Epicardium-derived cells are important for correct development of the Purkinje fibers in the avian heart.
During embryonic development, the proepicardial organ (PEO) grows out over the heart surface to form the epicardium. Following epithelial-mesenchymal transformation, epicardium-derived cells (EPDCs) migrate into the heart and contribute to the developing coronary arteries, to the valves, and to the myocardium. The peripheral Purkinje fiber network develops from differentiating cardiomyocytes in the ventricular myocardium. Intrigued by the close spatial relationship between the final destinations of migrating EPDCs and Purkinje fiber differentiation in the avian heart, that is, surrounding the coronary arteries and at subendocardial sites, we investigated whether inhibition of epicardial outgrowth would disturb cardiomyocyte differentiation into Purkinje fibers. To this end, epicardial development was inhibited mechanically with a membrane, or genetically, by suppressing epicardial epithelial-to-mesenchymal transformation with antisense retroviral vectors affecting Ets transcription factor levels (n=4, HH39-41). In both epicardial inhibition models, we evaluated Purkinje fiber development by EAP-300 immunohistochemistry and found that restraints on EPDC development resulted in morphologically aberrant differentiation of Purkinje fibers. Purkinje fiber hypoplasia was observed both periarterially and at subendocardial positions. Furthermore, the cells were morphologically abnormal and not aligned in orderly Purkinje fibers. We conclude that EPDCs are instrumental in Purkinje fiber differentiation, and we hypothesize that they cooperate directly with endothelial and endocardial cells in the development of the peripheral conduction system.
Eralp
Ismail
I
Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands.
Lie-Venema
Heleen
H
Bax
Noortje A M
NA
Wijffels
Maurits C E F
MC
Van Der Laarse
Arnoud
A
Deruiter
Marco C
MC
Bogers
Ad J J C
AJ
Van Den Akker
Nynke M S
NM
Gourdie
Robert G
RG
Schalij
Martin J
MJ
Poelmann
Robert E
RE
Gittenberger-De Groot
Adriana C
AC
D000818:Animals; D002450:Cell Communication; D002454:Cell Differentiation; D002465:Cell Movement; D048430:Cell Shape; D002642:Chick Embryo; D002645:Chickens; D003370:Coturnix; D016373:DNA, Antisense / Q000235:genetics / Q000378:metabolism; D006321:Heart / Q000196:embryology*; D010496:Pericardium / Q000196:embryology / Q000473:pathology*; D050784:Proto-Oncogene Protein c-ets-1 / Q000235:genetics / Q000378:metabolism; D050787:Proto-Oncogene Protein c-ets-2 / Q000235:genetics / Q000378:metabolism; D011690:Purkinje Fibers / Q000196:embryology / Q000473:pathology*; D013314:Stress, Mechanical
D016373:DNA, Antisense; D050784:Proto-Oncogene Protein c-ets-1; D050787:Proto-Oncogene Protein c-ets-2