Thesis (MSc (Physiological Sciences))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Background: IL-6 belongs to a cytokine super-family known to affect cell proliferation,
although other family members are better characterized. Proliferation promoting
factors (IL-6) compete with differentiation promoting factors (myogenic regulatory
factors: MyoD and myogenin) to affect cell cycle. Cell cycle progression is assessed by
determining the proportion of cells shifting from arrest to chromatin synthesis and
mitosis phases (G0/G1 and S and G2/M respectively).
Methods: This study assessed the effects of IL-6 on cell cycle progression and
proliferation vs. differentiation of C2C12 skeletal myoblasts. Physiological doses (10 or
100 pg/ml) were compared to a high dose (10 ng/ml), with exposure lasting 48 hours
(addition of IL-6 dose to proliferation medium at 0 and 24 hours). Acute signaling
downstream of the IL-6 gp130 receptor was assessed after the first exposure.
Results: Propidium iodide analysis of nuclear material using flow cytometry indicated
shifts in forward scatter. Both Low and Medium doses shifted a greater proportion
(p<0.05) of cells from G0/G1 to S and G2M phases at 24 hours and all doses resulted
in the same shift (p<0.05) at the 48 hour time point. However, the High dose
significantly (p<0.05) increased myogenin expression at the 48 hour time point.
Microscopy indicated that confluence was prevented by low seeding density and did
not influence the result. Cells harvested at 5 minutes post stimulation indicated that
all doses significantly increased STAT3 phosphorylation. 10 minutes post stimulation
the High dose group sustained elevated levels of STAT3 phosphorylation.
Conclusions: Low and medium doses of IL-6 increase proliferation in a muscle
satellite cell line by activating cell division and allowing myoblasts to remain in the
active cell cycle. High doses of IL-6 increase differentiation by mediating upregulation
of myogenic regulatory factors and this is thought to be due to prolonged STAT3
activation. Physiological control of myoblast behaviour by cytokines is evident and
such control would be influenced by the severity of the endogenous cytokine
response to various stimuli. / AFRIKAANSE OPSOMMING: Agtergrond: IL-6 behoort aan n sitokien super-familie bekend vir die affektering van
sel verspreiding, alhoewel ander familie lede beter gekenmerk is. Bevordering van
verspreiding faktore (IL-6) kompeteer met bevordering van differensiasie fatore
(myogenic regulatory factors: MyoD en myogenin) om die sel siklus te affekteer. Sel
siklus progressie word geassesseer deur die bepaling van die proporsie selle wat
verskuif van arrestasie na chromatien sintese en mitose fases (G0/G1 en S en G2/M
onderskeidelik).
Metodes: Hierdie studie het die effekte van IL-6 op die progressie van die sel siklus
geassesseer asook die proliferasie vs. differensiasie van C2C12 skelet spier satelliet
selle. Fisiologiese dosisse (10 en 100 pg/ml) was vergelyk tot n hoog dose (10 ng/ml),
met blywende blootstelling van 48 uur (byvoeging van IL-6 dose tot verspreidings
medium op 0 and 24 uur). Akute sein stroomaf van die IL-6 gp130 reseptor was ook
geassesseer na die eerste blootstelling.
Resultate: Propidium iodide analise van kern materiaal deur vloei sitometrie het
voorwaarts verskuiwing aangedui. Beide Laag and Medium doses het n groter
proporsie (p<0.05) selle verskuif van die G0/G1 tot die S en G2M fases na 24 uur en
alle dosisse het gelei in die selfde verskuiwing (p<0.05) by die 48 huur tyd punt.
Alhoewel die Hoog dose myogenin uitdrukking aansienlik (p<0.05) verhoog het na 48
uur. Mikroskopie het aangedui dat samevloeiing voorkom was deur n lae loting
digtheid en dit het nie resultate geaffekteer nie. Selle wat geoes was 5 minute na
stimulasie het aangedui dat alle dosisse STAT3 fosforilasie laat toeneem het. 10
minute na stimulasie het die Hoog dose groep volgehoue vlakke van STAT3 fosforilasie
besit.
Gevolgtrekkings: Laag en Medium dosisse van IL-6 verhoog verspreiding in n spier
satelliet sel lyn deur die aktivering van sel deling en deur selle toe te laat om in die
aktiewe sel siklus te bly. Hoog dosisse van IL-6 verhoog differensiase deur
bemiddelende opstoot van myogenic regulatory factors en die gedagte is dat dit
bewerkstellig word deur aanhoudende aktivering van STAT3. Fisiologies beheer van
satelliet selle deur sitokiene is duidelik en die beheer sal beinvloed word deur die erns
van die endogene sitokien reaksie op verskillende stimuli.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6550 |
| Date | 03 1900 |
| Creators | Steyn, Paul |
| Contributors | Myburgh, Kathryn H., Smith, Robert M., University of Stellenbosch. Faculty of Science. Dept. of Physiological Sciences. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 132 p. : ill. |
| Rights | University of Stellenbosch |
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