The Transplantation of 3-Dimensional Spheroids of Adipose-Derived Stem Cells Promotes Achilles Tendon Healing in Rabbits by Enhancing the Proliferation of Tenocytes and Suppressing M1 Macrophages

Shih Heng Chen*, Yun Wei Lee, Huang Kai Kao, Pei Ching Yang, Shih Hsien Chen, Shao Wen Liu, Pei Ching Yang, Yu Jie Lin, Chieh Cheng Huang*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

2 Scopus citations

Abstract

BACKGROUND: Tendons have limited regenerative potential, so healing of ruptured tendon tissue requires a prolonged period, and the prognosis is suboptimal. Although stem cell transplantation-based approaches show promise for accelerating tendon repair, the resultant therapeutic efficacy remains unsatisfactory.

HYPOTHESIS: The transplantation of stem cells preassembled as 3-dimensional spheroids achieves a superior therapeutic outcome compared with the transplantation of single-cell suspensions.

STUDY DESIGN: Controlled laboratory study.

METHODS: Adipose-derived stem cells (ADSCs) were assembled as spheroids using a methylcellulose hydrogel system. The secretome of ADSC suspensions or spheroids was collected and utilized to treat tenocytes and macrophages to evaluate their therapeutic potential and investigate the mechanisms underlying their effects. RNA sequencing was performed to investigate the global difference in gene expression between ADSC suspensions and spheroids in an in vitro inflammatory microenvironment. For the in vivo experiment, rabbits that underwent Achilles tendon transection, followed by stump suturing, were randomly assigned to 1 of 3 groups: intratendinous injection of saline, rabbit ADSCs as conventional single-cell suspensions, or preassembled ADSC spheroids. The tendons were harvested for biomechanical testing and histological analysis at 4 weeks postoperatively.

RESULTS: Our in vitro results demonstrated that the secretome of ADSCs assembled as spheroids exhibited enhanced modulatory activity in (1) tenocyte proliferation ( P = .015) and migration ( P = .001) by activating extracellular signal-regulated kinase (ERK) signaling and (2) the suppression of the secretion of interleukin-6 ( P = .005) and interleukin-1α ( P = .042) by M1 macrophages via the COX-2/PGE 2/EP 4 signaling axis. Gene expression profiling of cells exposed to an inflammatory milieu revealed significantly enriched terms that were associated with the immune response, cytokines, and tissue remodeling in preassembled ADSC spheroids. Ex vivo fluorescence imaging revealed that the engraftment efficiency of ADSCs in the form of spheroids was higher than that of ADSCs in single-cell suspensions ( P = .003). Furthermore, the transplantation of ADSC spheroids showed superior therapeutic effects in promoting the healing of sutured stumps, as evidenced by improvements in the tensile strength ( P = .019) and fiber alignment ( P < .001) of the repaired tendons.

CONCLUSION: The assembly of ADSCs as spheroids significantly advanced their potential to harness tenocytes and macrophages. As a proof of concept, this study clearly demonstrates the effectiveness of using ADSC spheroids to promote tendon regeneration.

CLINICAL RELEVANCE: The present study lays a foundation for future clinical applications of stem cell spheroid-based therapy for the management of tendon injuries.

Original languageEnglish
Pages (from-to)406-422
Number of pages17
JournalAmerican Journal of Sports Medicine
Volume52
Issue number2
DOIs
StatePublished - 02 2024

Bibliographical note

Publisher Copyright:
© 2024 The Author(s).

Keywords

  • cell spheroids
  • immunomodulation
  • stem cell therapy
  • tenocytes
  • Rabbits
  • Stem Cells/physiology
  • Cell Proliferation
  • Tendon Injuries/surgery
  • Achilles Tendon/pathology
  • Animals
  • Tenocytes
  • Adipose Tissue/pathology
  • Macrophages/pathology

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