Sustained release of GDF5 from a designed coacervate attenuates disc degeneration in a rat model.

Low back pain is often caused by intervertebral disc degeneration, which is characterized by nucleus pulposus (NP) and extracellular matrix (ECM) degeneration. Human adipose-derived stem cells (hADSCs) induced by growth and differentiation factor-5 (GDF5) can differentiate into an NP-like phenotype. Although stem cell-based therapy with prolonged exposure to growth factors is regarded as a promising treatment, the efficacy of this approach in attenuating the disc degeneration process is limited by the short lifespan of growth factors. In our study, a unique growth factor delivery vehicle composed of heparin and the synthetic polycation poly(ethylene argininylaspartate diglyceride) (PEAD) was used to sustain GDF5 release. The results showed that sustained release of GDF5 by the PEAD:heparin delivery system promoted hADSC differentiation to an NP-like phenotype in vitro. After injection of the PEAD:heparin:GDF5 delivery platform and hADSCs into intervertebral spaces of coccygeal (Co) vertebrae Co7/Co8 and Co8/Co9 of the rat, the disc height, water content, and structure of the NPs decreased more slowly than other treatment groups. This new strategy may be used as an alternative treatment for attenuating intervertebral disc degeneration with hADSCs without the need for gene therapy. STATEMENT OF SIGNIFICANCE: Low back pain is often caused by intervertebral disc degeneration, which is characterized by nucleus pulposus (NP) and extracellular matrix (ECM) degeneration. Human adipose-derived stem cells (hADSCs) induced by growth and differentiation factor-5 (GDF-5) can differentiate into an NP-like phenotype. Although stem cell-based therapy with prolonged exposure to growth factor is regarded as a promising treatment, the efficacy of this approach in the disc regeneration process is limited by the short life of growth factors. In our study, a unique growth factor delivery vehicle comprised of heparin and the synthetic polycation poly(ethylene argininylaspartate diglyceride) (PEAD) was used to sustain the release of GDF-5. Numerous groups have explored IDD regeneration methods in vitro and in vivo. Our study differs in that GDF5 was incorporated into a vehicle through charge attraction and exhibited a sustained release profile. Moreover, GDF-5 seeded coacervate combined with hADSC injection could be a minimally invasive approach for tissue engineering that is suitable for clinical application. We investigated the stimulatory effects of our GDF-5 seeded coacervate on the differentiation of ADSCs in vitro and the reparative effect of the delivery system on degenerated NP in vivo.

The GDF5 mutant BB-1 enhances the bone formation induced by an injectable, poly(l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming cement in a sheep defect model of lumbar osteopenia.

BACKGROUND CONTEXT: Targeted delivery of osteoinductive bone morphogenetic proteins (eg, GDF5) in bioresorbable calcium phosphate cement (CPC), potentially suitable for vertebroplasty and kyphoplasty of osteoporotic vertebral fractures, may be required to counteract augmented local bone catabolism and to support complete bone regeneration. The biologically optimized GDF5 mutant BB-1 may represent an attractive drug candidate for this purpose. PURPOSE: The aim of the current study was to test an injectable, poly(l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming CPC containing low-dose BB-1 in a sheep lumbar osteopenia model. STUDY DESIGN/ SETTING: This is a prospective experimental animal study. METHODS: Bone defects (diameter 5 mm) were generated in aged, osteopenic female sheep and were filled with fiber-reinforced CPC alone (L4; CPC+fibers) or with CPC containing different dosages of BB-1 (L5; CPC+fibers+BB-1; 5, 100, and 500 µg BB-1; n=6 each). The results were compared with those of untouched controls (L1). Three and 9 months after the operation, structural and functional effects of the CPC (±BB-1) were analyzed ex vivo by measuring (1) bone mineral density (BMD); (2) bone structure, that is, bone volume/total volume (BV/TV) (assessed by micro-CT and histomorphometry), trabecular thickness (Tb.Th), and trabecular number (Tb.N); (3) bone formation, that is, osteoid volume/bone volume (OV/BV), osteoid surface/bone surface (OS/BS), osteoid thickness, mineralizing surface/bone surface (MS/BS), mineral apposition rate, and bone formation rate/bone surface; (4) bone resorption, that is, eroded surface/bone surface; and (5) compressive strength. RESULTS: Compared with untouched controls (L1), CPC+fibers (L4) and/or CPC+fibers+BB-1 (L5) significantly improved all parameters of bone formation, bone resorption, and bone structure. These effects were observed at 3 and 9 months, but were less pronounced for some parameters at 9 months. Compared with CPC without BB-1, additional significant effects of BB-1 were demonstrated for BMD, bone structure (BV/TV, Tb.Th, and Tb.N), and bone formation (OS/BS and MS/BS). The BB-1 effects on bone formation at 3 and 9 months were dose dependent, with 100 µg as the potentially optimal dosage. CONCLUSIONS: BB-1 significantly enhanced the bone formation induced by a PLGA fiber-reinforced CPC in sheep lumbar osteopenia. A single local dose as low as 100 µg BB-1 was sufficient to augment middle- to long-term bone formation. A CPC containing the novel GDF5 mutant BB-1 may thus represent an alternative to the bioinert, supraphysiologically stiff polymethylmethacrylate cement presently used to treat osteoporotic vertebral fractures by vertebroplasty and kyphoplasty.

