Embryonic mechanical and soluble cues regulate tendon progenitor cell gene expression as a function of developmental stage and anatomical origin.
Stem cell-based engineering strategies for tendons have yet to yield a normal functional tissue, due in part to a need for tenogenic factors. Additionally, the ability to evaluate differentiation has been challenged by a lack of markers for differentiation. We propose to inform tendon regeneration with developmental cues involved in normal tissue formation and with phenotypic markers that are characteristic of differentiating tendon progenitor cells (TPCs). Mechanical forces, fibroblast growth factor (FGF)-4 and transforming growth factor (TGF)-β2 are implicated in embryonic tendon development, yet the isolated effects of these factors on differentiating TPCs are unknown. Additionally, developmental mechanisms vary between limb and axial tendons, suggesting the respective cell types are programmed to respond uniquely to exogenous factors. To characterize developmental cues and benchmarks for differentiation toward limb vs. axial phenotypes, we dynamically loaded and treated TPCs with growth factors and assessed gene expression profiles as a function of developmental stage and anatomical origin. Based on scleraxis expression, TGFβ2 was tenogenic for TPCs at all stages, while loading was for late-stage cells only, and FGF4 had no effect despite regulation of other genes. When factors were combined, TGFβ2 continued to be tenogenic, while FGF4 appeared anti-tenogenic. Various treatments elicited distinct responses by axial vs. limb TPCs of specific stages. These results identified tenogenic factors, suggest tendon engineering strategies should be customized for tissues by anatomical origin, and provide stage-specific gene expression profiles of limb and axial TPCs as benchmarks with which to monitor tenogenic differentiation of stem cells.
Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
Jeffrey P
JP
Brown
Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA.
Violet G
VG
Finley
Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, MA 02155, USA; Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA. Electronic address: CatherineK.Kuo@tufts.edu.
Catherine K
CK
Kuo
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D017931:DNA Primers; D051519:Fibroblast Growth Factor 4 / Q000378:metabolism; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D010641:Phenotype; D012038:Regeneration; D013234:Stem Cells / Q000166:cytology*; D013314:Stress, Mechanical; D013710:Tendons / Q000196:embryology*; D053781:Transforming Growth Factor beta2 / Q000378:metabolism
D017931:DNA Primers; C496446:Fgf4 protein, mouse; D051519:Fibroblast Growth Factor 4; C509042:Tgfb2 protein, mouse; D053781:Transforming Growth Factor beta2
Development; Differentiation; Embryonic; Growth factor; Mechanical loading; Tendon