Cardiac telocytes are double positive for CD34/PDGFR‐α

Telocytes (TCs) are a distinct type of interstitial cells, which are featured with a small cellular body and long and thin elongations called telopodes (Tps). TCs have been widely identified in lots of tissues and organs including heart. Double staining for CD34/PDGFR‐β (Platelet‐derived growth factor receptor β) or CD34/Vimentin is considered to be critical for TC phenotyping. It has recently been proposed that CD34/PDGFR‐α (Platelet‐derived growth factor receptor α) is actually a specific marker for TCs including cardiac TCs although the direct evidence is still lacking. Here, we showed that cardiac TCs were double positive for CD34/PDGFR‐α in primary culture. CD34/PDGFR‐α positive cells (putative cardiac TCs) also existed in mice ventricle and human cardiac valves including mitral valve, tricuspid valve and aortic valve. Over 87% of cells in a TC‐enriched culture of rat cardiac interstitial cells were positive for PDGFR‐α, while CD34/PDGFR‐α double positive cells accounted for 30.25% of the whole cell population. We show that cardiac TCs are double positive for CD34/PDGFR‐α. Better understanding of the immunocytochemical phenotypes of cardiac TCs might help using cardiac TCs as a novel source in cardiac repair.     

RNA Interference against Platelet-Derived Growth Factor Receptor α mRNA Inhibits Fibroblast Transdifferentiation in Skin Lesions of Patients with Systemic Sclerosis

Objective

To down-regulate expression of mRNA for the platelet-derived growth factor receptor (PDGFR)-α, block the signalling pathway of PDGF and its receptor, and study their influence on fibroblast transdifferentiation to myofibroblasts in systemic sclerosis (SSc).

Methods

Fibroblasts from skin lesions of SSc patients and health adult controls were cultured in vitro, and α-smooth muscle actin (α-SMA) expression was determined by immunocytochemistry. Both groups of fibroblasts were stimulated with PDGF-AA, transforming growth factor β₁ (TGF-β₁), and costimulated with PDGF-AA and TGF-β₁, then PDGFR-α and α-SMA mRNA and protein expression were detected with RT-PCR and WB respectively. Three pairs of siRNAs targeting different PDGFR-α mRNA sequences were synthesized for RNAi. SSc and control fibroblasts were transfected with PDGFR-α siRNA; stimulated with PDGF-AA; and assessed for PDGFR-α and α-SMA mRNA and protein expression.

Results

Although the fibroblasts from both groups had similar morphology, the SSc skin lesions had significantly more myofibroblasts than control skin lesions. PDGF-AA stimulation, TGF-β₁ stimulation, and costimulation significantly up-regulated PDGFR-α and α-SMA mRNA and protein expression in SSc fibroblasts compared to control (P<0.05), and costimulation had the strongest effects (P<0.05). All three pairs of siRNAs suppressed PDGFR-α mRNA and protein expression (P<0.05), but siRNA₁₄₉₅ had the highest gene-silencing efficiency (P<0.05). PDGFR-α siRNA attenuated the effects of PDGF-AA through up-regulating PDGFR-α and α-SMA mRNA and protein expression and inhibiting fibroblast transdifferentiation to myofibroblasts in SSc (P<0.05).

Conclusions

PDGFR-α over-expression in SSc fibroblasts bound PDGF-AA more efficiently and promoted fibroblast transdifferentiation, which was enhanced by TGF-β₁. PDGFR-α siRNA down-regulated PDGFR-α expression, blocked binding to PDGF-AA, and inhibited fibroblast transdifferentiation to myofibroblasts.     

