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Biomedical subjects

U Ripamonti

Publications and source records attributed to U Ripamonti.

At least 19 recordsLinked to original sources
PubMed2001

Induction of bone formation by recombinant human osteogenic protein-1 and sintered porous hydroxyapatite in adult primates.

A critical issue in tissue engineering and morphogenesis of bone is the development of novel biomimetic biomaterials that are capable of optimizing the biological activity of recombinant human bone morphogenetic and osteogenic proteins, which are molecules that initiate bone formation in vivo. From a therapeutic perspective, a carrier matrix is required for the local delivery of these proteins to evoke a desired osteogenic effect. In view of the affinity of these proteins for hydroxyapatite, which may reflect the in vivo supramolecular assembly of bone proteins bound to both the extracellular matrix and the mineral component of bone, we investigated the efficacy of single applications of different doses of human osteogenic protein-1 (hOP-1) adsorbed onto sintered porous hydroxyapatites for bone induction in orthotopic calvarial defects in 12 adult male baboons (Papio ursinus) and heterotopically in the rectus abdominis of four additional baboons. In orthotopic specimens, pretreatment of sintered porous hydroxyapatites with 100 microgram of hOP-1 in 500 microliter of 5 mM hydrochloric acid resulted in rapid and diffuse osteoinduction restricted within the porous spaces of the hydroxyapatite, as evaluated by histology and histomorphometry on day 30. Hydroxyapatites treated with 500 microgram of hOP-1 showed a different pattern of bone formation and distribution on day 30 as compared with the lower dose of the recombinant morphogen. Although bone formation was extensive with the higher dose, it was found on the endocranial and pericranial aspects of the specimens, enveloping the implanted hydroxyapatite carrier, and the internal porous spaces were occupied by a rich vascular network without any bone formation. By 90 and 365 days after the implantation of both doses of hOP-1, however, there was remodelling and complete penetration of the newly induced bone within the available porous spaces. The combination of hOP-1 and hydroxyapatite also showed extensive bone formation in heterotopic specimens harvested from the rectus abdominis muscle of the baboon using doses of 5, 25, and 45 microgram of hOP-1 per implant. These findings in the adult primate demonstrate extensive bone formation by hOP-1 adsorbed onto sintered porous hydroxyapatites and suggest that predictable osteogenesis in clinical contexts for treatment of craniofacial bone defects may be engineered using inorganic, nonimmunogenic, and carvable delivery systems that initiate osteogenesis with relatively low doses of recombinant osteogenic proteins, thus mimicking the macrostructure and microstructure of living bone.

Animals↗
PubMed2001

Periodontal tissue regeneration by combined applications of recombinant human osteogenic protein-1 and bone morphogenetic protein-2. A pilot study in Chacma baboons (Papio ursinus).

Native and recombinant human bone morphogenetic/osteogenic proteins (BMPs/ OPs) singly initiate bone induction in vivo. The finding of synchronous but spatially different BMPs/OPs expression during periodontal tissue morphogenesis suggests novel therapeutic approaches using morphogen combinations based on recapitulation of embryonic development. Twelve furcation defects prepared in the first and second mandibular molars of three adult baboons (Papio ursinus) were used to assess whether qualitative histological aspects of periodontal tissue regeneration could be enhanced and tissue morphogenesis modified by combined or single applications of recombinant hOP-1 and hBMP-2. Doses of BMPs/OPs were 100 microg of each protein per 1 g of insoluble collagenous bone matrix as carrier. Approximately 200 mg of carrier matrix was used per furcation defect. Undecalcified sections cut for histological analysis 60 d after healing of hOP-1-treated specimens showed substantial cementogenesis with scattered remnants of the collagenous carrier. hBMP-2 applied alone induced greater amounts of mineralized bone and osteoid when compared to hOP-1 alone or to combined morphogen applications. Combined applications of hOP-1 and hBMP-2 did not enhance alveolar bone regeneration or new attachment formation over and above the single applications of the morphogens. The results of this study, which is the first to attempt to address the structure-activity relationship amongst BMP/OP family members, indicate that tissue morphogenesis induced by hOP-1 and hBMP-2 is qualitatively different when the morphogens are applied singly, with hOP-1 inducing substantial cementogenesis. hBMP-2 treated defects, on the other hand, showed limited cementum formation but a temporal enhancement of alveolar bone regeneration and remodelling. The demonstration of therapeutic mosaicism in periodontal regeneration will require extensive testing of ratios and doses of recombinant morphogen combinations for optimal tissue engineering in clinical contexts.

