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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 alignment and proteoglycan scores.Representative microscopic images of (A) picrosirius red-stained sections (polarised light) and (C) toluidine blue-stained sections (normal light) from each location from a control and transected SDFT mapped to a diagram of the SDFT. Topographically-mapped box plots of (B) collagen fiber alignment scores and (D) proteoglycan scores of 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 indicated on the horizontal logarithmic scale, 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.
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pone.0122220.g003: Collagen alignment and proteoglycan scores.Representative microscopic images of (A) picrosirius red-stained sections (polarised light) and (C) toluidine blue-stained sections (normal light) from each location from a control and transected SDFT mapped to a diagram of the SDFT. Topographically-mapped box plots of (B) collagen fiber alignment scores and (D) proteoglycan scores of 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 indicated on the horizontal logarithmic scale, 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.

Mentions: At six weeks post surgery, there were no differences in the histology scores between non-operated control and sham-operated tendons. Data from these SDFT were pooled as the control group. Representative topographically mapped images of the H&E and PSR-stained sections of tendon are presented in Fig 2A and 3A respectively. All of the histological parameters were significantly increased in 9–12 regions of the partially transected compared with control tendons (Fig 2B and 2C, S1 Fig). The overall histopathology scores were significantly higher in the partially transected tendons compared to the control tendons in all regions (P < 0.02), except for the most distal (Fig 2B) and were higher in regions near the site of transection compared to regions further away (P < 0.009). Importantly, there were no significant differences found in histological parameters between medial and lateral halves of the tendons despite the presumed differences in loading resulting from the hemi-transection (over-stressed and stress-deprived for medial and lateral halves respectively). Hemi-transection decreased collagen fiber alignment with the magnitude of change being greater with proximity to the lesion but not different between medial and lateral halves (Fig 3A and 3B).


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 alignment and proteoglycan scores.Representative microscopic images of (A) picrosirius red-stained sections (polarised light) and (C) toluidine blue-stained sections (normal light) from each location from a control and transected SDFT mapped to a diagram of the SDFT. Topographically-mapped box plots of (B) collagen fiber alignment scores and (D) proteoglycan scores of 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 indicated on the horizontal logarithmic scale, 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.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0122220.g003: Collagen alignment and proteoglycan scores.Representative microscopic images of (A) picrosirius red-stained sections (polarised light) and (C) toluidine blue-stained sections (normal light) from each location from a control and transected SDFT mapped to a diagram of the SDFT. Topographically-mapped box plots of (B) collagen fiber alignment scores and (D) proteoglycan scores of 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 indicated on the horizontal logarithmic scale, 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.
Mentions: At six weeks post surgery, there were no differences in the histology scores between non-operated control and sham-operated tendons. Data from these SDFT were pooled as the control group. Representative topographically mapped images of the H&E and PSR-stained sections of tendon are presented in Fig 2A and 3A respectively. All of the histological parameters were significantly increased in 9–12 regions of the partially transected compared with control tendons (Fig 2B and 2C, S1 Fig). The overall histopathology scores were significantly higher in the partially transected tendons compared to the control tendons in all regions (P < 0.02), except for the most distal (Fig 2B) and were higher in regions near the site of transection compared to regions further away (P < 0.009). Importantly, there were no significant differences found in histological parameters between medial and lateral halves of the tendons despite the presumed differences in loading resulting from the hemi-transection (over-stressed and stress-deprived for medial and lateral halves respectively). Hemi-transection decreased collagen fiber alignment with the magnitude of change being greater with proximity to the lesion but not different between medial and lateral halves (Fig 3A and 3B).

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