Download - Disc regeneration
A GLIMPSE OF THE NOVEL INTERVENTIONAL APPROACHES
Babak Ashrafnejad MDPain FellowshipAnesthesiologist
Low back pain is a disorder that affects a considerableproportion of the population
About 60–80% of all people suffer from back pain atsome time during their life
Degeneration of the intervertebral disc (IVD) and discherniation are two distinct but related causes of lowback pain and radicular pain, respectively
At least 40% of patients with chronic low back painshowed characteristics of intervertebral discdegeneration (IVDD)
IVDD is an aberrant, cell-mediated response toprogressive structural failure
ANATOMY
Fibrocartilaginous tissues that allow motionbetween the vertebral bodies
They transmit load and absorb the shocks
Each IVD is composed of three distinct butconnected structures:
The Endplate
The NP
The AF
Endplates consist of hyaline cartilage and occupy theinferior and superior interfaces between theintervertebral disc
Collagen is greatest at the periphery of the endplates, while the centre contains most of the proteoglycansand water
CollagenProteoglican
+Water
They have approximately 1-mm-thick horizontal layer of hyaline cartilage
Early in life : the endplates are highly vascularized
First year : The degree of vascularity wanes dramatically
Third decade : No blood vessels present
Encases the NP and prevents the it from herniating
The AF is composed of :
Water (65–90% of its weight)
Collagen type I and II fibres (60% of dry weight)
Proteoglycans and other proteins (10–20% of dryweight)
The AF is composed of 15–25 loosely connected concentric rings of highly organized collagen fibres(lamellae)
Has a cell density of 9×106/cm3
Only at the outer layer, there is sensory nerves
Nutrition of the IVD is based on diffusion of nutrients through the subchondral bone and the endplates to the disc
Much less dense and nearly the consistency ofa gel.
Gel contains :
1- Type II collagen and elastin. These hold the gel-like area
2-Proteoglycan molecules that have hydrophilicchondroitin and keratin sulfate attached tothem.
3- Water > 90%
Water Molecules
proteoglycan
Collagen fibers
Is the disc framework structure
Composed of collagen and aggrican
Makes disc components more strenght (anchor)
MatrixChodrocytes
Collagenfibers
1, intervertebralDisc2, posterior longitudinal ligament 3, spinal nerveroot4, vertebral body
5, segmental artery 6, interosseous arteries7, dorsal root ganglion with accompanying blood vessel 8,descending branch of the sino-vertebral nerve 9, ascending branch of the sino-vertebral nerve 10, aorta
1, intervertebral disc
2, recurrent sino-vertebral nerve3, spinal nerve4, posterior branch of spinal nerve5, thecal sac with spinal roots6, paraspinal muscle
DISC DEGENERATION
Body weight
Lifting strength
Ageing
Occupational risks, such as exposure to vibrations
Smoking and atherosclerosis causing decrease in nutrient supply
Tissue weakening, which primarily occurs due to inherited genetic factors
Nutritional compromise
(Adams and Roughley, 2006)
catabolic processes exceeding anabolic ones
morphological changes, cell transformations and degeneration
loss of proteoglycans and a decrease in water content of the NP
Degeneration of the endplates impairs transport of nutrients into the disc and results in the accumulation of waste products such as
lactic acid, which reduce the pH
reduce the number of cells / reduction of extracellular matrix (ECM) synthesis
Dehydration of the NP
Reduced shock absorbance capacity
Loads will be transferred to the AF
Ruptures or cracks of the AF
Fibrosis
Narrowing of the disc space
Diffuse bulging of the annulus beyond the disc space
Extensive fissuring
Mucinous degeneration of the annulus
Defects and sclerosis of the endplates
Osteophytes at the vertebral apophyses
DISC REGENERATION
Anticatabolic agents
Growth factors
Gene Therapy
Cellular componentsNp cell transplantation Stem cell Therapy
Scaffolds
ANTICATABOLICS
The MMP (Matrix-Metalloproteinase) enzymefamily are responsible for the degradation of :Collagen
Aggrecan
Versican
Within the matrix, MMP activity is normallyinhibited by TIMPs (Tissue Inhibitor ofMetolloproteinase)
MMPs & TIMPs are balanced in normal discs
When imbalance Degeneration
Four TIMPs (TIMP-1, TIMP-2, TIMP-3, and TIMP-4) have been identified in discs.
