intervertebral disc degeneration · –vadala et al. spine 2008 ... discography, axial back pain...

Nam Vo, Ph.D. Assistant Professor

University of Pittsburgh

Intervertebral Disc Degeneration:

New concepts and current therapeutic

challenges and opportunities.

TALK OUTLINE

1. Traditional treatments of intervertebral disc degeneration (IDD) & back pain not optimal

2. New concepts and biologic treatments for IDD

3. Opportunities and challenges

Deyo et al. J Am Board Fam Med. 2009

Minimal change in office visits for low back pain since 1990

Increase Utilization

Deyo et al. J Am Board Fam Med. 2009

Self-reported functional limitations, mental health and social limitations worse in 2005 than 1997

Lack of improved outcomes

• Non-operative – Analgesic – Anti-inflammatory – Physical therapy

• Surgery – Fusion – Implant

• Treating symptoms, not cause

Traditional treatment not optimal

Address the underlying pathology/cause

Promote matrix synthesis and/or inhibit catabolic processes

Biologic approaches treating IDD

Matrix loss

Matrix homeostasis

TALK OUTLINE

1. Traditional treatments of IDD & back pain not optimal



Molecular Modify metabolism of resident cells

to boost matrix production Cellular

Replace cell loss/defective cells with functional cells

New concepts: preserving disc health

Tissue Replace part or whole disc

(matrix+cells)

Counteract disc matrix loss

• Molecular approaches

– Novel pharmaceuticals

– Gene therapy

• Cellular approaches

– Stem cell therapy

– Alternative cell therapy

• Tissue Approaches

– Scaffolds

– Biomaterials

• Mechanical Approaches

– Rationally Designed Loading

– Preservation of Optimal Biomechanics

New concepts & therapeutic options

Direct protein intradiscal injection…

BMP-2, OP-1, TGF- 1, GDF-5, IGF, FGF

Proteoglycan

Collagen

Thompson et al., Spine 1991 Gruber et al., Exp Cell Res 1997 Osada et al, J Orthop Res 1996 Takegami et al., Spine 2002

Molecular approaches

Kim et al. Spine 2003

BMPs (mainly -2 and -7)

OP-1 (BMP-7) in clinical trial: results unpublished

Direct protein intradiscal injection…

BMP-2, OP-1, TGF- 1, GDF-5, IGF, FGF

Concentration

Time

Proteoglycan

Collagen

Thompson et al., Spine 1991 Gruber et al., Exp Cell Res 1997 Osada et al, J Orthop Res 1996 Takegami et al., Spine 2002

Protein injection not long lasting

Gene Therapy for IDD: a s impler tactic

James Kang

Goal: restore an advantageous balance of anabolic and catabolic metabolism with sustained effect

Molecular approaches: Gene Therapy

CMV Promoter Therapeutic Gene

Constitutive expression

Viral vector

Stab, + Ad-BMP2

Stab, + Saline

MRI T2w at 0, 3, 6, 12 weeks

Gene Therapy: BMP-2

Delay of radiographic progression with Ad-BMP-2 (Shimer et al., ORS 2005)

Proteoglycan increases with Ad-TGF-β1 In Vivo (Nishida et al., 1999. Spine)

Wks: 0 3 6 12

Ad-BMP2

Wks: 0 3 6 12

Saline

Stab

be

d

Gene Therapy: BMP-2



– Gene therapy





– Scaffolds

– Biomaterials





The Problem:

Low cell division, phenotypic shift, decreased metabolic activity

A Potential Solution:

Repopulate the disc with healthy, metabolically active cells

Young

Old

Cell based therapy

MSC

adipocyte

osteocyte chondrocyte

myocyte

tenocyte

stromal cell

•Human bone marrow - Hematopoietic stem cells - Non-hematopoietic

• MSC

Undifferentiated cell (self-renewal)

Mesenchymal stem cell (MSC)

• Co-culture results in MSC differentiation to a more chondrogenic phenotype and stimulation of NP cells – Vadala et al. Spine 2008

• MSCs differentiate into IVD like cells (based on gene expression) when stimulated with TGF-beta – Steck et al. Stem Cells 2005