Alveolar Process↗
PubMed2001

Transforming growth factor-beta1 supports the rapid morphogenesis of heterotopic endochondral bone initiated by human osteogenic protein-1 via the synergistic upregulation of molecular markers.

Members of the transforming growth factor-beta (TGF-beta) superfamily of proteins, the bone morphogenetic proteins (BMPs) and the TGF-beta isoforms, are involved in the coordination of cartilage and bone differentiation both in embryonic development and in postnatal life. Both osteogenic protein-1 (OP-1) and TGF-beta1 have been shown to be potent regulators and inducers of heterotopic endochondral bone induction in non-human primates. In marked contrast, TGF-beta1 does not induce heterotopic endochondral bone in rodents. In the primate, the osteogenic properties of OP-1 are synergistically enhanced by the combined administration of TGF-beta1. The binary application of OP-1 (0.1, 0.3, 1.0 and 3.0 microg) and TGF-beta1 (0.01, 0.03 and 0.1 microg) to 25 mg of guanidinium-inactivated insoluble collagenous bone matrix as carrier in the rodent heterotopic bioassay for 7, 12 and 21 days resulted in a classical synergistic, dose-dependent and temporal up-regulation of OP-1-induced endochondral bone formation. There were significant increases in alkaline phosphatase activity (day 12) and calcium content (days 12 and 21). mRNA expression of OP-1, TGF-beta1, BMP-3 and collagens type II and IV, markers of bone formation, showed an up-regulation of the genes (days 12 and 21) by the binary applications of the morphogens. Histologically, single applications of OP-1 elicited a dose dependent induction of endochondral bone formation while the binary applications resulted in a temporal acceleration of the morphogenetic cascade. The optimal ratio of OP-1/TGF-beta1 was 30:1 by weight for endochondral bone formation and expression of molecular markers. The present data provides insights to the mechanisms of synergistic molecular therapeutics for endochondral bone formation in clinical contexts.

Alkaline Phosphatase↗
PubMed2001

Bone induction by BMPs/OPs and related family members in primates.

