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Cell transplantation to the rescue: Repairing the injured spinal cord

Mary Bartlett Bunge, PhD

Christine E. Lynn Distinguished Professor of Neuroscience

Professor of Cell Biology, Neurological Surgery, and Neurology

The Miami Project to Cure Paralysis University of Miami Miller School of Medicine

mbunge@miami.edu

Founders (1985) Current Staff -Barth Green, M.D. - 21 basic science faculty -Donald Misner - 16 clinical science faculty -Beth Roscoe - 12 management -Nick Buoniconti - 18 post-docs -Marc Buoniconti - 17 graduate students

- 104 research staffScientific Directors - 41 support staff

-ÅkeSeiger, M.D., Ph.D. - other students (high -Richard Bunge, M.D. school, undergrad, -W. Dalton Dietrich, Ph.D. medical, residents)

Spinal Cord Injury (SCI) • 12,000 new cases / year in the U.S.• Approx 1.275 million Americans with

paralysis due to SCI; 5.3 million with paralysis due to some type of CNS injury/disorder

• Nearly 50%, ages 16-30; 80%,males• Higher occurrence in military, Dept of

Defense funding • MVAs (36.5%), falls (28.5), violence (14)

Quality of Life Issues with SCI

Muscle paralysis, loss of feeling Reduced pulmonary function Early cardiovascular disease, stroke, DVTsLack of bowel and bladder control; infection Temperature, blood pressure vary widelyPressure ulcers, osteoporosis Sexual function/fertility impaired Pain long–term, 80 %Obesity, diabetes, cognitive decline

Cultured cells for CNS repair

“If we have normal cell types available in culture and if a nervous system disease stems from an absence or deficiency of one of these cell types, then it is an obvious step to transfer cultured cells into the diseased animal to attempt to correct the deficiency. Whereas at present this would not seem practical for many types of neurons, it may be practical for supporting cells (e.g. Schwann or glial).”

Richard P Bunge, The changing uses of nerve tissue culture 1950-1975 in The Nervous System, Donald B Tower, editor in chief, Vol 1 the Basic Neurosciences, 1975.

Nerve cell (neuron)

Peripheral nerve

Peripheral nerve Schwann cell myelinated axons

Myelin formation by Schwann cells

Albert J. Aguayo, M.D.

Photo of St. Louis Arch

Patrick M.Wood, PhD

Schwann cell biology in vitro

• SCs generate a number of ECM components• SCs require contact with ECM to

differentiate• SCs require contact with axons to form

basal lamina• SCs require basal lamina to form myelin• SCs require ascorbic acid to form myelin

(Type IV collagen)

[Defined medium (N2) supported SC profileration but not differentiation]

Schwann cell biology in vitro - 2

• Mitogenic signal on axons for SC proliferation (control of SC #)

• Perineurium formed in cultures of neurons, SCs and fibroblasts

• Perineurium formed from fibroblasts, not SCs (Lac-Z retrovirus)

• Circumnavigation by inner lip of SC cytoplasm a part of myelin formation mechanism

Why Schwann cells?• Promote axon regeneration/PN• Aguayo team; CNS axons regenerated into PN• Are readily accessible in PN• Produce growth factors, ECM • Myelinate axons in CNS, restore activity• Can obtain large numbers in culture• Can transplant person’s own cells• Can genetically engineer cells• Promising pre-clinical data in multiple species

(rats, pigs, primates) ; FDA approval for human SCs

Xu XM, Guénard V, Kleitman N, Bunge MB (1995) Axonal regeneration into Schwann cell-seeded guidance channels grafted into transected adult rat spinal cord. J Comp Neurol 351:145-160.

Xu XM, Guénard V, Kleitman N, Aebischer P, Bunge MB (1995) A combination of BDNF and NT-3 promotes supraspinal axonal regeneration into Schwann cell grafts in adult rat thoracic spinal cord. Exp Neurol 134:261-272.

Xu XM, Chen A, Guénard V, Kleitman N, Bunge MB (1997) Bridging Schwann cell transplants promote axonal regeneration from both the rostral and caudal stumps of transected adult rat spinal cord. J Neurocytol 26:1-16.

Xiao-Ming Xu, M.D., Ph.D.

PAN/PVC tube

SC

Scanning EM

*

How do we measure outcome?-Behavior: Walking? Pain assessment?-Histology: Lesion volume, overall tissue changes -Transplanted SC survival and number?-Count SC-myelinated axons? Total # axons?-Immunostaining

Scar formation?Types of axons in implant, and beyond?Inflammatory response?

-Neuroanatomical tracing What spinal and supraspinal neurons responded? What types of axons regenerated into implant?Did these axons leave implant?

