干细胞生物学概论
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Q1: What are the two key characteristics that allow stem cells to maintain pluripotency and self-renewal?
Stem cells maintain pluripotency and self-renewal through two related characteristics. First, they express specific genes essential for stemness and self-renewal. Second, stem cells are responsive to regulatory factors that affect the expression of these genes, allowing them to sustain their unique properties and capacity to generate more stem cells.
Q2: How do microarray technology and Oct4-GFP detection systems help researchers study stem cell gene expression?
Microarray technology isolates total RNA from cells and converts mRNA into fluorescently labeled probes hybridized to chips containing the entire human genome, revealing gene expression profiles. The Oct4-GFP detection system uses green fluorescent protein under Oct4 promoter control, since Oct4 is quickly down-regulated during differentiation, making it a reliable indicator of stemness for identifying genes that modulate self-renewal.
Q3: What is the difference between hematopoietic stem cells and embryonic stem cells?
Hematopoietic stem cells, discovered in the 1960s, are multipotent and can differentiate into limited cell types of the blood and immune systems. Embryonic stem cells, identified in 1981, are pluripotent and can differentiate into all cell types of the body. This fundamental difference makes embryonic stem cells more versatile for regenerative medicine applications.
Q4: How do feeder cells and feeder-free culture methods maintain stem cell stemness in vitro?
Feeder cells, such as mouse embryonic fibroblasts, secrete a complex mixture of pluripotency and self-renewal factors necessary for maintaining stemness. Feeder-free cultures achieve this by supplementing cell culture media with stock reagents of growth and inhibitory factors. Both approaches provide the particular microenvironment stem cells require to maintain their unique properties.
Q5: What breakthrough did Shinya Yamanaka achieve with induced pluripotent stem cells?
Shinya Yamanaka developed a method to reprogram differentiated cells to a pluripotent state using retrovirus to induce expression of transcription factors now called the Yamanaka factors. This breakthrough, building on John Gurdon's work, created induced pluripotent stem cells, or iPSCs, which can now model human diseases and support regeneration platforms in multiple tissues.
Q6: How do hanging drop and microencapsulation methods improve stem cell differentiation compared to traditional flat plate cultures?
Traditional flat plate cultures restrict three-dimensional cell growth. The hanging drop method forms embryoid bodies by culturing stem cell suspensions upside down in petri dish drops. Microencapsulation methods mix stem cells with alginate, a biocompatible semipermeable membrane, and deposit them as beads. Both techniques enable three-dimensional differentiation into specialized cells like dopaminergic neurons and cardiomyocytes.
Q7: How are stem cells being applied in regenerative medicine to treat degenerative diseases?
Regenerative medicine uses two main approaches: regrowing organs in the lab and delivering stem cells via transplantation to treat tissue degeneration. Somatic cells are reprogrammed into iPSCs, differentiated into specific cell types, and returned to patients to repair damaged tissue. Examples include neural stem cell injections for multiple sclerosis and mesenchymal stem cells with coagulation factors for cartilage repair.