Folie 1

Fracture healing and
osteoporosis in animal
models and humans
Franz Jakob
Musculoskeletal Center Würzburg MCW

Stem cells
Osteoblasts
Osteocytes
Osteoclasts
Monocytes

Mechanotransduction
Stem cells
Osteoblasts
Osteocytes
Osteoclasts
Monocytes
Many potent regulators are inhibitors, not stimulators!
Mechanotransduction

Humoral
Factors
Cellular
factors
Humoral
factors
Physiological regulators cause
Pathology when overexpressed
Osteoporosis
Activin
Sclerostin
Regeneration
Versus
Degeneration
Activin
Myostatin
bone
Sarcopenia
Degenerative tendon disease
tendon
Muscle
Mutations in man
demonstrate relevance
Kaplan et al. 2008
6 Tage 7 Monate
Schuelke et al., 2004

Jakob F, DMW 2011

Natural Inhibitors
Follistatin Inhibin
Therapeutic Inhibitors
MAB21l2
ACE-011
Sotatercept
Other competing
ligands
ActRIIA
ActRIIB
Barbara Klotz and Franz Jakob , Osteology 2011,
Activin Antagonists in the treatment of osteoporosis
Type II Receptor
Activin
Type I Receptor
Smad2, 3
GDF11
GDF8
ALK2
ALK4
ALK7
Smad
Complex
gene expression
BMP2
BMP7
GDF5
Myostatin
Cytoplasm
Nucleus

Ke et al., Sclerostin and Dickkopf-1 as Therapeutic Targets in Bone
Diseases. Endocrine Reviews, October 2012, 33(5):0000–0000

Cho et al., J Bone Miner Res 2002;17:513–520
Schindeler et al. Seminars in Cell & Developmental Biology 19 (2008) 459–466

Inflammatory
Chondrogenic
Osteogenic
Constitutive
Days 0 10 20 30
Cho et al., J Bone Miner Res 2002;17:513–520
BMP2, GDF8
GDF5, TGFβ2,3
BMP3a,4,7,8
BMP5, GDF10, TGFβ1

• Is there any evidence for altered fracture healing if we
inhibit osteogenic pathways?

Col1a1-Krm2 (Schulze, PlosOne 2010)
decreased bone formation
increased bone resorption
Lrp5 -/- (Gong, Cell 2001)
decreased bone formation
unchanged bone resorption
C57BL/6 wild type
all genotypes: 26 weeks, female, about 25 g
Peggy Benisch, Franz Jakob, Anita Igntius, Torsten Schinke, Michael Amling
SOST

Jochen Schulze,....Torsten Schinke, Michael Amling, PLoS
ONE April 2010 | Volume 5 | Issue 4 | e10309
***
BV/TV (%)
***
***
2 wks 6 wks 24wks
**
Lumbar Spine (cm)
2 wks 6 wks 24wks 52wks
Tb.N. (mm -1 )
***
**
2 wks 6 wks 24wks
Tb.Th. (µm)
***
2 wks 6 wks 24wks
***
52wks
***
52wks
***
52wks
3
1.5
0
30
15
0
10
5
0
30
15
0

Rigid external fixator Flexible external fixator
Research Implant System, RIS, Davos
Mini-Schanz screws: 0.45 mm
Weight: 0.22 g
Osteotomy gap: 0.5 mm
Peggy Benisch, Franz Jakob, Anita Igntius, Torsten Schinke, Michael Amling
F
Axial stiffness:
18.1 N/mm vs. 0.82 N/mm
22fold difference in stiffness
Difference in the healing outcome
(Röntgen, JOR 2010)

Bridging Score
Rigid
Flexible
Peggy Benisch, Franz Jakob, Anita Ignatius, Torsten Schinke, Michael Amling
Healed femur / intact femur
under rigid conditions

Enhanced gene expression
46 40 432
LRP5 -/- Col1a1-Krm2
Reduced gene expression
14 30 378
LRP5 -/- Col1a1-Krm2
Bone/ossification
Wnt signaling
Cartilage
Peggy Benisch, Franz Jakob, Anita Igntius, Torsten Schinke, Michael Amling
Relative gene expression
6,00
5,00
4,00
3,00
2,00
1,00
0,00
Lrp5 -/-
Col1a1-Krm2
Immune response

• Is there any evidence for analogous changes in the
human situation?

elative gene expression [%]
500
450
400
350
300
250
200
150
100
50
0
In vivo aging Senescence Osteoporosis
Osteogenic
differentiation
Marker genes for osteoporotic hMSC
PTH1R MAB21L2 SOST
Migration Proliferation Osteoclasto-
genesis
hMSC-K (n=9)
hMSC-OP (n=7)
Peggy Benisch, Franz Jakob, Anita Igntius, Torsten Schinke, Michael Amling
Hallmarks of osteoporotic MSC
Autoinhibition of wnt-signalling
Autoinhibition of BMP-signalling
Enhanced PTHR1 expression

Peggy Benisch, Franz Jakob, Anita Igntius, Torsten Schinke, Michael Amling
hMSC-OP hMSC-old hMSC-senescent

• Is there any preclinical or clinical evidence for
modulation of bone regeneration / fracture healing if
we inhibit the inhibitors?

Myostatin KO Sclerostin KO
Kellum et al. Bone 44 (2009) 17–23 Li et al., Bone 49 (2011) 1178–1185

Myostatin KO
Kellum et al. Bone 44 (2009) 17–23
Elkasrawy et al., JHistochem Cytochem 2012 60: 22

Agholm et al., Acta Orthopaedica 2011; 82 (5): 628–632
Sclerostin KO
Li et al., Bone 49 (2011) 1178–1185

Koncarevic A, Cornwall-Brady M, Pullen A, Davies M, Sako D, Liu J, Kumar R,
Tomkinson K, Baker T, Umiker B, Monnell T, Grinberg AV, Liharska K, Underwood KW,
Ucran JA, Howard E, Barberio J, Spaits M, Pearsall S, Seehra J, Lachey J. A
Soluble Activin Receptor Type IIB Prevents the Effects of Androgen Deprivation on
Body Composition and Bone Health. Endocrinology. 2010 Jun 23.
o ActRIIA receptor fused with the Fc portion of
human IgG1
o 10 monkeys /group
o Biweekly 10 mg/kg for 3 months
Lotinun S, Pearsall RS, Davies MV, Marvell TH, Monnell TE, Ucran J,
Fajardo RJ, Kumar R, Underwood KW, Seehra J, Bouxsein ML, Baron R.
Bone. 2010 Apr;46(4):1082-8. Epub 2010 Jan 18. PubMed PMID:
20080223.

• Fracture healing is impaired in severe osteoporosis
– aging may cause additional problems
• Defects /alterations in core osteogenic pathways
cause delayed healing in aged and transgenic animal
models
– Inhibiting inhibitors restores regeneration capacities in
preclinical settings
– Elevated inhibitors for osteogenic regeneration (activin,
myostatin, sclerostin) in serum of osteoporotic and elderly
people
• Human trials using „inhibitors of inhibitors“ are
already on their way to treatment in fragility
fracture healing
• New large animal models including transgenic
RANKL pigs are now available to establish proof of
principle for treatment with inhibitors (M. Schieker, W.
Mutschler, W. Böcker, E. Wolf)
hMSC-OP hMSC-old hMSC-senescent

Thank You for
Your attention