Characterization of differential properties of rabbit tendon stem cells and tenocytes.
BACKGROUND
Tendons are traditionally thought to consist of tenocytes only, the resident cells of tendons; however, a recent study has demonstrated that human and mouse tendons also contain stem cells, referred to as tendon stem/progenitor cells (TSCs). However, the differential properties of TSCs and tenocytes remain largely undefined. This study aims to characterize the properties of these tendon cells derived from rabbits.


METHODS
TSCs and tenocytes were isolated from patellar and Achilles tendons of rabbits. The differentiation potential and cell marker expression of the two types of cells were examined using histochemical, immunohistochemical, and qRT-PCR analysis as well as in vivo implantation. In addition, morphology, colony formation, and proliferation of TSCs and tenocytes were also compared.


RESULTS
It was found that TSCs were able to differentiate into adipocytes, chondrocytes, and osteocytes in vitro, and form tendon-like, cartilage-like, and bone-like tissues in vivo. In contrast, tenocytes had little such differentiation potential. Moreover, TSCs expressed the stem cell markers Oct-4, SSEA-4, and nucleostemin, whereas tenocytes expressed none of these markers. Morphologically, TSCs possessed smaller cell bodies and larger nuclei than ordinary tenocytes and had cobblestone-like morphology in confluent culture whereas tenocytes were highly elongated. TSCs also proliferated more quickly than tenocytes in culture. Additionally, TSCs from patellar tendons formed more numerous and larger colonies and proliferated more rapidly than TSCs from Achilles tendons.


CONCLUSIONS
TSCs exhibit distinct properties compared to tenocytes, including differences in cell marker expression, proliferative and differentiation potential, and cell morphology in culture. Future research should investigate the mechanobiology of TSCs and explore the possibility of using TSCs to more effectively repair or regenerate injured tendons.
Zhang
Jianying
J
MechanoBiology Laboratory, Departments of Orthopaedic Surgery, Bioengineering, and Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Wang
James H-C
JH
D000818:Animals; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation / Q000502:physiology*; D019070:Cell Lineage / Q000502:physiology; D048430:Cell Shape / Q000502:physiology; D002478:Cells, Cultured; D003239:Connective Tissue Cells / Q000166:cytology / Q000502:physiology*; D005260:Female; D019204:GTP-Binding Proteins; D009687:Nuclear Proteins / Q000235:genetics; D050814:Octamer Transcription Factor-3 / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D012038:Regeneration / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055746:Stage-Specific Embryonic Antigens / Q000235:genetics; D033581:Stem Cell Transplantation / Q000379:methods*; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D013708:Tendon Injuries / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D013710:Tendons / Q000166:cytology / Q000502:physiology*
D015415:Biomarkers; D002352:Carrier Proteins; C470310:Gnl3 protein, rat; D009687:Nuclear Proteins; D050814:Octamer Transcription Factor-3; D012333:RNA, Messenger; D055746:Stage-Specific Embryonic Antigens; C066584:stage-specific embryonic antigen-4; D019204:GTP-Binding Proteins