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p38 MAPK signaling in postnatal tendon growth and remodeling.

Schwartz AJ, Sarver DC, Sugg KB, Dzierzawski JT, Gumucio JP, Mendias CL - PLoS ONE (2015)

Bottom Line: By 28 days after overload, tendon mass had increased by 30% compared to non-overloaded samples, and cross-sectional area (CSA) increased by around 50%, with most of the change occurring in the neotendon.Inhibition of p38 MAPK resulted in a profound decrease in IL6 expression, and had a modest effect on the expression of other ECM and cell proliferation genes, but had a negligible impact on overall tendon growth.The combined results from this study provided novel insights into tendon mechanobiology, and suggest that p38 MAPK signaling does not appear to be necessary for tendon growth in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, Michigan, United States of America; Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America.

ABSTRACT
Tendon is a dynamic tissue whose structure and function is influenced by mechanical loading, but little is known about the fundamental mechanisms that regulate tendon growth and remodeling in vivo. Data from cultured tendon fibroblasts indicated that the p38 MAPK pathway plays an important role in tendon fibroblast proliferation and collagen synthesis in vitro. To gain greater insight into the mechanisms of tendon growth, and explore the role of p38 MAPK signaling in this process, we tested the hypotheses that inducing plantaris tendon growth through the ablation of the synergist Achilles tendon would result in rapid expansion of a neotendon matrix surrounding the original tendon, and that treatment with the p38 MAPK inhibitor SB203580 would prevent this growth. Rats were treated with vehicle or SB203580, and subjected to synergist ablation by bilateral tenectomy of the Achilles tendon. Changes in histological and biochemical properties of plantaris tendons were analyzed 3, 7, or 28 days after overload, and comparisons were made to non-overloaded animals. By 28 days after overload, tendon mass had increased by 30% compared to non-overloaded samples, and cross-sectional area (CSA) increased by around 50%, with most of the change occurring in the neotendon. The expansion in CSA initially occurred through the synthesis of a hyaluronic acid rich matrix that was progressively replaced with mature collagen. Pericytes were present in areas of active tendon growth, but never in the original tendon ECM. Inhibition of p38 MAPK resulted in a profound decrease in IL6 expression, and had a modest effect on the expression of other ECM and cell proliferation genes, but had a negligible impact on overall tendon growth. The combined results from this study provided novel insights into tendon mechanobiology, and suggest that p38 MAPK signaling does not appear to be necessary for tendon growth in vivo.

No MeSH data available.


Expression of MMP and TIMP genes.Target gene expression was normalized to the stable housekeeping gene beta 2 microglobulin (B2M), and further normalized to plantaris tendons that were not subjected to synergist ablation. Values are mean±SD, N = 8 tendons for each group. Differences between groups were tested using a two-way ANOVA (α = 0.05) followed by Newman-Keuls post hoc sorting: a, different (P<0.05) from 3D vehicle; b, different (P<0.05) from 3D p38 MAPK inhibitor; c, different (P<0.05) from 7D vehicle; d, different (P<0.05) from 7D p38 MAPK inhibitor; e, different (P<0.05) from 28D vehicle.
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pone.0120044.g007: Expression of MMP and TIMP genes.Target gene expression was normalized to the stable housekeeping gene beta 2 microglobulin (B2M), and further normalized to plantaris tendons that were not subjected to synergist ablation. Values are mean±SD, N = 8 tendons for each group. Differences between groups were tested using a two-way ANOVA (α = 0.05) followed by Newman-Keuls post hoc sorting: a, different (P<0.05) from 3D vehicle; b, different (P<0.05) from 3D p38 MAPK inhibitor; c, different (P<0.05) from 7D vehicle; d, different (P<0.05) from 7D p38 MAPK inhibitor; e, different (P<0.05) from 28D vehicle.