SC/Matrigel bridge at 30 dpt

Thoracic complete transection model: Schwann cells

• Axons grow onto SC bridge from both stumps

• 2000 myelinated axons on bridge• 8x more non-myelinated axons/bridge

Transplants at 12 wk after contusion injury

LV-GFP

Dr. Damien Pearse

Thoracic contusion model: Schwann cells

• Reduce cyst formation• Protect spinal cord tissue from

secondary damage • Support axonal growth into SC graft• ~5000 SC-myelinated axons in graft• Some improvement in walking after

paralysis

Injured spinal cord tissue environment -1

• Excessive EAA (e.g., glutamate) release• EAA receptor activation• Excessive Ca++ entry into cells• Ca++ stimulated activation of proteolytic and

other degradative enzymes• Cytoskeletal protein breakdown• Oxygen free radical release leading to

membrane damage• Cytokine, chemokine release

Injured spinal cord tissue environment-2

• Many tissue damaging sequelae initiated, leading to secondary damage

• Substances inhibitory to repair appear• Inflammation begins• Barrier to axon growth (scar) forms• Sustenance for surviving nerve cells cut off• Cyst created due to tissue loss, preventing

axon regrowth

To repair the cord - 1

• Halt spread of secondary tissue damage

• Save as many nerve cells as possible• Curb inflammation• Reduce scar formation• Neutralize inhibitory factors

To repair the cord - 2

• Awaken nerve cells to regrow axons• Provide sustenance to nerve cells• Promote axon growth across injury• Guide growth to appropriate area• Enable formation of connections

Combination strategies: SCs +

• Steroid (used clinically)• Variety of growth factors• Another cell type (olfactory ensheathing

cells)• An enzyme (to reduce scar formation)• Elevation of a cell signaling molecule, cAMP• Introduction of genes to improve Schwann

cell efficacy

ALL THESE IMPROVED REPAIR/FUNCTION

Combination strategies: SCs +

• More SC-myelinated axons in graft • Increase in regenerated axons from

neurons above spinal cord (Distance factor overcome)

• Exit of regenerated axons from graft into the cord

• More improvement in walking

SCs with added growth factor gene survive better and improve axon growth

Control SCs

SCs + growth factor

GF levels signif. increased in cord at 2 dpt, low levels up to 6 wpt

GF led to 5X increase in graft vol, SC #GF led to a signif. increase in myel.

axons (SC 5,100; LV-GFP SCs 4,600; LV-GFP/GF SCS 26,000) and total axons (~75,000)

DβH+ fiber length signif. increased with GFNo improvement in walking

Viral Vector/growth factor (GF)-

engineered SC study (2007)

Combined engineering of Schwann cell implantsto secrete neurotrophin and chondroitinase promotes

axonal regeneration and locomotion after SCI

H Kanno, Y Pressman, A Moody, R Berg, E Muir, J Rogers, H Ozawa, E Itoi, D Pearse, M Bunge

Haruo Kanno, M.D., Ph.D.

Experiment Adult female Fischer rats (160-180g)

• Moderate contusion injury at thoracic 8 level

Schwann cell transplantation:• 1 week after injury, 1+1 million cells

Experimental groups:1. Vehicle (no cells) (control)2. green-SCs + red-SCs (control)3. green/GF-SCs + red-SCs4. green-SCs + red/ENZ-SCs5. green/GF-SCs + red/ENZ-SCs

Presenter

Presentation Notes

These are CS56 staining at 12weeks. These 3 groups without chondroitinase show higher immunoreactivity. The immunoreactivity is observed inside the implant and outside the implant, especially in the dorsal side of the spinal cord. In contrast, the groups with chondroitinase don’t have high intensity area.

2B6 staining

GFPmCherry/ChABC2B6

1000μm

Chondroitinase activity in vivo

SC-transplanted spinal cord

Combination strategyControl

0

10000

20000

30000

40000

50000

60000

70000

80000

1) DMEM/F122) GFP + mCherry3) GFP/D15A + mCherry4) GFP + mCherry/Ch'ase5) GFP/D15A + mCherry/Ch'ase

# SC

mye

linat

ed a

xons

/ se

ctio

n

SC myelination in implant

**

DMEM/F12GFP + mCherryGFP/GF+ mCherryGFP + mCherry/ChABCGFP/GF + mCherry/ChABC

#

Combination vs single treatments

• Further increase in implant compared to GF or ENZ

• Further increase in SC myel axons compared to ENZ

• Higher number of responding neurons above cord than with GF or ENZ

• Higher number of their axons in implant and in cord beyond than with GF or ENZ

• Improved walking scores• Lessened pain in hindpaws

Experimental Neurology 1997;148:502-22

The ability of human Schwann cell grafts to promote regeneration in the transected nude rat spinal cordGuest JD, Rao A, Olson L, Bunge MB, Bunge RP

The Miami Project to Cure Paralysis, The Organ Procurement Team, Department of Neurological Surgery, University of Miami School of Medicine, Miami, Florida__________________________________________________________________________

Nude athymic rats Human SCs/Matrigel, with or without PAN/PVC

channels T8 complete transection, T9-10 cord removed Methylprednisolone

Myelinated axons, ~2,000

Propriospinal, sensory, motoneuronal, brainstem

(DβH, 5HT) axons in SC bridgePropriospinal and sensory axons re-entered the

spinal cord (up to 2.6 mm)Walking scores significantly improved __________________________________________________

Robust axon growth into SC bridge, some growth beyond and modest improvement in locomotion

