Intrinsic differentiation potential of adolescent human tendon tissue: an in-vitro cell differentiation study.
BACKGROUND
Tendinosis lesions show an increase of glycosaminoglycan amount, calcifications, and lipid accumulation. Therefore, altered cellular differentiation might play a role in the etiology of tendinosis. This study investigates whether adolescent human tendon tissue contains a population of cells with intrinsic differentiation potential.


METHODS
Cells derived from adolescent non-degenerative hamstring tendons were characterized by immunohistochemistry and FACS-analysis. Cells were cultured for 21 days in osteogenic, adipogenic, and chondrogenic medium and phenotypical evaluation was carried out by immunohistochemical and qPCR analysis. The results were compared with the results of similar experiments on adult bone marrow-derived stromal cells (BMSCs).


RESULTS
Tendon-derived cells stained D7-FIB (fibroblast-marker) positive, but alpha-SMA (marker for smooth muscle cells and pericytes) negative. Tendon-derived cells were 99% negative for CD34 (endothelial cell marker), and 73% positive for CD105 (mesenchymal progenitor-cell marker). In adipogenic medium, intracellular lipid vacuoles were visible and tendon-derived fibroblasts showed upregulation of adipogenic markers FABP4 (fatty-acid binding protein 4) and PPARG (peroxisome proliferative activated receptor gamma). In chondrogenic medium, some cells stained positive for collagen 2 and tendon-derived fibroblasts showed upregulation of collagen 2 and collagen 10. In osteogenic medium Von Kossa staining showed calcium deposition although osteogenic markers remained unaltered. Tendon-derived cells and BMCSs behaved largely comparable, although some distinct differences were present between the two cell populations.


CONCLUSIONS
This study suggests that our population of explanted human tendon cells has an intrinsic differentiation potential. These results support the hypothesis that there might be a role for altered tendon-cell differentiation in the pathophysiology of tendinosis.
de Mos
Marieke
M
Department of Orthopaedics, Erasmus MC, University Medical Centre Rotterdam, CA, The Netherlands. m.demos@erasmusmc.nl <m.demos@erasmusmc.nl>
Koevoet
Wendy J L M
WJ
Jahr
Holger
H
Verstegen
Monique M A
MM
Heijboer
Marinus P
MP
Kops
Nicole
N
van Leeuwen
Johannes P T M
JP
Weinans
Harrie
H
Verhaar
Jan A N
JA
van Osch
Gerjo J V M
GJ
D017667:Adipocytes / Q000166:cytology; D000293:Adolescent; D002454:Cell Differentiation; D002478:Cells, Cultured; D024043:Collagen Type II / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D047495:PPAR gamma / Q000378:metabolism; D013710:Tendons / Q000166:cytology* / Q000378:metabolism; D015854:Up-Regulation
C499177:COL2A1 protein, human; D024043:Collagen Type II; C493410:FABP4 protein, human; D050556:Fatty Acid-Binding Proteins; D047495:PPAR gamma