Mentions: To further evaluate changes in tendon ECM after overload, we measured the expression of genes related to ECM composition and remodeling, and generally observed an effect of both time following overload and p38 MAPK inhibition (Figs. 6 and 7). Transcripts for the HAS enzymes, which synthesize the immature ECM scaffolding hyaluronic acid, were affected by both time after overload and p38 MAPK inhibition. In the vehicle group, the expression of the HAS genes was greatest 7 days after overload, and p38 MAPK inhibition markedly decreased the expression of both transcripts at 7 days and 28 days. The proteoglycan genes aggrecan (Acan), biglycan (Bgn), and versican (Vcan), which are typically enriched at the enthesis, generally followed the same trends observed for the HAS enzymes, although the expression of decorin (Dcn), fibromodulin (Fmod) and the intermediate filament vimentin (Vim) displayed little to no effect of time nor treatment. Type I (Col1a1) and Type III (Col3a1) collagen, which are the major structural proteins of tendon, had the greatest level of expression at 7 days. Inhibition of p38 MAPK did not impact type I or type III collagen expression at 3 or 28 days, although there was a slight decrease in expression for both transcripts at the 7 day time point. Genes controlling members of the matrix metalloproteinase (MMP) and tissue inhibitors of metalloproteinase (TIMPs) families were influenced overall by time following synergist ablation and the inhibition of p38 MAPK (Fig. 7). Transcripts for MMP2 and MMP14 were of highest abundance at 7 days, and p38 MAPK inhibition significantly decreased both transcripts at the 7 and 28 day time points. MMP3 was expressed at its greatest at 3 days in the vehicle group, but its expression remained largely unchanged with p38 MAPK inhibition until increasing significantly at the 28 day time point. There were no differences in MMP8 expression across treatment or time. MMP13 was highly upregulated at all time points compared to non-overloaded tendons, with an overall modest reduction in expression over time, and a negative effect of p38 MAPK inhibition at 3 and 7 days following overload. For TIMP1 and TIMP2 transcripts, expression was maximal at 7 days in the vehicle group but remained significantly downregulated with p38 MAPK inhibition at that time point.


p38 MAPK signaling in postnatal tendon growth and remodeling.

Schwartz AJ, Sarver DC, Sugg KB, Dzierzawski JT, Gumucio JP, Mendias CL - PLoS ONE (2015)

Expression of MMP and TIMP genes.Target gene expression was normalized to the stable housekeeping gene beta 2 microglobulin (B2M), and further normalized to plantaris tendons that were not subjected to synergist ablation. Values are mean±SD, N = 8 tendons for each group. Differences between groups were tested using a two-way ANOVA (α = 0.05) followed by Newman-Keuls post hoc sorting: a, different (P<0.05) from 3D vehicle; b, different (P<0.05) from 3D p38 MAPK inhibitor; c, different (P<0.05) from 7D vehicle; d, different (P<0.05) from 7D p38 MAPK inhibitor; e, different (P<0.05) from 28D vehicle.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4359143&req=5

