Adam J. Schuldt

3rd Year Graduate Student

Department: Biomedical Engineering

Graduate Program: Biomedical Engineering

Advisor: Ira Cohen

Abstract:

Title:  Regenerating the Mammalian Heart: Inducing Adult Cardiomyocytes to Proliferate

Adam J.T. Schuldt, Amy B. Rosen, Damon J. Kelly, Sergey V. Doronin, Irina A. Potapova, Peter R. Brink, Glenn R. Gaudette, Ira S. Cohen

The human heart has long been considered a postmitotic organ, unable to regenerate contractile cells. Recent evidence has challenged this notion, indicating that the heart does regenerate cardiomyocytes, but at a rate too slow to be therapeutic in a setting of heart disease. A large body of recent work has aimed to improve the rate of cardiomyocyte regeneration to therapeutic levels. Most of this research has focused on the potential of stem cells to reconstitute the diseased heart, some even suggesting the existence of resident cardiac stem cells. However, a second source of cardiac regeneration may reside in the proliferation of adult cardiomyocytes. Our laboratory has shown that human mesenchymal stem cells (hMSCs) can stimulate adult cardiomyocytes to proliferate in vitro. Based on our results and the work of others, we hypothesize that paracrine factors from the stem cells may permit cardiomyocyte re-entry into the cell cycle. Porous membrane-separated co-cultures of adult canine cardiomyocytes and hMSCs or hMSCs transfected with the genes that encode proteins relevant to cardiomyocyte proliferation will be employed to investigate the role of paracrine signaling. Additionally, media conditioned by transfected or non-transfected hMSCs will be transferred onto cardiomyocyte cultures. Cardiomyocyte colony formation and expression of cell cycle markers will be used to assess cardiomyocyte proliferation. To determine whether proliferating cardiomyocytes transiently dedifferentiate to a “cardiac stem cell-like” state, proliferating myocytes will be stained for the stem cell markers c-kit, sca-1, islet-1, and CD34. To investigate the therapeutic potential of these paracrine factors, transfected or non-transfected hMSCs will be delivered on an extracellular matrix (ECM) patch to a full-thickness defect in the canine right ventricle. Cardiac function in the region of the patch will be assessed at 2 or 8 weeks. Immunohistochemistry will be used to quantitate re-entry of native cardiomyocytes into the cell cycle. The ability of proliferating dedifferentiated cardiomyocytes to redifferentiate into mature cardiomyocytes will be investigated by in vitro differentiation protocols, as well as injection into a cardiac environment in vivo. Finally, the ability of cardiomyocytes expanded in vitro to contribute to cardiac function in vivo will be assessed by implanting an ECM patch seeded with cultured cardiomyocytes in the canine right ventricle. Cardiac function in the patch region will be measured at 4 or 8 weeks.

Publications:
(MSTP-supported publications indicated with an *)

Liu FF, Stone JR, Schuldt AJ, Okoshi K, Okoshi MP, Nakayama M, Ho KK, Manning WJ, Marchionni MA, Lorell BH, Morgan JP, Yan X (2005). Heterozygous knockout of neuregulin-1 gene in mice exacerbates doxorubicin-induced heart failure. Am J Physiol Heart Circ Physiol. 289(2):H660-6.

Okoshi MP, Yan X, Okoshi K, Nakayama M, Schuldt AJ, O’Connell TD, Simpson PC, Lorell BH (2004). Aldosterone directly stimulates cardiac myocyte hypertrophy. J Card Fail. 10(6):511-8.

Okoshi K, Nakayama M, Yan X, Okoshi MP, Schuldt AJ, Marchionni MA, Lorell BH (2004). Neuregulins regulate cardiac parasympathetic activity: muscarinic modulation of ß-adrenergic activity in myocytes from mice with neuregulin-1 gene deletion. Circulation. 110(6):713-7.

Soper BW, Duffy TM, Lessard MD, Jude CD, Schuldt AJ, Vogler CA, Levy B, Barker JE (2004). Transplanted ER-MP12hi20-58med/hi myeloid progenitors produce resident macrophages from marrow that are therapeutic for lysosomal storage disease. Blood Cells Mol Dis. 32(1):199-213.

Schuldt AJ, Hampton TJ, Chu V, Vogler CA, Galvin N, Lessard MD, Barker JE (2004). Electrocardiographic and other cardiac anomalies in beta-glucuronidase-null mice corrected by nonablative neonatal marrow transplantation. Proc Natl Acad Sci USA. 101(2):603-8.

Barker JE, Schuldt AJ, Lessard ML, Jude CD, Vogler CA, Soper BW (2003). Donor cell expansion is delayed following nonablative in utero transplantation to treat murine mucopolysaccharidosis type VII. Exp Hematol. 31(11):1112-8.

Barker JE, Schuldt AJ, Lessard MD, Jude CD, Vogler CA, Soper BW (2003). Donor cell replacement in mice transplanted in utero is limited by immune-independent mechanisms. Blood Cells Mol Dis. 31:291-7.

Soper BW, Lessard MD, Jude CD, Schuldt AJ, Bunte RM, Barker JE (2003). Successful allogeneic neonatal bone marrow transplantation devoid of myeloablation requires costimulatory blockade. J Immunol 171:3270-7.

Yan X, Price RL, Nakayama M, Ito K, Schuldt AJ, Manning WJ, Sanbe A, Borg TK, Robbins J, Lorell BH (2003). Ventricular-specific expression of angiotensin II type 2 receptors causes dilated cardiomyopathy and heart failure in transgenic mice. Am J Physiol Heart Circ Physiol. 285(5):H2179-87.

Soper BW, Lessard MD, Jude CD, Schuldt AJ, Barker JE (2002). Delayed administration of carrier marrow can decrease competition on donor stem cells during engraftment and maintain radioprotection of the host. Exp Hematol. 30(7):837-45.

Schuldt AJ, Johnson A, Dickinson P (2000). The effects of temperature on contractions of the gm1 and gm4 muscles from the gastric mill of the crab Cancer irroratus: modulation of neural output by a passive muscle property. (published at Bowdoin College)

Submitted Manuscripts

* Rosen AB, Kelly DJ, Schuldt AJT, Lu J, Potapova IA, Doronin SV, Robinson RB, Rosen MR, Brink PB, Gaudette GR, Cohen IS. Long term tracking of human mesenchymal stem cells loaded with quantum dots for quantitative in vivo 3-D fluorescence analysis. Submitted.

Yan X †, Schuldt AJT †, Price RL, Liu F, Okoshi K, Ho KK, Pope A, Borg TK, Lorell BH, Morgan JP. Ventricular myocyte-specific expression of the angiotensin II type 2 receptor depresses contractile function but does not modify the hypertrophic response to chronic pressure overload. Submitted

† indicates co-first author