Induced pluripotent stem cells in cardiovascular diseases

Cardiovascular diseases (CVDs)

• An estimate shows that 17.3 million people died from CVDs in 2008, representing 30% of all global deaths.

• The number of people who die from CVDs, mainly from heart disease and stroke, will increase to reach 23.3. million by 2030

• Group of disorders of the heart and blood vessels coronary heart disease -48%cerebrovascular disease -25%peripheral arterial disease-11%rheumatic heart disease – 6%

• Treatment Options Coronary Angioplasty Radiofrequency ablation Pacemaker insertion Cardiac defibrillator Resynchronization therapy

• Risk factors associated with various therapies includes discomfort and bleeding, blood vessel damages, arrhthymia Kidney damage.

• hESC therapy could potentially repair and regenerate damaged heart tissue.

Induced pluripotent stem cells

• Overexpression of four genes (or ‘Yamanaka factors’) was able to turn back the developmental clock of somatic cells .

(Yamanaka et al; Cell,2006)

Generating patient-specific iPSCs

• Methods to reprogramme somatic cells integrating methods non-integrating methods

Integrating methods• Retoviral transduction (eg. Moloney murine leukemia virus)

• Lentiviral transduction (eg.Sendai viruse)

Non-integrating methods• Minicircle vectors• Protein transduction

Cardiovascular disease modelling

• Models for CVDs Myocardial infarction(mice) arterial thrombosis (rat) venous thrombosis (rat) venous stasis thrombosis (rabbit)

• Derivation of iPSCs from human somatic cells circumvent the ethical roadblock associated with the acquisition of hESCs.

• iPSC-CMs can recapitulate the disease phenotype in humans(Moretti et al,cell,2010) .

Modelling the long QT syndrome

• Autosomal dominant inheritance of a 596G/A missense mutation in the KCNQ1 gene.

• Electrophysiological parameters in iPSC-CMs generated from two patients with LQTS1 were compared with healthy control.

• Similarly, two other studies reported the use of iPSC-CM disease models for LQTS2(Itzhaki et al ,Nature 2011.)

• The investigators further tested drugs that could either relieve or aggravate the clinical phenotype of LQTS

• The potential therapeutic effects of nifedipine and pinacidil was tested in this in vitro model.

• Generation of iPSC-CMs from two patients with Timothy syndrome (LQTS8)(Yazawa et al, Nature, 2011).

• Timothy syndrome had APs that were significantly prolonged compared with controls, while atrial and nodal Timothy syndrome iPSC-CMs did not.

significant hurdles still exist in modelling the more complex cardiovascular diseases using

iPSC technology• Difficulty in ensuring a purified cardiomyocyte population

from iPSCs .

• The complexities of reproducing a heterogeneous disease phenotype

• Limitations of modelling essentially adult-onset diseases using iPSC-CMs.

Applications in drug testing and discovery

• Part of the process of drug development and testing is to demonstrate that the product does not have any significant cardiac toxicities.

• To ascertain the cardiac response or side effects of an individual to a new drug in vitro.

• Targeted gene modification of patient-specific iPSCs

Applications in regenerative medicineMyocardial repair• Research in regenerative medicine using these cells is still at

an early stage.

Intramyocardial iPSC-MC delivery

Proper engrafting

Cytoarchitecture maintanance

Contractile perfomance restoration

Electrical stability & ventricular wall

thickness (Nelson et al ,circulation,2009)

Conclusion

• Mininizing the potential of transplanted undifferentiated iPSCs to form teratomas.

• Methods ensuring a purified cardiomyocyte population from iPSCs.

• Safe and effective methods of cell delivery and ensuring that transplanted cells remain in the myocardium.

References • Nelson TJ, Martinez-Fernandez A, Yamada S, et al. Repair of

acute myocardial infarction by human stemness factors induced pluripotent stem cells. Circulation, 2009;120:408e16

• Moretti A, Bellin M, Welling A, et al. Patient-specific induced pluripotent stem-cell models for long-QT syndrome. N Engl J Med 2010;363:1397e409

• Yazawa M, Hsueh B, Jia X, et al. Using induced pluripotent stem cells to investigate cardiac phenotypes in Timothy syndrome. Nature, 2011;471:230e4