pone.0120044.g007: Expression of MMP and TIMP genes.Target gene expression was normalized to the stable housekeeping gene beta 2 microglobulin (B2M), and further normalized to plantaris tendons that were not subjected to synergist ablation. Values are mean±SD, N = 8 tendons for each group. Differences between groups were tested using a two-way ANOVA (α = 0.05) followed by Newman-Keuls post hoc sorting: a, different (P<0.05) from 3D vehicle; b, different (P<0.05) from 3D p38 MAPK inhibitor; c, different (P<0.05) from 7D vehicle; d, different (P<0.05) from 7D p38 MAPK inhibitor; e, different (P<0.05) from 28D vehicle.
Mentions: To further evaluate changes in tendon ECM after overload, we measured the expression of genes related to ECM composition and remodeling, and generally observed an effect of both time following overload and p38 MAPK inhibition (Figs. 6 and 7). Transcripts for the HAS enzymes, which synthesize the immature ECM scaffolding hyaluronic acid, were affected by both time after overload and p38 MAPK inhibition. In the vehicle group, the expression of the HAS genes was greatest 7 days after overload, and p38 MAPK inhibition markedly decreased the expression of both transcripts at 7 days and 28 days. The proteoglycan genes aggrecan (Acan), biglycan (Bgn), and versican (Vcan), which are typically enriched at the enthesis, generally followed the same trends observed for the HAS enzymes, although the expression of decorin (Dcn), fibromodulin (Fmod) and the intermediate filament vimentin (Vim) displayed little to no effect of time nor treatment. Type I (Col1a1) and Type III (Col3a1) collagen, which are the major structural proteins of tendon, had the greatest level of expression at 7 days. Inhibition of p38 MAPK did not impact type I or type III collagen expression at 3 or 28 days, although there was a slight decrease in expression for both transcripts at the 7 day time point. Genes controlling members of the matrix metalloproteinase (MMP) and tissue inhibitors of metalloproteinase (TIMPs) families were influenced overall by time following synergist ablation and the inhibition of p38 MAPK (Fig. 7). Transcripts for MMP2 and MMP14 were of highest abundance at 7 days, and p38 MAPK inhibition significantly decreased both transcripts at the 7 and 28 day time points. MMP3 was expressed at its greatest at 3 days in the vehicle group, but its expression remained largely unchanged with p38 MAPK inhibition until increasing significantly at the 28 day time point. There were no differences in MMP8 expression across treatment or time. MMP13 was highly upregulated at all time points compared to non-overloaded tendons, with an overall modest reduction in expression over time, and a negative effect of p38 MAPK inhibition at 3 and 7 days following overload. For TIMP1 and TIMP2 transcripts, expression was maximal at 7 days in the vehicle group but remained significantly downregulated with p38 MAPK inhibition at that time point.

Bottom Line: By 28 days after overload, tendon mass had increased by 30% compared to non-overloaded samples, and cross-sectional area (CSA) increased by around 50%, with most of the change occurring in the neotendon.Inhibition of p38 MAPK resulted in a profound decrease in IL6 expression, and had a modest effect on the expression of other ECM and cell proliferation genes, but had a negligible impact on overall tendon growth.The combined results from this study provided novel insights into tendon mechanobiology, and suggest that p38 MAPK signaling does not appear to be necessary for tendon growth in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, Michigan, United States of America; Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America.

ABSTRACT
Tendon is a dynamic tissue whose structure and function is influenced by mechanical loading, but little is known about the fundamental mechanisms that regulate tendon growth and remodeling in vivo. Data from cultured tendon fibroblasts indicated that the p38 MAPK pathway plays an important role in tendon fibroblast proliferation and collagen synthesis in vitro. To gain greater insight into the mechanisms of tendon growth, and explore the role of p38 MAPK signaling in this process, we tested the hypotheses that inducing plantaris tendon growth through the ablation of the synergist Achilles tendon would result in rapid expansion of a neotendon matrix surrounding the original tendon, and that treatment with the p38 MAPK inhibitor SB203580 would prevent this growth. Rats were treated with vehicle or SB203580, and subjected to synergist ablation by bilateral tenectomy of the Achilles tendon. Changes in histological and biochemical properties of plantaris tendons were analyzed 3, 7, or 28 days after overload, and comparisons were made to non-overloaded animals. By 28 days after overload, tendon mass had increased by 30% compared to non-overloaded samples, and cross-sectional area (CSA) increased by around 50%, with most of the change occurring in the neotendon. The expansion in CSA initially occurred through the synthesis of a hyaluronic acid rich matrix that was progressively replaced with mature collagen. Pericytes were present in areas of active tendon growth, but never in the original tendon ECM. Inhibition of p38 MAPK resulted in a profound decrease in IL6 expression, and had a modest effect on the expression of other ECM and cell proliferation genes, but had a negligible impact on overall tendon growth. The combined results from this study provided novel insights into tendon mechanobiology, and suggest that p38 MAPK signaling does not appear to be necessary for tendon growth in vivo.

No MeSH data available.