**5. Conclusions**

In this study, we developed 3D printed PCL scaffolds with wavy or linear patterns to investigate the effects of a wavy scaffold architecture on the osteogenic differentiation of hMSCs. When cultured in growth media, hMSCs attached and proliferated, forming confluent layers on the scaffolds within seven days. We found that hMSCs spread by taking the shape of the curved surfaces and exhibited elongated F-actin filaments and mature focal adhesion sites (vinculin staining). In contrast, hMSCs were bulkier in shape and showed dispersed vinculin staining on the orthogonal scaffold. We found that hMSCs showed significantly higher calcium deposition, higher ALP activity, and significantly pronounced osteocalcin staining when cultured on wavy scaffolds as compared to orthogonal scaffolds. These results are important in that they clearly showed the importance of scaffold architecture on hMSC osteogenesis and may provide guidance on novel bone scaffold/graft design for pre-clinical and clinical applications.

**Author Contributions:** S.J. and M.G. designed the experiments, analyzed the data, and wrote the manuscript. S.J. conducted the experiments. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work is funded by the National Science Foundation Award Number DMR-1714882 (M.G.) and the Faculty Seed Grant from the Center for Engineering MechanoBiology (CEMB), an NSF Science and Technology Center, under Grant Agreement CMMI: 15-48571. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

**Acknowledgments:** The authors acknowledge Andrew House and Chya-Yan for their help with micro-CT imaging. **Conflicts of Interest:** The authors declare no conflict of interest.
