Example 1: influence of biomaterials on osteogenic gene expression and mineralization in hPDL cells
In the first example, we will consider how to utilize gene expression to assess whether biomaterial “X” can induce bone formation or osteogenesis. There are multiple ways in which these experiments can be conducted, and proper quantification of bone formation must be assayed using different, but complementary, methods, of which mRNA analysis is only one.
Choosing an appropriate cell model
Before testing the osteogenic properties of a biomaterial, the first criterion that has to be established is what type of cells will be used in the study. The endogenous transcriptome of different cell populations is highly variable; the amount and types of mRNA transcripts they express can differ greatly. Such differences are particularly noticeable when mesenchymal progenitor cells, osteoblasts, or osteogenic cell lines are used as a starting point.
Cell culture experiments often include osteogenic cell lines (MC3T3-E1, MG-63), which have the advantage of well-characterized patterns of mineralization and predictable gene expression profiles. Yet, they have limited value as the cells are transformed and as their overall phenotype is not necessarily indicative of cells in the human body (Czekanska et al., 2012). Primary cell cultures are always preferable, particularly if human cells can be utilized, but these typically are more heterogeneous with respect to the phenotypes of the cells (Czekanska et al., 2012).