Effect of strain on bone nodule formation by rat osteogenic cells in vitro

The purpose of this study was to assess in vitro bone nodule formation by cells exposed to a range of microstrain, at a sub-optimal oscillation frequency for bone formation. Fetal rat calvarial cells experienced a Flexercell™ regimen within either FLEX I™ (deformable) or FLEX II™ (non-deformable) substrates. Cells in FLEX I™ plates were exposed to growth medium only; those in FLEX II™ plates were exposed to either growth medium only, or growth medium+10 −7 M IGF-1. Cell numbers were assessed from 1 to 6 days. Other cells were exposed to the Flexercell™ regimen (−2 kPa, 0.05 Hz) for 1–3 (Group 1), 3–6 (Group 2), 1–9 (Group 3) or 10–15 (Group 4) days and were maintained, at other times, under standard conditions. After 21 days, nodules were counted within each well and within the compression,