GDF5 significantly augments the bone formation induced by an injectable, PLGA fiber-reinforced, brushite-forming cement in a sheep defect model of lumbar osteopenia.

BACKGROUND CONTEXT: Biodegradable calcium phosphate cement (CPC) represents a promising option for the surgical treatment of osteoporotic vertebral fractures. Because of augmented local bone catabolism, however, additional targeted delivery of bone morphogenetic proteins with the CPC may be needed to promote rapid and complete bone regeneration. PURPOSE: In the present study, an injectable, poly(l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming cement (CPC) containing the bone morphogenetic protein GDF5 was tested in a sheep lumbar osteopenia model. STUDY DESIGN/SETTING: This is a prospective experimental animal study. METHODS: Defined bone defects (diameter 5 mm) were placed in aged, osteopenic female sheep. Defects were treated with fiber-reinforced CPC alone (L4; CPC+fibers) or with CPC containing different dosages of GDF5 (L5; CPC+fibers+GDF5; 1, 5, 100, and 500 µg GDF5; n=5 or 6 each). The results were compared with those of untouched controls (L1). Three and 9 months postoperation, structural and functional effects of the CPC (±GDF5) were assessed ex vivo by measuring (1) bone mineral density (BMD); (2) bone structure, that is, bone volume/total volume (assessed by micro-computed tomography and histomorphometry), trabecular thickness, and trabecular number; (3) bone formation, that is, osteoid volume/bone volume, osteoid surface/bone surface, osteoid thickness, mineralized surface/bone surface, mineral apposition rate, and bone formation rate/bone surface; (4) bone resorption, that is, eroded surface/bone surface; and (5) compressive strength. RESULTS: Compared with untouched controls (L1), both CPC+fibers (L4) and CPC+fibers+GDF5 (L5) numerically or significantly improved all parameters of bone formation, bone resorption, and bone structure. These significant effects were observed both at 3 and 9 months, but for some parameters they were less pronounced at 9 months. Compared with CPC without GDF5, additional significant effects of CPC with GDF5 were demonstrated for BMD and parameters of bone formation and structure (bone volume/total volume, trabecular thickness, and trabecular number, as well as mineralized surface/bone surface). The GDF5 effects were dose-dependent (predominantly in the 5-100 µg range) at 3 and 9 months. CONCLUSIONS: GDF5 significantly enhanced the bone formation induced by a PLGA fiber-reinforced CPC in sheep lumbar osteopenia. The results indicated that a local dose as low as ≤100 µg GDF5 may be sufficient to augment middle to long-term bone formation. The novel CPC+GDF5 combination may thus qualify as an alternative to the bioinert, supraphysiologically stiff poly(methyl methacrylate) cement currently applied for vertebroplasty/kyphoplasty of osteoporotic vertebral fractures.

Growth Differentiation Factor 5 Accelerates Wound Closure and Improves Skin Quality During Repair of Full-Thickness Skin Defects.