BACKGROUND: In a series of studies in the primate Papio ursinus, we have examined the capacity of bone morphogenetic proteins (BMPs/OPs) delivered in a variety of biomaterial carrier systems to elicit bone formation in heterotopic and orthotopic sites. In this review, we compare the osteoinductive effects of different biomaterial delivery systems that have or have not been pretreated with BMPs/OPs. In particular, we focus on the geometric induction of bone formation by sintered porous hydroxyapatite (SPHA) discs with concavities on their planar surfaces, which elicit bone formation without exogenously applied BMPs/OPs. METHODS: Heterotopic bone formation was examined by bilaterally implanting 100-mg pellets of a collagenous carrier containing BMPs/OPs in the rectus abdominis muscle of the adult baboon. Orthotopic bone formation was examined by implanting 1 g of a collagenous carrier containing BMPs/OPs into two full-thickness critical-sized 25-mm-diameter defects on each side of the calvaria of adult baboons. The BMPs/OPs whose effects were examined included recombinant human osteogenic protein-1 (rhOP-1), recombinant human transforming growth factor-beta1 (rhTGF-beta1), rhTGF-beta2, and porcine platelet derived transforming growth factor-beta1 (pTGF-beta1). Tissue from the rectus abdominis muscle was harvested 30 or 90 days after implantation. Tissue from the orthotopic calvarial model was examined at 1, 3, 6, 9, and 12 months after implantation. To demonstrate the effect of surface geometry on bone induction, hydroxyapatite powders were sintered to form solid discs with a series of concavities on the planar surfaces of the SPHA discs. The discs were either pretreated with exogenous rhOP-1 or not treated with exogenous OP-1. They were then implanted heterotopically or orthotopically into calvarial defects. Bone formation was evaluated histologically in undecalcified sections stained with Goldner's trichrome stain or 0.1% toluidine blue. RESULTS: Naturally derived BMPs/OPs or rhOP-1 in a collagenous carrier elicit heterotopic bone formation and the complete healing of 25-mm-diameter critical-sized defects by day 90 following implantation. Binary applications of TGF-beta1 together with rhOP-1 in the collagen carrier induced massive endochondral ossicles in heterotopic sites and bone formation in calvarial defects. pTGF-beta1, rhTGF-beta1, and rhTGF-beta2 are powerful inducers of heterotopic endochondral bone formation but elicit limited bone formation in calvarial defects. SPHA discs pretreated with rhOP-1 elicited extensive bone formation in both heterotopic and orthotopic sites. However, SPHA without rhOP-1 also elicited bone formation in heterotopic and orthotopic sites and complete healing of the calvarial defects. CONCLUSION: We have prepared SPHA discs with concavities on their planar surfaces that induce bone formation in heterotopic or orthotopic critical-sized calvarial defects without exogenously applied BMPs/OPs. This biomaterial induces bone formation by intrinsic osteoinductivity regulated by the geometry of the substratum. The incorporation of specific biological activities into biomaterials by manipulating the geometry of the substratum, defined as geometric induction of bone formation, may make it possible to engineer morphogenetic responses for therapeutic osteogenesis in clinical contexts. CLINICAL RELEVANCE: We have implemented a clinical trial using naturally derived BMPs/OPs extracted and purified from bovine bone matrices and implanted in craniofacial defects in humans. In addition, the discovery that specific geometric and surface characteristics of sintered hydroxyapatites can induce intrinsic osteoinductivity in primates paves the way for formulation and therapeutic application of porous substrata designed to obtain predictable intrinsic osteoinductivity in clinical contexts.

Abdominal Muscles↗
PubMed2000

Osteogenic protein-1, a bone morphogenetic protein, induces angiogenesis in the chick chorioallantoic membrane and synergizes with basic fibroblast growth factor and transforming growth factor-beta1.

Capillary invasion is a vital regulatory signal during bone morphogenesis that is influenced by angiogenic molecules such as fibroblast growth factor (FGF) and some members of the transforming growth factor-beta (TGF-beta) superfamily, including TGF-betas themselves. Bone morphogenetic proteins (BMPs), which are members of the TGF-beta superfamily, have previously not been shown to possess direct angiogenic properties. Osteogenic protein-1 (OP-1; BMP-7) is a potent regulator of cartilage and bone differentiation in vivo. The osteogenic and angiogenic properties of OP-1 at both ortho- and heterotopic sites in adult chacma baboons (Papio ursinus) are enhanced synergistically by the simultaneous application of relatively low doses of TGF-beta1. The single application of relatively high doses of TGF-beta1 (20 ng), and bFGF (500 ng) or relatively low (100 ng) and high (1,000 ng) doses of OP-1 in the chick chorioallantoic membrane (CAM) assay elicited a prominent and (for OP-1) dose-dependent angiogenic response. The binary application of a relatively low dose of OP-1 (100 ng) with a relatively low dose of bFGF (100 ng) or with a relatively low (5 ng) or high (20 ng) dose of TGF-beta1 resulted in a synergistic enhancement of the angiogenic response. The angiogenic effect of the relatively low doses of the combined morphogens was distinctly more pronounced than that of the single application of the relatively high doses of the respective factors. The present findings suggest that these morphogens may be deployed in binary combination in order to accentuate experimental angiogenesis. The cooperative interaction of the different morphogens in the CAM assay may provide important biological clues towards the control of clinical angiogenesis.

Allantois↗
PubMed2000

Long-term evaluation of bone formation by osteogenic protein 1 in the baboon and relative efficacy of bone-derived bone morphogenetic proteins delivered by irradiated xenogeneic collagenous matrices.

