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What are the phases of the cell cycle?
- 1) G0 (resting)
- 2) G1 (presynthetic)
- 3) S (DNA synthesis)
- 4) G2 (premitotic)
- 5) M (mitotic)
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What is meant by assymetric replication of stem cells?
One cell is self-renewing and the other differentiates after division.
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Name the GFs/cytokines involved in differentiation of specific cell lineages:
Endoth cells
Chondroblasts
Osteoblasts
Fat cells
Muscle
- Endo - VEGF, FGF
- Chondroblasts - Sox9
- Osteoblasts - CBFA1
- Fat - PPARg
- Muscle - Myo D, myogenin
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Name the three germ layers and what they develop into.
- Endoderm - epith cells of lung, liver, GI
- Mesoderm - comprise both mesodermal and BM progenitor cells
- mesodermal progenitors develop into myocytes, osteoblasts, chondrocytes, adipocytes, endoth cells
- BM prog diff into hematopoietic cells but can also generate cells for tissues of endo and ectoderm origin
- Ectoderm - keratinocyte precursores, neurons, oligodendricytes, ependymal cells
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What is the source and function of EGF?
- Source: Plts, macs, saliva, urine, milk, plasma
- Fxn: mitogenic for keratinocytes, stim migration and granulation tissue formation
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What is the source and function of TGF-a?
- Source: Macs, T lymphs, keratinocytes, many tissues
- Fxn: similar to EGF, stim hepatic replication and some epi cells
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What is the source and function of HGF?
- Also called scatter factor.
- Source: mesenchymal cells
- Function: prolif of epi cells and hepatocytes, increases cell motility
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What is the source and function of VEGF?
- Source: Mesench cells
- Fxn: Incr vascular perm, mitogenic for endoth cells
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What is the source and function of PDGF?
- Source: plts, macs, endo, keratinocytes, smooth mm
- Fxn:
- 1) chemotactic for PMNs, macs, fibroblats, smooth mm cells
- 2) activates PMNs, macs, fibroblasts
- 3) mitogenic for fibroblasts, endoth, sm mm
- 4) stim prod of MMPs, fibronectin, and HA
- 5) stim angiogenesis, wound contraction
- 6) inh plt ag
- 7) regulates integrin expression
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What is the source and function of FGF?
- Source: Macs, mast cells, T cells, endo cells, fibroblasts, many
- Fx:
- 1) chemotactic for fibroblasts
- 2) mitogenic for fibroblasts and keratinocytes
- 3) stim keratinocyte migration, angiogenesis, wound contraction and matric deposition
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What is the source and function of TGF-b?
- Source: plts, T cells, macs, endo, keratinocytes, sm mm, fibro
- Fxn:
- 1) chemotactic for PMNs, macs, lymphs, fibroblasts and sm mm
- 2) stim TIMP synthesis, keratinocyte migration, angiogenesis and fibroplasia
- 3) inh MMP prod and keratinocyte prolif
- 4) regulates integrin expression and other cytokines
- 5) induces TGF-b production
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What is the source and function of KGF?
- Source: fibroblasts
- Fxn: stim keratinocyte migration, prolif, and diff
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What is the source and function of IGF-1?
- Source: Macs, fibro, other
- Fxn:
- 1) synthesis of sulfated proteoglycans, collagen, keratinocyte migration, fibroblast prolif
- 2) GH-like endocrine effects
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What is the source and function of TNF?
- Source: macs, mast cell, Tcells
- Fxn: activates macs, regulates other cytokines
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What is the source and function of ILs?
- Source: macs, mast cells, keratinocytes, lymphs, many tissues
- Fxn: many - ex.
- 1) IL1 - chemotactic for PMNs and stim MMP-1 synthesis
- 2) IL4 - chemotactic for fibroblasts
- 3) IL8 - angiogenesis
- 4) IL6 - TIMP synthesis
- 5) Regulates other cytokines
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What is the source and function of IFNs?
- Source: lymphs and fibroblasts
- Fxn:
- 1) activates macs
- 2) inh fibroblast prolif and synthesis of MMPs
- 3) cytokine regulation
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Hints for the cytokines involved in tissue repair.
