Lecture 7.1: Cellular Adaptations Flashcards
Types of Cell Adaptation (5)
1) Regeneration
2) Hyperplasia
3) Hypertrophy
4) Atrophy
5) Metaplasia
What does size of cell population depend on?
• Rate of Cell Proliferation
• Cell Differentiation
• Cell Death by Apoptosis
What is Cell Proliferation controlled by?
• Signals from microenvironment which stimulate/ inhibit cell proliferation
• Hormones
• Local mediators
• Direct cell-cell or cell-stroma contact
Autocrine Cell Signalling
The same secreting and responding cell
Paracrine Cell Signalling
Secreting cell and responding cell are different, but co-located
Endocrine Cell Signalling
Endocrine organs synthesise hormones conveyed through blood stream-target organs distant from site of synthesis
Final Outcomes of Signalling Biochemistry (4)
• Survive (resist apoptosis)
• Divide (enter cell cycle)
• Differentiate (take on specialised form and function)
• Die (undergo apoptosis)
Epidermal Growth Factor [EGF]: What is it? What produces it? Receptor?
• Mitogenic for epithelial cells, hepatocytes and fibroblasts
• Produced by keratinocytes, macrophages and inflammatory cells
• Binds to epidermal growth factor receptor (EGFR)
Vascular Endothelial Growth Factor [VEGF]: What is it? What produces it?
• Potent inducer of blood vessel development (vasculogenesis)
• Role in growth of new blood vessels (angiogenesis) in tumours
• Role in chronic inflammation and wound healing
• Tumour cells, Macrophages, Platelets, Keratinocytes, Renal Mesangial
Platelet-Derived Growth Factor [PDGF]: What is it? What produces it?
• Causes migration & proliferation of fibroblasts, smooth muscle cells &
monocytes
• Stored in platelet alpha granules and released on platelet activation
• Produced by macrophages, endothelial cells, smooth muscle cells and
tumour cells
Granulocyte Colony Stimulating Factor [GCSF]
• Treatment to stimulate poorly functioning bone marrow
• Glycoprotein that stimulates the bone marrow to produce granulocytes and
stem cells and release them into the bloodstream
What is the most important checkpoint in the cell cycle?
• The Restriction (R) Point
• It is towards the end of G1, is the most critical checkpoint
• Is most commonly altered checkpoint in cancer cells
What is Control of the Cell Cycle managed by?
• Tightly regulated by proteins called cyclins and associated enzymes called
cyclin-dependent kinases (CDKs)
• CDKs become active by binding to and complexing with cyclins
How do CDKs drive the Cell Cycle?
• Activated CDKs drive the cell cycle
• They phosphorylate proteins critical for cell cycle transitions
• E.g. retinoblastoma susceptibility protein
• Activity of cyclin-CDK complexes is tightly regulated by CDK inhibitors
• Some growth factors shut off production of these inhibitors
What are Labile Cells? Examples?
• Cells that continuously multiply and divide throughout life
• Skin Epidermis
• Gut Epithelium
• Bone Marrow
What are Stable Cells? Examples?
• Cells that multiply only when needed
• Spend most of the time in the quiescent G0 phase of the cell cycle
• But can be stimulated to enter the cell cycle when needed
• Liver Hepatocytes
• Bone Osteoblasts
• Proximal Tubules of the Kidney
• Endocrine Glands
What are Permanent Cells? Examples?
• Cells that are unable to replicate in postnatal life
• Cannot mount an effective proliferative response to significant cell loss
• Nervous Cells
• Cardiac Muscle Cells
• Skeletal Muscle Cells
What is Regeneration?
Regeneration is the natural process of replacing or restoring damaged or missing cells, tissues and organs by by identical cells to maintain tissue or organ size
What is Hyperplasia?
An increase in the number of cells in an organ or tissue, these cells are also enlarged
What is Hypertrophy?
A considerable increase in the size of an organ or tissue, caused by enlargement of its cellular components not hyperplasia
What is Atrophy?
A decrease in the size of a tissue or organ due to cellular shrinkage
What is Metaplasia?
The replacement of one differentiated somatic cell type with another differentiated somatic cell type in the same tissue, it is a reversible change
What is Aplasia?
The lack of development of a tissue/limb/organ during embryonic life
What is Hypoplasia?
A condition of arrested development in which an organ or part remains below the normal size or in an immature state
