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Focal experimental injury leads to widespread gene expression and histologic changes in equine flexor tendons.

Jacobsen E, Dart AJ, Mondori T, Horadogoda N, Jeffcott LB, Little CB, Smith MM - PLoS ONE (2015)

Bottom Line: The histopathology score was significantly higher in transected tendons compared to control tendons in all regions except for the most distal (P ≤ 0.03) with no differences between overstressed (medial) and stress-deprived (lateral) tendon halves.After correcting for location within the tendon, gene expression for aggrecan, versican, biglycan, lumican, collagen types I, II and III, MMP14 and TIMP1 was increased in transected tendons compared with control tendons (P < 0.02) and decreased for ADAMTS4, MMP3 and TIMP3 (P < 0.001).Our data suggest that successful treatments of focal injuries will need to address pathology in the entire tendon, and that better methods to monitor the development and resolution of tendinopathy are required.

View Article: PubMed Central - PubMed

Affiliation: Research and Clinical Training Unit, University Veterinary Teaching Hospital, University of Sydney, Camden, New South Wales, Australia.

ABSTRACT
It is not known how extensively a localised flexor tendon injury affects the entire tendon. This study examined the extent of and relationship between histopathologic and gene expression changes in equine superficial digital flexor tendon after a surgical injury. One forelimb tendon was hemi-transected in six horses, and in three other horses, one tendon underwent a sham operation. After euthanasia at six weeks, transected and control (sham and non-operated contralateral) tendons were regionally sampled (medial and lateral halves each divided into six 3 cm regions) for histologic (scoring and immunohistochemistry) and gene expression (real time PCR) analysis of extracellular matrix changes. The histopathology score was significantly higher in transected tendons compared to control tendons in all regions except for the most distal (P ≤ 0.03) with no differences between overstressed (medial) and stress-deprived (lateral) tendon halves. Proteoglycan scores were increased by transection in all but the most proximal region (P < 0.02), with increased immunostaining for aggrecan, biglycan and versican. After correcting for location within the tendon, gene expression for aggrecan, versican, biglycan, lumican, collagen types I, II and III, MMP14 and TIMP1 was increased in transected tendons compared with control tendons (P < 0.02) and decreased for ADAMTS4, MMP3 and TIMP3 (P < 0.001). Aggrecan, biglycan, fibromodulin, and collagen types I and III expression positively correlated with all histopathology scores (P < 0.001), whereas lumican, ADAMTS4 and MMP14 expression positively correlated only with collagen fiber malalignment (P < 0.001). In summary, histologic and associated gene expression changes were significant and widespread six weeks after injury to the equine SDFT, suggesting rapid and active development of tendinopathy throughout the entire length of the tendon. These extensive changes distant to the focal injury may contribute to poor functional outcomes and re-injury in clinical cases. Our data suggest that successful treatments of focal injuries will need to address pathology in the entire tendon, and that better methods to monitor the development and resolution of tendinopathy are required.

No MeSH data available.


Related in: MedlinePlus

Collagen gene expression.Topographically-mapped box plots of the alpha-1 chains of collagen types I (COL1A1; A); II (COL2A1; B) and III (COL3A1; C) gene expression (n = 6 per group and region) by partially transected tendons (dark bars) compared with control SDFT (light bars). The lateral lesion site in the transected tendons is indicated by a triangle. As the horizontal logarithmic scale indicates, expression on lateral side increases from right to left for display symmetry. Tendon regions in the central diagram are shaded if the score difference between control and transected tendons (indicated P values) is significant at the 5% level by Mann-Whitney U. D) RFU = relative fluorescent units. Differences in expression between different locations as assessed by mixed model regression are summarized in Table 2.
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pone.0122220.g006: Collagen gene expression.Topographically-mapped box plots of the alpha-1 chains of collagen types I (COL1A1; A); II (COL2A1; B) and III (COL3A1; C) gene expression (n = 6 per group and region) by partially transected tendons (dark bars) compared with control SDFT (light bars). The lateral lesion site in the transected tendons is indicated by a triangle. As the horizontal logarithmic scale indicates, expression on lateral side increases from right to left for display symmetry. Tendon regions in the central diagram are shaded if the score difference between control and transected tendons (indicated P values) is significant at the 5% level by Mann-Whitney U. D) RFU = relative fluorescent units. Differences in expression between different locations as assessed by mixed model regression are summarized in Table 2.

Mentions: As there were no significant differences in expression for any of the genes measured between non-operated control and sham-operated SDFT, these data were combined as the control group. Gene expression data are presented as topographically-mapped box plots in Figs 4–6 and the direction of change and significances from mixed model analyses of effect of surgery and regional variations are presented in Table 2. Model-generated estimates of beta coefficients (with 95% confidence intervals) are given as supplementary data (S1 Table). The coefficients are not reiterated in the text below as the actual relative fluorescent unit values are arbitrary but fold differences between control and transected samples are given where appropriate.


