Open Access
Telocytes and putative stem cells in ageing human heart
Author(s) -
Popescu Laurentiu M.,
Curici Antoanela,
Wang Enshi,
Zhang Hao,
Hu Shengshou,
Gherghiceanu Mihaela
Publication year - 2015
Publication title -
journal of cellular and molecular medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.44
H-Index - 130
eISSN - 1582-4934
pISSN - 1582-1838
DOI - 10.1111/jcmm.12509
Subject(s) - stem cell , myocyte , lipofuscin , ageing , pathology , cell type , stereology , biology , medicine , anatomy , cell , microbiology and biotechnology , andrology , genetics
Abstract Tradition considers that mammalian heart consists of about 70% non‐myocytes (interstitial cells) and 30% cardiomyocytes ( CM s). Anyway, the presence of telocytes ( TC s) has been overlooked, since they were described in 2010 (visit www.telocytes.com ). Also, the number of cardiac stem cells ( CSC s) has not accurately estimated in humans during ageing. We used electron microscopy to identify and estimate the number of cells in human atrial myocardium (appendages). Three age‐related groups were studied: newborns (17 days–1 year), children (6–17 years) and adults (34–60 years). Morphometry was performed on low‐magnification electron microscope images using computer‐assisted technology. We found that interstitial area gradually increases with age from 31.3 ± 4.9% in newborns to 41 ± 5.2% in adults. Also, the number of blood capillaries (per mm 2 ) increased with several hundreds in children and adults versus newborns. CM s are the most numerous cells, representing 76% in newborns, 88% in children and 86% in adults. Images of CM s mitoses were seen in the 17‐day newborns. Interestingly, no lipofuscin granules were found in CM s of human newborns and children. The percentage of cells that occupy interstitium were (depending on age): endothelial cells 52–62%; vascular smooth muscle cells and pericytes 22–28%, Schwann cells with nerve endings 6–7%, fibroblasts 3–10%, macrophages 1–8%, TC s about 1% and stem cells less than 1%. We cannot confirm the popular belief that cardiac fibroblasts are the most prevalent cell type in the heart and account for about 20% of myocardial volume. Numerically, TC s represent a small fraction of human cardiac interstitial cells, but because of their extensive telopodes, they achieve a 3D network that, for instance, supports CSC s. The myocardial (very) low capability to regenerate may be explained by the number of CSC s, which decreases fivefold by age (from 0.5% to 0.1% in newborns versus adults).