# Immortalized Rat Tendon-Derived Stem Cells for Tendon Tissue Engineering

## TL;DR

Researchers created an immortalized rat tendon stem cell line that can be used to study tendon biology and develop regenerative therapies.

## Contribution

The first well-characterized immortalized rat tendon-derived stem cell line with stable MSC-like properties is established.

## Key findings

- iTDSC#6 maintains MSC-like phenotypes and tendon-specific traits at both early and late passages.
- The cell line can form 3D tendon-like structures with aligned collagen and upregulated tendon markers.
- iTDSC#6 shows increased senescence markers in response to hydrogen peroxide, useful for aging studies.

## Abstract

Tendon-derived stem cells (TDSCs) are a unique cell population found in tendons, exhibiting both mesenchymal stem cell (MSC)-like phenotypes and tendon-specific markers. They have emerged as a promising research tool in tendon-related tissue engineering studies. However, there is currently no well-characterized TDSC line with MSC-related phenotypes for investigating tendon biology or developing therapeutics. Here, we established an immortalized monoclonal TDSC, named iTDSC#6, from the Achilles tendon of an adult male Sprague-Dawley rat. Cell clones were characterized for MSC-associated cell surface markers, colony formation capacity, and trilineage differentiation potentials, tenogenic potential and SV40LT expression at both early (passage < 10) and late (passage > 30) stages. iTDSC#6 showed stable expression of Simian virus 40 large T antigen (SV40LT) and demonstrated similar MSC-like phenotypes as its wild-type counterpart at both early and late passages, including colony formation capability and multi-lineage differentiation potentials. iTDSC#6 was positive for the MSC markers CD90, CD44, CD29 and CD73 (≥95%) and negative for the hematopoietic markers CD34 and CD45 (<1%). Regarding its utility for basic research and therapeutic development, iTDSC#6 showed potential for modelling cells with increased levels of senescence-associated beta-galactosidase activity in response to hydrogen peroxide and for bioengineering scaffold-free, tendon-like 3D constructs as evidenced by its upregulation of tendon-related markers, high nuclear aspect ratio, and aligned collagen organization. In conclusion, an immortalized TDSC line was successfully established that shows promise as a useful research tool to study tendon biology and aid the development of therapeutics for tissue engineering and regenerative medicine.