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Tissue Engineering

Samuel E. Lynch

Robert J. GencoRobert E. Marx

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Part IV:

Periodontal Regeneration14. Periodontal tissue regeneration by polypeptide

growth factors and gene transfer

15. Periodontal regeneration and localizedregeneration in the oral cavity16. Freeze-dried bone allografts in periodontics17. Application of rhBMP-2 to alveolar and

peiodontal defects

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Chap 14. periodontal tissueregeneration by polypeptide

growth factors and gene

transfer

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Polypeptide Growth Factor (GFs)

Natural biologic mediators Regulate crucial cellular events involved in

tissue repair DNA synthesis, chemotaxis, differenciation,matrix synthesis

Growth Factors PDGF, TGF-B, aFGF, bFGF, IGF-I and

IGF-II, CGF, BMPs

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Effects of GF

Growth factors : bone matrix Bone formation & resorption

Several GFs : cementum matrix Not understood

Several in vivo animal studies

Periodontal regeneration Coronal reestablishment of PDL

PLF proliferation, migration, collagenbiosynthesis

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Role of PDGF

Mitogen & Chemoattractant Fibroblast, osteoblast

Wound healing, fracture repair

Suramin (inhibitor of PDGF action) inject Ruduced intramembranous bone formation

Nash et al 4 weeks later Density and volume increased

Three-point bending : Indistinguishable from unoperatedcontrols

PDGF-a receptor deleted mice (Patch mouse) PDGF targets : essential for development

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Role of IGF-I

Pleiotrophic effects on bone homeostasis

Regulate bone cells in an autocrine or paracrinefashion by elevating DNA synthesis, osteocalcin

synthesis, and alkaline phosphatase activity

Promote bone matrix apposition

Effects on the mitogenesis of osteoblasts and PLFs

Chemotactic for PDL fibroblasts, osteoblasts andosteoclast-progenitor cells

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Interactions between GFs

Numerous GFs are sequestered in bonematrix at high concentrations Bone cells release several different GFs

During bone repair : temporal expression ofmultiple GF genes and gene products

IGF-I with PDGF

IGF-I with TGF-b or PDGF-BB IGF-I with bFGF, PDGF, TGF-b IGF-I, PDGF, TGF-b and EGF

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Effects of PDGF and IGF-I

Piche et al PDGF stimulate proliferation of isolate cell from the PDL

Oates et al

Both PDGF-AA and PDGF-BB enhance mitogenic activity ina dose-dependent manner in human PLFs

Matsuda et al Increased mitogenic activity with PDGF-BB and PDGF-AB

on rat PLFs as well as promotion of both PLF chemotaxis

and collagen synthesis P. gingivalis : suppressed

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Periodontal and peri-implant

bone regeneration by PDGF-

based therapeutics

A.PDGF-BB/IGF-I treated site (3M)

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Preclinical Trials

Lynch et al PDGF/IGF-I stimulates bone wound healing (2~3 times of no Tx.)

Becker et al Immediate extraction socket implants

Gore-Tex Mb with PDGF/IGF-1 Bone density and bone-to-implant contacts were twofold greater

than Mb alone or Mb combined with bone graft Failing dental implant sites : significantly higher concentration of

PDGF Chronic inflammaton

PDGF combined with dexamethasone Increases new bone and attachment within 4 weeks Park et al

Class III furcation defect New bone and attachment structures : 5~11 weeks after PDGF and

GTR

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IGF-I Not clearly demonstrate differences in periodontal

regeneration

Dose level, potential role of IGF-1 binding protein

IGFBP Enhance the action of IGF-I

Prolonging the plasma half-life of IGF-I Control the rate of IGF transport from the vasculature

Control the regulation of type I IGF receptor on the cellsurface

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Clinical trials

Howell and coworker Primary objective of this study Assess the safety of PDGF and IGF-I

Obtain preliminary efficacy data on periodontal regeneration

2 dose level treatment group (in 4% methycellulose vehicle) 50 / : rhPDGF-BB rhIGF-I (LD-PDGF/IGF-I)

150 / : HD-PDGF/IGF-I

6~9 month later HD-PDGF/IGF-I : statistically significant increases in alv. bone

2.08 mm new vertical bone height, 43.2% osseous defect fill

(control : 0.75 mm new bone height, 18.5% osseous)

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Comparison of periodontal

regeneration (osseous fill) in non-

human primates and human

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Novel methods of GF delivery by

gene transfer

,

:

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Chap. 15Periodontal Regeneration and

Localized Osseous

Regeneration in the Oral Cavity

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Periodontal regeneration

Autogenous iliac bone grafting No immune response

Obtained in sufficient quantities

Ambulation discomfort

Second surgical site that required hospitalconditions

Root resorption and/or ankylosis

GTR

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Osseous regeneration

DFDBA(demineralized Freeze-dried Bone Allografts) Bowers et al Regeneration of a new attachment apparatus was greater

Cementogenesis occurred more frequently

Predictability of results and the amount of regeneration vary

Utilize different types of lesions

Potential heterogeneity

BMPs Urist : ectopic sites

Sampath & Reddi : reconstitution of the solubilized extracts

Wozney et al : BMP purify and clone

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Biologic activity of commercially

prepared graft materials

Shigeyama et al : freshly obtained humanbone grafts or commercially obtained bonegrafts

