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Differential expression of lumican and fibromodulin regulate collagen fibrillogenesis in developing mouse tendons.

Ezura Y, Chakravarti S, Oldberg A, Chervoneva I, Birk DE - J. Cell Biol. (2000)

Bottom Line: With development, the amount of lumican decreases to barely detectable levels while fibromodulin increases significantly, and these changing patterns may regulate this process.The observed increased ratio of fibromodulin to lumican and a competition for the same binding site could mediate these transitions.These studies indicate that lumican and fibromodulin have different developmental stage and leucine-rich repeat protein specific functions in the regulation of fibrillogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.

ABSTRACT
Collagen fibrillogenesis is finely regulated during development of tissue-specific extracellular matrices. The role(s) of a leucine-rich repeat protein subfamily in the regulation of fibrillogenesis during tendon development were defined. Lumican-, fibromodulin-, and double-deficient mice demonstrated disruptions in fibrillogenesis. With development, the amount of lumican decreases to barely detectable levels while fibromodulin increases significantly, and these changing patterns may regulate this process. Electron microscopic analysis demonstrated structural abnormalities in the fibrils and alterations in the progression through different assembly steps. In lumican-deficient tendons, alterations were observed early and the mature tendon was nearly normal. Fibromodulin-deficient tendons were comparable with the lumican- in early developmental periods and acquired a severe phenotype by maturation. The double-deficient mice had a phenotype that was additive early and comparable with the fibromodulin-deficient mice at maturation. Therefore, lumican and fibromodulin both influence initial assembly of intermediates and the entry into fibril growth, while fibromodulin facilitates the progression through growth steps leading to mature fibrils. The observed increased ratio of fibromodulin to lumican and a competition for the same binding site could mediate these transitions. These studies indicate that lumican and fibromodulin have different developmental stage and leucine-rich repeat protein specific functions in the regulation of fibrillogenesis.

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Collagen fibril diameter distributions during development of wild-type, lumican-, fibromodulin-, and double lumican/fibromodulin– tendons. Collagen fibril diameter distributions are presented as histograms for wild-type (a–d), lumican-deficient (e–h), fibromodulin-deficient (i–l), and double lumican/fibromodulin–deficient (m–p) mouse tendons. Vertical dotted lines indicate peaks observed in wild-type mouse tendons at ∼65, 120, 240, and 280 nm. (a–d) Means, SD, and number of fibrils measured (n)/number of different animals (na) are presented as mean ± SD (n/na) in the graphs.
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Figure 6: Collagen fibril diameter distributions during development of wild-type, lumican-, fibromodulin-, and double lumican/fibromodulin– tendons. Collagen fibril diameter distributions are presented as histograms for wild-type (a–d), lumican-deficient (e–h), fibromodulin-deficient (i–l), and double lumican/fibromodulin–deficient (m–p) mouse tendons. Vertical dotted lines indicate peaks observed in wild-type mouse tendons at ∼65, 120, 240, and 280 nm. (a–d) Means, SD, and number of fibrils measured (n)/number of different animals (na) are presented as mean ± SD (n/na) in the graphs.

Mentions: Mice were killed at 4 d, 10 d, 1 mo, and 3 mo after birth. Between three and six mice were used for each of the 16 groups. The exact numbers for each group are indicated in Fig. 6 (below). Hind limbs were fixed in situ in 4% paraformaldehyde, 2.5% glutaraldehyde, 0.1 M sodium cacodylate, pH 7.4, with 8.0 mM CaCl2 for 15 min at room temperature, during which time the flexor digitorium tendons were dissected. This was followed by 100 min at 4°C and processing as previously described (Birk and Trelstad 1986; Birk et al. 1997). In brief, the tendons were post-fixed with 1% osmium tetroxide and enbloc stained with 2% uranyl acetate/50% ethanol. After dehydration in an ethanol series followed by propylene oxide, the tendons were infiltrated and embedded in a mixture of Polybed 812, nadic methyl anhydride, dodecenylsuccinic anhydride, and DMP-30 (Polysciences, Inc.). Thick sections (1 μm) were cut and stained with methylene blue–azur blue for examination and selection of specific regions for EM analysis. Thin sections were prepared using a Reichert UCT ultramicrotome and a diamond knife. Staining was with 2% aqueous uranyl acetate followed by 1% phosphotungstic acid, pH 3.2. Cross sections of midplantar regions of flexor digitorum tendons were analyzed in fibromodulin-, lumican-, fibromodulin/lumican-deficient and wild-type mice using electron microscopy. Sections were examined and photographed at 75 kV using a transmission electron microscope (Hitachi 7000).