To investigate the long-term efficacy of irradiated recombinant human osteogenic protein 1 (hOP-1) in bone regeneration and morphogenesis, hOP-1 was combined with a bovine collagenous matrix carrier (0, 0.1, 0.5, and 2.5 mg hOP-1/g of matrix), sterilized with 2.5 Mrads of y-irradiation, and implanted in 80 calvarial defects in 20 adult baboons (Papio ursinus). The relative efficacy of partially purified bone-derived baboon bone morphogenetic proteins (BMPs), known to contain several osteogenic proteins, was compared with the recombinant hOP-1 device in an additional four baboons. Histology and histomorphometry on serial undecalcified sections prepared from the specimens harvested on day 90 and day 365 showed that gamma-irradiated hOP-1 devices induced regeneration of the calvarial defects by day 90, although with reduced bone area compared with a previous published series of calvarial defects treated with nonirradiated hOP-1 devices. One year after application of the irradiated hOP-1 devices, bone and osteoid volumes and generated bone tissue areas were comparable with nonirradiated hOP-1 specimens. Moreover, 365 days after healing regenerates induced by 0.5 mg and 2.5 mg of irradiated hOP-1 devices showed greater amounts of bone and osteoid volumes when compared with those induced by nonirradiated hOP-1 devices. On day 90, defects treated with 0.1 mg and 0.5 mg of bone-derived baboon BMPs, combined with irradiated matrix, showed significantly less bone compared with defects receiving irradiated devices containing 0.1 mg and 0.5 mg hOP-1; 2.5 mg of partially purified BMPs induced bone and osteoid volumes comparable with the 0.1-mg and 0.5-mg hOP-1 devices. Control specimens of y-irradiated collagenous matrix without hOP-1 displayed a nearly 2-fold reduction in osteoconductive bone repair when compared with nonirradiated controls. These findings suggest that the reduction in bone volume and bone tissue area on day 90 may be caused by a reduced performance of the irradiated collagenous matrix substratum rather than to a reduction in the biological activity of the irradiated recombinant osteogenic protein. This is supported by the results of in vitro and in vivo studies performed to determine the structural integrity of the recovered gamma-irradiated hOP-1 before application in the baboon. Recoveries by high-performance liquid chromatography (HPLC) and sodium dodecyl sulfate/ polyacrylamide gel electrophoresis (SDS/PAGE)/immunoblot analyses indicated that doses of 2.5-3 Mrads of gamma-irradiation did not significantly affect the structural integrity of the recovered hOP-1. Biological activity of the recovered hOP-1 was confirmed in vitro by showing induction of alkaline phosphatase activity in rat osteosarcoma cells (ROS) and in vivo by de novo endochondral bone formation in the subcutaneous space of the rat. These findings in the adult primate indicate that a single application of gamma-irradiated hOP-1 combined with the irradiated xenogeneic bovine collagenous matrix carrier is effective in regenerating and maintaining the architecture of the induced bone at doses of 0.5 mg/g and 2.5 mg/g of carrier matrix.

Alkaline Phosphatase↗
PubMed2000

Advances in biotechnology for tissue engineering of bone.

Tissue engineering is a rapidly developing field applying the disciplines of cell biology, developmental biology, molecular biology and biomimetic engineering to regenerate new tissues for replacement therapies in clinical contexts. To aid in the elicitation and reiteration of the processes of morphogenesis of tissues, the cascade of chemotaxis of progenitor cells, their differentiation and pattern formation is redeployed in postnatal tissues, effected by a variety of ever-increasing morphogens and biomaterials. The extensive recent progress in elucidating the molecular biology of BMPs and their receptors shall aid in promoting and extending the great operational future of this field. Although the BMP family of proteins and osteogenesis have been the subject of several recent reviews, we focus here on their activity in primates and on the novel localization of BMPs in the cerebellum and other areas of the nervous system, and the "mosaicism" of their localisation in the periodontal tissues followed by a discussion on the use of BMPs in periodontal regeneration. Lastly, we report on the unique osteoinductive activity of TGF-beta proteins in heterotopic sites of primates and their synergistic interaction with a recombinant human BMP, and finally we present unique data on novel biomaterials endowed with intrinsic osteoinductive activity, capable of initiating de novo bone formation in heterotopic sites even in the absence of exogenously applied BMPs, and the results of a clinical trial in humans using naturally-derived BMPs.