Defective Pericyte Recruitment of Villous Stromal Vessels as the Possible Etiologic Cause of Hydropic Change in Complete Hydatidiform Mole

The pathogenetic mechanism underlying the hydropic change in complete hydatidiform moles (CHMs) is poorly understood. A growing body of data suggests that pericytes play a role in vascular maturation. Since maturation of villous stromal vessels in CHMs is markedly impaired at early stages, we postulated that a defect in pericytes around stromal vessels in chorionic villi might cause vascular immaturity and subsequent hydropic change. To investigate this, we examined several markers of pericytes, namely, α-smooth muscle actin (α-SMA), platelet-derived growth factor receptor-β (PDGFR-β), and desmin, in 61 normally developing placentas and 41 CHMs with gestational ages of 4–12 weeks. The ultrastructure of villous stromal vessels was also examined. Mature blood vessels from normal placentas show patent vascular lumens and formed hematopoietic components in the villous stroma. α-SMA and PDGFR-β expression in the villous stroma gradually increased and extended from the chorionic plate to peripheral villous branches. The labeled cells formed a reticular network in the villous stroma and, after week 7, encircled villous stromal vessels. In comparison, α-SMA and PDGFR-β expression in the villous stroma and stromal vessels of CHMs was significantly lower (p<0.05). Ultrastructurally, endothelial cells in villous stromal vessels in normal placentas were consistently attached by pericytes after week 7 when the vessels formed distinct lumen, whereas the villous stromal vessels in CHMs consisted of linear chains of endothelial cells, often disclosing primitive clefts without hematopoietic cells inside, and neither pericytes nor basal lamina surrounded the endothelial cells at any gestational age studied. This suggests that pericytes recruitment around villous stromal vessels is defective in CHMs and links to the persistent vascular immaturity of the villous stroma in CHMs, which in turns leads to hydropic villi.     

Telocytes in the human kidney cortex

Renal interstitial cells play an important role in the physiology and pathology of the kidneys. As a novel type of interstitial cell, telocytes (TCs) have been described in various tissues and organs, including the heart, lung, skeletal muscle, urinary tract, etc. ( www.telocytes.com ). However, it is not known if TCs are present in the kidney interstitium. We demonstrated the presence of TCs in human kidney cortex interstitium using primary cell culture, transmission electron microscopy (TEM) and in situ immunohistochemistry (IHC). Renal TCs were positive for CD34, CD117 and vimentin. They were localized in the kidney cortex interstitial compartment, partially covering the tubules and vascular walls. Morphologically, renal TCs resemble TCs described in other organs, with very long telopodes (Tps) composed of thin segments (podomers) and dilated segments (podoms). However, their possible roles (beyond intercellular signalling) as well as their specific phenotype in the kidney remain to be established.     

Endocardial Tip Cells in the Human Embryo – Facts and Hypotheses

Experimental studies regarding coronary embryogenesis suggest that the endocardium is a source of endothelial cells for the myocardial networks. As this was not previously documented in human embryos, we aimed to study whether or not endothelial tip cells could be correlated with endocardial-dependent mechanisms of sprouting angiogenesis. Six human embryos (43–56 days) were obtained and processed in accordance with ethical regulations; immunohistochemistry was performed for CD105 (endoglin), CD31, CD34, α-smooth muscle actin, desmin and vimentin antibodies. Primitive main vessels were found deriving from both the sinus venosus and aorta, and were sought to be the primordia of the venous and arterial ends of cardiac microcirculation. Subepicardial vessels were found branching into the outer ventricular myocardium, with a pattern of recruiting α-SMA+/desmin+ vascular smooth muscle cells and pericytes. Endothelial sprouts were guided by CD31+/CD34+/CD105+/vimentin+ endothelial tip cells. Within the inner myocardium, we found endothelial networks rooted from endocardium, guided by filopodia-projecting CD31+/CD34+/CD105+/ vimentin+ endocardial tip cells. The myocardial microcirculatory bed in the atria was mostly originated from endocardium, as well. Nevertheless, endocardial tip cells were also found in cardiac cushions, but they were not related to cushion endothelial networks. A general anatomical pattern of cardiac microvascular embryogenesis was thus hypothesized; the arterial and venous ends being linked, respectively, to the aorta and sinus venosus. Further elongation of the vessels may be related to the epicardium and subepicardial stroma and the intramyocardial network, depending on either endothelial and endocardial filopodia-guided tip cells in ventricles, or mostly on endocardium, in atria.     