Application of TIMPs for treatment of DDD through gene therapy or direct protein application (is still in an early phase of development)
ABSTRACT Cells from degenerated intervertebral discs were transduced with an adenoviral vector delivering cDNA of the catabolic
inhibitor, TIMP-1, and alterations in the measured proteoglycan were assessed.To assess the potential of TIMP-1 to favorably modify the proteoglycan content of degenerated intervertebral disc cells.Gene therapy with anabolic factors has resulted in increased proteoglycan synthesis in intervertebral disc cells. Biochemical analysis of degenerated discs has revealed elevated levels of the catabolic enzymes, matrix metalloproteinase, suggesting an intimate role of these factors in the degenerative process. The use of TIMP-1, an endogenous inhibitor of matrix metalloproteinase, via gene therapy may provide an additional method to alter the degenerative processes occurring in the intervertebral disc.Degenerated intervertebral disc were isolated from eight patients undergoing elective surgical procedures. Cells were cultured in monolayer and transduced with different concentrations of either an adenoviral-tissue inhibitor of metalloproteinase-1 (Ad-TIMP-1) or adenoviral-bone morphogenic protein-2 (Ad-BMP-2) construct. Cells were cultured in a three-dimensional pellet and proteoglycan synthesis was assessed via 35S-sulfur incorporation.Gene delivery of TIMP-1 and BMP-2 increased measured proteoglycan synthesis at each concentration assessed. IVD cells treated with Ad-TIMP-1 demonstrated an optimal response at a multiplicity of infection (MOI) of 100. Cells treated with Ad-BMP-2 demonstrated a progressive increase in proteoglycan synthesis with increasing viral concentrations.
Successful delivery of the anticatabolic gene, TIMP-1, results in increased measured proteoglycan in cultured degenerated disc cells. This finding supports catabolic inhibition as a promising avenue of research for the treatment of degenerative disc disease via gene therapy.
Wallach C J .et al. Spine , Oct 2003
IL-1 and TNF have been shown to mediate the inflammatory cascade in discs and
contrariwise,
anticatabolic agents, such as inhibitors of IL-1 & TNF have been shown to be
chondro-protective
Disc degeneration diagnosis based on history, physical exam and Imaging studies.
Positive discography ( VAS>6 at <50psi above opening pressure)
Intradiscal etanercept injection
Sainoh et al. 2014 Intradiscal etanercept inj. (RCT) (10 mg)Results : positive response
Cohen et al. 2007. Intradiscal etanercept inj. (RCT) (0.1-1.5 mg)
Results : no positive response
Cohen et al. 2009. Transforaminal epidural etanerceptinjection (RCT) (2-6 mg)
Results : is superior to systemic application in sciatica pain relief
GROWTH FACTORS
Growth factors bind to cell membranes(receptors)
activation of an intercellular signaling cascade
exert biological effects, such as :
1- Stimulates cell proliferation, differentiation, migration
2- Regulates matrix production and repair
Autologous Platelet-Rich-Plasma (PRP)
Platelet derived transforming growth factor-13 (TGF-I3)
Epidermal growth factor (EGF)
Osteogenic protein-l (OP-l) also known as bone morphogenic protein-7 (BMP)
LIM mineralization Protein 1 (LMP1)
Link N
SOX-9
EGF : increases in matrix synthesis and cell proliferation
TGF-I3I : matrix synthesis alone (TGF-I3I)‘
Increases in matrix synthesis with TGF-131 is dramatic.
