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Induced Pluripotent Stem Cells
Stem cells are undifferentiated cells that divide and produce different types of cells. Ordinarily, cells that have differentiated into a specific cel…
Induced pluripotent stem cells, iPSCs, are mature, differentiated cells, such as skin cells, that are reprogrammed in the laboratory to be similar to undifferentiated embryonic stem cells. That is, they divide and are pluripotent, able to produce any cell type in the body. For example, retinal cells that could be used to replace damaged retinal tissue.
To create iPSCs, mature cells, like skin fibroblasts, are taken from a patient and put into culture. Then, typically, genes for transcription factors, are delivered by viral vectors into the cell nuclei, where they are incorporated into the genome.
The transcription factors then turn on genes that are expressed by embryonic stem cells. Effectively, dedifferentiating them and bringing them to a pluripotent state.
The cells can now divide, and ideally, be directed to produce a specific cell type in culture. The new cells could then be transplanted back into the patient to treat damage or disease with minimal risk of rejection, because they originated from the patient's own cells.
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Q1: What are induced pluripotent stem cells and how do they differ from regular mature cells?
Induced pluripotent stem cells (iPSCs) are mature, differentiated cells like skin fibroblasts that have been reprogrammed in the laboratory to behave like embryonic stem cells. Unlike ordinary mature cells that stop dividing, iPSCs are pluripotent—they can divide and produce any cell type in the body. This reprogramming reverses the normal differentiation process, returning cells to an undifferentiated, proliferative state.
Q2: How are induced pluripotent stem cells created in the laboratory?
To create iPSCs, mature cells such as skin fibroblasts are grown in culture. Genes for transcription factors are then delivered into the cells using viral vectors and incorporated into the genome. These transcription factors activate genes normally expressed by embryonic stem cells, effectively dedifferentiating the mature cells and returning them to a pluripotent state capable of division.
Q3: What role do transcription factors play in iPSC reprogramming?
Transcription factors are proteins that turn on specific genes. In iPSC creation, transcription factor genes are delivered into mature cells where they activate genes expressed by embryonic stem cells. This gene activation triggers the dedifferentiation process, converting specialized cells back into an undifferentiated, pluripotent state capable of producing multiple cell types.
Q4: Why are induced pluripotent stem cells valuable for medical treatment?
iPSCs enable autologous transplantation, where patients receive cells derived from their own body. Since the transplanted cells originate from the patient's own tissues, there is minimal risk of transplant rejection. For example, patients with macular degeneration could receive retinal cells generated from their own skin cells, providing personalized treatment with reduced complications.
Q5: What are the current clinical applications of induced pluripotent stem cells?
The first iPSC clinical trial transplanted retinal cells into patients with age-related macular degeneration. Since then, iPSC trials have been approved for treating Parkinson's disease, heart disease, and spinal cord injury. Additionally, iPSCs derived from patients are used to study diseases in the laboratory, providing another valuable source of stem cells for scientific research.
Q6: How do viral vectors contribute to the iPSC reprogramming process?
Viral vectors are delivery vehicles used to introduce transcription factor genes into mature cells. These vectors carry the reprogramming genes into the cell nuclei, where they integrate into the genome. Once incorporated, the transcription factor genes are expressed using the cell's own machinery, initiating the dedifferentiation process that converts mature cells into pluripotent stem cells.
Q7: Can induced pluripotent stem cells produce all cell types in the body?
Yes, iPSCs are pluripotent and can theoretically produce all cell types in the body, including cells from all three germ layers. Scientists are actively learning how to efficiently direct iPSCs to differentiate into specific cell types in culture, such as retinal cells or neural cells, so that needed cell types can be produced in adequate quantities for therapeutic use.