Morphologic evidence of telocytes in human thyroid stromal tissue

Despite the evidence accumulated over the past decade that telocytes (TCs) are a distinctive, though long neglected, cell entity of the stromal microenvironment of several organs of the human body, to date their localization in the endocrine glands remains almost unexplored. This study was therefore undertaken to examine the presence and characteristics of TCs in normal human thyroid stromal tissue through an integrated morphologic approach featuring light microscopy and ultrastructural analysis. TCs were first identified by immunohistochemistry that revealed the existence of an intricate network of CD34⁺ stromal cells spread throughout the thyroid interfollicular connective tissue. Double immunofluorescence allowed to clearly differentiate CD34⁺ stromal cells lacking CD31 immunoreactivity from neighbour CD31⁺ microvascular structures, and the evidence that these stromal cells coexpressed CD34 and platelet‐derived growth factor receptor α further strengthened their identification as TCs. Transmission electron microscopy confirmed the presence of stromal cells ultrastructurally identifiable as TCs projecting their characteristic cytoplasmic processes (i.e., telopodes) into the narrow interstitium between thyroid follicles and blood microvessels, where telopodes intimately surrounded the basement membrane of thyrocytes. Collectively, these morphologic findings provide the first comprehensive demonstration that TCs are main constituents of the human thyroid stroma and lay the necessary groundwork for further in‐depth studies aimed at clarifying their putative implications in glandular homeostasis and pathophysiology.     

Correlation between Fibrillin-1 Degradation and mRNA Downregulation and Myofibroblast Differentiation in Cultured Human Dental Pulp Tissue

Myofibroblasts and extracellular matrix are important components in wound healing. Alpha-smooth muscle actin (α-SMA) is a marker of myofibroblasts. Fibrillin-1 is a major constituent of microfibrils and an extracellular-regulator of TGF-β1, an important cytokine in the transdifferentiation of resident fibroblasts into myofibroblasts. To study the correlation between changes in fibrillin-1 expression and myofibroblast differentiation, we examined alterations in fibrillin-1 and α-SMA expression in organotypic cultures of dental pulp in vitro. Extracted healthy human teeth were cut to 1-mm-thick slices and cultured for 7 days. In intact dental pulp, fibrillin-1 was broadly distributed, and α-SMA was observed in pericytes and vascular smooth muscle cells. After 7 days of culture, immunostaining for fibrillin-1 became faint concomitant with a downregulation in its mRNA levels. Furthermore, fibroblasts, odontoblasts and Schwann cells were immunoreactive for α-SMA with a significant increase in α-SMA mRNA expression. Double immunofluorescence staining was positive for pSmad2/3, central mediators of TGF-β signaling, and α-SMA. The administration of inhibitors for extracellular matrix proteases recovered fibrillin-1 immunostaining; moreover, fibroblasts lost their immunoreactivity for α-SMA along with a downregulation in α-SMA mRNA. These findings suggest that the expression of α-SMA is TGF-β1 dependent, and fibrillin-1 degradation and downregulation might be implicated in the differentiation of myofibroblasts in dental pulp wound healing.     

