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Mechanical strain stabilizes reconstituted collagen fibrils against enzymatic degradation by mammalian collagenase matrix metalloproteinase 8 (MMP-8).

Flynn BP, Bhole AP, Saeidi N, Liles M, Dimarzio CA, Ruberti JW - PLoS ONE (2010)

Bottom Line: It is found in bone, ligament, tendon, cartilage, intervertebral disc, skin, blood vessel, and cornea.These results have the potential to contribute to our understanding of many collagen matrix phenomena including development, adaptation, remodeling and disease.Additionally, tissue engineering could benefit from the ability to sculpt desired structures from physiologically compatible and mutable collagen.

View Article: PubMed Central - PubMed

Affiliation: Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America.

ABSTRACT

Background: Collagen, a triple-helical, self-organizing protein, is the predominant structural protein in mammals. It is found in bone, ligament, tendon, cartilage, intervertebral disc, skin, blood vessel, and cornea. We have recently postulated that fibrillar collagens (and their complementary enzymes) comprise the basis of a smart structural system which appears to support the retention of molecules in fibrils which are under tensile mechanical strain. The theory suggests that the mechanisms which drive the preferential accumulation of collagen in loaded tissue operate at the molecular level and are not solely cell-driven. The concept reduces control of matrix morphology to an interaction between molecules and the most relevant, physical, and persistent signal: mechanical strain.

Methodology/principal findings: The investigation was carried out in an environmentally-controlled microbioreactor in which reconstituted type I collagen micronetworks were gently strained between micropipettes. The strained micronetworks were exposed to active matrix metalloproteinase 8 (MMP-8) and relative degradation rates for loaded and unloaded fibrils were tracked simultaneously using label-free differential interference contrast (DIC) imaging. It was found that applied tensile mechanical strain significantly increased degradation time of loaded fibrils compared to unloaded, paired controls. In many cases, strained fibrils were detectable long after unstrained fibrils were degraded.

Conclusions/significance: In this investigation we demonstrate for the first time that applied mechanical strain preferentially preserves collagen fibrils in the presence of a physiologically-important mammalian enzyme: MMP-8. These results have the potential to contribute to our understanding of many collagen matrix phenomena including development, adaptation, remodeling and disease. Additionally, tissue engineering could benefit from the ability to sculpt desired structures from physiologically compatible and mutable collagen.

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Related in: MedlinePlus

DIC image showing pipette drift stretching fibrils to over 100% initial length during enzymatic degradation.Experimental time series images show the micropipettes drifting 30–40 µm apart, without fracturing or significantly thinning attached collagen fibrils, indicating either additional collagen deposition or structural changes within the fibrils. Note, in the last frame, stretched fibrils remain visible in the microbioreactor while peripheral fibrils have degraded. Experiments with large pipette drift were excluded from analysis. Bar  = 10 µm.
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pone-0012337-g002: DIC image showing pipette drift stretching fibrils to over 100% initial length during enzymatic degradation.Experimental time series images show the micropipettes drifting 30–40 µm apart, without fracturing or significantly thinning attached collagen fibrils, indicating either additional collagen deposition or structural changes within the fibrils. Note, in the last frame, stretched fibrils remain visible in the microbioreactor while peripheral fibrils have degraded. Experiments with large pipette drift were excluded from analysis. Bar  = 10 µm.

Mentions: From direct visual assessment of collagen micronetwork behavior it was clear that the strained region is more dense than the peripheral fibril network prior to the degradation process (n = 8). In addition, it could be readily observed that one or more strained fibrils remain between pipettes well after all peripheral fibrils have degraded (n = 8). In the unloaded networks, large fibrils perpendicular to the field of view (and the direction of stretch) can often be observed as high contrast dots with light and dark edges (DIC effect). These dots are easy to visually track throughout the degradation event and cannot move out of the thin DIC focal plane because they are perpendicular to it. These perpendicular fibrils appear to lose intensity more quickly than the fibrils oriented in between pipettes (Fig. 1). In some experiments (n = 3, excluded from analysis) one or both of the pipettes drifted far from the starting position, greatly increasing the separation distance and fibril stretch (∼100% increase). Despite this drift, one or more of the strained fibrils persisted between the pipettes after peripheral unstrained fibrils had degraded (Fig. 2).


