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Cervical collagen and biomechanical strength in non-pregnant women with a history of cervical insufficiency.

Oxlund BS, Ørtoft G, Brüel A, Danielsen CC, Oxlund H, Uldbjerg N - Reprod. Biol. Endocrinol. (2010)

Bottom Line: Maximum load of the specimens did not differ between the groups (p = 0.78).No differences in the volume density of extracellular matrix or smooth muscle cells were found between the two groups.Cervical insufficiency does not appear to be associated with a constitutionally low collagen concentration or collagen of inferior mechanical quality.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Skejby, DK-8200 Aarhus N, Denmark. boxlund@dadlnet.dk

ABSTRACT

Background: It has been suggested that cervical insufficiency (CI) is characterized by a "muscular cervix" with low collagen and high smooth muscle concentrations also in the non-pregnant state. Therefore, the aim of this study was to investigate the biomechanical properties, collagen concentration, smooth muscle cell density, and collagen fiber orientation in cervical biopsies from non-pregnant women with a history of CI.

Methods: Cervical punch biopsies (2 x 15 mm) were obtained from 57 normal non-pregnant women and 22 women with a history of CI. Biomechanical tensile testing was performed, and collagen content was determined by hydroxyproline quantification. Histomorphometry was used to determine the volume densities of extracellular matrix and smooth muscle cells from the distal to the proximal part of each sample. Smooth muscle cells were identified using immunohistochemistry. Finally, collagen fiber orientation was investigated. Data are given as mean +/- SD.

Results: Collagen concentration was lower in the CI group (58.6 +/- 8.8%) compared with the control group (62.2 +/- 6.6%) (p = 0.033). However, when data were adjusted for age and parity, no difference in collagen concentration was found between the two groups. Maximum load of the specimens did not differ between the groups (p = 0.78). The tensile strength of cervical collagen, i.e. maximum load normalized per unit collagen (mg of collagen per mm of specimen length), was increased in the CI group compared with controls (p = 0.033). No differences in the volume density of extracellular matrix or smooth muscle cells were found between the two groups. Fibers not oriented in the plane of sectioning were increased in CI patients compared with controls.

Conclusions: Cervical insufficiency does not appear to be associated with a constitutionally low collagen concentration or collagen of inferior mechanical quality. Furthermore, the hypothesis that a "muscular cervix" with an abundance of smooth muscle cells contributes to the development of cervical insufficiency is not supported by the present study.

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Collagen fiber orientation. Picro-Sirius stained sections from the human cervix. (A) Longitudinal section of a biopsy including epithelium (Bar: 500 μm); (B) collagen fibers in the center of the grid were divided into three categories based on their orientation (longitudinal axis of sections horizontal): 1) longitudinal or "parallel" fibers (deviating less than ± 45° from the longitudinal axis), 2) perpendicular fibers, (deviating between 46° and 90° or -46° to -90° from the longitudinal axis) representing circular or radial fibers, and 3) fibers shorter than 27 μm (not oriented parallel with the sectioning plane) representing circular, radial or wavy longitudinal fibers (arrows point at a longitudinal collagen fiber. Bar: 25 μm).
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Figure 4: Collagen fiber orientation. Picro-Sirius stained sections from the human cervix. (A) Longitudinal section of a biopsy including epithelium (Bar: 500 μm); (B) collagen fibers in the center of the grid were divided into three categories based on their orientation (longitudinal axis of sections horizontal): 1) longitudinal or "parallel" fibers (deviating less than ± 45° from the longitudinal axis), 2) perpendicular fibers, (deviating between 46° and 90° or -46° to -90° from the longitudinal axis) representing circular or radial fibers, and 3) fibers shorter than 27 μm (not oriented parallel with the sectioning plane) representing circular, radial or wavy longitudinal fibers (arrows point at a longitudinal collagen fiber. Bar: 25 μm).

Mentions: Collagen fiber orientation was determined in order to evaluate whether the increase in normalized load found in the CI group could be explained from a different orientation of collagen fibers. The percentage of collagen fibers which was not oriented in the plane of sectioning was increased in CI patients (48.5 ± 13.2%) compared with control (40.6 ± 11.6%) (p = 0.033) (Table 6). No differences between the two groups in the percentage of collagen fibers considered "parallel" (less than ± 45°) with (Figure 4A and 4B) or "perpendicular" (between 46° and 90° or -46° to -90°) to the longitudinal axis were found.