Telocytes form networks in normal cardiac tissues

Telocytes (TC) are a class of interstitial cells present in heart. Their characteristic feature is the presence of extremely long and thin prolongations (called telopodes). Therefore, we were interested to see whether or not TCs form networks in normal cardiac tissues, as previously suggested. Autopsy samples of cardiac tissues were obtained from 13 young human cadavers, without identifiable cardiac pathology and with a negative personal history of cardiovascular disease. Immunohistochemistry on formalin-fixed paraffin-embedded tissues was performed using monoclonal antibodies for CD117/c-kit. Additionally, ventricular samples from 5 Sprague-Dawley rats were ultrastructurally evaluated under transmission electron microscopy. We found c-kit positive cells with TC features in subepicardium, as well in subepicardial arteries and in subepicardial fat. TCs were also present in the subendocardium. Light and electron microscopy revealed the existence of intramyocardial networks built up by bipolar TCs. Larger c-kit positive multipolar TCs were found between cardiac muscle bundles. Our results support the existence of a cardiac network of telocytes.     

Comparative Characterization of Stroma Cells and Ductal Epithelium in Chronic Pancreatitis and Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extensive stroma being also present in chronic pancreatitis (CP). Using immunohistochemistry, the stroma of CP and PDAC was comprehensively analyzed and correlated with epithelial/carcinoma-related alterations and clinicopathological patient characteristics. While there were no significant differences between CP and PDAC regarding the distribution of CD3+ T cells and α-SMA+ fibroblasts, proportions of CD4+ and CD8+ T cells were significantly lower and numbers of CD25+(CD4+) and FoxP3+(CD4+) regulatory T cells were greater in PDAC compared with CP. Macrophages were more prevalent in CP, but localized more closely to carcinoma cells in PDAC, as were γδ-T cells. Duct-related FoxP3 and L1CAM expression increased from CP to PDAC, while vimentin expression was similarly abundant in both diseases. Moreover, stromal and epithelial compartments of well-differentiated tumors and CPs shared considerable similarities, while moderately and poorly differentiated tumors significantly differed from CP tissues. Analysis of 27 parameters within each pancreatic disease revealed a significant correlation of i) CD4+ and FoxP3+CD4+ T cells with FoxP3 expression in PDAC cells, ii) α-SMA+ fibroblasts with L1CAM expression and proliferation in PDAC cells, iii) CD3 and CD8 expression with γδ-TCR expression in both pancreatic diseases and iv) CD68+ and CD163+ macrophages with vimentin expression in PDAC cells. High expression of FoxP3, vimentin and L1CAM in PDAC cells as well as a tumor-related localization of macrophages each tended to correlate with higher tumor grade. Multivariate survival analysis revealed a younger age at time of surgery as a positive prognostic marker for PDAC patients with the most frequently operated disease stage T3N1M0. Overall this study identified several interrelationships between stroma and epithelial/carcinoma cells in PDACs but also in CP, which in light of previous experimental data strongly support the view that the inflammatory stroma contributes to malignancy-associated alterations already in precursor cells during CP.     

Hyperplasia of Pericytes Is One of the Main Characteristics of Microvascular Architecture in Malignant Glioma

Objectives

To investigate the role of pericytes in constructing the malformed microvessels (MVs) and participating microvascular architecture heterogeneity of glioma.

Methods

Forty human glioma tissue samples (WHO grade II-IV) were included in present study. Observation of blood vessel patterns, quantitative analysis of endothelial cells (ECs)- and pericyte-labeled MVs and comparison between malignant grades based on single- or double-immunohistochemical staining. The MV number density (MVND), microvascular pericyte number density (MPND), and microvascular pericyte area density (MPAD) were calculated. The expression of PDGFβ was also scored after immunostaining.

Results

In grade II glioma, most of tumor MVs were the thin-wall CD34⁺ vessels with near normal morphology. In addition to thin-wall CD34⁺ MVs, more thick-wall MVs were found in grade III glioma, which often showed α-SMA positive. Most of MVs in grade IV glioma were in the form of plexus, curled cell cords and glomeruloid microvascular proliferation while the α-SMA⁺ cells were the main components. The MVs usually showed disordered arrangement, loose connection and active cell proliferation as shown by Ki67 and α-SMA coexpression. With the increase of glioma grades, the α-SMA⁺ MVND, CD34⁺ MVND and MPND were significantly augmented although the increase of CD34⁺ MVND but not MPAD was statistically insignificant between grade III and IV. It was interesting that some vessel-like structures only consist of α-SMA⁺ cells, assuming the guiding role of pericytes in angiogenesis. The expression level of PDGFβ was upregulated and directly correlated with the MPND in different glioma grades.

