Limits...
Mechanical Forces Accelerate Collagen Digestion by Bacterial Collagenase in Lung Tissue Strips.

Yi E, Sato S, Takahashi A, Parameswaran H, Blute TA, Bartolák-Suki E, Suki B - Front Physiol (2016)

Bottom Line: Most tissues in the body are under mechanical tension, and while enzymes mediate many cellular and extracellular processes, the effects of mechanical forces on enzyme reactions in the native extracellular matrix (ECM) are not fully understood.Generally, mechanical loading increased the effects of enzyme activity characterized by an irreversible decline in stiffness and tissue deterioration seen on both confocal and electron microscopic images.These results suggest that the decline in stiffness results from rupture of collagen followed by load transfer and subsequent rupture of alveolar walls.

View Article: PubMed Central - PubMed

Affiliation: Cell and Tissue Mechanics, Department of Biomedical Engineering, Boston University Boston, MA, USA.

ABSTRACT
Most tissues in the body are under mechanical tension, and while enzymes mediate many cellular and extracellular processes, the effects of mechanical forces on enzyme reactions in the native extracellular matrix (ECM) are not fully understood. We hypothesized that physiological levels of mechanical forces are capable of modifying the activity of collagenase, a key remodeling enzyme of the ECM. To test this, lung tissue Young's modulus and a nonlinearity index characterizing the shape of the stress-strain curve were measured in the presence of bacterial collagenase under static uniaxial strain of 0, 20, 40, and 80%, as well as during cyclic mechanical loading with strain amplitudes of ±10 or ±20% superimposed on 40% static strain, and frequencies of 0.1 or 1 Hz. Confocal and electron microscopy was used to determine and quantify changes in ECM structure. Generally, mechanical loading increased the effects of enzyme activity characterized by an irreversible decline in stiffness and tissue deterioration seen on both confocal and electron microscopic images. However, a static strain of 20% provided protection against digestion compared to both higher and lower strains. The decline in stiffness during digestion positively correlated with the increase in equivalent alveolar diameters and negatively correlated with the nonlinearity index. These results suggest that the decline in stiffness results from rupture of collagen followed by load transfer and subsequent rupture of alveolar walls. This study may provide new understanding of the role of collagen degradation in general tissue remodeling and disease progression.

No MeSH data available.


Related in: MedlinePlus

(A) Time course of mean and SD of the nonlinearity index defined as the relative change in modulus between 36 and 15% strain, normalized to unity at time 0 during 60 min in the tissue bath with or without adding bacterial collagenase. (B) Comparison of the percent increase in the normalized nonlinearity index from time 0 to 60 min. For the definition of the groups see the caption in Figure 3. The D0% group was statistically different from both the D40% and D80% groups.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4940411&req=5

Figure 4: (A) Time course of mean and SD of the nonlinearity index defined as the relative change in modulus between 36 and 15% strain, normalized to unity at time 0 during 60 min in the tissue bath with or without adding bacterial collagenase. (B) Comparison of the percent increase in the normalized nonlinearity index from time 0 to 60 min. For the definition of the groups see the caption in Figure 3. The D0% group was statistically different from both the D40% and D80% groups.

Mentions: The nonlinearity index k, normalized to unity at t = 0, generally increased with time for the stretched and digested groups (D40% and D80% in Figure 4A). First, limiting the analysis to data at 0 and 40% strains, application of a three-way ANOVA showed that there were statistically significant interactions among time, stretch and digestion (p < 0.01). Specifically, the effect of stretch is significant (p < 0.001) when averaged over time within the control samples. The effect of time is also significant at 40% strain for the digested samples only (p < 0.001). Figure 4B compares the percent increase of k at 60 min using one-way ANOVA. Since the SD values are high, significant difference was only found between the D0% and D40% and the D0% and D80% groups.


Mechanical Forces Accelerate Collagen Digestion by Bacterial Collagenase in Lung Tissue Strips.

Yi E, Sato S, Takahashi A, Parameswaran H, Blute TA, Bartolák-Suki E, Suki B - Front Physiol (2016)

(A) Time course of mean and SD of the nonlinearity index defined as the relative change in modulus between 36 and 15% strain, normalized to unity at time 0 during 60 min in the tissue bath with or without adding bacterial collagenase. (B) Comparison of the percent increase in the normalized nonlinearity index from time 0 to 60 min. For the definition of the groups see the caption in Figure 3. The D0% group was statistically different from both the D40% and D80% groups.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940411&req=5

Figure 4: (A) Time course of mean and SD of the nonlinearity index defined as the relative change in modulus between 36 and 15% strain, normalized to unity at time 0 during 60 min in the tissue bath with or without adding bacterial collagenase. (B) Comparison of the percent increase in the normalized nonlinearity index from time 0 to 60 min. For the definition of the groups see the caption in Figure 3. The D0% group was statistically different from both the D40% and D80% groups.
Mentions: The nonlinearity index k, normalized to unity at t = 0, generally increased with time for the stretched and digested groups (D40% and D80% in Figure 4A). First, limiting the analysis to data at 0 and 40% strains, application of a three-way ANOVA showed that there were statistically significant interactions among time, stretch and digestion (p < 0.01). Specifically, the effect of stretch is significant (p < 0.001) when averaged over time within the control samples. The effect of time is also significant at 40% strain for the digested samples only (p < 0.001). Figure 4B compares the percent increase of k at 60 min using one-way ANOVA. Since the SD values are high, significant difference was only found between the D0% and D40% and the D0% and D80% groups.

Bottom Line: Most tissues in the body are under mechanical tension, and while enzymes mediate many cellular and extracellular processes, the effects of mechanical forces on enzyme reactions in the native extracellular matrix (ECM) are not fully understood.Generally, mechanical loading increased the effects of enzyme activity characterized by an irreversible decline in stiffness and tissue deterioration seen on both confocal and electron microscopic images.These results suggest that the decline in stiffness results from rupture of collagen followed by load transfer and subsequent rupture of alveolar walls.

View Article: PubMed Central - PubMed

Affiliation: Cell and Tissue Mechanics, Department of Biomedical Engineering, Boston University Boston, MA, USA.

ABSTRACT
Most tissues in the body are under mechanical tension, and while enzymes mediate many cellular and extracellular processes, the effects of mechanical forces on enzyme reactions in the native extracellular matrix (ECM) are not fully understood. We hypothesized that physiological levels of mechanical forces are capable of modifying the activity of collagenase, a key remodeling enzyme of the ECM. To test this, lung tissue Young's modulus and a nonlinearity index characterizing the shape of the stress-strain curve were measured in the presence of bacterial collagenase under static uniaxial strain of 0, 20, 40, and 80%, as well as during cyclic mechanical loading with strain amplitudes of ±10 or ±20% superimposed on 40% static strain, and frequencies of 0.1 or 1 Hz. Confocal and electron microscopy was used to determine and quantify changes in ECM structure. Generally, mechanical loading increased the effects of enzyme activity characterized by an irreversible decline in stiffness and tissue deterioration seen on both confocal and electron microscopic images. However, a static strain of 20% provided protection against digestion compared to both higher and lower strains. The decline in stiffness during digestion positively correlated with the increase in equivalent alveolar diameters and negatively correlated with the nonlinearity index. These results suggest that the decline in stiffness results from rupture of collagen followed by load transfer and subsequent rupture of alveolar walls. This study may provide new understanding of the role of collagen degradation in general tissue remodeling and disease progression.

No MeSH data available.


Related in: MedlinePlus