Telocytes in neuromuscular spindles

Authors

  • Lucio Díaz-Flores,

    Corresponding author
    • Department of Anatomy, Pathology, Histology and Radiology, Faculty of Medicine, University of La Laguna, Tenerife, Spain
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  • Ricardo Gutiérrez,

    1. Department of Anatomy, Pathology, Histology and Radiology, Faculty of Medicine, University of La Laguna, Tenerife, Spain
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  • Francisco J. Sáez,

    1. Department of Cell Biology and Histology UFI11/44, School of Medicine and Dentistry, University of the Basque Country, UPV/EHU, Leioa, Spain
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  • Lucio Díaz-Flores Jr.,

    1. Department of Anatomy, Pathology, Histology and Radiology, Faculty of Medicine, University of La Laguna, Tenerife, Spain
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  • Juan F. Madrid

    1. Department of Cell Biology and Histology, School of Medicine, Regional Campus of International Excellence, “Campus Mare Nostrum”, University of Murcia, Espinardo, Spain
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Correspondence to: Lucio DÍAZ-FLORES, Universidad de La Laguna, Facultad de Medicina, Departamento de Anatomía, Anatomía Patológica e Histología. Ofra-La Cuesta, s/n, La Laguna, 38071 Tenerife, Islas Canarias, Spain.

Tel.: +34 922 319317

Fax: +34 922 319279

E-mail: kayto54@gmail.com

Abstract

A new cell type named telocyte (TC) has recently been identified in various stromal tissues, including skeletal muscle interstitium. The aim of this study was to investigate by means of light (conventional and immunohistochemical procedures) and electron microscopy the presence of TCs in adult human neuromuscular spindles (NMSs) and lay the foundations for future research on their behaviour during human foetal development and in skeletal muscle pathology. A large number of TCs were observed in NMSs and were characterized ultrastructurally by very long, initially thin, moniliform prolongations (telopodes – Tps), in which thin segments (podomeres) alternated with dilations (podoms). TCs formed the innermost and (partially) the outermost layers of the external NMS capsule and the entire NMS internal capsule. In the latter, the Tps were organized in a dense network, which surrounded intrafusal striated muscle cells, nerve fibres and vessels, suggesting a passive and active role in controlling NMS activity, including their participation in cell-to-cell signalling. Immunohistochemically, TCs expressed vimentin, CD34 and occasionally c-kit/CD117. In human foetus (22–23 weeks of gestational age), TCs and perineural cells formed a sheath, serving as an interconnection guide for the intrafusal structures. In pathological conditions, the number of CD34-positive TCs increased in residual NMSs between infiltrative musculoaponeurotic fibromatosis and varied in NMSs surrounded by lymphocytic infiltrate in inflammatory myopathy. We conclude that TCs are numerous in NMSs (where striated muscle cells, nerves and vessels converge), which provide an ideal microanatomic structure for TC study.

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