BACKGROUND: A fast and stable wound closure is important, especially for extended and unstable wounds found after burn injuries. Growth can regulate a variety of cellular processes, including those involved in wound healing. Growth differentiation factor 5 (GDF-5) can accelerate fibroblast cell migration, cell proliferation, and collagen synthesis, which are essential for wound healing. Nevertheless, no standardized evaluation of the effect of GDF-5 on the healing of full-thickness wounds has been published to date. METHODS: Five full-thickness skin defects were created on the backs of 6 minipigs. Three wounds were treated with GDF-5 in different concentrations with the help of a gelatin-collagen carrier, and 2 wounds served as control group. The first was treated with the gelatin carrier and an Opsite film (Smith & Nephew, Fort Worth, Texas), and the other was treated solely with an Opsite film that was placed above all wounds and renewed every second day. RESULTS: Growth differentiation factor 5 accelerates wound closure (10.91 [SD, 0.99] days) compared with treatment with the carrier alone (11.3 [SD, 1.49] days) and control wounds (13.3 [SD, 0.94] days). Epidermal cell count of wounds treated with GDF-5 revealed a higher number of cells compared with the control group. In addition, mean epidermal thickness was significantly increased in GDF-5-treated wounds compared with the control wounds. CONCLUSIONS: Because of its ability to improve skin quality, GDF-5 should be considered when developing composite biomaterials for wound healing.

TGF-ß1 and GDF5 Act Synergistically to Drive the Differentiation of Human Adipose Stromal Cells toward Nucleus Pulposus-like Cells.

Degenerative disc disease (DDD) primarily affects the central part of the intervertebral disc namely the nucleus pulposus (NP). DDD explains about 40% of low back pain and is characterized by massive cellular alterations that ultimately result in the disappearance of resident NP cells. Thus, repopulating the NP with regenerative cells is a promising therapeutic approach and remains a great challenge. The objectives of this study were to evaluate the potential of growth factor-driven protocols to commit human adipose stromal cells (hASCs) toward NP-like cell phenotype and the involvement of Smad proteins in this differentiation process. Here, we demonstrate that the transforming growth factor-ß1 and the growth differentiation factor 5 synergistically drive the nucleopulpogenic differentiation process. The commitment of the hASCs was robust and highly specific as attested by the expression of NP-related genes characteristic of young healthy human NP cells. In addition, the engineered NP-like cells secreted an abundant aggrecan and type II collagen rich extracellular matrix comparable with that of native NP. Furthermore, we demonstrate that these in vitro engineered cells survived, maintained their specialized phenotype and secretory activity after in vivo transplantation in nude mice subcutis. Finally, we provide evidence suggesting that the Smad 2/3 pathway mainly governed the acquisition of the NP cell molecular identity while the Smad1/5/8 pathway controlled the NP cell morphology. This study offers valuable insights for the development of biologically-inspired treatments for DDD by generating adapted and exhaustively characterized autologous regenerative cells.

Effects of lubricant and autologous bone marrow stromal cell augmentation on immobilized flexor tendon repairs.

The purpose of the study was to test a novel treatment that carbodiimide-derivatized-hyaluronic acid-lubricin (cd-HA-lubricin) combined cell-based therapy in an immobilized flexor tendon repair in a canine model. Seventy-eight flexor tendons from 39 dogs were transected. One tendon was treated with cd-HA-lubricin plus an interpositional graft of 8 × 10(5) BMSCs and GDF-5. The other tendon was repaired without treatment. After 21 day of immobilization, 19 dogs were sacrificed; the remaining 20 dogs underwent a 21-day rehabilitation protocol before euthanasia. The work of flexion, tendon gliding resistance, and adhesion score in treated tendons were significantly less than the untreated tendons (p < 0.05). The failure strength of the untreated tendons was higher than the treated tendons at 21 and 42 days (p < 0.05). However, there is no significant difference in stiffness between two groups at day 42. Histologic analysis of treated tendons showed a smooth surface and viable transplanted cells 42 days after the repair, whereas untreated tendons showed severe adhesion formation around the repair site. The combination of lubricant and cell treatment resulted in significantly improved digit function, reduced adhesion formation. This novel treatment can address the unmet needs of patients who are unable to commence an early mobilization protocol after flexor tendon repair.

Biologic Agents for Periodontal Regeneration and Implant Site Development.