Osteogenic protein-l (OP-l) into rabbits resulted in mild increases (12%-15%) in disc height up to 8 weeks following injection
BMPs are members of the TGF super family
Stimulates cells to express a more chondrocyticphenotype
Increase cell proliferation, and collagen Type II synthesis, aggrecan
Gene Therapy
transfer of ‘‘the gene of interest “ (RNA,DNA)
into the target cells using a so-called vector (Virus, main cells)
produce the desired gene products (RNAs or proteins) in a continuous fashion
Regeneration
1- Virus Vectors (Adenovirus/ Retrovirus)2- Non viral Vectors (direct gene transfer)
Vectors
Gens
Target Cell
Continuous Production
RNA
DNA
Continuous Biological Effects
Vector binds to cell memebrane
DNA injected to vector
Vector is packaged in vesicle
Vesicle breaks down releasing vector
Cell makes protein using new gen
Vector (Adenovirus)
Vector injects new gen into nucleous
Microbubbles Ultrasound Gene Therapy
NUCLEUS PULPOSIS CELL TRANSPLANTATION
Autologous reinsertion of the NP from normal disc to degenerated one has been shown to :
Delay degeneration of the disc, including the AF, NP, and endplate
Restoration of disc height
Retard disc degeneration in vivo
Increases production of collagen 2
No host-versus-graft response
Reimplantation of disc cells from discectomyspecimens in a nonrandomized series of human patients demonstrated MRI scan improvements consistent with increased
proteoglycan matrix within the NP and relief of symptoms
STEM CELL THERAPY
MSCs and bone marrow stem cells (BMSC) are the main stem cells
Readily available source of autologous cells, with minimal donor-associated complications
Adipose tissues are good source of stem cells(ADSC)
MSCs differentiated into cells expressing a chondrocyte-like phenotype (NP cells)
with increased production of :
matrix components, such as
Aggrecan
Collagen Type II
There are two main strategies for acquisition of these desired somatic stem cells:
Embryonic stem cells (ESCs)
from the fat or bone marrow
Stem Cell Therapy Procedure no general anesthetics are used.
The out-patient procedure takes about 3-4 hours:
1. Collection of adipose tissue by tickle lipo, centrifugal separation of stem cells
2. Collection of bone marrow aspirate from the posterior iliac crest, centrifugal separation of stem cells
4. Injection of the cells into the affected site under x-ray fluoroscopic guidance
to your disc
Yoshikawa et al , 2010
percutaneously grafted MSCs into degenerated IVDs in two women aged 67 and 70 years.
After two years, both individuals had alleviation of symptoms and radiographic changes
Haufe et al., 2006
intradiscal injection of hematopoietic stem cells into ten patients
none of these individuals had any relief of symptoms
SCAFFOLDS
The purpose of a cellular scaffold is to provide an optimal microenvironment
for
cellular migration and proliferation
that allows the cells to maintain the appropriate phenotype
Collagen is a physiological biomolecularscaffold (collagen gels)
hyaluronan acts as an anchor for aggrecanretention
Chitosan-based polymers a soluble polymer atroom temperature, and induced to gel at bodytemperature
Polyglycolic acid, polylactic acid
copolymers
Bioglass
Poly ε-caprolactone (PCL)
Polyurethanes
Silk (natural biopolymer)
BIOMATERIALS
Two broad categories :
polymers that are preformed
polymers that are formed in situ
Injectable
Require minimally invasive procedure
Radiopaque
The mechanical properties of polymers: Viscoelasticity
Toughness
Permeability
Conformable structure
Flowable materials may be injected via a smallincision, allowing minimally invasive access tothe disc space
Derived from silk and elastin
Mimics the protein content, water content, pH of the natural nucleus pulposus
Indications : early stages of Degenerative Disc Disease (DDD) and as an adjunct to microdiscectomy