Conclusion

Hyperplasia of pericytes was one of the significant characteristics of malignant glioma and locally proliferated pericytes were the main constituent of MVs in high grade glioma. The pathological characteristics of pericytes could be used as indexes of malignant grades of glioma.     

Calcium and integrin binding protein 1 (CIB1) induces myocardial fibrosis in myocardial infarction via regulating the PI3K/Akt pathway

Myocardial infarction (MI) is a severe coronary artery disease resulted from substantial and sustained ischemia. Abnormal upregulation of calcium and integrin binding protein 1 (CIB1) has been found in several cardiovascular diseases. In this study, we established a mouse model of MI by permanent ligation of the left anterior descending coronary artery. CIB1 was upregulated in the heart of MI mice. Notably, CIB1 knockdown by intramuscular injection of lentivirus-mediated short hairpin RNA (shRNA) targeting Cib1 improved cardiac function and attenuated myocardial hypertrophy and infarct area in MI mice. MI-induced upregulation of α-SMA, vimentin, Collagen I, and Collagen III, which resulted in collagen production and myocardial fibrosis, were regressed by CIB1 silencing. In vitro, cardiac fibroblasts (CFs) isolated from mice were subjected to angiotensin II (Ang II) treatment. Inhibition of CIB1 downregulated the expression of α-SMA, vimentin, Collagen I, and Collagen III in Ang II-treated CFs. Moreover, CIB1 knockdown inhibited Ang II-induced phosphorylation of PI3K-p85 and Akt in CFs. The effect of CIB1 knockdown on Ang II-induced cellular injury was comparable to that of LY294002, a specific inhibitor of the PI3K/Akt pathway. We demonstrated that MI-induced cardiac hypertrophy, myocardial fibrosis, and cardiac dysfunction might be attributed to the upregulation of CIB1 in MI mice. Downregulation of CIB1 alleviated myocardial fibrosis and cardiac dysfunction by decreasing the expression of α-SMA, vimentin, Collagen I, and Collagen III via inhibiting the PI3K/Akt pathway. Therefore, CIB1 may be a potential target for MI treatment.     

Telocytes in exercise‐induced cardiac growth

Exercise can induce physiological cardiac growth, which is featured by enlarged cardiomyocyte cell size and formation of new cardiomyocytes. Telocytes (TCs) are a recently identified distinct interstitial cell type, existing in many tissues and organs including heart. TCs have been shown to form a tandem with cardiac stem/progenitor cells in cardiac stem cell niches, participating in cardiac regeneration and repair. Although exercise‐induced cardiac growth has been confirmed as an important way to promote cardiac regeneration and repair, the response of cardiac TCs to exercise is still unclear. In this study, 4 weeks of swimming training was used to induce robust healthy cardiac growth. Exercise can induce an increase in cardiomyocyte cell size and formation of new cardiomyocytes as determined by Wheat Germ Lectin and EdU staining respectively. TCs were identified by three immunofluorescence stainings including double labelling for CD34/vimentin, CD34/platelet‐derived growth factor (PDGF) receptor‐α and CD34/PDGF receptor‐β. We found that cardiac TCs were significantly increased in exercised heart, suggesting that TCs might help control the activity of cardiac stem/progenitor cells, cardiomyocytes or endothelial cells. Adding cardiac TCs might help promote cardiac regeneration and renewal.     

