LS-11-P-2266 In vitro electrophysiology of human myometrial telocytes

Background. Newly described telocytes (TCs) are a novel cell type in the interstitial space of human myometrium. TCs are characterized by very long and distinctive prolongations named telopodes (Tps). It was suggested that TCs could influence the contractile activity of myometrial smooth muscle cells (SMCs). Therefore, our aim was an in vitro electrophysiological evaluation of myometrial TCs.
Methods. We used whole-cell patch-clamp recordings and immunofluorescence on TCs from human myometrium.
Results. In non-pregnant myometrium, patch-clamp recordings on TCs in voltage-clamp mode revealed a hyperpolarization-activated chloride inward current with calcium dependence and the absence of L-type calcium channels. Measurements of membrane capacitance showed the in vitro electrical coupling of TCs to SMCs. In human non-pregnant myometrium, T-type calcium currents have been evoked by brief ramp depolarization in TCs electrically coupled to SMCs, but not by standard protocols of step-depolarizing pulses. Mibefradil (1 μM) inhibits the T-type calcium currents. TCs exposed to oxytocin (40 nM) present a slight oscillating activity in current clamp mode generated by action potential like protocols. Immunofluorescence of TCs in pregnant myometrium using isoform selective T-type calcium channel antibodies indicates strong expression of CaV3.1 and CaV3.2 on the cell body and in Tps. The expression in TCs from the non-pregnant uterus is less intense, being confined to the cell body for CaV3.2, while CaV3.1 was expressed both on the cell body and in Tps.
Conclusion. The presence of T-type calcium channels in human myometrium could be a key issue in understanding the excitatory-coupling events during pregnancy and labor.