Proteins from freshly prepared bone

Higher concentrations of BMP

Significantly greater ability to promote proliferation offibroblasts

But, proteins from commercial bone

Significantly promote cellular proliferation

Some activity was lost as a result of tissue processing

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Methods and materials

6 different bone banks, 200~500,14 sample 17~73years (mean 46.5years), 3 female/11 male Preparation methods : proprietary Sterilization : varied from no sterilization to gas sterilization or

irradiation

3 different mice for 28 days DFDBA particle from six sample : seven mice for 56 days DFDBA 10 ; intramuscular implantation

Two independent observers masked to treatment Score 1 : DFDBA Score 2 : 40% Score 3 : 40%

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Results

Physical properties of DFDBAs Particle size : 200~500 Surface area : 63.8~347.5 *2 pH : 1 hour (4.37~6.43), 48 hours (4.07~6.65)

Not completely neutralized after demineralization

Osteoinductive activity of DFDBAs Amount of bone and cartilage was varied with the source of

the DFDBA particles (Table 15-1) After 4 weeks

7 of the 14 sample : no new bone or cartilage in the tissuearound the particle 1 lot : new bone or cartilage in more than 40% 6 lots : less than 40%

Following 8 weeks 4 of the 7 lots : time-dependent change

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Discussion

Commercially obtained DFDBAs vary greatlyin their ability to induce bone in ectopic sites Different lots from the same tissue bank

Variable inductive ability

Contributing Factors ofvariable osteoinductive activity Donor age, host systemic condition, genetic

factors, and/or sex, differences among and withintissue banks regarding tissue collection andpreparation, size and shape, surface morphologyand roughness, pH, sterilization method.

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Clinical response to rhBMP-2

Method and materials 6 , 41~64( 55), 4/ 2

Results Safety of rhBMP-2/ACS volume : 0.12~0.88( 0.27)

No complication & adverse effect

Osteoconductive activity of rhBMP-2/ACS

Remodeling of the lamina dura : 4 weeks postextraction CT : 0.32 mm

Increased bone density

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6W

7M

6M

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Chap. 16

Freeze-dried bone allografts in

periodontics

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Mineralized freeze-dried bone

allograft (FDBA)

In 1976 : introduced to adult peiodontitis Tx.

89 clinicians 997 periodontal bone defects with FDBA alone,

524 defects with FDBA plus autogenous bone 1 year : complete or more than 50% bone fill FDBA : 220 site (67%)

combine : 137 site (78%)

Especially in furcation defects of multirooted teeth

Regeneration of periodontium 5~12

FDBA : 16/30 defects, Control : 5/30 defects

, ,

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DFDBA

DFDBA, FDBA DFDBA, , FDBA. DFDBA.

11, 27 DFDBA

6 (125~1,000 ) DFDBA : 65% (50% : 78%) Control : 38% (50% : 40%)

(6) 250~500 : 39% 850~1,000 : 35%

Bower et al , ,

Rummelhart et al DFDBA FDBA

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Freeze-dried allografts combined

with antibiotics

The addition of tetracycline to the bone graftwill theoretically enhance its osteogenicpotential.

Enhance fibroblast chemotaxis

Anticollagenolytic

Antibacterial activity DFDBA TC 4:1 : LJP FDBA TC : significant bone fill and defect

resolution AP : DFDBA TC 50 /

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FDBA versus Alloplasts

FDBA DFDBA porous praticulatehydroxyapatite

,

DFDBA polyacetic acid granule DFDBA

:

:

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GTR and FDBA

DFDBA

Anderegg DFDBA,

:

DFDBA, , ,

,

GTR, .

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GBR and FDBA

(naturally space-

making defects), (large non-space-making defects) .

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Safety of FDBA

Donor-specific anti-HLA antibody

20, Amos-modified microcytotoxicity assay

1/8

HIV : AIDS virus

28 1

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Future directions with DFDBA

DFDBA BMP.

BMPs DFDBABMP.

Bower et al DFDBA osteogenin(BMP-3) DFDBA osteogenin 6

DFDBA osteogenin submerged .

Nevin et al rhBMP-2/ACS, , 1.77~3.40 rhBMP-2

8.51 mm

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Chap. 17Application of rhBMP-2 to

alveolar and periodontal defects

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Critical-size, supra-alveolar,

periodontal defect model

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Flap surgery

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10mm implant : 5mm supraalveolar, periimplant defect

If only flap surgery : 10% regeneration

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8 weeks : 75% alv. B. , 40% cementum regeneration

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16 weeks : 20% peri-implant defects regeneration

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rhBMP-2/PLGA

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rhBMP-2/PLGA rhBMP-2/Bio-Oss

8 W

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rhBMP-2/ACS rhBMP-2/Drilac

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rhBMP-2/ACS

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Osseointegration within the extentof the defect(DOSS), within the extent of newly formed bone(BOSS), and within the adjacent resident bone(AOSS)

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rhBMP-2/ACS

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rhBMP-2/ACS

12W 24W

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Osseointegration

AOSS:subantral aug.

OSS:adjacennt resident bone

BG:vertical bone gain

ABD:cancellous b. density

BD:adjacent resident b. density

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rhBMP-2/ACS

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Thank you !