Original Paper

Histochemistry and Cell Biology

, Volume 132, Issue 2, pp 191-198

Expression of CPI-17 in smooth muscle during embryonic development and in neointimal lesion formation

  • Jee In KimAffiliated withDepartment of Molecular Physiology and Biophysics, Thomas Jefferson University
  • , Garbo D. YoungAffiliated withDepartment of Molecular Physiology and Biophysics, Thomas Jefferson University
  • , Li JinAffiliated withDepartment of Molecular Physiology and Biological Physics, The University of Virginia
  • , Avril V. SomlyoAffiliated withDepartment of Molecular Physiology and Biological Physics, The University of Virginia
  • , Masumi EtoAffiliated withDepartment of Molecular Physiology and Biophysics, Thomas Jefferson UniversityKimmel Cancer Center, Thomas Jefferson University Email author 

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Abstract

Ca2+ sensitivity of smooth muscle (SM) contraction is determined by CPI-17, an inhibitor protein for myosin light chain phosphatase (MLCP). CPI-17 is highly expressed in mature SM cells, but the expression level varies under pathological conditions. Here, we determined the expression of CPI-17 in embryonic SM tissues and arterial neointimal lesions using immunohistochemistry. As seen in adult animals, the predominant expression of CPI-17 was detected at SM tissues on mouse embryonic sections, whereas MLCP was ubiquitously expressed. Compared with SM α-actin, CPI-17 expression doubled in arterial SM from embryonic day E10 to E14. Like SM α-actin and other SM marker proteins, CPI-17 was expressed in embryonic heart, and the expression was down-regulated at E17. In adult rat, CPI-17 expression level was reduced to 30% in the neointima of injured rat aorta, compared with the SM layers, whereas the expression of MLCP was unchanged in both regions. Unlike other SM proteins, CPI-17 was detected at non-SM organs in the mouse embryo, such as embryonic neurons and epithelium. Thus, CPI-17 expression is reversibly controlled in response to the phenotype transition of SM cells that restricts the signal to differentiated SM cells and particular cell types.

Keywords

Smooth muscle contraction Smooth muscle development Vascular biology Vascular injury CPI-17 Myosin light chain phosphatase Myocardin PKC ROCK