Bone marrow derived cells are involved in the pathogenesis of cardiac hypertrophy in response to pressure overload.
BACKGROUND
Bone marrow (BM) cells possess broad differentiation potential and can form various cell lineages in response to pathophysiological cues. The present study investigated whether BM-derived cells contribute to the pathogenesis of cardiac hypertrophy, as well as the possible cellular mechanisms involved in such a role.


RESULTS
Lethally irradiated wild-type mice were transplanted with BM cells from enhanced green fluorescent protein-transgenic mice. The chimeric mice were subjected to either prolonged hypoxia or transverse aortic constriction. BM-derived enhanced green fluorescent protein-expressing cardiomyocytes increased in number over time, emerging predominantly in the pressure-overloaded ventricular myocardium, although they constituted <0.01% of recipient cardiomyocytes. To determine whether BM-derived cardiomyocytes were derived from cell fusion or transdifferentiation at the single-cell level, lethally irradiated Cre mice were transplanted with BM cells from the double-conditional Cre reporter mouse line Z/EG. BM-derived cardiomyocytes were shown to arise from both cell fusion and transdifferentiation. Interestingly, BM-derived myofibroblasts expressing both vimentin and alpha-smooth muscle actin were concentrated in the perivascular fibrotic area. These cells initially expressed MAC-1/CD14 but lost expression of these markers during the chronic phase, which suggests that they were derived from monocytes. A similar phenomenon occurred in cultured human monocytes, most of which ultimately expressed vimentin and alpha-smooth muscle actin.


CONCLUSIONS
We found that BM-derived cells were involved in the pathogenesis of cardiac hypertrophy via the dual mechanisms of cell fusion and transdifferentiation. Moreover, the present results suggest that BM-derived monocytes accumulating in the perivascular space might play an important role in the formation of perivascular fibrosis via direct differentiation into myofibroblasts.
Endo
Jin
J
Department of Regenerative Medicine and Advanced Cardiac Therapeutics, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan.
Sano
Motoaki
M
Fujita
Jun
J
Hayashida
Kentaro
K
Yuasa
Shinsuke
S
Aoyama
Naoki
N
Takehara
Yuji
Y
Kato
Osamu
O
Makino
Shinji
S
Ogawa
Satoshi
S
Fukuda
Keiichi
K
D000818:Animals; D001854:Bone Marrow Cells / Q000473:pathology*; D006332:Cardiomegaly / Q000209:etiology* / Q000473:pathology*; D002459:Cell Fusion / Q000379:methods; D002645:Chickens; D006976:Hypertension, Pulmonary / Q000150:complications / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000473:pathology