Cell Mimicking Microparticles Influence the Organization, Growth, and Mechanophenotype of Stem Cell Spheroids
Substrate stiffness is known to alter cell behavior and drive stem cell differentiation, though most research in this area has been restricted to traditional, two-dimensional culture systems rather than more physiologically relevant, three-dimensional (3D) platforms. In this study, we utilized polymer-based, cell mimicking microparticles (CMMPs) to deliver distinct, stable mechanical cues to human adipose derived stem cells in 3D spheroid culture to examine changes in adipogenic differentiation response and mechanophenotype. After 21 days of adipogenic induction, spheroids containing CMMPs (composite spheroids) stiffened in accordance with CMMP elasticity such that spheroids containing the stiffest, ~ 10 kPa, CMMPs were over 27% stiffer than those incorporating the most compliant, ~ 0.25 kPa CMMPs. Adipogenically induced, cell-only spheroids were over 180% larger and 50% more compliant than matched controls. Interestingly, composite spheroids cultured without chemical induction factors dissociated when presented with CMMPs stiffer than ~ 1 kPa, while adipogenic induction factors mitigated this behavior. Gene expression for PPARG and FABP4 were upregulated more than 45-fold in adipogenically induced samples compared to controls but were unaffected by CMMP elasticity, attributed to insufficient cell-CMMP contacts throughout the composite spheroid. In summary, mechanically tuned CMMPs influenced whole-spheroid mechanophenotype and stability but minimally affected differentiation response.
KeywordsStem cell differentiation Adipogenesis Elastic and viscoelastic properties 3D spheroid culture Self-assembly Atomic force microscopy (AFM) Hyper-compliant microparticles Tissue engineering
Atomic force microscopy
Adipose derived stem cells
Cell mimicking microparticle
Young’s modulus/elastic modulus
Fatty acid binding protein 4
Phosphate buffered saline
Peroxisome proliferator-activated receptor gamma
The authors would like to thank Manisha K. Shah for her assistance with confocal imaging. This work was supported by awards from the National Institute of General Medical Sciences (EMD, P20 GM104937), National Institute of Arthritis and Musculoskeletal and Skin Diseases (EMD, R01 AR063642), and the National Science Foundation (EMD, CAREER Award, CBET1253189). The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the National Science Foundation or National Institutes of Health.
Conflict of interest
NRL, EM, and EMD have patent filings relevant to the technology in this study. EMD owns MimicSphere, LLC, which focuses on the same technology.
NRL and EMD designed the study. NRL performed all CMMP/substrate preparation, cell culture, mechanical testing, and imaging. NRL, EMD, and JSS analyzed the data. NRL, EMD, JSS, JRM, and EM wrote and edited the manuscript. JRM and EM provided materials and consultation on the design, execution, and interpretation of the experiment and data sets.