Cervical collagen and biomechanical strength in non-pregnant women with a history of cervical insufficiency.

Oxlund BS, Ørtoft G, Brüel A, Danielsen CC, Oxlund H, Uldbjerg N - Reprod. Biol. Endocrinol. (2010)

Collagen fiber orientation. Picro-Sirius stained sections from the human cervix. (A) Longitudinal section of a biopsy including epithelium (Bar: 500 μm); (B) collagen fibers in the center of the grid were divided into three categories based on their orientation (longitudinal axis of sections horizontal): 1) longitudinal or "parallel" fibers (deviating less than ± 45° from the longitudinal axis), 2) perpendicular fibers, (deviating between 46° and 90° or -46° to -90° from the longitudinal axis) representing circular or radial fibers, and 3) fibers shorter than 27 μm (not oriented parallel with the sectioning plane) representing circular, radial or wavy longitudinal fibers (arrows point at a longitudinal collagen fiber. Bar: 25 μm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927597&req=5

Figure 4: Collagen fiber orientation. Picro-Sirius stained sections from the human cervix. (A) Longitudinal section of a biopsy including epithelium (Bar: 500 μm); (B) collagen fibers in the center of the grid were divided into three categories based on their orientation (longitudinal axis of sections horizontal): 1) longitudinal or "parallel" fibers (deviating less than ± 45° from the longitudinal axis), 2) perpendicular fibers, (deviating between 46° and 90° or -46° to -90° from the longitudinal axis) representing circular or radial fibers, and 3) fibers shorter than 27 μm (not oriented parallel with the sectioning plane) representing circular, radial or wavy longitudinal fibers (arrows point at a longitudinal collagen fiber. Bar: 25 μm).
Mentions: Collagen fiber orientation was determined in order to evaluate whether the increase in normalized load found in the CI group could be explained from a different orientation of collagen fibers. The percentage of collagen fibers which was not oriented in the plane of sectioning was increased in CI patients (48.5 ± 13.2%) compared with control (40.6 ± 11.6%) (p = 0.033) (Table 6). No differences between the two groups in the percentage of collagen fibers considered "parallel" (less than ± 45°) with (Figure 4A and 4B) or "perpendicular" (between 46° and 90° or -46° to -90°) to the longitudinal axis were found.

Bottom Line: Maximum load of the specimens did not differ between the groups (p = 0.78).No differences in the volume density of extracellular matrix or smooth muscle cells were found between the two groups.Cervical insufficiency does not appear to be associated with a constitutionally low collagen concentration or collagen of inferior mechanical quality.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Skejby, DK-8200 Aarhus N, Denmark. boxlund@dadlnet.dk

ABSTRACT

Background: It has been suggested that cervical insufficiency (CI) is characterized by a "muscular cervix" with low collagen and high smooth muscle concentrations also in the non-pregnant state. Therefore, the aim of this study was to investigate the biomechanical properties, collagen concentration, smooth muscle cell density, and collagen fiber orientation in cervical biopsies from non-pregnant women with a history of CI.

Methods: Cervical punch biopsies (2 x 15 mm) were obtained from 57 normal non-pregnant women and 22 women with a history of CI. Biomechanical tensile testing was performed, and collagen content was determined by hydroxyproline quantification. Histomorphometry was used to determine the volume densities of extracellular matrix and smooth muscle cells from the distal to the proximal part of each sample. Smooth muscle cells were identified using immunohistochemistry. Finally, collagen fiber orientation was investigated. Data are given as mean +/- SD.

Results: Collagen concentration was lower in the CI group (58.6 +/- 8.8%) compared with the control group (62.2 +/- 6.6%) (p = 0.033). However, when data were adjusted for age and parity, no difference in collagen concentration was found between the two groups. Maximum load of the specimens did not differ between the groups (p = 0.78). The tensile strength of cervical collagen, i.e. maximum load normalized per unit collagen (mg of collagen per mm of specimen length), was increased in the CI group compared with controls (p = 0.033). No differences in the volume density of extracellular matrix or smooth muscle cells were found between the two groups. Fibers not oriented in the plane of sectioning were increased in CI patients compared with controls.

Conclusions: Cervical insufficiency does not appear to be associated with a constitutionally low collagen concentration or collagen of inferior mechanical quality. Furthermore, the hypothesis that a "muscular cervix" with an abundance of smooth muscle cells contributes to the development of cervical insufficiency is not supported by the present study.

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