Human Schwann cells

Can be isolated and readily increased in # in culture Up to 10 m SCs, single adult sural nerve biopsy

100 m SCs in 3-4 wk Variation in rate of increase from donor to donor Preparation: Careful dissection of bundles Intro culture medium with forskolin (↑cAMP) and heregulin

(mitogenic), 1 wk Overnight incubation in collagenase and dispase; then

mechanical dissociation of fascicles by trituration Onto laminin, with forskolin and heregulin (all reduce

fibroblasts, leading to 95% SCs or higher)

APPROVAL FROM THE FDA FOR OUR FIRST SC TRIAL

Phase 1 (for safety) Clinical trial: to inject person’s own Schwann cells (from peripheral nerve*) into site of SCI

SC number increased in culture for 3-5 wkSCs injected into lesion epicenter_______________*From single adult sural nerve biopsy, 100 m

SCs/ 3-4 wk

Feasibility for trial? (Many rodent studies over nearly 20 years)Detailed characterization of manufactured hSCsPreclinical safety studies (rodents, pigs,

primates)Development of clinical cell injection methodAdequate outcome assessment methods for a

valid appraisal of patient

Guest et al. 2013

Miami Project Schwann Cell Team

MilestonesDec ‘07 Organized SC clinical trial team, weekly meetings

‘08- ‘09 Developed GMP cell manufacturing procedures for human SCs

‘09-’10 -Tested toxicology and tumorigenicity in rats -SCI studies in pigs to determine safest cell

injection procedure

‘10-’11 -More toxicology and tumorigenicity studies on rats-Studies in pigs to determine safest dose and

volume for clinical protocol

July ‘11 Submitted IND application to the FDA

July ‘12 Approval!

Dec ‘12 Performed 1st transplantation

IND submission

The autologous hSC trial • Open label, unblinded, non-randomized and

non- placebo dose escalation study, looking at safety of transplantation of autologous hSCs with long term follow-up in subjects with subacute SCI

• Cell preparation protocols are FDA approved and cell processing is conducted in a facility with extensive experience producing clinical grade cells (GMP)

• Piece of sural nerve is harvested within 5 days post- injury

What did the FDA require?

Studies to detect: Tumors? Biodistribution?Appropriate dose (MTD)? Toxicity?Cell survival for 6 mo?

Characterization of cell product (GMP)Every substance FDA approvedEach step in protocol recorded + witnessedMode of SC injection

Challenges• $$$, rats, ramping up personnel (training),

paper work• Documentation of outcome of EVERY rat,

including cause of death• SOPs for every step in every procedure• Sectioning of entire brain and spinal cord

to detect migration of transplanted SCs• Certified Pathologist to examine

sections

Next steps?New clinical trial for combination approachTranslatable:

-Improve implant survival-Slow release of added components in

implant and beyond-Growth factor gradients beyond implant-Provide environment for axon

growth/implant and beyond-Provide oxygen for early implant

Collaborate with bioengineers

“Dream” biomaterialNon-toxic, biocompatible, biodegradableNon-inflammatory, non–scar response Injectable as fluid (with cells) for closed

injuryGels upon filling injury site, linear

arrangement (tunnels) Promotes axon growth Protects viability of cells Slowly releases growth factors, other

Funding: MBB• NIH Fellowship• NIH research grant 1971-2017 (3 Javits

Awards)Renewed every 5 or 7 yr

• Private FoundationsDonors to The Miami Project, 25 yrThe Buoniconti Foundation The C and D Reeve Foundation, 15 yr

Christine E. Lynn Disting Professor, 11 yr• State of Florida

“If you want to go quickly, go alone. If you want to go far, go together.” – African Proverb

Thank You !

The Miami Project to Cure Paralysis

Neurotrophins• Family Members:

-Nerve Growth Factor (NGF)-Brain Derived Neurotrophic Factor (BDNF)-Neurotrophin 3 (NT–3)-Neurotrophin 4 and/or 5 (NT- 4/5)

• Functions:-Control of proliferation, survival, differentiation-Central and peripheral nervous systems-Developing and adult nervous systems

Inclusion Criteria• Traumatic thoracic SCI between levels T3-T11• ASIA grade A, 18-50 years of age • Consents to spinal nerve biopsy, implantation,

one year follow-up and 5-year protocol

Cohort Target dose Injections Total volume # subjects 1 5 x 106 1 50 µl 22 10 x 106 1 100 µl 33 15 x 106 1 150 µl 3

Dose Escalation

Exclusion criteria

• Penetrating injury• Spinal cord transection• Lesions involving conus• Multi-system trauma• Closed head injury• Severe neuropathic pain at admission• BMI < 35

Outcomes• 1° outcome – assess safety

– Serious adverse events– Changes in sensory and motor scores – Changes in pain or spasticity– Electrophysiology for MEP and SSEP– MRI

• 2° outcome – evaluate functional scales– Functional Independence Measure (FIM)– Spinal Cord Independence Measure (SCIM)– Autonomic (BP, HR, tilt table response, etc.)

• Follow-up of above for one year• Follow-up (MRI annually for 4 years after first year)