Animals↗
PubMed2000

Induction of endochondral bone formation by recombinant human transforming growth factor-beta2 in the baboon (Papio ursinus).

Members of the transforming growth factor-beta (TGF-beta) superfamily, the bone morphogenetic and osteogenic proteins (BMPs/OPs) but not the TGF-beta proteins themselves, induce endochondral bone formation in vivo, when implanted in extraskeletal heterotopic sites of rodents. Here we show that recombinant human TGF-beta2 (hTGF-beta2) induces endochondral bone formation 30 days after implantation in heterotopic intramuscular sites of the baboon (Papio ursinus) at doses of 1, 5 and 25 microg per 100 mg of guanidinium-inactivated collagenous bone matrix as carrier. On day 90 there was generation of large radiopaque and corticalized intramuscular ossicles. Five and 25 microg hTGF-beta2 induced large ossicles in the rectus abdominis of the primate as evaluated by key parameters of bone formation, including generated tissue area, mineralized bone and osteoid volumes, and tissue alkaline phosphatase activity. On day 30 and 90 after healing, hTGF-beta2 also induced bone formation when implanted in the rectus abdominis in conjunction with a sintered porous hydroxyapatite as carrier. mRNA expression in tissues from heterotopic specimens showed OP-1 (BMP-7) and BMP-3 transcripts in low abundance and with a linear dose-dependent increase both in collagenous matrix and hydroxyapatite samples. Type IV collagen mRNA expression, a marker of angiogenesis, was stronger in collagenous than hydroxyapatite samples. Growth and differentiation factor-10 (GDF-10) mRNA transcripts were expressed in ossicles with a distinctly chondrogenic phase, but its expression was greater in ossicles generated in porous hydroxyapatites, in which bone formation is not via a chondrogenic phase, but is rather intramembranous, without expression of type II collagen mRNA. In the same animals, however, 10 and 100 microg of the recombinant morphogen delivered by identical carriers (collagenous matrix and sintered hydroxyapatite) failed to heal calvarial defects. Thus in the primate, TGF-betas themselves are inducers of endochondral bone formation, although the present data strongly indicate that the bone inductive activity of hTGF-beta2 is site and tissue specific, since a single application of hTGF-beta2, or hTGF-beta1 in previously published experiments, did not induce bone in calvarial defects, but did induce endochondral bone differentiation in heterotopic sites.

Animals↗
PubMed1999

A supernumerary tooth in a 1.7 million-year-old Australopithecus robustus from Swartkrans, South Africa.

The maxillary dental arch of a partial cranium of an adult specimen of Australopithecus robustus shows the presence of a supernumerary tooth between the right first and second incisors. The fossil specimen, SK 83, is from Swartkrans Member 1 sediments, considered, on the basis of associated fauna, to be approximately 1.7 million yr old. The specimen was analyzed macroscopically, stereomacroscopically and by X-ray computed tomography. The anatomic position and the morphology of the tooth are consistent with a diagnosis of supernumerary lateral incisor rather than a mesiodens or a retained deciduous tooth. This is the first description of a supernumerary tooth found in Plio-Pleistocene hominid fossils from South African cave deposits.

Adult↗
PubMed1999

Immunolocalization of Bone Morphogenetic Protein-2 and -3 and Osteogenic Protein-1 during murine tooth root morphogenesis and in other craniofacial structures.

