Ultraslow myosin molecular motors of placental contractile stem villi in humans.

Yves Lecarpentier,Catherine Guerin,Xénophon Krokidis,Francine Michel,Victor Claes,Edouard Lecarpentier,Oumar Timbely,Abdelouahab Moumen,Abdelilah Arsalane,Jean-Louis Hébert,Maria Cristina Vinci

doi:10.1371/journal.pone.0108814

Abstract

Human placental stem villi (PSV) present contractile properties. In vitro mechanics were investigated in 40 human PSV. Contraction of PSV was induced by both KCl exposure (n = 20) and electrical tetanic stimulation (n = 20). Isotonic contractions were registered at several load levels ranging from zero-load up to isometric load. The tension-velocity relationship was found to be hyperbolic. This made it possible to apply the A. Huxley formalism for determining the rate constants for myosin cross-bridge (CB) attachment and detachment, CB single force, catalytic constant, myosin content, and maximum myosin ATPase activity. These molecular characteristics of myosin CBs did not differ under either KCl exposure or tetanus. A comparative approach was established from studies previously published in the literature and driven by mean of a similar method. As compared to that described in mammalian striated muscles, we showed that in human PSV, myosin CB rate constants for attachment and detachment were about 103 times lower whereas myosin ATPase activity was 105 times lower. Up to now, CB kinetics of contractile cells arranged along the long axis of the placental sheath appeared to be the slowest ever observed in any mammalian contractile tissue.

Highlights

Contractile properties of the human placenta have been suggested for a long time
Huxley formalism [17], we showed that the TV relationship was hyperbolic and that kinetics of myosins cycling in isolated human placental stem villi (PSV) were dramatically slower by far than those previously reported for any contractile tissue
The tension-velocity (T-V) relationship of isolated PSV was successively recorded after electrical tetanus and after KCl exposure

Summary

Introduction

Contractile properties of the human placenta have been suggested for a long time This was supported by numerous histological, morphological and biochemical arguments such as the presence of smooth muscle-like cells [1,2,3,4], the particular structure of the extra vascular part of human placental stem villi (PSV) [5,6,7], and the determination of both myosin ATPase activity and myosin content [8,9,10]. Huxley formalism [17], we showed that the TV relationship was hyperbolic and that kinetics of myosins cycling in isolated human PSV were dramatically slower by far than those previously reported for any contractile tissue. Comparisons between muscle myosin molecular characteristics were based on previous studies in which CB kinetics were determined by means of a similar method [18,19,22,23]

Results

Discussion

Conclusion