The advancement of molecular mediators or biologic agents has increased tremendously during the last decade in periodontology and dental implantology. Implant site development and reconstruction of the lost periodontium represent main fields in which these molecular mediators have been employed and investigated. Different growth factors trigger different reactions in the tissues of the periodontium at various cellular levels. Proliferation, migration, and differentiation constitute the main target areas of these molecular mediators. It was the purpose of this comprehensive review to describe the origin and rationale, evidence, and the most current understanding of the following biologic agents: Recombinant Human Platelet-Derived Growth Factor-BB (rhPDGF-BB), Enamel Matrix Derivate (EMD), Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF), Recombinant Human Fibroblast Growth Factor-2 (rhFGF-2), Bone Morphogenic Proteins (BMPs, BMP-2 and BMP-7), Teriparatide PTH, and Growth Differential Factor-5 (GDF-5).

Growth/differentiation factor-5: pre-clinical and clinical evaluations of periodontal regeneration and alveolar augmentation--review.

AIM: Growth/differentiation factor-5 (GDF-5) plays critical roles in mesenchymal cell differentiation and stimulates human periodontal ligament cell proliferation. Potentially, GDF-5 may also play roles in wound healing including periodontal regeneration and alveolar augmentation. The objective of this review was to provide up-to-date information from pre-clinical/clinical studies evaluating GDF-5 for these indications. METHODS: A comprehensive search using PubMed and Google search engines was conducted to identify reports on GDF-5 applied to periodontal and alveolar indications. Two reviewers independently screened the titles and abstracts from a total of 479 reports. Full-length articles of 17 pre-clinical and four clinical studies were selected and reviewed. RESULTS: Canine-, porcine- and non-human primate-based models as well as human clinical trials were used in the evaluation of GDF-5 in support of periodontal regeneration and alveolar augmentation. An absorbable collagen sponge (ACS), ß-tricalcium phosphate (ß-TCP) and a poly(lactic-co-glycolic) acid (PLGA) were evaluated as candidate carriers for GDF-5 using various dose and healing intervals demonstrating significantly enhanced periodontal regeneration/alveolar augmentation including cementum, periodontal ligament and alveolar bone with limited, if any, adverse effects. CONCLUSION: Growth/differentiation factor-5 supports periodontal regeneration/alveolar augmentation without aberrant healing events documented in qualified pre-clinical models and clinical pilot studies. In perspective, GDF-5 appears a promising technology for periodontal regeneration/alveolar augmentation.

Growth differentiation factor 5 regulation in bone regeneration.

Growth differentiation factor 5 (GDF5) is a member of the bone morphogenic protein (BMP) family and plays critical roles in organ development processes including bone, cartilage, ligament, and joint formation. GDF5 is expressed in the cartilage primordium in the early limb development, and in the interzone of joint formation sites. GDF5 is also observed in adult tissue and cell lines. This spatialtemporal expression pattern of GDF5 proves its essential role in the formation of bone and cartilage. Similar to other members of BMPs, the signaling cascade of GDF5 is originated through binding to type I and type II receptors and thus regulating the downstream intracellular biochemical processes. Mutations of GDF5 are associated with several human and animal diseases that are characterized by skeletal deformity such as short digits and short limbs. In vitro and in vivo studies demonstrated that overexpression of GDF5 or administration of recombinant protein promotes chondrogenesis and osteogenesis. Moreover, a promising feature of GDF5 is osteoinduction, which is used in tissue engineering for bone repair with or without a carrier in animal platforms and in human preclinical settings. The exciting results signify that GDF5 is a compelling candidate for bone tissue engineering by enhancing osteogenesis and angiogenesis. In this review, we will focus the discussion on the basic structure, signaling pathways, function in cartilage and bone formation, and potential clinical application of GDF5 in bone tissue regeneration.

Comparison between a ß-tricalcium phosphate and an absorbable collagen sponge carrier technology for rhGDF-5-stimulated periodontal wound healing/regeneration.

