? ? Smad3 Katzel et al. JOR 2011 Differentiation Matrix - - PowerPoint PPT Presentation

5/10/2013 1 Smad3 Regulates Tendon Matrix Organization and Binds Key Tendon Transcription Factors

Ellora Berthet, Carol Chen, Kristin Butcher, Richard A. Schneider, Tamara Alliston, Mohana Amirtharajah

We have nothing to disclose Current challenges to tendon repair

• Flexor tendon injury remains a significant

problem

• Repair complicated by adhesion and re-rupture
• “Biologic” Solution
• Limited knowledge of pathways of normal

tendon development

How can we apply a molecular understanding of tendon development to improve tendon healing?

TGFβ signaling in tendon development and repair

Tendon Progenitors

Differentiation

Tenocytes

Matrix Production Injury & Repair

Tenocytes

TβRI TβRII TGFβ

Pryce et al. Dev. 2009

? ?

Smad3

Katzel et al. JOR 2011

5/10/2013 2 Matrix production is regulated by tissue specific transcription factors

Collagen1

Mkx

Tenomodulin

Liu et al. Molec Cell Bio 2010

Scx

Collagen1 Tenomodulin

Léjard et al. JBC 2007 Shukunami et al. Dev Bio 2006

Mkx-/- Scx-/- WT

Murchison et al. Dev 2007

Smad3 is essential for the formation

• f normal tendon architecture

WT Smad3-/- H & E SHG WT Smad3-/- Dispersion Angle (° )

Smad3 is required for normal matrix protein expression in tendon

Col1 Tnc IgG WT Smad3-/-

Smad3 is required for normal gene expression in tendon

5/10/2013 3

HDAC4/5 Runx2 CBP

Smad3 modulates the activity of tissue specific transcription factors

Bone X

Sox9

Cartilage

Scx/Mkx Collagen I Smad3

Smad3?

Collagen II

Smad3

Osteocalcin

Smad3 ???

Tendon

+ + + +

Scx-HA

Scx-HA-FLAG Smad3-HA +

• +
• Smad3

Scx-HA Smad3

WCE IP: FLAG α-Scx α-Smad3 α-Scx α-Smad3

Smad3 binds the critical tendon transcription factors Scx and Mkx

Scx

HA Flag HA

Smad3

+

• +
• WCE

IP: FLAG Mkx-Myc Smad3-FLAG α-Smad3 α-Myc α-Myc

Mkx-Myc IgG

α-Smad3

Smad3 Mkx-Myc Smad3

+ + + +

Smad3 binds the critical tendon transcription factors Scx and Mkx

Flag

Smad3 Mkx

My c

Conclusions

• Smad3 is a critical

regulator of tendon formation

• Smad3 regulates gene

and protein expression in mature tendon

• Smad3 can bind

Scleraxis and Mohawk

Matrix Production Tenascin-C Collagen1 TβRI TβRII TGFβ Mkx Smad3 Scx Smad3

5/10/2013 4 Acknowledgements

• Mohana Amirtharajah
• Tamara Alliston
• Richard Schneider
• Carol Chen
• Kristin Butcher
• Alliston Lab
• Funding:

– American Society for Surgery of the Hand – NIH NIDCR – UCSF Department of Orthopedic Surgery