MSC may restore disc cell population

Sakai et al. Biomaterials 2006

MSC restores disc height and MRI signal

A: Control B: Puncture

0wks 6wks 12wks 0wks 3wks 6wks 12wks

Umbilical derived stem cell therapy

0wks 3wks 6wks 12wks

C: Cells+carrier



– Gene therapy





– Scaffolds

– Biomaterials





TALK OUTLINE

1. Traditional treatments of IDD & back pain not optimal



1. Immune response from adenoviral vector

Gene Therapy: safety issues

Challenges: Safety issues with gene therapy

Concern Over Misguided Injections

Intradural therapeutic doses of Ad-TGF and BMP-2 demonstrated no clinical or histologic changes

Supratherapeutic doses of Ad-BMP-2 demonstrated evidence of paralysis or paresthesias, dural fibrosis and fibroblastic infiltration

Wallach et al. Spine 2006; 6:107

Gene therapy using

adeno-associated viral (AAV) vector

more safe than

adenoviral vector (AV)

AAV safer than AV

0 wks 6 wks 12 wks

Control

Stab

0 wks 6 wks 12 wks

AAV2-

BMP2

AAV2-

TIMP1

MRI T2w

AAV gene therapy ( L e c k i e e t a l . , 2 0 1 2 . T S J )

1. Immune response from adenoviral vector

2. Uncontrolled expression of therapeutic gene

CMV Promoter Therapeutic Gene

Constitutive expression

Excessive amount of therapeutic protein!

BMP

Osteophyte formation Neurological complication Cancer (Carragee et al., ISSLS 2012)

Gene Therapy: safety issues

Also need a titratable “on” switch Control through use of activator compounds without human activity

RheoSwitch Mammalian Inducible Expression system (Intrexon, VA)

Improved Safety Through Control of Gene Expression

Inducible systems: tet-off mechanisms

transcription

GENE OF INTEREST TRE P pA

tTA

GENE OF INTEREST TRE P pA

tTA transcription +TC Vadala et al.

Spine 2007


Improved safety through regulated expression

VIRUS ONLY

VIRUS + LIGAND

L2-3 L3-4 L4-5

5 DAYS POST-LIGAND

No GFP expression was evident in the adjacent discs, spinal cord, dura, bone, liver, or brain of any animals

Sowa et al. Spine 2011

Challenges: Safety issues with cell therapy

Vadala et al. J Tissue Eng Regen Med. 2012

Mesenchymal stem cells injection in degenerated disc: cell leakage may induce osteophyte formation

• Haufe et al. Stem Cells Dev. 2006

– Case series of 10 patients with provocative discography, axial back pain

– Injection of BM derived MSCs

– One year follow up demonstrating no improvement in symptoms

Cell therapy: human a different beast

Human studies

Access and need for multiple procedures Carragee et al. ISSLS Prize 2009

Timing of interventions Prior to end-stage anatomic disc disease

Hostile IVD environment and safety

Current limitations and remaining questions


Timing of interventions Prior to end-stage anatomic disc disease


Attention to treating the pain component


Effects of GDF-5 treatment in animal model of IDD

– Improved disc height, T2 weighted signal, histological changes, and GAG content

– Suppressed mRNA expression of… • IL-1beta, IL-6, TNF-alpha (inflammatory mediators) • ADAMTS-4, COX-2 (catabolic enzymes) • NGF, VEGF (pain related markers)

Clinical success may require specific attention to modulating PAIN!

Liang et al. Spine J. 2009 Nov 17 Masuda et al. ISSLS 2009


Timing of interventions



Need for further elucidation of key pathways


Molecular Modify metabolism of resident cells

to boost matrix production Cellular

Replace cell loss/defective cells with functional cells

New biologics for preserving disc health

Tissue Replace part or whole disc

(matrix+cells)

Specific pathway

•DNA damage •Oxidative stress

•NF- B


Timing of interventions



Need for further elucidation of key pathways

Biologic approaches should be viewed with cautious optimism


University of Pittsburgh Hillman Cancer Institute

Laura Niedernhofer Paul Robbins Jeremy Tilstra Andria Robison Cheryl Clauson

Ferguson Laboratory of Orthopaedics Research

James Kang (Director) Gwen Sowa Nam Vo

Luigi Nasto Fabrizio Russo, Hyoung-Yeon Seo Kevin Ngo, Qing Dong Takashi Yurube, Robert Hartman, Wan Huang, Paulo

