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Interstitial Cajal-like cells (ICLC) in human resting mammary gland stroma. Transmission electron microscope (TEM) identification

Authors

  • Mihaela Gherghiceanu,

    1. “Victor Babes” National Institute of Pathology, Bucharest, Romania
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  • L. M. Popescu

    Corresponding author
    1. “Victor Babes” National Institute of Pathology, Bucharest, Romania
    2. Department of Cellular and Molecular Medicine, “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania
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*Correspondence to: L. M. POPESCU, M.D., Ph.D. Department of Cellular and Molecular Medicine, “Carol Davila” University of Medicine and Pharmacy, P.O. Box 35-29, Bucharest 35, Romania. E-mail: LMP@univermed-cdgm.roLMP@jcmm.org

Abstract

We have previously shown the existence of ICLC in human resting mammary gland stroma by means of methylene blue (vital) staining and c-kit immunopositivity (immunofluorescence and immunohistochemistry). In addition, we reported the phenotype characteristics of these ICLC in vitro (primary cell cultures). Since the identification of ICLC outside the gut requires, at this moment, the obligatory use of TEM, we used this technique and provide unequivocal evidence for the presence of ICLC in the intralobular stroma of human resting mammary gland.

According to the‘platinum standard’ (10 TEM criteria for the certitude diagnosis of ICLC), we found interstitial cells with the following characteristics: 1. location: among the tubulo-alveolar structures, in the non-epithelial space; 2. caveolae:˜2.5% of cell volume; 3. mitochondria:˜10% of cell volume; 4. endoplasmic reticulum: either smooth or rough, ˜2–3% of cell volume; 5. cytoskeleton: intermediate and thin filaments, as well as microtubules are present; 6.myosin thick filaments: undetectable; 7. basal lamina: occasionally found; 8. gap junctions: occasionally found; 9. close contacts with targets: nerve fibers, capillaries, immunoreactive cells by ‘stromal synapses’; 10. characteristic cytoplasmic processes: i) number: frequently 2–3; ii) lenght: several tens of ˜m; iii) thickness: uneven caliber, 0.1–0.5 ˜m, with dilations, but very thin from the emerging point; iv) aspect: moniliform, usually with mitochondria located in dilations; y) branching: dichotomous pattern; vi) Ca2+ release units: are present; vii) network labyrinthic system: overlapping cytoplasmic processes.

It remains to be established which of the possible roles that we previously suggested for ICLC (e.g. juxta- and/or paracrine secretion, uncommited progenitor cells, immunological surveillance, intercellular signaling, etc.) are essential for the epithelium/stroma equilibrium in the mammary gland under normal or pathological conditions.

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