Monitoring and Engineering of the Stem Cell Microenvironment: Inkjet Printing of Growth Factors onto Novel Scaffolds for Controlling Musculoskeletal Stem Cell Differentiation and Alignment

The primary objective of this study was to develop approaches for controlling and monitoring stem cell behavior in vitro and in vivo for potential applications in regenerative medicine. To control stem cell behavior in vitro and in vivo, signaling molecules including growth factors (GFs) were spatially patterned onto novel substrates and scaffolds to instruct stem cells to undergo desired cell behaviors such as musculoskeletal differentiation in register to the biochemical and geometric cues supplied. The premise for this approach is based on the biological phenomenon whereby stem cell behavior can be directed by instructive cues present in its immediate vicinity or microenvironment. Using this methodology, a primitive muscle-tendonbone (MTB) unit was patterned in vitro while ectopic bone tissue was patterned in vivo. In addition, the effect of inflammatory and anti-inflammatory microenvironments on osteoblast differentiation was characterized since inflammation is an important component of the wound healing response. In such studies, inflammatory microenvironments were found to inhibit osteoblast differentiation in several musculoskeletal progenitor cells and this inhibition could be reversed with anti-inflammatory IL-10. Primary cells such as muscle-derived stem cells (MDSCs) were also found to display differing levels of sensitivity to such osteoblast inhibition. To monitor stem cell behavior in vitro, a computer-vision based system was developed for realtime adaptive subculture of muscle-progenitor cells. This computer-directed subculture system minimizes human labor and subjectivity during progenitor cell expansion and cells cultured with this system were comparable to those grown by a human operator. The work described here illustrates methods for controlling and monitoring stem cell behavior and may have potential applications in regenerative medicine.