Coelho, Kevin Bell

Funding Sources

The Pittsburgh Foundation UPMC Department of Orthopaedics Surgery

Orthopaedic Research and Education Foundation AOSpine North America Young Investigators Research Grant

“BioSpina” Italian Spine Society Research Grant NIH (R21 AG033046), NIH (ES016114)

Acknowledgements

Dept of Orthopaedic Surgery, Catholic University of Rome, Italy

Thank you!

Urban et al. 2004

Barriers: Discs have limited nutrition and capacity for repair

Human studies

• Yoshikawa et al. Spine 2010 – Case report of two patients

– Low back pain, radicular

symptoms, lack of response to conservative therapy

– Symptom improvement seen 2 yrs after collagen sponge containing autologous MSCs were grafted into degenerated discs

Cell therapy: human a different beast

Goal: restore an advantageous balance of anabolic and catabolic metabolism with sustained effect

In Vivo Approach: single procedure, low efficiency

Ex Vivo Approach: no host exposure to virus, requires cell source

Molecular approaches: Gene Therapy

Other treatments

• NBD peptide

• N-link protein peptide

• Glucosamine

• Omega-3 fatty acid

• Platelet rich plasma (PRP)

Articular chondrocytes transduced with ad-BMP and co-cultured with NP cells increased proteoglycan and collagen

Implications for improving native NP cell matrix production while providing the disc with metabolically active chondrocytes

Zhang et al. Spine 2005;30(23):2601.

Cell therapy with Ex Vivo gene therapy

Stimulation of differentiation or progenitor cells NP cells show chondrogenic/osteogenic phenotypes in vitro

Notochordal cells

EUROdisc use of autologous cells from herniated NP Meisel, Biomol Eng 2007

Synovium derived mesenchymal stem cells

Adipose derived stem cells

Combine cell based therapy with ex vivo gene therapy Zhang et al. Spine 2005, 2008

Immortalization to increase cell lifespan and increase matrix (concerns regarding oncogenesis)

Chung et al. Spine 2007

Alternative cell-based therapy approaches


o An insect pheromone receptor, whose synthetic ligand has no pleiotropic effects in mammalian cells and exhibits no cross talk with endogenous transcription factors…limiting potential toxicity in humans.

o Inducible and adjustable control (0-10000x) of gene expression. No leaky basal expression

polyA GENE Preg polyA Gal4-EcR IRES PUbC VP16-RXR

RG-115830

Just because it is “natural” doesn’t mean it is safe!

Disc Loading in vivo • Traumatic forces result

in matrix degradation1

• Inflammatory and mechanical signaling linked

• The most serious spine pathology relates to the highest and lowest degrees of physical activity (Videman et al. Spine 1990)

1Guerhing et al., Spine 2005; 30(22): 2510.

Evidence for the Beneficial Effects of Motion

• Lack of effectiveness of bed rest – Deyo et al, NEJM 1986

• Motion sparing technology • Both tensile and compressive loading have been

shown to be anti-catabolic and anti-inflammatory in vitro – Sowa et al. JOR 2011; Sowa et al. Spine J. 2011

Regenerative Rehabilitation

control 6% tensile strain

Inflammatory stimulus

Inflammatory stimulus + 6% tensile strain

C o l l a g e n P r o t e o g l y c a n s

P T T

Heinegard et al., 2005

Load is resisted by bouncing ball-like structures (PG) retained in a network of rope-like collagen fibers

Normal

Degenerated

Construction

quality &

maintenance

GENETICS

(faulty)

MECHANICAL

(trauma)

Excessive loads (sudden)

ENVIRONMENTAL smoking

nutrition

occupation

Assaults radiation

wind

current

Time-dependent

wears and tears (slow)

AGING (time-dep damage of

macromolecules)

POSSIBLE CAUSES OF BREAKDOWN OF A BRIDGE: AN ANALOGY TO DISC DEGENERATION

intervertebral disc degeneration · –vadala et al. spine 2008 ... discography, axial back pain...

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