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1,25-Dihydroxyvitamin D3 regulation of cardiac myocyte proliferation and hypertrophy
T D O'Connell1, J E Berry, A K Jarvis
1Department of Pharmacology, University of Michigan Medical School, Ann Arbor 48109-0632, USA.
Abstract:
We previously demonstrated that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] inhibits myocyte maturation (T. D. O'Connell, D. A. Giacherio, A. K. Jarvis, and R. U. Simpson. Endocrinology 136: 482-488, 1995). To define further the role of 1,25(OH)2D3 in regulating myocardial development, we examined the effects of 1,25(OH)2D3 on proliferation and growth of primary cultures of ventricular myocytes isolated from neonatal rat hearts. When neonatal myocytes were grown in a serum-supplemented medium, cell number approximately doubled, and treating these myocytes with 1,25(OH)2D3 inhibited their proliferation by 56.56% after 4 days. Flow cytometry revealed that 1,25(OH)2D3 reduced the percentage of cells in the S phase of the cell cycle by 31.39% after 4 days. We show for the first time that proliferating cell nuclear antigen protein levels were specifically reduced by 1,25(OH)2D3. Protooncogene c-myc protein levels were also reduced by this hormone. Interestingly, a phorbol ester had a similar effect on myocyte proliferation. Furthermore, 1,25(OH)2D3 increased myocyte protein levels and increased cell size, suggesting that it induces cardiac myocyte hypertrophy. Our findings indicate that 1,25(OH)2D3 and phorbol esters directly regulate myocyte proliferation and induce myocyte hypertrophy. Finally, the data demonstrate that the mechanism by which 1,25(OH)2D3 regulates myocyte proliferation involves blocking entry into the S phase of the cell cycle.
Insights
1,25-dihydroxyvitamin D3 inhibits neonatal rat cardiac myocyte proliferation and induces hypertrophy. This vitamin D metabolite blocks cell cycle entry into the S phase, impacting myocardial development.
Area of Science:
- Cardiovascular Biology
- Endocrinology
- Cell Biology
Background:
- 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] was previously shown to inhibit myocyte maturation.
- Understanding the role of 1,25(OH)2D3 in myocardial development requires further investigation into its effects on myocyte proliferation and growth.
Purpose of the Study:
- To investigate the effects of 1,25(OH)2D3 on the proliferation and growth of primary neonatal rat ventricular myocytes.
- To elucidate the molecular mechanisms by which 1,25(OH)2D3 influences myocyte cell cycle progression and differentiation.
Main Methods:
- Primary cultures of neonatal rat ventricular myocytes were established.
- Cells were treated with 1,25(OH)2D3 and analyzed for proliferation, cell cycle distribution (flow cytometry), protein levels (proliferating cell nuclear antigen, c-myc), and cell size.
- Phorbol ester was used as a comparative agent.
Main Results:
- 1,25(OH)2D3 significantly inhibited myocyte proliferation by 56.56% after 4 days.
- Flow cytometry indicated a 31.39% reduction in S phase cells, suggesting cell cycle arrest.
- 1,25(OH)2D3 decreased proliferating cell nuclear antigen and c-myc protein levels, and induced myocyte hypertrophy (increased protein content and cell size).
Conclusions:
- 1,25(OH)2D3 directly regulates cardiac myocyte proliferation and induces hypertrophy.
- The mechanism involves blocking myocyte entry into the S phase of the cell cycle.
- Phorbol esters exhibit similar effects on myocyte proliferation, suggesting shared signaling pathways.