Growth Factor Function
Growth factors act as signaling molecules between cells. The signaling may occur between local cells (paracrine signaling), between distant cells (endocrine signaling) or the same cell that produced the signal binds its “own” growth factor (autocrine signaling). To induce the signal cascade, growth factors bind to their specific receptor situated on the cell membrane or, in the case of the fat-soluble steroid hormones, inside of the cell. Growth factors often target receptors of the tyrosine kinase family followed by downstream signaling transduction pathways like the MAP kinase signaling cascade.
Growth Factor Stimulation
Growth factors are important for the regulation of many different cellular processes. Usually, they are naturally occurring proteins or steroid hormones and are capable of stimulating:
• cell growth
• tissue repair
• cellular differentiation
• cell survival
There are many different growth factors which are often grouped into families like the Transforming Growth Factor (TGF) family or the family of Interleukins (IL).
Applications In Vivo and In Vitro
In vivo, many cells require the presence of different growth factors to proliferate or differentiate and to maintain their viability. In in vitro cell cultures, some cell lines require the addition of growth factors to the culture medium in order to proliferate. Additionally, they could be used to stimulate differentiation of cell lines.
In the clinic, growth factors may be utilized in the treatment of different diseases. For example, neutropenia may be treated with hematopoietic growth factors (granulocyte-colony stimulating factor (G-CSF)).
Available growth factors are often produced by genetic engineering. Therefore, recombinant bacteria, which have the particular genes inserted and are able to transcribe these genes as well as to translate the mRNA into the corresponding proteins, are produced. After protein extraction and purification, the growth factors are ready to be used in your experiments.