Hypertonic Dextrose Stimulates Chondrogenic Cells to Deposit Collagen and Proliferate

Objective: Hypertonic dextrose (HD) injections (prolotherapy) for osteoarthritis are reported to reduce pain. Cartilage regeneration is hypothesized as a mechanism. This in vitro study identifies an HD concentration that stimulates chondrogenic cells to increase metabolic activity and assesses whether this concentration affects collagen deposition and proliferation. Design: ATDC5 chondrogenic cells were cultured in normoglycemic DMEM/F12 medium, treated with concentrations of HD (4-400 mM), and assessed with PrestoBlue. Advanced light microscopy was used to conduct live imaging of collagen deposition through second harmonic generation microscopy (SHG) and proliferation via 2-photon excitation microscopy. Proliferation was additionally assessed with hemocytometer counts. Results: A linear regression model found that, relative to the 4 mM baseline control, cells treated with 200 mM had a higher mean absorbance (P = 0.023) and cells treated with 250 mM were trending toward a higher mean absorbance (P = 0.076). Polynomial regression interpolated 240 mM as producing the highest average absorbance. Hemocytometer counts validated 250 mM as stimulating proliferation compared with the 4 mM control (P < 0.01). A concentration of 250 mM HD led to an increase in collagen deposition compared with that observed in control (P < 0.05). This HD concentration also led to increases in proliferation of ATDC5 cells relative to that of control (P < 0.001). Conclusions: A 250 mM HD solution appears to be associated with increased metabolic activity of chondrocytes, increased collagen deposition, and increased chondrocyte proliferation. These results support clinical prolotherapy research suggesting that intra-articular HD joint injections reduce knee pain. Further study of HD and cellular processes is warranted.