Article Text

Download PDFPDF

Mechanical stress potentiates the differentiation of periodontal ligament stem cells into keratocytes
  1. Jialin Chen1,
  2. Wei Zhang1,
  3. Ludvig J Backman1,
  4. Peyman Kelk1,
  5. Patrik Danielson1,2
  1. 1 Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
  2. 2 Unit of Ophthalmology, Department of Clinical Sciences, Umeå University, Umeå, Sweden
  1. Correspondence to Professor Patrik Danielson, Department of Integrative Medical Biology, Anatomy, Umeå University, Umeå, SE-901 87, Sweden; patrik.danielson{at}


Aims To explore the role of corneal-shaped static mechanical strain on the differentiation of human periodontal ligament stem cells (PDLSCs) into keratocytes and the possible synergistic effects of mechanics and inducing medium.

Methods PDLSCs were exposed to 3% static dome-shaped mechanical strain in a Flexcell Tension System for 3 days and 7 days. Keratocyte phenotype was determined by gene expression of keratocyte markers. Keratocyte differentiation (inducing) medium was introduced in the Flexcell system, either continuously or intermittently combined with mechanical stimulation. The synergistic effects of mechanics and inducing medium on keratocyte differentiation was evaluated by gene and protein expression of keratocyte markers. Finally, a multilamellar cell sheet was assembled by seeding PDLSCs on a collagen membrane and inducing keratocyte differentiation. The transparency of the cell sheet was assessed, and typical markers of native human corneal stroma were evaluated by immunofluorescence staining.

Results Dome-shaped mechanical stimulation promoted PDLSCs to differentiate into keratocytes, as shown by the upregulation of ALDH3A1, CD34, LUM, COL I and COL V. The expression of integrins were also upregulated after mechanical stimulation, including integrin alpha 1, alpha 2, beta 1 and non-muscle myosin II B. A synergistic effect of mechanics and inducing medium was found on keratocyte differentiation. The cell sheets were assembled under the treatment of mechanics and inducing medium simultaneously. The cell sheets were transparent, multilamellar and expressed typical markers of corneal stroma.

Conclusion Dome-shaped mechanical stimulation promotes differentiation of PDLSCs into keratocytes and has synergistic effects with inducing medium. Multilamellar cell sheets that resemble native human corneal stroma show potential for future clinical applications.

  • PDLSCs
  • corneal stroma
  • mechanics
  • inducing medium
  • differentiation
  • cell-sheet

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • JC and WZ contributed equally.

  • Contributors JC and PD conceived the idea and designed the experiments. JC and WZ performed the experiments. All authors analysed the data and wrote the manuscript. PD and PK financially supported the study.

  • Funding Financial support was obtained by PD from the national Swedish Research Council (grant no: 521-2013-2612), the Swedish Society of Medicine, the Cronqvist foundation, the foundation Kronprinsessan Margaretas Arbetsnämnd för synskadade (KMA), the foundation Ögonfonden and Västerbotten County Council (VLL ‘Spjutspetsmedel’). Financial support was furthermore provided to PD through a regional agreement (ALF) between Umeå University and Västerbotten County Council. In addition, this project was further financed by grants obtained by PK from Västerbotten County Council (VLL and TUA) and the Swedish Dental Society.

  • Competing interests None declared.

  • Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.

  • Ethics approval The study protocol was approved by the Regional Ethical Review Board in Umeå (2013-276-31M).

  • Provenance and peer review Not commissioned; externally peer reviewed.