Stem Cell Biology – mmrl.edu

The recent technology termed Cellular Reprogramming enables creation of a versatile type of stem cells called induced Pluripotent Stem Cells (iPSC) from any somatic tissue, such as skin, blood, adipose tissue from liposuction and hair follicles from plucked hair. These stem cells have 2 important characteristics: 1) the potential to proliferate indefinitely in culture and 2) the potential to give rise to any cell type including heart, brain, liver and insulin secreting beta cells, when provided with appropriate environment and stimuli. These cells hold promise for cell-based regenerative therapy of degenerative diseases, including heart failure, Parkinsons disease, Alzheimers disease, blindness and diabetes mellitus.

These induced pluripotent stem cells also permit the development of human models of disease using cells isolated from patients with various diseases. These cells, for example, can be directed to differentiate into heart cells, thus providing cells that have the genetic defect that the patients heart has, paving the way for the development of personalized treatments.

Sudden cardiac death claims the lives of approximately 350,000 Americans each year. Nearly 50% of all coronary deaths are sudden, occurring within 1 hour of the onset of symptoms. Sudden death after a heart attack is commonly due to a cardiac arrhythmia known as ventricular fibrillation and evidence is emerging that a genetic predisposition contributes to the development of life-threatening arrhythmias. In the absence of coronary disease, sudden cardiac death is often due to inherited cardiac arrhythmia syndromes such as long QT, short QT, Brugada and Early Repolarization syndromes that involve genetic defects. To better understand the molecular and cellular mechanisms underlying these arrhythmic syndromes and to develop effective therapeutic measures, reliable experimental models of the disease are needed and are being developed using these induced pluripotent stem cells.

The principal research focus at the MMRL Stem Cell Center is therefore 1) to elucidate the pathophysiological mechanisms underlying life threatening arrhythmic cardiac diseases using patient-specific iPSC-based human in vitro models and 2) to generate heart cells from skin cells-derived iPSCs using genetic engineering and pharmacological approaches for cell-based regenerative therapy of heart failure.

Fig 1

A 3mm by 3 mm skin punch biopsy excised by the physician as shown in Figure 1 provides enough material to generate these stem cells. Immediately after excision, the skin biopsy is processed to isolate fibroblasts. The fibroblasts are then reprogrammed using transcriptional factors (Oct4, Sox2, Klf4 and c-Myc) to generate induced Pluripotent Stem Cells over a period of 4-5 weeks in culture, as shown in Figure 2. These stem cells have the same genetic makeup including the genetic information responsible for the disease, as that of the patient whose skin biopsy was obtained. These stem cells are later directed to become beating heart cells using distinct molecules and micro-environmental factors. These beating miniaturized heart tissues in the petri dish have the ability to mirror the patients heart problem and can therefore serve as experimental models of the human disease to be used to determine the underlying disease mechanism and to formulate effective therapeutic measures. Figure 3 shows rhythmically contracting iPSC-derived heart tissue from a healthy individual and the recording of the electrical signals and contraction.

Fig 2 ( Left ) and Fig 3 ( Right )

Over 5 million Americans suffer from congestive heart failure. Heart failure is characterized by the loss of functional heart cells and thereby its inability to pump enough blood to maintain physiological functions. The last resort for the patients with end stage heart failure is heart transplantation. Often, this is limited by the availability of a perfectly matched organ. The demand for organ supply is increasing steadily, necessitating development of new therapeutic options. iPSCs-derived heart tissues hold great potential for cellular transplantation in failing hearts in that these cells could be derived from the skin biopsy of the patient needing transplantation and will be transplanted back to the same individual thereby hopefully obviating the need for immune rejection therapy. The replacement of scar tissue by stem cell-derived heart cells could improve heart function obviating the need for heart transplantation. Scientists in our Stem Cell Center are working to generate billions of clinical grade heart cells from skin cells-derived iPSC using genetic engineering and pharmacological approaches for cell-based regenerative therapy of heart failure.

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Stem Cell Biology - mmrl.edu