Document Detail

Cell density regulates in vitro activation of heart valve interstitial cells.
MedLine Citation:
PMID:  21397521     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Valve interstitial cells, the most prominent cell type in the heart valve, are activated and express α-smooth muscle actin in valve repair and in diseased valves. We hypothesize that cell density, time in culture, and the establishment of cell-cell contacts may be involved in regulating valve interstitial cell activation in vitro.
METHODS: To study cell density, valve interstitial cells were plated at passages 3 to 5, at a density of 17,000 cells/22 × 22 mm(2) coverslip, and grown for 1, 2, 4, 7, and 10 days. Valve interstitial cells were stained for α-smooth muscle actin and viewed under confocal microscopy to characterize the intensity of staining. To study time in culture, valve interstitial cells were plated at a 10-fold higher density to achieve similar growth densities over a shorter time period compared with valve interstitial cells plated at low density. α-Smooth muscle actin staining was compared at the same time points between those plated at high and low densities. To confirm valve interstitial cell activation as indicated by α-smooth muscle actin staining, valve interstitial cells were stained for cofilin at days 2, 5, 8, and 14 days postplating. To study the association of transforming growth factor β with valve interstitial cell activation with respect to cell density, valve interstitial cells were stained for α-smooth muscle actin and transforming growth factor β at 2, 4, 6, and 8 days postplating. To study the activation of the transforming growth factor β signaling pathway, valve interstitial cells were stained for pSmad2/3 at days 2, 4, 6, 8, 10, and 12 days postplating. To study cell contacts and activation, subconfluent and confluent cultures of valve interstitial cells were stained for β-catenin, N-cadherin, and α-smooth muscle actin. Also, whole-cell lysates of subconfluent and confluent valve interstitial cell cultures were probed by Western blot analysis for phospho-β-catenin at Ser33/37/Thr41, which is the form of β-catenin targeted for proteosomal degradation.
RESULTS: The percentage valve interstitial cells with high-intensity α-smooth muscle actin staining decreases significantly between days 1 and 4, and at confluency, most cells show absent or low-intensity staining, regardless of time in culture. Similar results are obtained with cofilin staining. Transforming growth factor β and nuclear pSmad2/3 staining in valve interstitial cells decreases concurrently with valve interstitial cell activation as cell density increases. Examining β-catenin and N-cadherin staining, single valve interstitial cells show no cell-cell contact with strong cytoplasmic staining, with some showing nuclear staining of β-catenin, while confluent monolayers show strong staining of fully established cell-cell contacts, weak cytoplasmic staining, and absent nuclear staining. The presence of cell-cell contacts is associated with a decreased α-smooth muscle actin. The level of phospho-β-catenin at Ser33/37/Thr41 is lower in confluent cultures compared with low-density subconfluent valve interstitial cell cultures.
CONCLUSION: Cell-cell contacts may inhibit valve interstitial cell activation, while absence of cell-cell contacts may contribute to activation.
Songyi Xu; Amber Chang Liu; Hyunjun Kim; Avrum I Gotlieb
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-03-11
Journal Detail:
Title:  Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology     Volume:  21     ISSN:  1879-1336     ISO Abbreviation:  Cardiovasc. Pathol.     Publication Date:    2012 Mar-Apr
Date Detail:
Created Date:  2012-02-13     Completed Date:  2012-06-01     Revised Date:  2012-06-22    
Medline Journal Info:
Nlm Unique ID:  9212060     Medline TA:  Cardiovasc Pathol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  65-73     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Department of Pathology, Toronto General Research Institute, University Health Network, Ontario, Canada.
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MeSH Terms
Actins / metabolism
Cell Communication / physiology*
Cell Count
Cell Proliferation*
Cells, Cultured
Mitral Valve / cytology*,  metabolism
Signal Transduction
Stress Fibers / metabolism*
Transforming Growth Factor beta / metabolism
Wound Healing / physiology*
beta Catenin / metabolism
Grant Support
84228//Canadian Institutes of Health Research
Reg. No./Substance:
0/Actins; 0/Transforming Growth Factor beta; 0/beta Catenin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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