Endogenous Brain Pericytes Are Widely Activated and Contribute to Mouse Glioma Microvasculature

Glioblastoma multiforme (GBM) is the most common brain tumor in adults. It presents an extremely challenging clinical problem, and treatment very frequently fails due to the infiltrative growth, facilitated by extensive angiogenesis and neovascularization. Pericytes constitute an important part of the GBM microvasculature. The contribution of endogenous brain pericytes to the tumor vasculature in GBM is, however, unclear. In this study, we determine the site of activation and the extent of contribution of endogenous brain pericytes to the GBM vasculature. GL261 mouse glioma was orthotopically implanted in mice expressing green fluorescent protein (GFP) under the pericyte marker regulator of G protein signaling 5 (RGS5). Host pericytes were not only activated within the glioma, but also in cortical areas overlying the tumor, the ipsilateral subventricular zone and within the hemisphere contralateral to the tumor. The host-derived activated pericytes that infiltrated the glioma were mainly localized to the tumor vessel wall. Infiltrating GFP positive pericytes co-expressed the pericyte markers platelet-derived growth factor receptor-β (PDGFR-β) and neuron-glial antigen 2. Interestingly, more than half of all PDGFR-β positive pericytes within the tumor were contributed by the host brain. We did not find any evidence that RGS5 positive pericytes adopt another phenotype within glioma in this paradigm. We conclude that endogenous pericytes become activated in widespread areas of the brain in response to an orthotopic mouse glioma. Host pericytes are recruited into the tumor and constitute a major part of the tumor pericyte population.     

Characterization of Endoneurial Fibroblast-like Cells from Human and Rat Peripheral Nerves

Endoneurial fibroblast-like cells (EFLCs) are one of the cell populations present in the peripheral nervous system. The role and immunophenotypic characteristics of EFLCs are not well known and led us to perform a histological and cytological study of EFLCs in normal human and rat peripheral nerves. We found that all EFLCs express CD34, neural/glial antigen 2 (NG2), and prolyl-4-hydrolase-beta. In addition, half of the EFLCs in normal peripheral nerves express platelet-derived growth factor receptor-β (PDGFR-β) and some also express the intermediate filament nestin in vivo (at a lower level than Schwann cells, which express high levels of nestin). Using cell cultures of purified EFLCs, we characterized subpopulations of EFLCs expressing PDGFR-β alone or PDGFR-β and nestin. Experimental nerve lesions in rat resulted in an increase in nestin-positive EFLCs, which returned to normal levels after 8 days. This suggests that some EFLCs could have a different proliferative and/or regenerative potential than others, and these EFLCs may play a role in the initial phase of nerve repair. These “activated” EFLCs share some immunophenotypic similarities with pericytes and Interstitial cells of Cajal, which have progenitor cell potentials. This raises the questions as to whether a proportion of EFLCs have a possible role as endoneurial progenitor cells.     

Telocytes in human skin – are they involved in skin regeneration?

Telocytes (TCs), a particular interstitial cell type, have been recently described in a wide variety of mammalian organs ( www.telocytes.com ). The TCs are identified morphologically by a small cell body and extremely long (tens to hundreds of μm), thin prolongations (less than 100 nm in diameter, below the resolving power of light microscopy) called telopodes. Here, we demonstrated with electron microscopy and immunofluorescence that TCs were present in human dermis. In particular, TCs were found in the reticular dermis, around blood vessels, in the perifollicular sheath, outside the glassy membrane and surrounding sebaceous glands, arrector pili muscles and both the secretory and excretory portions of eccrine sweat glands. Immunofluorescence screening and laser scanning confocal microscopy showed two subpopulations of dermal TCs; one expressed c‐kit/CD117 and the other was positive for CD34. Both subpopulations were also positive for vimentin. The TCs were connected to each other by homocellular junctions, and they formed an interstitial 3D network. We also found TCs adjoined to stem cells in the bulge region of hair follicles. Moreover, TCs established atypical heterocellular junctions with stem cells (clusters of undifferentiated cells). Given the frequency of allergic skin pathologies, we would like to emphasize the finding that close, planar junctions were frequently observed between TCs and mast cells. In conclusion, based on TC distribution and intercellular connections, our results suggested that TCs might be involved in skin homeostasis, skin remodelling, skin regeneration and skin repair.     