BACKGROUND: The objective of this study is to compare a candidate ß-tricalcium phosphate (ß-TCP) carrier technology with the absorbable collagen sponge (ACS) benchmark to support recombinant human growth/differentiation factor-5 (rhGDF-5)-stimulated periodontal wound healing/regeneration. METHODS: Routine, bilateral, critical-size (5-mm), 1-wall, intrabony periodontal defects were surgically created in the mandibular premolar region in 10 beagle dogs. Five animals received rhGDF-5/ß-TCP and five animals received rhGDF-5/ACS, with a total of 20 µg rhGDF-5 per defect. The animals were euthanized for histologic and histometric analyses at 8 weeks postsurgery. RESULTS: Both rhGDF-5/ACS and rhGDF-5/ß-TCP stimulated the formation of functionally oriented periodontal ligament, cellular mixed fiber cementum, and woven/lamellar bone. Bone regeneration (height and area) was significantly greater for the rhGDF-5/ß-TCP construct than for the rhGDF-5/ACS (3.26 ± 0.30 mm versus 2.22 ± 0.82 mm, P <0.01; and 10.45 ± 2.26 mm(2) versus 5.62 ± 2.39 mm(2), P <0.01, respectively). Cementum formation ranged from 3.83 ± 0.73 mm to 3.03 ± 1.18 mm without significant differences between groups. Root resorption/ankylosis was not observed. CONCLUSIONS: The ß-TCP carrier technology significantly enhanced rhGDF-5-stimulated bone formation compared with the ACS benchmark in this discriminating periodontal defect model. The structural integrity of the ß-TCP carrier, preventing compression while providing a framework for bone ingrowth, may account for the observed results.

Maturation of alveolar bone following implantation of an rhGDF-5/PLGA composite into 1-wall intra-bony defects in dogs: 24-week histometric observations.

OBJECTIVE: The aim of this study was to evaluate long-term (24 weeks) alveolar bone maturation following surgical application of recombinant human growth/differentiation factor-5 (rhGDF-5) in an injectable poly-lactide-co-glycolide-acid (PLGA) composite carrier using an established periodontal defect model. METHODS: Routine, bilateral, 4 × 5 mm (width × depth), 1-wall, critical-size, intra-bony periodontal defects were surgically created at the 2nd and 4th mandibular premolar teeth in 10 Beagle dogs. The animals were randomized to receive (split-mouth design; defect sites in the same jaw quadrant getting the same treatment) rhGDF-5/PLGA high dose (188 µg/defect) versus sham-surgery control (5 animals), and rhGDF-5/PLGA low dose (37 µg/defect) versus carrier control (5 animals). The animals were euthanized for histometric analysis following a 24-week healing interval. RESULTS: Clinical healing was uneventful. The rhGDF-5 high dose significantly increased bone formation compared with controls in terms of bone area (p < 0.05), and a high degree of bone maturation was observed in the rhGDF-5/PLGA high dose group. Root resorption/ankylosis or other aberrant healing events were not observed. CONCLUSION: The rhGDF-5/PLGA appears to support alveolar bone healing/regeneration and the rhGDF-5/PLGA high dose uniquely increased maturation of the regenerated bone.

Maturation of periodontal tissues following implantation of rhGDF-5/ß-TCP in one-wall intra-bony defects in dogs: 24-week histological observations.

OBJECTIVE: Although a previous study reported that recombinant human growth/differentiation factor-5 (rhGDF-5) coated onto a ß-tricalciumphosphate (ß-TCP) significantly enhanced periodontal regeneration, the long-term stability/maturation of the regenerated tissues has not been demonstrated. The objective of this study was to evaluate periodontal regeneration/maturation following application of rhGDF-5/ß-TCP using an established periodontal defect model and a 24-week healing interval. MATERIAL & METHODS: Unilateral, surgically created, 4 × 4 × 5 mm (length × width × height), one-wall, critical-size, intra-bony periodontal defects at the mandibular second and fourth premolar teeth in five young adult Beagle dogs received rhGDF-5/ß-TCP. Bilateral sites at the fourth premolar in the other four dogs served as pristine controls receiving mucogingival flap surgery without defect induction. The animals were euthanized at 24 weeks for histological analysis. Unpublished data from the previous 8-week study were used to compare tissue maturation between 8 and 24 weeks. RESULTS: Linear histometric observations of cementum and alveolar regeneration showed no significant differences between the 8- and 24-week observation intervals. However, parameters of periodontal tissue maturation showed significant differences between the observation intervals including increased fraction mineralized tissue and lamellar bone (p < 0.05) and decreased osteocyte counts (p < 0.05) at 24 weeks compared with 8 weeks. Although the count inserting Sharpey's fibre did not significantly change, regenerated cementum remote from the intact periodontal ligament appeared more highly mineralized and thicker at 24 weeks compared with 8 weeks, and compared with the pristine cementum. Minimal ß-TCP remained. CONCLUSIONS: These 24-week observations suggest that regenerated periodontal tissues in sites receiving rhGDF-5/ß-TCP undergo progressive maturation without debilitating aberrant tissue reactions.

