ABSTRACT
Human insulin-like growth factor 1 Ec (IGF-1Ec), also called mechano growth factor (MGF), is a splice variant of insulin-like growth factor 1 (IGF-1), which has been shown in vitro as well as in vivo to induce growth and hypertrophy in mechanically stimulated or damaged muscle. Growth, hypertrophy and responses to mechanical stimulation are important reactions of cartilaginous tissues, especially those in growth plates. Therefore, we wanted to ascertain if MGF is expressed in growth plate cartilage and if it influences proliferation of chondrocytes, as it does in musculoskeletal tissues. MGF expression was analyzed in growth plate and control tissue samples from piglets aged 3 to 6 weeks. Furthermore, growth plate chondrocyte cell culture was used to evaluate the effects of the MGF peptide on proliferation. We showed that MGF is expressed in considerable amounts in the tissues evaluated. We found the MGF peptide to be primarily located in the cytoplasm, and in some instances, it was also found in the nucleus of the cells. Addition of MGF peptides was not associated with growth plate chondrocyte proliferation.
Subject(s)
Alternative Splicing , Chondrocytes/metabolism , Growth Plate/metabolism , Insulin-Like Growth Factor I/genetics , Peptides/genetics , RNA, Messenger/genetics , Amino Acid Sequence , Animals , Cell Nucleus/metabolism , Cell Proliferation/drug effects , Chondrocytes/cytology , Chondrocytes/drug effects , Cytosol/metabolism , Gene Expression , Growth Plate/cytology , Growth Plate/drug effects , Humans , Insulin-Like Growth Factor I/metabolism , Mechanotransduction, Cellular , Molecular Sequence Data , Muscle, Skeletal/cytology , Muscle, Skeletal/metabolism , Peptides/metabolism , Peptides/pharmacology , Primary Cell Culture , RNA, Messenger/metabolism , Sequence Alignment , Sequence Homology, Amino Acid , SwineABSTRACT
IGF-I and IGF-II are key regulators of growth and metabolism. Still, data about their expression and distribution within the growth plate in different animal models remain contradictory. Inferences drawn from rodent animal models can only be applied to human conditions to a limited extent as the rodent's growth plate never fuses. In this study, we compared the expression of IGF-I and IGF-II in native growth plates of prepubertal piglets and under different cell culture conditions. We detected IGF-I mRNA expression and abundantly expressed IGF-II within the growth plate. IGF-I expression increased during monolayer cell culture while IGF-II expression dramatically decreased. Our studies revealed that these expression patterns remained unaffected by growth hormone stimulation in vitro. The abundant expression of IGF-II in porcine growth plate tissue, both on the mRNA and on the protein level, suggests that IGF-II also has a role in growth regulation at the early postnatal stage.
