aortic Msx2 and Msx1 were decreased by 95% and 34% in SM22Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- animals, respectively, vs. Msx1(fl/fl);Msx2(fl/fl);LDLR-/- controls. Aortic calcium was reduced by 31% and pulse wave velocity – an index of stiffness - was decreased in SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- mice vs. controls. Fasting blood glucose and lipids did not differ, yet SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- siblings became more obese. Aortic adventitial myofibroblasts from SM22-Cre;Msx1(fl/fl);Msx2(fl/fl);LDLR-/- mice exhibited reduced osteogenic gene expression and mineralizing potential with concomitant reduction in multiple Wnt genes. Sonic hedgehog (Shh) and Sca1 – markers of aortic osteogenic progenitors – were also reduced, paralleling a 78% reduction in alkaline phosphatase (TNAP)-positive adventitial myofibroblasts. RNAi interference revealed that while Msx1+Msx2 support TNAP and Wnt7b expression, Msx1 selectively maintains Shh and Msx2 sustains Wnt2, Wnt5a, and Sca1 expression in aortic adventitial myofibroblast cultures. Thus, Msx1 and Msx2 support vascular mineralization by directing the osteogenic programming of aortic progenitors in diabetic arteriosclerosis.

  • Received February 24, 2014.
  • Accepted July 9, 2014.

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