Imaging human bone marrow stem cell morphogenesis in polyglycolic acid scaffold by multiphoton microscopy.

The noninvasive imaging of tissue engineering constructs is vital for understanding the physiological changes in construct formation and the design of improved products for therapeutic purposes. In this work, we use the combination of multiphoton autofluorescence and second harmonic generation (SHG) microscopy to image the physiological changes to the engineered constructs of human mesenchymal stem cells seeded in a polyglycolic acid (PGA) scaffold under induction by chondrogenic transforming growth factor-beta3. Without histological procedures, we found that multiphoton autofluorescence is useful for imaging the PGA scaffold and stem cells while SHG is useful for following the progress of extracellular matrix (ECM) formation. We found that the initial ECM formation tends to align along the PGA scaffold orientation and progressive induction alters the scaffold conformation, indicating that biomechanical forces or the chemical environment generated by chondrogenesis is sufficient for scaffold reorganization. Our results suggest that in the future this approach may be used for real-time monitoring of the physiological processes associated with tissue engineering.