- VEGF and HGF - only prod by mes cells
- Macs produce them all except - VEGF, HGF, KGF and IFNs
- KGF - only prod by fibroblasts
- T Lymphs produce - TGF-a, FGF, TGF-b, TNF, ILs (T and B), IFNs (T and B)
- Plts produce: EGF, PDGF, TGF-b
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Name the four types of receptors and signal transduction pathways and explain how they work. (look at figures)
- 1) Receptors with intrinsic tyrosine kinase activity: most growth factors - ex. EGF, VEGF, PDGF....
- - binding of ligand --- dimerization of receptor --- tyrosine phosphorylation --- activate tyrosine kinase
- - activates downstream effector molecules
- - acts as dock for other effector molecules (PI3K- activates akt - cell prol and inh apop, PLC-g - breaks down membrane PL into IP3 which incr. Ca and DAG which activate transcr factors, Src)
- - phosphorylates GRB2-SOS bridging protein - activates RAS - then RAF - then MEK - then ERK - synthesis and phosphorylation of c-jun and c-fos - prod of GF controling entry of cell into cycle
- 2) Receptors that recruit kinases - cytokines (ex. IL2, IL3), IFNs, CSF, GH, prolactin
- - transmit extra cell signals to nucleus via JAK STAT pathway
- 3) Seven TM G-coupled receptors - serotonin, hist, vasopressin, epi, norepi, calcitonin, gluc, PTH, ACTH
- - binding of ligand - conformational change - activation of G prot by exchange of GDP with GTP
- - also produces IP3 which incr. Ca release from ER (like TK receptors)
- 4) Steroid hormone receptors
- - ligands diffuse through cell membrane and bine to nuclear receptors
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List the phases of the cell cycle. What is the rate limiting step? What controls progression through the cell cycle?
- G0-G1-S-G2-M
- G1-S is rate limiting (point of no return) - checks DNA before replication
- Cyclins and cyclin dependent kinases control progression
- G2/M checks DNA after replication
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What is the role of RB protein in the cell cycle
Normally bound to E2F transcription factor but phos of RB releases it and E2F is activated and stimulates transcription
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What triggers tissue regeneration (liver)? Describe the gene expression phases.
- Cytokines and GFs trigger cells to enter cell cycle. The two major restriction points are G0-G1 and G1-S.
- Early gene response --- cFOS and cJUN dimerize to form tf AP1, cMYC and other tfs such as NFkB, STAT3 and C-EBP
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What primes hepatocytes to enter cell cycle during liver regeneration? What acts on primed hepatocytes to stim progression through cell cycle? What inhibits continued growth and prolif?
- Priming - IL6, TNF, others
- Proliferation - HGF, TGFa, others
- - adjuvants are: norepi, insulin, GF, T4
- Growth inhibitors: TGF-b, activin, others - basically get incr in cell cycle inh and decr in GF and/or metabolic demands of the liver
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Name the three types of macromolecules in the ECM?
- 1) structural proteins (collagens, elastins)
- 2) adhesive glycoprot
- 3) proteoglycans and hyaluronic acid
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Name the components of the basement membrane.
collagen IV, laminin, heparan sulfate, proteoglycan, other glycoproteins
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Name the types of collagen and their tissue distribution.
- I - hard and soft tissue (defects - osteogenesis imperf and ehlers-danlos syndrome -arth type)
- II - cartilage, IV disk, vitreous
- III - hollow organs, soft tissues (ED - vascular)
- IV - BM (non-fibrillar - present in sheets)
- V - soft tissues, BV (classical ED)
- VI - microfibrils
- VII - anchoring fibrisl at dermal-epi jxn (dystrophic epidermolysis bullosa)
- IX - cartilage, vitreous (stickler syndrome)
- XVII - transmembrane collagen in epi cells (epidermolysis bullosa - benign atrophic)
- XV and XVIII - endostatin-forming collagens, endoth cells (knoblock syn)
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How is collagen formed?
- 1) procollagen transcribed by collagen genes and hydroxylated to form a triple helix (Vit c needed)
- 2) procollagen secreted from cell and cleaved by proteases
- 3) fibrils formed by extracellular lysyl oxidase
- 4) fibrils are then cross-linked
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What are the 4 main families of the cell adhesion molecules (CAMs)? What are their functions?
- 1) Ig family
- 2) Cadherins - Ca dep adhesion prot
- 3) integrins
- 4) Selectins
- Functions - cell-to-cell adhesion, adhesion of cell to ECM, integrins and cadherins link cell surface with to cytoskeleton by binding to actin and intermed filaments - signal transduction, motility
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How are cadherins linked to the cytoskeleton?
b-catenin links cadherin to a-catenin which connects to actin -
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Name the 7 phases of healing.
