| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2144754 | Matrix Biology | 2014 | 10 Pages |
•A charged synthetic hydrogel is employed to study chondrocyte mechanobiology.•A link among ionic osmolytes, dynamic loading, and intracellular calcium is shown.•Dynamic changes in osmolarity enhanced chondrocyte synthesis of proteoglycans.•Intracellular calcium mediates tissue production under loading and no loading.
The goal of this study was to investigate the role of fixed negative charges in regulating cartilage-like tissue production by chondrocytes under static and dynamic three-dimensional culture, and to determine whether intracellular calcium ([Ca2 +]i) is involved in mediating this response. Initial experiments using the 3D neutral hydrogel were conducted in static isotonic culture with ionic and non-ionic osmolytes added to the culture medium. Tissue production by bovine chondrocytes with non-ionic osmolytes was 1.9-fold greater than with ionic osmolytes, suggesting that the ionic nature of the osmolyte is an important regulator of tissue production. To investigate fixed negative charges, a 3D culture system containing encapsulated chondrocytes was employed based on a synthetic and neutral hydrogel platform within which negatively charged chondroitin sulfate was incorporated in a controlled manner. Incorporation of negative charges did not affect the mechanical properties of the hydrogel; however, intracellular ion concentration was elevated from the culture medium (330 mOsm) and estimated to be similar to that in ~ 400 mOsm culture medium. With dynamic loading, GAG synthesis decreased by 26% in neutral hydrogels cultured in 400 mOsm medium, and increased by 26% in charged gels cultured in 330 mOsm. Treatment of chondrocyte-seeded hydrogels with the Ca2 + chelator BAPTA-AM decreased GAG synthesis by 32–46% and was similar among all conditions, suggesting multiple roles for Ca2 + mediated tissue production including with ionic osmolytes. In conclusion, findings from this study suggest that a dynamic ionic environment regulates tissue synthesis and points to [Ca2 +]i signaling as a potential mediator.