The distribution of Bone Morphogenetic Protein-2, and -3 (BMP-2 and BMP-3) and Osteogenic Protein-1 (OP-1, also known as BMP-7) during root morphogenesis and in other craniofacial structures was examined in sections of 12- to 18-d-old mouse heads using polyclonal and monoclonal antibodies. BMP-3 and OP-1 were localized in alveolar bone, cementum, and periodontal ligament, whereas BMP-2 was only localized in the alveolar bone of periodontium. All three BMPs were localized in predentine, dentine, odontoblasts, osteoblasts, osteocytes, osteoid, cartilage, chondrocytes and spiral limbus. BMP-2 and OP-1 were also localized in spiral ligament and interdentate cells of the cochlea, whilst BMP-3 was restricted to the spiral ganglion. BMP-3 was also localized in ducts of submandibular and sublingual salivary glands, acini of the lacrimal gland, Purkinje cells in the cerebellum, nerve fibres of the cerebellum and brain, afferent cells of the dorsal root ganglia, inferior alveolar nerve, and peripheral processes of the vestibulocochlear nerve. OP-1 was also localized in hair and whisker follicles, sclera of the eye and in ameloblasts. The demonstration of BMP-3 in the nervous system suggests that this protein may be neurotrophic during development and maintenance of the nervous system. The composite expression of BMPs/OPs during periodontal tissue morphogenesis suggests that optimal therapeutic regeneration may entail the combined use of different BMPs/OPs.

Afferent Pathways↗
PubMed1998

Transforming growth factor-beta 1: induction of bone morphogenetic protein genes expression during endochondral bone formation in the baboon, and synergistic interaction with osteogenic protein-1 (BMP-7).

Certain members of the bone morphogenetic protein (BMP) and transforming growth factor-beta (TGF-beta) families are inducers of endochondral bone formation in vivo. TGF-betas, however, do not initiate bone formation when implanted in heterotopic (extraskeletal) sites of rodents. Here we show that platelet-derived porcine TGF-beta 1 (pTGF-beta 1) induces endochondral bone in heterotopic sites of the baboon (Papio ursinus) at doses of 5 microgram per 100 mg of guanidinium-inactivated collagenous bone matrix as carrier, with an inductive efficiency comparable to 5 and 25 micrograms of recombinant osteogenic protein-1 (hOP-1, BMP-7), a well characterized inducer of bone formation. We further demonstrate that pTGF-beta 1 and hOP-1 interact synergistically to induce large ossicles in the rectus abdominis of the primate as evaluated by key parameters of bone formation on day 14 and 30. Tissue generated on day 30 by 5 microgram pTGF-beta 1 or 25 micrograms hOP-1 induced comparable expression levels of OP-1, BMP-3 and type IV collagen mRNA transcripts, whereas TGF-beta 1 and type II collagen expression was 2 to 3 fold higher in pTGF-beta 1-treated implants, as determined by Northern analysis. In ossicles generated by 25 micrograms hOP-1 in combination with relatively low doses of pTGF-beta 1 (0.5, 1.5 and 5 micrograms), type II collagen expression increased in a pTGF-beta 1 dose-dependent manner, whilst type IV collagen was synergistically upregulated with a 3 to 4 fold increase compared to ossicles generated by a single application of 5 micrograms pTGF-beta 1 or 25 micrograms hOP-1. Morphogen combinations (5 micrograms pTGF-beta 1 with 20 micrograms hOP-1, and 5 and 15 micrograms pTGF-beta 1 with 100 micrograms hOP-1 per g of collagenous matrix as carrier) induced exuberant tissue formation and greater amounts of osteoid than hOP-1 alone when implanted in calvarial defects of the baboon as evaluated. on day 30 and 90, with displacement of the temporalis muscle above the defects. Since a single application of TGF-beta 1 in the primate did not induce bone formation in calvarial defects, whilst it induces endochondral bone differentiation in heterotopic sites, our data indicate that the bone inductive activity of TGF-beta 1 is site and tissue specific. mRNA expression of multiple members of the TGF-beta superfamily suggests complex autocrine and paracrine activities of the ligands and different signalling pathways on responding cells during the cascade of endochondral bone formation in the primate. The present findings may provide the basis for synergistic molecular therapeutics for cartilage and bone regeneration in clinical contexts.

Animals↗
PubMed1997

Tissue engineering, morphogenesis, and regeneration of the periodontal tissues by bone morphogenetic proteins.