A phase IIa randomized controlled pilot study evaluating the safety and clinical outcomes following the use of rhGDF-5/ß-TCP in regenerative periodontal therapy.

To present the safety profile, the early healing phase and the clinical outcomes at 24 weeks following treatment of human intrabony defects with open flap debridement (OFD) alone or with OFD and rhGDF-5 adsorbed onto a particulate ß-tricalcium phosphate (ß-TCP) carrier. Twenty chronic periodontitis patients, each with at least one tooth exhibiting a probing depth ≥6 mm and an associated intrabony defect ≥4 mm entered the study. Ten subjects (one defect/patient) were randomized to receive OFD alone (control) and ten subjects OFD combined with rhGDF-5/ß-TCP. Blood samples were collected at screening, and at weeks 2 and 24 to evaluate routine hematology and clinical chemistry, rhGDF-5 plasma levels, and antirhGDF-5 antibody formation. Plaque and gingival indices, bleeding on probing, probing depth, clinical attachment level, and radiographs were recorded pre- and 24 weeks postsurgery. Comparable safety profiles were found in the two treatment groups. Neither antirhGDF-5 antibody formation nor relevant rhGDF-5 plasma levels were detected in any patient. At 6 months, treatment with OFD + rhGDF-5/ß-TCP resulted in higher but statistically not significant PD reduction (3.7 ± 1.2 vs. 3.1 ± 1.8 mm; p = 0.26) and CAL gain (3.2 ± 1.7 vs. 1.7 ± 2.2 mm; p = 0.14) compared to OFD alone. In the tested concentration, the use of rhGDF-5/ß-TCP appeared to be safe and the material possesses a sound biological rationale. Thus, further adequately powered, randomized controlled clinical trials are warranted to confirm the clinical relevance of this new approach in regenerative periodontal therapy. rhGDF-5/ß-TCP may represent a promising new techology in regenerative periodontal therapy.

The effects of growth and differentiation factor 5 on bone marrow stromal cell transplants in an in vitro tendon healing model.

The effects of growth differentiation factor-5 (GDF-5) and bone marrow stromal cells (BMSCs) on tendon healing were investigated under in vitro tissue culture conditions. BMSCs and GDF-5 placed in a collagen gel were interpositioned between the cut ends of dog flexor digitorum profundus tendons. The tendons were randomly assigned into four groups: 1) repaired tendon without gel; 2) repaired tendon with BMSC-seeded gel; 3) repaired tendon with GDF-5 gel without cells; and 4) repaired tendon with GDF-5 treated BMSC-seeded gel. At 2 and 4 weeks, the maximal strength of repaired tendons with GDF-5 treated BMSCs-seeded gel was significantly higher than in tendons without gel interposition. However, neither BMSCs nor GDF-5 alone significantly increased the maximal strength of healing tendons at 2 or 4 weeks. These results suggest that the combination of BMSCs and GDF-5 accelerates tendon healing, but either BMSCs or GDF-5 alone are not effective in this model.

Wound healing/regeneration using recombinant human growth/differentiation factor-5 in an injectable poly-lactide-co-glycolide-acid composite carrier and a one-wall intra-bony defect model in dogs.

OBJECTIVE: The purpose of this study was to evaluate the effect of recombinant human growth/differentiation factor-5 (rhGDF-5) on periodontal wound healing/regeneration using an injectable poly-lactide-co-glycolide-acid (PLGA) composite carrier and an established defect model. METHODS: Bilateral 4 × 5 mm (width × depth) one-wall, critical-size, intra-bony periodontal defects were surgically created at the second and the fourth mandibular pre-molar teeth in 15 Beagle dogs. The animals were randomized to receive (using a split-mouth design; defect sites in the same jaw quadrant getting the same treatment) rhGDF-5 high dose (188 µg/defect) versus sham-surgery control (five animals), rhGDF-5 mid dose (37 µg/defect) versus carrier control (five animals), and rhGDF-5 low dose (1.8 µg/defect) versus treatment reported elsewhere (five animals). The animals were euthanized for histometric analysis following an 8-week healing interval. RESULTS: Clinical healing was uneventful. The rhGDF-5/PLGA construct was easy to assemble and apply. The rhGDF-5 high dose supported significantly increased bone formation compared with the low-dose, sham-surgery, and carrier controls (p<0.05) and induced significantly increased cementum formation compared with the controls (p<0.05). Root resorption/ankylosis or other aberrant healing events were not observed. CONCLUSION: rhGDF-5 appears to effectively support periodontal wound healing/regeneration in a dose-dependent order; the PLGA composite appears to be an effective ease-of-use candidate for carrier technology.

