Isolated human uterine telocytes: immunocytochemistry and electrophysiology of T-type calcium channels.

Sanda Maria Cretoiu,Daniel Dumitru Banciu,Dragos Cretoiu,Adela Banciu,Laura Cristina Ceafalan,Laurentiu Mircea Popescu,Beatrice Mihaela Radu

doi:10.1007/s00418-014-1268-0

Abstract

Recently, telocytes (TCs) were described as a new cell type in the interstitial space of many organs, including myometrium. TCs are cells with very long, distinctive extensions named telopodes (Tps). It is suggested that TCs play a major role in intercellular signaling, as well as in morphogenesis, especially in morphogenetic bioelectrical signaling. However, TC plasma membrane is yet unexplored regarding the presence and activity of ion channels and pumps. Here, we used a combination of in vitro immunofluorescence and patch-clamp technique to characterize T-type calcium channels in TCs. Myometrial TCs were identified in cell culture (non-pregnant and pregnant myometrium) as cells having very long Tps and which were positive for CD34 and platelet-derived growth factor receptor-α. Immunofluorescence analysis of the subfamily of T-type (transient) calcium channels CaV3.1 and CaV3.2 presence revealed the expression of these ion channels on the cell body and Tps of non-pregnant and pregnant myometrium TCs. The expression in TCs from the non-pregnant myometrium 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. Moreover, the presence of T-type calcium channels in TCs from non-pregnant myometrium is also confirmed by applying brief ramp depolarization protocols. In conclusion, our results show that T-type calcium channels are present in TCs from human myometrium and could participate in the generation of endogenous bioelectric signals responsible for the regulation of the surrounding cell behavior, during pregnancy and labor.

Highlights

Regulation of contractile activity of the uterus is an important process, and numerous studies aimed to determine the mechanism of uterine activation during term and preterm parturition (Aguilar and Mitchell 2010)
Human myometrium exhibits in vitro spontaneous contractions which can be influenced by multiple factors (Hutchings et al 2009; Cretoiu et al 2011), including the interrelation between SMCs and TCs
We assume that, in the myometrium, some other influences could be involved, like, as yet unknown, pathways involving the effects of female sex steroids on the regulation of TCs activity and/or interrelation with SMCs, as suggested by our previous studies (Cretoiu et al 2006, 2009; Bassotti et al 2013)

Summary

Introduction

Regulation of contractile activity of the uterus is an important process, and numerous studies aimed to determine the mechanism of uterine activation during term and preterm parturition (Aguilar and Mitchell 2010). The immunohistochemical profile of TCs is not yet defined by specific markers; several studies claim that TCs are frequently found to be positive for CD34 and PDGFRα or PDGFRβ within the connective tissue in mucosa and submucosa of different organs or in the interstitium of the muscular coat of cavitary organs (Vannucchi et al 2013; Chen et al 2013; Milia et al 2013; Xiao et al 2013), as well as for Oct in mouse lung (Galiger et al 2014). The TCs proteome certified that TCs are different from fibroblasts and from endothelial cells (Zheng et al 2014a, b)

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Conclusion