Tissue engineering is the emerging field of science developing techniques for fabrication of new tissues for replacement based on principles of cell and developmental biology and biomaterials. Morphogenesis is the cascade of pattern formation and the attainment of form of the various organs and the organism as a whole. The periodontium consist of the periodontal ligament, cementum, and alveolar bone. Bone has considerable potential for regeneration and therefore is a prototypic model for tissue engineering. The three main ingredients for tissue engineering are regulatory signals, responding stem cells, and extracellular matrix. Recent advances in molecular biology of the bone morphogenetic proteins (BMPs) have set the stage for tissue engineering of bone and related tissues, including the periodontium. Bone-derived BMPs, with a collagenous matrix as carrier, induced cementum and alveolar bone regeneration in surgically created furcation defects in the primate. It is noteworthy that there was morphogenesis of periodontal ligament and a faithful insertion of Sharpey's fibers into cementum. In the same furcation model, recombinant human osteogenic protein-1 (rhOP-1, also known as BMP-7), in conjunction with the collagenous carrier, induced extensive cementogenesis with insertion of Sharpey's fibers into the newly formed cementum. The observation that BMPs induce cementogenesis and periodontal ligament formation indicates that these proteins may have multiple functions in vivo not limited to cartilage and bone induction. The rapid advances in the molecular biology of BMPs and their receptors bode well for novel strategies to engineer the regeneration of the periodontal tissues.

Alveolar Process↗
PubMed1997

Recombinant transforming growth factor-beta1 induces endochondral bone in the baboon and synergizes with recombinant osteogenic protein-1 (bone morphogenetic protein-7) to initiate rapid bone formation.

Several members of the bone morphogenetic protein (BMP) and transforming growth factor-beta (TGF-beta) families are molecular regulators of cartilage and bone regeneration, although their actual roles and combined interactions in skeletal repair are poorly understood. The presence of several molecular forms suggests multiple functions in vivo as well as synergistic interactions during both embryonic bone development and regeneration of cartilage and bone in postfetal life. Here we show for the first time that recombinant human transforming growth factor-beta1 (TGF-beta1) induces endochondral bone formation in extraskeletal sites of adult baboons. We also show that TGF-beta1 and recombinant human osteogenic protein-1 (OP-1, bone morphogenetic protein-7) synergize in inducing large ossicles in extraskeletal sites of the primate as early as 15 days after implantation. A single application of OP-1, in conjunction with an insoluble collagenous matrix as carrier (5, 25, and 125 microg/100 mg of carrier matrix) induced bone differentiation in the rectus abdominis of the baboon. This level of tissue induction was raised several-fold by the simultaneous addition of comparatively low doses of TGF-beta1 (0.5, 1.5, and 5 microg), which by itself induces bone formation in the rectus abdominis at doses of 5 microg/100 mg of carrier matrix. Combinations of OP-1 and TGF-beta1 yielded a 2- to 3-fold increase in cross-sectional area of the newly generated ossicles, with markedly elevated key parameters of bone formation, and corticalization of the newly formed bone by day 15, culminating in bone marrow generation by day 30. The tissue generated by the combined application of OP-1 and TGF-beta1 showed distinct morphological differences when compared with OP-1-treated specimens, with large zones of endochondral development and extensive bone marrow formation. At the doses tested, synergy was optimal at a ratio of 1:20 by weight of TGF-beta1 and OP-1, respectively. These results provide evidence for a novel function of TGF-beta1 in the primate and the scientific basis for synergistic molecular therapeutics for the rapid regeneration of cartilage and bone.

Animals↗
PubMed1996

Limited chondro-osteogenesis by recombinant human transforming growth factor-beta 1 in calvarial defects of adult baboons (Papio ursinus).