Growth/differentiation factor-5 significantly enhances periodontal wound healing/regeneration compared with platelet-derived growth factor-BB in dogs.

OBJECTIVE: Recombinant human growth/differentiation factor-5 (rhGDF-5) in a particulate beta-tricalcium phosphate (beta-TCP) carrier is being evaluated to support periodontal regeneration. The objective of this study was to evaluate periodontal wound healing/regeneration following an established clinical (benchmark) protocol including surgical implantation of rhGDF-5/beta-TCP in comparison with that following implantation of recombinant human platelet-derived growth factor-BB (rhPDGF) combined with a particulate beta-TCP biomaterial using an established canine defect model. MATERIALS AND METHODS: Bilateral, 4 x 5 mm (width x depth), one-wall, critical-size, intrabony periodontal defects were surgically created at the mandibular second and fourth pre-molar teeth in five adult Beagle dogs. Defect sites were randomized to receive rhGDF-5/beta-TCP or the rhPDGF construct followed by wound closure for primary intention healing. The animals were sacrificed following an 8-week healing interval for histological and histometric examination. RESULTS: Clinical healing was generally uneventful. Sites receiving rhGDF-5/beta-TCP exhibited a significantly enhanced cementum formation compared with sites receiving the rhPDGF construct, averaging (+/-SD) 4.49+/-0.48 versus 2.72+/-0.91 mm (p<0.001). Similarly, bone regeneration height and area were significantly enhanced at sites receiving rhGDF-5/beta-TCP versus that of the rhPDGF construct averaging, 3.08+/-0.74 versus 1.29+/-0.78 mm (p<0.001) and 6.03+/-1.28 versus 2.98+/-2.61 mm(2) (p<0.01), respectively. Cementum regeneration included cellular/acellular mixed (extrinsic/intrinsic) fibre cementum at sites receiving rhGDF-5/beta-TCP; sites receiving the rhPDGF/beta-TCP showed a pre-dominantly acellular cementum. Newly formed cementum generally extended above the adjoining alveolar bone. Both protocols displayed beta-TCP residues apparently undergoing resorption. Application of both materials appears safe, as they were associated with limited, if any, adverse events. CONCLUSION: rhGDF-5/beta-TCP shows a significant potential to support/accelerate periodontal wound healing/regeneration. Application of rhGDF-5/beta-TCP appears safe and should be further evaluated in human clinical trials.

Growth/differentiation factor-5: a candidate therapeutic agent for periodontal regeneration? A review of pre-clinical data.

AIM: Therapeutic concepts involving the application of matrix, growth and differentiation factors have been advocated in support of periodontal wound healing/regeneration. Growth/differentiation factor-5 (GDF-5), a member of the bone morphogenetic protein family, represents one such factor. The purpose of this review is to provide a background of the therapeutic effects of GDF-5 expressed in various musculoskeletal settings using small and large animal platforms. METHODS: A comprehensive literature search was conducted to identify all reports in the English language evaluating GDF-5 using the PubMed and Google search engines, and a manual search of the reference lists from the electronically retrieved reports. Two reviewers independently screened the titles and abstracts from a total of 69 reports, 22 of which were identified as pre-clinical (in vivo) evaluations of GDF-5. The full-length article of the 22 pre-clinical reports was then reviewed. RESULTS: Various applications including cranial and craniofacial bone formation, spine fusion, long bone fracture healing, cartilage, and tendon/ligament repair using a variety of small and large animal platforms evaluating GDF-5 as a therapeutic agent were identified. A majority of studies, using biomechanical, radiographic, and histological analysis, demonstrated significant dose-dependent effects of GDF-5. These include increased/enhanced local bone formation, fracture healing/repair, and cartilage and tendon/ligament formation. GDF-5 frequently was shown to accelerate wound maturation. Several studies demonstrated GDF-5 to be a realistic alternative to autograft bone. Studies using pre-clinical models and human histology suggest GDF-5 may also increase/enhance periodontal wound healing/regeneration. CONCLUSIONS: GDF-5 appears a promising therapeutic agent for periodontal wound healing/regeneration as GDF-5 supports/accelerates bone and tendon/ligament formation in several musculoskeletal settings including periodontal tissues.