Mechanical strain stabilizes reconstituted collagen fibrils against enzymatic degradation by mammalian collagenase matrix metalloproteinase 8 (MMP-8).

Flynn BP, Bhole AP, Saeidi N, Liles M, Dimarzio CA, Ruberti JW - PLoS ONE (2010)

DIC image showing pipette drift stretching fibrils to over 100% initial length during enzymatic degradation.Experimental time series images show the micropipettes drifting 30–40 µm apart, without fracturing or significantly thinning attached collagen fibrils, indicating either additional collagen deposition or structural changes within the fibrils. Note, in the last frame, stretched fibrils remain visible in the microbioreactor while peripheral fibrils have degraded. Experiments with large pipette drift were excluded from analysis. Bar  = 10 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2925882&req=5

pone-0012337-g002: DIC image showing pipette drift stretching fibrils to over 100% initial length during enzymatic degradation.Experimental time series images show the micropipettes drifting 30–40 µm apart, without fracturing or significantly thinning attached collagen fibrils, indicating either additional collagen deposition or structural changes within the fibrils. Note, in the last frame, stretched fibrils remain visible in the microbioreactor while peripheral fibrils have degraded. Experiments with large pipette drift were excluded from analysis. Bar  = 10 µm.
Mentions: From direct visual assessment of collagen micronetwork behavior it was clear that the strained region is more dense than the peripheral fibril network prior to the degradation process (n = 8). In addition, it could be readily observed that one or more strained fibrils remain between pipettes well after all peripheral fibrils have degraded (n = 8). In the unloaded networks, large fibrils perpendicular to the field of view (and the direction of stretch) can often be observed as high contrast dots with light and dark edges (DIC effect). These dots are easy to visually track throughout the degradation event and cannot move out of the thin DIC focal plane because they are perpendicular to it. These perpendicular fibrils appear to lose intensity more quickly than the fibrils oriented in between pipettes (Fig. 1). In some experiments (n = 3, excluded from analysis) one or both of the pipettes drifted far from the starting position, greatly increasing the separation distance and fibril stretch (∼100% increase). Despite this drift, one or more of the strained fibrils persisted between the pipettes after peripheral unstrained fibrils had degraded (Fig. 2).

Bottom Line: It is found in bone, ligament, tendon, cartilage, intervertebral disc, skin, blood vessel, and cornea.These results have the potential to contribute to our understanding of many collagen matrix phenomena including development, adaptation, remodeling and disease.Additionally, tissue engineering could benefit from the ability to sculpt desired structures from physiologically compatible and mutable collagen.

View Article: PubMed Central - PubMed

Affiliation: Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts, United States of America.

ABSTRACT

Background: Collagen, a triple-helical, self-organizing protein, is the predominant structural protein in mammals. It is found in bone, ligament, tendon, cartilage, intervertebral disc, skin, blood vessel, and cornea. We have recently postulated that fibrillar collagens (and their complementary enzymes) comprise the basis of a smart structural system which appears to support the retention of molecules in fibrils which are under tensile mechanical strain. The theory suggests that the mechanisms which drive the preferential accumulation of collagen in loaded tissue operate at the molecular level and are not solely cell-driven. The concept reduces control of matrix morphology to an interaction between molecules and the most relevant, physical, and persistent signal: mechanical strain.

Methodology/principal findings: The investigation was carried out in an environmentally-controlled microbioreactor in which reconstituted type I collagen micronetworks were gently strained between micropipettes. The strained micronetworks were exposed to active matrix metalloproteinase 8 (MMP-8) and relative degradation rates for loaded and unloaded fibrils were tracked simultaneously using label-free differential interference contrast (DIC) imaging. It was found that applied tensile mechanical strain significantly increased degradation time of loaded fibrils compared to unloaded, paired controls. In many cases, strained fibrils were detectable long after unstrained fibrils were degraded.

Conclusions/significance: In this investigation we demonstrate for the first time that applied mechanical strain preferentially preserves collagen fibrils in the presence of a physiologically-important mammalian enzyme: MMP-8. These results have the potential to contribute to our understanding of many collagen matrix phenomena including development, adaptation, remodeling and disease. Additionally, tissue engineering could benefit from the ability to sculpt desired structures from physiologically compatible and mutable collagen.

Show MeSH
Related in: MedlinePlus