The therapeutic utility of a single application of recombinant human transforming growth factor-beta (hTGF-beta) has not been previously tested in large osseous wounds in primates. Sixteen calvarial defects, 25 mm in diameter, were prepared in four adult male baboons (Papio ursinus). In each animal, three defects were treated with increasing doses of hTGF-beta 1 in conjunction with baboon insoluble collagenous bone matrix as carrier (5, 30, and 100 micrograms of hTGF-beta 1/g of matrix). The fourth defect was implanted with collagenous matrix without hTGF-beta 1 as control. Serial undecalcified sections were prepared from the specimens harvested on day 30. Islands of cartilage and endochondral osteogenesis were found in hTGF-beta 1-treated defects, irrespective of the doses used. Histomorphometry of the defect site showed no significant differences between control and hTGF-beta 1-treated specimens with regard to bone and osteoid volumes. However, analysis of the regenerated tissue in proximity to the defect margins only showed that, on average, greater amounts of bone formed in specimens that were treated with 5 and 30 micrograms of hTGF-beta 1 when compared with controls. This suggests a possible effect on osteoblastic cells originating from the periosteal and endosteal spaces of the severed calvaria. Overall, however, this difference has no therapeutic implications for the healing of large cranial wounds in primates. The present findings indicate that a single application of hTGF-beta 1, in conjunction with collagenous matrix, results in limited chondro-osteogenesis in defects of membranous bone of adult baboons.

Analysis of Variance↗
PubMed1996

Induction of cementogenesis by recombinant human osteogenic protein-1 (hop-1/bmp-7) in the baboon (Papio ursinus).

Recombinant human osteogenic protein-1 (hOP-1), a member of the bone morphogenetic protein family, was examined for its efficacy in periodontal regeneration. Twelve furcation defects, surgically prepared in the first and second mandibular molars, were treated with bovine insoluble collagenous matrix in conjunction with 0.0 (control), 100 and 500 mu g of recombinant hOP-1 per g of matrix. After 60 days of healing, histological and histometric analyses on serial, undemineralized sections cut at 7 mu m showed substantial cementogenesis on the exposed dentine of furcations treated with both doses of hOP-1 (p < 0.01 vs control). Foci of nascent mineralization were seen within the newly deposited cementoid along the coronal areas of hOP-1-treated defects. Within the furcations, there were substantial amounts of residual collagenous carrier, interspersed with a mineralized matrix having histological features of cementum. This mineralized cementum-like material was predominantly deposited around the carrier, and blended into newly formed cementum along the root surfaces. In the apical area, the cementum-like material and the remaining alveolar bony housing were not connected; indeed the two components were separated by a fibrovascular tissue that had numerous features of the periodontal ligament space. Formation and insertion of Sharpey's fibres into newly formed root cementum were also observed. It is likely that the expression of specific cell phenotypes by hOP-1 is regulated, in part, by the extracellular matrix microenvironment, including dentine. Thus, exposed dentine, in the presence of exogenous hOP-1 at the doses tested, may preferentially modulate the expression of the cementogenic phenotype. These findings in a non-human primate show that hOP-1, at the doses tested, induced cementogenesis on surgically denuded root surfaces, indicating a specific function during repair and regeneration of periodontal tissues.

Alveolar Process↗
PubMed1996

Osteoinduction in porous hydroxyapatite implanted in heterotopic sites of different animal models.

Previous studies have demonstrated the induction of bone in coral-derived porous hydroxyapatite when implanted intramuscularly in baboons. This hydroxyapatite-induced bone differentiation model was used to study the effect of different animal species on heterotopic bone formation. Porous hydroxyapatite, obtained after hydrothermal conversion of the calcium carbonate exoskeleton of coral (genus Goniopora), was implanted in the rectus abdominis of adult rabbits, dogs and baboons (Papio ursinus). Specimens were harvested on day 90 after implantation and subjected to histological and histomorphometrical analysis. Minimal amounts of bone formed in hydroxyapatite specimens harvested from rabbits and dogs. Substantial bone differentiation did occur, however, in hydroxyapatite specimens harvested from the rectus abdominis of the baboons. In primates, the porous hydroxyapatite, as used in this study, may act as a solid matrix for adsorption, storage and controlled release of circulating or locally produced bone morphogenetic proteins, which locally initiate bone formation. The results of this study on heterotopic bone formation in porous hydroxyapatite underscore the importance of primate models in biomaterial research, which should be exploited for the formulation of porous substrata with intrinsic osteoinductive activity.

Animals↗