The effects of recombinant human growth/differentiation factor-5 (rhGDF-5) on bone regeneration around titanium dental implants in barrier membrane-protected defects: a pilot study in the mandible of beagle dogs.

PURPOSE: This dog study sought to evaluate guided bone regeneration (GBR) in peri-implant defects following implantation of beta-tricalcium phosphate (beta-TCP) with and without osteoinductive recombinant human growth/differentiation factor-5 (rhGDF-5). MATERIALS AND METHODS: In five beagle dogs, all mandibular premolars and the first molar were extracted. After 2 months, six buccolingual critical-size defects were created, and an implant was inserted into the center of each defect. One defect was filled with beta-TCP coated with rhGDF-5 (600 microg/g beta-TCP) and covered with a titanium-reinforced e-PTFE membrane (GDF group). A second defect received the same treatment, but pure uncoated beta-TCP was used (TCP group). A third defect was filled with beta-TCP mixed with autograft and not protected with a membrane (control group). The remaining three defects were filled with other biomaterials. After 2 months, total new bone area, regenerated bone height, and residual amount of beta-TCP were determined histomorphometrically. RESULTS: All implants osseointegrated. One membrane in each group became exposed. Mean new bone area for GDF, TCP, and control sites was 43.9 +/- 18.7 mm2, 32.3 +/- 16.1 mm2, and 13.1 +/- 4.0 mm2, respectively, with a significant difference between GDF and control groups. Mean regenerated bone height was 103.8 +/- 29.7%, 75.4 +/- 36.6%, and 67.2 +/- 19.1% for the GDF, TCP, and control groups, respectively. Mean residual matrix volumes were 25.9 +/- 13.6%, 30.0 +/- 13.0%, and 13.4 +/- 6.5%, respectively. Membrane protection of peri-implant defects filled with beta-TCP resulted in a stronger effect on bone regeneration, although this was not statistically significant. The most pronounced regenerative results were achieved in rhGDF-5/beta-TCP filled membrane-protected defects. CONCLUSION: Delivery of rhGDF-5 on beta-TCP might have the potential to enhance the results of GBR in peri-implant defects.

A preliminary report on the effect of dimeric rhGDF-5 and its monomeric form rhGDF-5C465A on bone healing of rat cranial defects.

INTRODUCTION: The purpose of the study was to compare the efficacy on rat skull defects of two bone growth factors derived from the GDF-5 family. MATERIAL AND METHODS: The study was conducted on 17 adult Wistar rats. On each animal, two symmetrical 6-mm wide, full-thickness, skull defects were carried out in the parietal regions. In 15 out of 17 animals, both experimental defects were filled by the implants. In the group I (n=2), both defects were left empty for control. The 15 other rats were divided into 3 groups: In group II (n=5), a collagen sponge was implanted. In group III (n=5), a collagen sponge impregnated with rhGDF-5 (the genuine dimeric form) was implanted. In group IV (n=5), a collagen sponge impregnated with rhGDF-5C465A (a monomeric form of GDF-5) was implanted. All animals were sacrificed at 8 weeks. The harvested specimens were processed for contact radiography and standard histological examination. The quantitative results were assessed with a semi-quantitative histological scoring system. RESULTS: One animal in the group II was excluded because it died of unknown reasons. In group I, no bone healing was observed in the defects. In group II, no bone healing was observed in 4 out of 10 defects, and partial bone healing was observed in 5 out of 10 defects. In group III, partial bone healing was also observed in 3 out of 8 defects and complete bone healing in 4 out of 8 defects. In group IV, partial bone healing was observed in 8 out of 10 defects and complete bone healing in 2 out of 10 defects. CONCLUSION: Bone healing was improved in all treated groups. Further studies are necessary to determine the optimal formulation of these composite implants.