Differential expression of lumican and fibromodulin regulate collagen fibrillogenesis in developing mouse tendons.

Ezura Y, Chakravarti S, Oldberg A, Chervoneva I, Birk DE - J. Cell Biol. (2000)

Collagen fibril diameter distributions during development of wild-type, lumican-, fibromodulin-, and double lumican/fibromodulin– tendons. Collagen fibril diameter distributions are presented as histograms for wild-type (a–d), lumican-deficient (e–h), fibromodulin-deficient (i–l), and double lumican/fibromodulin–deficient (m–p) mouse tendons. Vertical dotted lines indicate peaks observed in wild-type mouse tendons at ∼65, 120, 240, and 280 nm. (a–d) Means, SD, and number of fibrils measured (n)/number of different animals (na) are presented as mean ± SD (n/na) in the graphs.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2169450&req=5

Figure 6: Collagen fibril diameter distributions during development of wild-type, lumican-, fibromodulin-, and double lumican/fibromodulin– tendons. Collagen fibril diameter distributions are presented as histograms for wild-type (a–d), lumican-deficient (e–h), fibromodulin-deficient (i–l), and double lumican/fibromodulin–deficient (m–p) mouse tendons. Vertical dotted lines indicate peaks observed in wild-type mouse tendons at ∼65, 120, 240, and 280 nm. (a–d) Means, SD, and number of fibrils measured (n)/number of different animals (na) are presented as mean ± SD (n/na) in the graphs.
Mentions: Mice were killed at 4 d, 10 d, 1 mo, and 3 mo after birth. Between three and six mice were used for each of the 16 groups. The exact numbers for each group are indicated in Fig. 6 (below). Hind limbs were fixed in situ in 4% paraformaldehyde, 2.5% glutaraldehyde, 0.1 M sodium cacodylate, pH 7.4, with 8.0 mM CaCl2 for 15 min at room temperature, during which time the flexor digitorium tendons were dissected. This was followed by 100 min at 4°C and processing as previously described (Birk and Trelstad 1986; Birk et al. 1997). In brief, the tendons were post-fixed with 1% osmium tetroxide and enbloc stained with 2% uranyl acetate/50% ethanol. After dehydration in an ethanol series followed by propylene oxide, the tendons were infiltrated and embedded in a mixture of Polybed 812, nadic methyl anhydride, dodecenylsuccinic anhydride, and DMP-30 (Polysciences, Inc.). Thick sections (1 μm) were cut and stained with methylene blue–azur blue for examination and selection of specific regions for EM analysis. Thin sections were prepared using a Reichert UCT ultramicrotome and a diamond knife. Staining was with 2% aqueous uranyl acetate followed by 1% phosphotungstic acid, pH 3.2. Cross sections of midplantar regions of flexor digitorum tendons were analyzed in fibromodulin-, lumican-, fibromodulin/lumican-deficient and wild-type mice using electron microscopy. Sections were examined and photographed at 75 kV using a transmission electron microscope (Hitachi 7000).

Bottom Line: With development, the amount of lumican decreases to barely detectable levels while fibromodulin increases significantly, and these changing patterns may regulate this process.The observed increased ratio of fibromodulin to lumican and a competition for the same binding site could mediate these transitions.These studies indicate that lumican and fibromodulin have different developmental stage and leucine-rich repeat protein specific functions in the regulation of fibrillogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.

ABSTRACT
Collagen fibrillogenesis is finely regulated during development of tissue-specific extracellular matrices. The role(s) of a leucine-rich repeat protein subfamily in the regulation of fibrillogenesis during tendon development were defined. Lumican-, fibromodulin-, and double-deficient mice demonstrated disruptions in fibrillogenesis. With development, the amount of lumican decreases to barely detectable levels while fibromodulin increases significantly, and these changing patterns may regulate this process. Electron microscopic analysis demonstrated structural abnormalities in the fibrils and alterations in the progression through different assembly steps. In lumican-deficient tendons, alterations were observed early and the mature tendon was nearly normal. Fibromodulin-deficient tendons were comparable with the lumican- in early developmental periods and acquired a severe phenotype by maturation. The double-deficient mice had a phenotype that was additive early and comparable with the fibromodulin-deficient mice at maturation. Therefore, lumican and fibromodulin both influence initial assembly of intermediates and the entry into fibril growth, while fibromodulin facilitates the progression through growth steps leading to mature fibrils. The observed increased ratio of fibromodulin to lumican and a competition for the same binding site could mediate these transitions. These studies indicate that lumican and fibromodulin have different developmental stage and leucine-rich repeat protein specific functions in the regulation of fibrillogenesis.

Show MeSH
Related in: MedlinePlus