CHAPTER 31 VALVULAR INTERSTITIAL CELLS 31-1

CHAPTER 31 VALVULAR INTERSTITIAL CELLS 31-1

MITRAL VALVE MECHANICS by Neil B. Ingels, Jr. and Matts Karlsson

Figure 31.2 VIC-Collagen-Integrin interaction schematics. See text. Figure 31.1 Schematic by Julia Swanson showing

actin-containing VIC extensions binding to collagen fibers via a2b1 integrin and linking proteins.

CHAPTER 31 VALVULAR INTERSTITIAL CELLS

The stiffening “twitch” of the annular half of the anterior mitral leaflet at the beginning of each beat likely arises from P-wave-stimulated, dependent, neurally-insensitive myocytes located in this region. The source of the ubiquitous, β-independent, neurally-sensitive, steady-state stiffness “tone” of the entire anterior leaflet is less clear, but may involve contractile Valvular Interstitial Cells (VICs) bound to leaflet collagen by α2β1 integrins, as discussed by Stephens et al.1

Figure 31.1, by Dr. Julia Swanson, schematically shows actin-containing VIC extensions binding to collagen fibers via α2β1 integrin and linking proteins.

Figure 31.2 schematically illustrates some of the results from Stephens et al.1

• TOP: KCL induces contractile force in VICs that is transmitted to collagen via integrin binding and results in the development of leaflet contractile force. • MIDDLE: VIC/Collagen binding is prevented by α2β1 integrin antibody,

resulting in uncoupling KCL-induced VIC contractile force from leaflet contractile force.

• BOTTOM: Cytochalasin prevents KCL-induced VIC contraction and thus leaflet contractile force, in spite of α2β1 integrin binding of VICs and collagen.

1 _{Stephens EH, Durst CA, Swanson JC, Grande-Allen KJ, Ingels NB, Jr., Miller DC. Functional coupling of valvular interstitial cells and}