Comparison of Surface Markers between Human and Rabbit Mesenchymal Stem Cells

This study investigated whether there are marked differences in surface markers between rabbit and human mesenchymal stem cells (MSCs). Murine and rabbit MSCs have been reported to be CD90-negative. Rat MSCs have been reported to be CD71-negative. Our previous study also shows that rabbit MSCs are CD29-negative. However, human MSCs are generally considered to be CD29-, CD71-, and CD90-positive. Therefore, the surface markers of human MSCs might differ from those of other species. Rabbit bone marrow MSCs were obtained that had a multi-differentiation potential. The phenotype of these cells was studied using flow cytometry antibodies for 25 rabbit surface markers, namely, CD13, CD14, CD29, CD31, CD34, CD44, CD45, CD49d, CD49f, CD51, CD54, CD59, CD71, CD73, CD90, CD105, CD106, CD133, CD166, MHC I, MHC II, α-smooth muscle actin (α-SMA), cytokeratin, desmin, and vimentin. The phenotype of commercially available human MSCs was similarly studied using antibodies for human surface markers. CD14, CD31, CD34, CD45, CD49d, CD49f, CD51, CD54, CD71, CD106, CD133, MHC II, and cytokeratin were absent from both rabbit and human MSCs, while CD44, α-SMA, and vimentin were present on both cell lines. CD13, CD29, CD59, CD73, CD90, CD105, CD166, and MHC I were present on human MSCs, but not on rabbit MSCs. However, desmin was present on rabbit MSCs, but not on human MSCs. In total, the surface expression of nine markers differed between human and rabbit MSCs, whereas the surface expression of 16 markers was the same in the two cell lines.     

Variations of chromosomes 2 and 3 gene expression profiles among pulmonary telocytes,pneumocytes, airway cells,mesenchymal stem cells and lymphocytes

Telocytes (TCs) were identified as a distinct cellular type of the interstitial tissue and defined as cells with extremely long telopodes (Tps). Our previous data demonstrated patterns of mouse TC‐specific gene profiles on chromosome 1. The present study focuses on the identification of characters and patterns of TC‐specific or TC‐dominated gene expression profiles in chromosome 2 and 3, the network of principle genes and potential functional association. We compared gene expression profiles of pulmonary TCs, mesenchymal stem cells, fibroblasts, alveolar type II cells, airway basal cells, proximal airway cells, CD8⁺T cells from bronchial lymph nodes (T‐BL), and CD8⁺ T cells from lungs (T‐LL). We identified that 26 or 80 genes of TCs in chromosome 2 and 13 or 59 genes of TCs up‐ or down‐regulated in chromosome 3, as compared with other cells respectively. Obvious overexpression of Myl9 in chromosome 2 of TCs different from other cells, indicates that biological functions of TCs are mainly associated with tissue/organ injury and ageing, while down‐expression of Pltp implies that TCs may be associated with inhibition or reduction of inflammation in the lung. Dominant overexpression of Sh3glb1, Tm4sf1 or Csf1 in chromosome 3 of TCs is mainly associated with tumour promotion in lung cancer, while most down‐expression of Pde5 may be involved in the development of pulmonary fibrosis and other acute and chronic interstitial lung disease.     

