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

Distribution of the incremental modulus Y of normal lung tissue strips. Note the highly asymmetric nature of the distribution.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Distribution of the incremental modulus Y of normal lung tissue strips. Note the highly asymmetric nature of the distribution.

Mentions: Example stress-strain curves before and after 60 min of digestion are shown in Figure 1. Both the stress and the Young's modulus (Y), computed as the slope of the curve at 15% strain, are significantly reduced following digestion. Since Y values were obtained for all samples including additional control groups not reported, we obtained a large number of control measurements (n = 140) which allowed us to construct a distribution of Y (Figure 2). The distribution is skewed showing an exponential tail with a median and 95% confidence interval of 899 ± 134 Pa.


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)

Distribution of the incremental modulus Y of normal lung tissue strips. Note the highly asymmetric nature of the distribution.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Distribution of the incremental modulus Y of normal lung tissue strips. Note the highly asymmetric nature of the distribution.
Mentions: Example stress-strain curves before and after 60 min of digestion are shown in Figure 1. Both the stress and the Young's modulus (Y), computed as the slope of the curve at 15% strain, are significantly reduced following digestion. Since Y values were obtained for all samples including additional control groups not reported, we obtained a large number of control measurements (n = 140) which allowed us to construct a distribution of Y (Figure 2). The distribution is skewed showing an exponential tail with a median and 95% confidence interval of 899 ± 134 Pa.

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