- 1) Inflammation
- 2) Prol and migration of CT cells
- 3) Angiogenesis
- 4) Synthesis of ECM proteins
- 5) Tissue remodeling
- 6) Wound contraction
- 7) Wound stregth
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Name the steps involved in angiogenesis from pre-existing vessels.
- 1) Vasodilation d/t NO and incr. perm d/t VEGF
- 2) Degredation of BM and break cell to cell contact between endo
- 3) Migration of endo cells to angiogenic stim
- 4) Proliferation of endo cells behind leading edge
- 5) Recruit periendo cells for support - ex pericytes, sm mm
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Name inducing agents for VEGF.
Hypoxia, TGF-a, TGF-b, PDGF
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Receptors for VEGF and where located?
- VEGFR1, 2 and 3
- 2 - only on endo cells, binding of receptor stim mobilization of precursors from BM
- 3 - only on lymphatic endo cells
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Functions of VEGF
- angiogenesis
- vascular perm
- endo migration and prol
- hyperplasia of lymphatics
- upreg expression of plasminogen activator, plasminogen activator inhibitor-1, TF, interstitial collagenase
- NOTE: Effects enhanced by FGF-2
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What are the actions fo angiopoietins, PDGF and TGF-b in angiogenesis?
- Ang1 interacts with Tie2 (on endo) to recruits periendoth cells and matures vessels
- Ang2/Tie2 has oposite effect and loosens endo cells so more responsive to VEGF (if present) or angiogenic inhib if VEGF absent
- PDGF - recruits sm mm
- TGF-b - incr prod of ECM proteins to stabalize vessels
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What stimulates fibroblast migration and proliferation?
- TGF-b, FGF, EGF, PDGF, IL1 and TNF
- TGF-b most NB GF in inflammatory fibrosis
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What is the most NB GF in inflammatory fibrosis and what are its actions?
- TGF-b
- 1) migration and proliferation of fibroblasts
- 2) incr synthesis of collagen/fibronectin
- 3) decr degredation of ECM
- 4) chemotactic for monos
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What GF stimulates collagen synthesis?
TGF-b, PDGF, FGF, IL1, IL13
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List some of the critical steps/processes in wound healing and the GF and cytokines involved.
- Mono chemotaxis: PDGF, FGF, TGF-b
- Fibroblast migration: PDGF, FGF, TGF-b, IL1, TNF
- Fibroblast prol: PDGF, FGF, EGF, TNF
- Angiogenesis: VEGF, Ang, FGF
- Collagen synthesis: PDGF, FGF, IL1, IL13, TGF-b
- Collagenase secretion: PDGF, FGF, EGF, TNF, TGF-b (inhibits)
- NOTE: FGF (all steps), PDGF (all except angiogenesis), ILs in coll syn and fib migration, TGF-b inh. collagenase
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Name the factors that retard wound healing.
- Local: bld supply, denervation, infection, FB, hematoma, mech stress, necrosis, dressings, tissue type
- Systemic: age, anemia, drugs, DM, neoplasia, genetic dz, malnut, obesity, infection, temp, uremia, mineral def, hormones
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Name the three phases of cutaneous wound healing.
- 1) Inflammation
- 2) Granulation tissue and reepithelialization
- 3) Wound contraction, ECM depo and remodeling
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Detail the stages involved in first intention wound healing.
- 1) 1st 24-48 hrs: neuts at margin, fibrin clot formation, at 24-48 hrs epis move from edges and deposit BM - fuse at midline under scab
- 2) day 3: neuts replaced by macs, gran tissue, collagen at margins vertically oriented, epi layer thickens
- 3) day 5: fills with gran tissue, neovasc, collagen more numerous and bridge
- 4) 2 wk: accum of collagen and prol of fibrobasts, WBCs and edema gone, scar formation, new vessels disappear
- 5) 30d - scar made of cellular CT
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How does 2nd intention healing differ from 1st?
- 1) larger clot, more inflammation
- 2) more gran tissue
- 3) wound contraction occurs
- 4) more scarring
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What is the progression of wound strength over time?
approx. 10% at 1 wk, then incr to about 70-80% over 3 mos
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