Elisha Johnston1, Yi Kou2, Jason Junge3, Lin Chen4, Andrew Kochan5, Michael Johnston6, David Rabago7. 1. University of California Los Angeles, Los Angeles, CA, USA. 2. Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA. 3. Imaging Services, Advanced Light Microscopy Core, Translational Imaging Center, University of Southern California, Los Angeles, CA, USA. 4. Department of Chemistry and Biological Sciences, University of Southern California, Los Angeles, CA, USA. 5. Healing Arts Research, Sherman Oaks, CA, USA. 6. Independent Researcher, Rancho Palos Verdes, CA, USA. 7. Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA.
Abstract
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.
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.