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Inflammation induces irreversible biophysical changes in isolated nucleus pulposus cells.

Maidhof R, Jacobsen T, Papatheodorou A, Chahine NO - PLoS ONE (2014)

Bottom Line: Intracellular water content did not vary between treatment groups, but hydraulic permeability increased significantly with inflammatory treatment.Cell radius was also significantly increased both after 24 hours of treatment and after 1 week recovery.Inflammatory treated cells exhibited altered F-actin cytoskeleton expression relative to untreated cells.

View Article: PubMed Central - PubMed

Affiliation: Center for Autoimmune and Musculoskeletal Diseases, The Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, New York, United States of America.

ABSTRACT
Intervertebral disc degeneration is accompanied by elevated levels of inflammatory cytokines that have been implicated in disease etiology and matrix degradation. While the effects of inflammatory stimulation on disc cell metabolism have been well-studied, their effects on cell biophysical properties have not been investigated. The hypothesis of this study is that inflammatory stimulation alters the biomechanical properties of isolated disc cells and volume responses to step osmotic loading. Cells from the nucleus pulposus (NP) of bovine discs were isolated and treated with either lipopolysaccharide (LPS), an inflammatory ligand, or with the recombinant cytokine TNF-α for 24 hours. We measured cellular volume regulation responses to osmotic loading either immediately after stimulation or after a 1 week recovery period from the inflammatory stimuli. Cells from each group were tested under step osmotic loading and the transient volume-response was captured via time-lapse microscopy. Volume-responses were analyzed using mixture theory framework to investigate two biomechanical properties of the cell, the intracellular water content and the hydraulic permeability. Intracellular water content did not vary between treatment groups, but hydraulic permeability increased significantly with inflammatory treatment. In the 1 week recovery group, hydraulic permeability remained elevated relative to the untreated recovery control. Cell radius was also significantly increased both after 24 hours of treatment and after 1 week recovery. A significant linear correlation was observed between hydraulic permeability and cell radius in untreated cells at 24 hours and at 1-week recovery, though not in the inflammatory stimulated groups at either time point. This loss of correlation between cell size and hydraulic permeability suggests that regulation of volume change is disrupted irreversibly due to inflammatory stimulation. Inflammatory treated cells exhibited altered F-actin cytoskeleton expression relative to untreated cells. We also found a significant decrease in the expression of aquaporin-1, the predominant water channel in disc NP cells, with inflammatory stimulation. To our knowledge, this is the first study providing evidence that inflammatory stimulation directly alters the mechanobiology of NP cells. The cellular biophysical changes observed in this study are coincident with documented changes in the extracellular matrix induced by inflammation, and may be important in disease etiology.

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Mean intracellular water content (A, B) and mean hydraulic permeability (C, D) at 333 mOsm/L step for cells at (A, C) 24 hour and (B, D) 7-day recovery time points, respectively.*p<0.05 vs. untreated or untreated recovery control. n = 7–12 cells per condition.
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pone-0099621-g004: Mean intracellular water content (A, B) and mean hydraulic permeability (C, D) at 333 mOsm/L step for cells at (A, C) 24 hour and (B, D) 7-day recovery time points, respectively.*p<0.05 vs. untreated or untreated recovery control. n = 7–12 cells per condition.

Mentions: Intracellular water content () increased monotonically as cells were exposed to decreasing osmolarity steps (Table 1). Significant increase in were observed at the most hypotonic step (333 to 200 mOsm/L) relative to 466 to 300 mOsm/L step for cells from TNF-α group, and all groups at recovery time points (Table 1). Treatment with LPS or TNF-α for 24 hours had no significant effect on relative to untreated cells, and only the TNF-α recovery group had a significantly greater relative to untreated recovery group (Figure 4A, B; p<0.05). Cell hydraulic permeability () are presented in table 2. Significant increases in were observed at the most hypotonic step (333 to 200 mOsm/L) relative to 466 to 300 mOsm/L step for cells in the LPS, TNF-α and TNF-α recovery groups (Table 2, p<0.05). Significant increases in were observed after 24 hours of LPS or TNF-α treatment relative to untreated control (Figure 4C; p<0.05). Significantly increased was also observed in LPS and TNF-α recovery groups versus untreated recovery group (Figure 4D; p<0.03). The week-long culture duration did not significantly alter in untreated cells (p>0.33, Figure 4C, D). Overall, curve-fitting of the transient cell response to osmotic loading with the mixture-theory model resulted in a high mean coefficient of determination (R2 = 0.87±0.17).


Inflammation induces irreversible biophysical changes in isolated nucleus pulposus cells.