Focal experimental injury leads to widespread gene expression and histologic changes in equine flexor tendons.

Jacobsen E, Dart AJ, Mondori T, Horadogoda N, Jeffcott LB, Little CB, Smith MM - PLoS ONE (2015)

Collagen gene expression.Topographically-mapped box plots of the alpha-1 chains of collagen types I (COL1A1; A); II (COL2A1; B) and III (COL3A1; C) gene expression (n = 6 per group and region) by partially transected tendons (dark bars) compared with control SDFT (light bars). The lateral lesion site in the transected tendons is indicated by a triangle. As the horizontal logarithmic scale indicates, expression on lateral side increases from right to left for display symmetry. Tendon regions in the central diagram are shaded if the score difference between control and transected tendons (indicated P values) is significant at the 5% level by Mann-Whitney U. D) RFU = relative fluorescent units. Differences in expression between different locations as assessed by mixed model regression are summarized in Table 2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383631&req=5

pone.0122220.g006: Collagen gene expression.Topographically-mapped box plots of the alpha-1 chains of collagen types I (COL1A1; A); II (COL2A1; B) and III (COL3A1; C) gene expression (n = 6 per group and region) by partially transected tendons (dark bars) compared with control SDFT (light bars). The lateral lesion site in the transected tendons is indicated by a triangle. As the horizontal logarithmic scale indicates, expression on lateral side increases from right to left for display symmetry. Tendon regions in the central diagram are shaded if the score difference between control and transected tendons (indicated P values) is significant at the 5% level by Mann-Whitney U. D) RFU = relative fluorescent units. Differences in expression between different locations as assessed by mixed model regression are summarized in Table 2.
Mentions: As there were no significant differences in expression for any of the genes measured between non-operated control and sham-operated SDFT, these data were combined as the control group. Gene expression data are presented as topographically-mapped box plots in Figs 4–6 and the direction of change and significances from mixed model analyses of effect of surgery and regional variations are presented in Table 2. Model-generated estimates of beta coefficients (with 95% confidence intervals) are given as supplementary data (S1 Table). The coefficients are not reiterated in the text below as the actual relative fluorescent unit values are arbitrary but fold differences between control and transected samples are given where appropriate.

Bottom Line: The histopathology score was significantly higher in transected tendons compared to control tendons in all regions except for the most distal (P ≤ 0.03) with no differences between overstressed (medial) and stress-deprived (lateral) tendon halves.After correcting for location within the tendon, gene expression for aggrecan, versican, biglycan, lumican, collagen types I, II and III, MMP14 and TIMP1 was increased in transected tendons compared with control tendons (P < 0.02) and decreased for ADAMTS4, MMP3 and TIMP3 (P < 0.001).Our data suggest that successful treatments of focal injuries will need to address pathology in the entire tendon, and that better methods to monitor the development and resolution of tendinopathy are required.

View Article: PubMed Central - PubMed

Affiliation: Research and Clinical Training Unit, University Veterinary Teaching Hospital, University of Sydney, Camden, New South Wales, Australia.

ABSTRACT
It is not known how extensively a localised flexor tendon injury affects the entire tendon. This study examined the extent of and relationship between histopathologic and gene expression changes in equine superficial digital flexor tendon after a surgical injury. One forelimb tendon was hemi-transected in six horses, and in three other horses, one tendon underwent a sham operation. After euthanasia at six weeks, transected and control (sham and non-operated contralateral) tendons were regionally sampled (medial and lateral halves each divided into six 3 cm regions) for histologic (scoring and immunohistochemistry) and gene expression (real time PCR) analysis of extracellular matrix changes. The histopathology score was significantly higher in transected tendons compared to control tendons in all regions except for the most distal (P ≤ 0.03) with no differences between overstressed (medial) and stress-deprived (lateral) tendon halves. Proteoglycan scores were increased by transection in all but the most proximal region (P < 0.02), with increased immunostaining for aggrecan, biglycan and versican. After correcting for location within the tendon, gene expression for aggrecan, versican, biglycan, lumican, collagen types I, II and III, MMP14 and TIMP1 was increased in transected tendons compared with control tendons (P < 0.02) and decreased for ADAMTS4, MMP3 and TIMP3 (P < 0.001). Aggrecan, biglycan, fibromodulin, and collagen types I and III expression positively correlated with all histopathology scores (P < 0.001), whereas lumican, ADAMTS4 and MMP14 expression positively correlated only with collagen fiber malalignment (P < 0.001). In summary, histologic and associated gene expression changes were significant and widespread six weeks after injury to the equine SDFT, suggesting rapid and active development of tendinopathy throughout the entire length of the tendon. These extensive changes distant to the focal injury may contribute to poor functional outcomes and re-injury in clinical cases. Our data suggest that successful treatments of focal injuries will need to address pathology in the entire tendon, and that better methods to monitor the development and resolution of tendinopathy are required.

No MeSH data available.


Related in: MedlinePlus