Telocytes and putative stem cells in ageing human heart

Tradition considers that mammalian heart consists of about 70% non‐myocytes (interstitial cells) and 30% cardiomyocytes (CMs). Anyway, the presence of telocytes (TCs) has been overlooked, since they were described in 2010 (visit www.telocytes.com ). Also, the number of cardiac stem cells (CSCs) 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 mm²) increased with several hundreds in children and adults versus newborns. CMs are the most numerous cells, representing 76% in newborns, 88% in children and 86% in adults. Images of CMs mitoses were seen in the 17‐day newborns. Interestingly, no lipofuscin granules were found in CMs 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%, TCs 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, TCs represent a small fraction of human cardiac interstitial cells, but because of their extensive telopodes, they achieve a 3D network that, for instance, supports CSCs. The myocardial (very) low capability to regenerate may be explained by the number of CSCs, which decreases fivefold by age (from 0.5% to 0.1% in newborns versus adults).     

CCR2 Regulates the Uptake of Bone Marrow-Derived Fibroblasts in Renal Fibrosis

Recent studies have shown that bone marrow-derived fibroblasts contribute significantly to the pathogenesis of renal fibrosis. However, the molecular mechanisms underlying the recruitment of bone marrow-derived fibroblasts into the kidney are incompletely understood. Bone marrow-derived fibroblasts express the chemokine receptor - CCR2. In this study, we tested the hypothesis that CCR2 participates in the recruitment of fibroblasts into the kidney during the development of renal fibrosis. Bone marrow-derived collagen-expressing GFP⁺ fibroblasts were detected in the obstructed kidneys of chimeric mice transplanted with donor bone marrow from collagen α1(I)-GFP reporter mice. These bone marrow-derived fibroblasts expressed PDGFR-β and CCR2. CCR2 knockout mice accumulated significantly fewer bone marrow-derived fibroblast precursors expressing the hematopoietic marker-CD45 and the mesenchymal markers-PDGFR-β or procollagen I in the obstructed kidneys compared with wild-type mice. Furthermore, CCR2 knockout mice displayed fewer bone marrow-derived myofibroblasts and expressed less α-SMA or FSP-1 in the obstructed kidneys compared with wild-type mice. Consistent with these findings, genetic deletion of CCR2 inhibited total collagen deposition and suppressed expression of collagen I and fibronectin. Moreover, genetic deletion of CCR2 inhibits MCP-1 and CXCL16 gene expression associated with a reduction of inflammatory cytokine expression and macrophage infiltration, suggesting a linear interaction between two chemokines/ligand receptors in tubular epithelial cells. Taken together, our results demonstrate that CCR2 signaling plays an important role in the pathogenesis of renal fibrosis through regulation of bone marrow-derived fibroblasts. These data suggest that inhibition of CCR2 signaling could constitute a novel therapeutic approach for fibrotic kidney disease.     

Differences in the expression of chromosome 1 genes between lung telocytes and other cells: mesenchymal stem cells,fibroblasts, alveolar type II cells,airway epithelial cells and lymphocytes

Telocytes (TCs) are a unique type of interstitial cells with specific, extremely long prolongations named telopodes (Tps). Our previous study showed that TCs are distinct from fibroblasts (Fbs) and mesenchymal stem cells (MSCs) as concerns gene expression and proteomics. The present study explores patterns of mouse TC‐specific gene profiles on chromosome 1. We investigated the network of main genes and the potential functional correlations. We compared gene expression profiles of mouse pulmonary TCs, MSCs, Fbs, alveolar type II cells (ATII), airway basal cells (ABCs), proximal airway cells (PACs), CD8⁺ T cells from bronchial lymph nodes (T‐BL) and CD8⁺ T cells from lungs (T‐LL). The functional and feature networks were identified and compared by bioinformatics tools. Our data showed that on TC chromosome 1, there are about 25% up‐regulated and 70% down‐regulated genes (more than onefold) as compared with the other cells respectively. Capn2, Fhl2 and Qsox1 were over‐expressed in TCs compared to the other cells, indicating that biological functions of TCs are mainly associated with morphogenesis and local tissue homoeostasis. TCs seem to have important roles in the prevention of tissue inflammation and fibrogenesis development in lung inflammatory diseases and as modulators of immune cell response. In conclusion, TCs are distinct from the other cell types.