Table 1.

Cell markers detected by RNA-in situ hybridization, cells known to express the markers and their functions.^a

Marker	Cells known to express the marker and its functions
CCR2	C-C chemokine receptor 2. Chemokine receptor of monocyte chemoattractant protein-1 (MCP-1). Myocardium: contains CCR2− and CCR2+ macrophages. CCR2− macrophages: derived from primitive yolk sac and fetal monocyte progenitors, self-maintained in the heart independently from the bone marrow; regenerative functions. CCR+ macrophages: maintained through gradual monocyte recruitment and local proliferation; pro-inflammatory functions. 9,27,36
CD14	LPS receptor. Humans: expression in monocytes, with variable intensity depending on monocyte subset (ie, classical, nonclassical, and intermediate monocytes) and macrophages; 27 cultured circulating CD14+ monocytes differentiate into mesenchymal and endothelial lineages, so-called monocyte-derived multipotential cells. 54 Cats: expression in proportion of monocytes in bone marrow and peripheral blood; cultured dendritic cells. 5,28 Myocardium (humans): contains CD14+ macrophages. 9
CD29	Cell surface receptor with roles in cell adhesion and migration, and regulation of cellular phenotype. 86 Myocardium: receptor for different extracellular matrix proteins including collagens, involved in myofibroblast differentiation and facilitation of interaction between cardiomyocytes, fibroblasts, and endothelial cells; 86 also known to be involved in cardiac remodeling and fibrosis as well as cardiac hypertrophy. 18 Cats: CD29 expression found in cultured cardiomyocytes, bone marrow cells, fibroblasts of the renal cortex, and adipose tissue derived mesenchymal stem cells. 5,46,56,100
CD34	Transmembrane phosphoglycoprotein expressed in hematopoietic stem cells, hematopoietic progenitor cells, and wide range of non-hematopoietic stem cells including mesenchymal stem cells and endothelial progenitor cells. 66,90 Function largely unknown but regulation of cell stemness and proliferation, cell adhesion, and hematopoietic cell trafficking is suggested. 66,90 Myocardium: expressed by various endogenous cardiac stem cells with cardiogenic or vascular phenotype, 30 and by interstitial Cajal-like cells (so-called telocytes). 52 Cats: protein expression in endothelial cells of renal capillaries and various tumors, progenitor cells from the umbilical cord; 14,39,72 mRNA expression in different organs (ie, brain, spleen, heart, testis, thymus, liver) with highest levels in the heart (no information on cellular source). 103
CD133	Membrane glycoprotein expressed by wide range of stem cells, cancer stem cells, and differentiated cells (mainly polarized epithelial cells, glial cells, and photoreceptors). 11,34 Function: not clear; involved in maintenance of the plasma membrane in differentiated epithelial cells; linked to molecular pathways associated with cell proliferation, angiogenesis and migration in cancer cells. Humans: used as a marker of circulating endothelial progenitor cells, together with CD34 and VEGFR2. 41,97 Cats: used as a marker for cancer stem cells. 77,78
KIT	Tyrosine kinase receptor expressed in several cell types including germ and hematopoietic stem cells, mast cells, melanocytes, and Cajal interstitial cells. 69 Function: activation of various transcription factors involved in apoptosis, cell differentiation, proliferation, chemotaxis, and cell adhesion. 69 Myocardium: expression by cells regarded as cardiac stem cells (humans, mice, cats) 30,35,93,104 and by telocytes. 52
Col1A1	Collagen type I alpha 1 chain. Gene encoding the α chain of type I collagen; expressed by fibroblasts. 42
MEF2C	Myocyte enhancer factor 2C. Transcription factor with central roles in embryological differentiation and morphogenesis of cardiac, skeletal, and smooth muscle cells, the nervous system and B cells. Myocardium: promotes cardiac hypertrophy upon pathological stimuli; genetic variants leading to increased MEF2C expression have been described in human HCM. 3,4,16
Nanog	Transcription factor expressed in embryonic stem cells to maintain cell pluripotency. 70 Myocardium: cardiac stem cell marker in rat and mouse. 59,101 Cats: identified in amniotic epithelial cells and mesenchymal stem cells; used as transcription factor to generate induced pluripotent stem cells. 20,46,87,105
Oct4	Transcription factor expressed by embryonic stem cells to maintain cell pluripotency. 95 Myocardium: cardiac stem cell marker in rat and mouse. 101,102 Cats: identified in amniotic epithelial cells and mesenchymal stem cells; used as transcription factor to generate induced pluripotent stem cells. 20,46,87,105
PDGFRB	Platelet derived growth factor receptor beta. Cell-surface receptor with tyrosine kinase domain, expressed in vascular smooth muscle cells and pericytes. 43 Myocardium: expressed by telocytes. 52 Functions: role in maintenance of vasculature homeostasis, 43 regulation of angiogenesis by mediating pericyte and vascular smooth muscle cell migration for stabilization of newly formed vessels. 2 Cats: expression in normal endocrine pancreas and endothelial cells and histiocytic cells in histiocytic disorders. 96
VEGFR2	Vascular endothelial growth factor receptor 2. Transmembrane receptor with tyrosine kinase domain, expressed in endothelial cells and endothelial progenitor cells. 41,97 Functions: role in vascular permeability and angiogenesis; promoting proliferating, differentiation, and sprouting of endothelial cells during angiogenesis. 2 Cats: expressed by neoplastic cells in renal cell carcinoma and mammary cell carcinoma. 13,73

^aUnless specifically stated, the information originates from studies in mice and humans.