Maidhof R, Jacobsen T, Papatheodorou A, Chahine NO - PLoS ONE (2014)

Mean intracellular water content (A, B) and mean hydraulic permeability (C, D) at 333 mOsm/L step for cells at (A, C) 24 hour and (B, D) 7-day recovery time points, respectively.*p<0.05 vs. untreated or untreated recovery control. n = 7–12 cells per condition.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061011&req=5

pone-0099621-g004: Mean intracellular water content (A, B) and mean hydraulic permeability (C, D) at 333 mOsm/L step for cells at (A, C) 24 hour and (B, D) 7-day recovery time points, respectively.*p<0.05 vs. untreated or untreated recovery control. n = 7–12 cells per condition.
Mentions: Intracellular water content () increased monotonically as cells were exposed to decreasing osmolarity steps (Table 1). Significant increase in were observed at the most hypotonic step (333 to 200 mOsm/L) relative to 466 to 300 mOsm/L step for cells from TNF-α group, and all groups at recovery time points (Table 1). Treatment with LPS or TNF-α for 24 hours had no significant effect on relative to untreated cells, and only the TNF-α recovery group had a significantly greater relative to untreated recovery group (Figure 4A, B; p<0.05). Cell hydraulic permeability () are presented in table 2. Significant increases in were observed at the most hypotonic step (333 to 200 mOsm/L) relative to 466 to 300 mOsm/L step for cells in the LPS, TNF-α and TNF-α recovery groups (Table 2, p<0.05). Significant increases in were observed after 24 hours of LPS or TNF-α treatment relative to untreated control (Figure 4C; p<0.05). Significantly increased was also observed in LPS and TNF-α recovery groups versus untreated recovery group (Figure 4D; p<0.03). The week-long culture duration did not significantly alter in untreated cells (p>0.33, Figure 4C, D). Overall, curve-fitting of the transient cell response to osmotic loading with the mixture-theory model resulted in a high mean coefficient of determination (R2 = 0.87±0.17).

Bottom Line: Intracellular water content did not vary between treatment groups, but hydraulic permeability increased significantly with inflammatory treatment.Cell radius was also significantly increased both after 24 hours of treatment and after 1 week recovery.Inflammatory treated cells exhibited altered F-actin cytoskeleton expression relative to untreated cells.

View Article: PubMed Central - PubMed

Affiliation: Center for Autoimmune and Musculoskeletal Diseases, The Feinstein Institute for Medical Research, North Shore-LIJ Health System, Manhasset, New York, United States of America.

ABSTRACT
Intervertebral disc degeneration is accompanied by elevated levels of inflammatory cytokines that have been implicated in disease etiology and matrix degradation. While the effects of inflammatory stimulation on disc cell metabolism have been well-studied, their effects on cell biophysical properties have not been investigated. The hypothesis of this study is that inflammatory stimulation alters the biomechanical properties of isolated disc cells and volume responses to step osmotic loading. Cells from the nucleus pulposus (NP) of bovine discs were isolated and treated with either lipopolysaccharide (LPS), an inflammatory ligand, or with the recombinant cytokine TNF-α for 24 hours. We measured cellular volume regulation responses to osmotic loading either immediately after stimulation or after a 1 week recovery period from the inflammatory stimuli. Cells from each group were tested under step osmotic loading and the transient volume-response was captured via time-lapse microscopy. Volume-responses were analyzed using mixture theory framework to investigate two biomechanical properties of the cell, the intracellular water content and the hydraulic permeability. Intracellular water content did not vary between treatment groups, but hydraulic permeability increased significantly with inflammatory treatment. In the 1 week recovery group, hydraulic permeability remained elevated relative to the untreated recovery control. Cell radius was also significantly increased both after 24 hours of treatment and after 1 week recovery. A significant linear correlation was observed between hydraulic permeability and cell radius in untreated cells at 24 hours and at 1-week recovery, though not in the inflammatory stimulated groups at either time point. This loss of correlation between cell size and hydraulic permeability suggests that regulation of volume change is disrupted irreversibly due to inflammatory stimulation. Inflammatory treated cells exhibited altered F-actin cytoskeleton expression relative to untreated cells. We also found a significant decrease in the expression of aquaporin-1, the predominant water channel in disc NP cells, with inflammatory stimulation. To our knowledge, this is the first study providing evidence that inflammatory stimulation directly alters the mechanobiology of NP cells. The cellular biophysical changes observed in this study are coincident with documented changes in the extracellular matrix induced by inflammation, and may be important in disease etiology.

Show MeSH
Related in: MedlinePlus