Overview
This lecture explains how unspecialized cells become specialized through cellular differentiation, focusing on stem cell types, differentiation mechanisms, and applications in research and therapy.
Cellular Differentiation Process
- Differentiation is when unspecialized cells transform into specialized cells with distinct functions and structures.
- It is crucial in both embryonic development and adult tissue repair.
Types and Categories of Stem Cells
- Stem cells are unspecialized cells with the ability to divide indefinitely and differentiate under certain conditions.
- Totipotent stem cells can form all cell types necessary for organism growth and development.
- Pluripotent stem cells can become any human tissue but cannot produce an entire organism.
- Multipotent stem cells differentiate into a limited range of cell types within a specific lineage.
- Oligopotent stem cells can become a few closely related cell types.
- Unipotent cells are fully specialized, only giving rise to their own type.
Sources and Examples of Stem Cells
- Embryonic, fetal, and adult stem cells exist at different life stages.
- Adult stem cells examples: epithelial stem cells (skin), and bone marrow stem cells (hematopoietic, endothelial, mesenchymal).
- Hematopoietic stem cells generate blood and immune cells through hematopoiesis.
Mechanisms of Differentiation
- All cells contain the same DNA but specialize by expressing only certain genes.
- Gene expression is controlled mainly by transcription factors, proteins that regulate transcription of specific genes.
Stem Cell Research and Applications
- Stem cell research seeks to use stem cells for repairing or regenerating tissues.
- Human embryonic stem cells (hESCs) are pluripotent, isolated from embryos.
- Adult stem cells and those from umbilical cord blood or baby teeth are usually multipotent.
- Induced pluripotent stem cells (iPSCs) are reprogrammed adult cells acting like embryonic stem cells.
- Cell-based therapy uses differentiated stem cells to treat diseases but faces challenges like immune rejection and ethical concerns.
Key Terms & Definitions
- Differentiation — process where unspecialized cells become specialized.
- Stem cell — unspecialized cell with self-renewal and differentiation abilities.
- Totipotent — can become any cell type, including all embryonic tissues.
- Pluripotent — can become almost any tissue type, but not an entire organism.
- Multipotent — limited to differentiating within certain lineages.
- Oligopotent — can become a few related cell types.
- Unipotent — can produce only its own cell type.
- Transcription factor — protein that helps regulate which genes are expressed.
- Hematopoiesis — process of forming blood and immune cells.
- Induced pluripotent stem cell (iPSC) — adult cell reprogrammed to behave like an embryonic stem cell.
Action Items / Next Steps
- Review the categories and characteristics of stem cells.
- Understand the role of transcription factors in gene expression.
- Read about the ethical considerations in stem cell research.