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Valproic acid modulates collagen architecture in the postoperative conjunctival scar

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Abstract

Valproic acid (VPA), widely used for the treatment of neurological disorders, has anti-fibrotic activity by reducing collagen production in the postoperative conjunctiva. In this study, we investigated the capacity of VPA to modulate the postoperative collagen architecture. Histochemical examination revealed that VPA treatment was associated with the formation of thinner collagen fibers in the postoperative days 7 and 14 scars. At the micrometer scale, measurements by quantitative multiphoton microscopy indicated that VPA reduced mean collagen fiber thickness by 1.25-fold. At the nanometer scale, collagen fibril thickness and diameter measured by transmission electron microscopy were decreased by 1.08- and 1.20-fold, respectively. Moreover, delicate filamentous structures in random aggregates or closely associated with collagen fibrils were frequently observed in VPA-treated tissue. At the molecular level, VPA reduced Col1a1 but induced Matn2, Matn3, and Matn4 in the postoperative day 7 conjunctival tissue. Elevation of matrilin protein expression induced by VPA was sustained till at least postoperative day 14. In primary conjunctival fibroblasts, Matn2 expression was resistant to both VPA and TGF-β2, Matn3 was sensitive to both VPA and TGF-β2 individually and synergistically, while Matn4 was modulable by VPA but not TGF-β2. MATN2, MATN3, and MATN4 localized in close association with COL1A1 in the postoperative conjunctiva. These data indicate that VPA has the capacity to reduce collagen fiber thickness and potentially collagen assembly, in association with matrilin upregulation. These properties suggest potential VPA application for the prevention of fibrotic progression in the postoperative conjunctiva.

Key messages

  • VPA reduces collagen fiber and fibril thickness in the postoperative scar.

  • VPA disrupts collagen fiber assembly in conjunctival wound healing.

  • VPA induces MATN2, MATN3, and MATN4 in the postoperative scar.

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Acknowledgements

We thank the SingHealth Advanced Bioimaging Core Facilities (Singapore) for facilitating the transmission electron microscopy.

Funding

This research was supported by a SERI-Lee Foundation Pilot Grant (R1582/81/2018), NMRC Senior Investigator Clinician Scientist Award (NMRC/CSA-SI/0001/2015) and grants from the Singapore National Research Foundation under its Translational and Clinical Research (TCR) Program (NMRC/TCR/008-SERI/2013). Animal studies were partially funded by the SERI core grant (NMRC/CG/015/2013). All grants were administered by the Singapore Ministry of Health’s National Medical Research Council.

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Authors and Affiliations

  1. Ocular Therapeutics and Drug Delivery, Singapore Eye Research Institute, Singapore, Singapore

    Li-Fong Seet, Stephanie WL Chu, Li Zhen Toh & Tina T. Wong

  2. Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore

    Li-Fong Seet & Tina T. Wong

  3. Duke-NUS Medical School Singapore, Singapore, Singapore

    Li-Fong Seet, Gary HF Yam & Tina T. Wong

  4. Histoindex Pte Ltd, Singapore, Singapore

    Xiao Teng

  5. Experimental Microscopy Platform, Singapore Eye Research Institute, Singapore, Singapore

    Gary HF Yam

  6. Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA

    Gary HF Yam

  7. Glaucoma Service, Singapore National Eye Center, Singapore, Singapore

    Tina T. Wong

  8. School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore

    Tina T. Wong

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  1. Li-Fong Seet
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  2. Stephanie WL Chu
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  4. Xiao Teng
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Contributions

LFS conceptualized, designed, and performed research, analyzed and interpreted data, and wrote the paper; SWLC, LZT, XT, and GHFY performed research; GHFY and TTW edited the manuscript.

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Correspondence to Li-Fong Seet or Tina T. Wong.

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This study was approved by the Institutional Animal Care and Use Committee (IACUC) and treated in accordance with the Association for Research in Vision and Ophthalmology (ARVO) Statement on the Use of Animals in Ophthalmic and Vision Research.

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Seet, LF., Chu, S.W., Toh, L.Z. et al. Valproic acid modulates collagen architecture in the postoperative conjunctival scar. J Mol Med 100, 947–961 (2022). https://doi.org/10.1007/s00109-021-02171-2

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