Dose-specific or dose-dependent effect of growth hormone treatment on the proliferation and differentiation of cultured neuronal cells.
OBJECTIVE
GH controls the proliferation of cartilage, fibroblasts or the differentiation of adipose and muscle tissue. However, the effect of GH on neuronal cells remains unknown. The present study was conducted to determine the proliferative or differentiating effect of GH on the nervous system in vitro.


METHODS
Neuronal hybrid cells (VSC4.1) were cultured with GH. The concentration ranged from 0.134 microg/ml up to 1.34 mg/ml. A cell confluency and MTT assay, cell cycle phase analysis with flow cytometry, extracellular receptor kinase (ERK) phosphorylation and mitogen activated protein kinase (MAPK) inhibitor (PD98050) assays were all performed to determine the effect on proliferation. Differentiation was evaluated by neurite outgrowth and neurofilament expression. Terminally differentiated neurons were stained by Hoechst 33342 for apoptotic nuclear fragmentation by degeneration. Poly-adenosyl ribose polymerase (PARP) expression and its cleavage products were evaluated.


RESULTS
Cells at concentrations between 0.134 microg/ml and 1.34 microg/ml of GH proliferated with ERK phosphorylation, which was attenuated by MAPK inhibitors. Proliferation decreased at concentrations higher than 13.4 microg/ml; however, neurite outgrowth was observed at these concentrations. Terminally differentiated cells underwent apoptosis and showed nuclear fragmentation by Hoechst 33342 staining. PARP expression was increased with caspase-3 dependent-cleaved fragment.


CONCLUSIONS
Our in vitro data demonstrate that GH exerts dual effects; proliferation with a specific GH dose window, or differentiation in a dose-dependent manner in cultured neuronal hybrid cells.
Lyuh
Esther
E
Department of Preventive Medicine, Seoul National University, Esther Clinic, Seoul 110-744, Republic of Korea.
Kim
Hyun-Jung
HJ
Kim
Manho
M
Lee
Jung-Kwon
JK
Park
Kyong-Soo
KS
Yoo
Keun-Young
KY
Lee
Kwang-Woo
KW
Ahn
Yoon-Ok
YO
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D013006:Growth Hormone / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D051381:Rats
D013006:Growth Hormone