The induction of endochondral bone formation by transforming growth factor-beta(3): experimental studies in the non-human primate Papio ursinus

Transforming growth factor-β₃ (TGF-β₃), a multi-functional growth modulator of embryonic development, tissue repair and morphogenesis, immunoregulation, fibrosis, angiogenesis and carcinogenesis, is the third mammalian isoform of the TGF-β subfamily of proteins. The pleiotropism of the signalling proteins of the TGF-β superfamily, including the TGF-β proteins per se, are highlighted by the apparent redundancy of soluble molecular signals initiating de novo endochondral bone induction in the primate only. In the heterotopic bioassay for bone induction in the subcutaneous site of rodents, the TGF-β₃ isoform does not initiate endochondral bone formation. Strikingly and in marked contrast to the rodent bioassay, recombinant human (h)TGF-β₃, when implanted in the rectus abdominis muscle of adult non-human primates Papio ursinus at doses of 5, 25 and 125 μg per 100 mg of insoluble collagenous matrix as carrier, induces rapid endochondral bone formation resulting in large corticalized ossicles by day 30 and 90. In the same animals, the delivery of identical or higher doses of theTGF-β₃ protein results in minimal repair of calvarial defects on day 30 with limited bone regeneration across the pericranial aspect of the defects on day 90. Partial restoration of the bone induction cascade by the hTGF-β₃ protein is obtained by mixing the hTGF-β₃ device with minced fragments of autogenous rectus abdominis muscle thus adding responding stem cells for further bone induction by the hTGF-β₃ protein. The observed limited bone induction in hTGF-β₃/treated and untreated calvarial defects in Papio ursinus and therefore by extension to Homo sapiens, is due to the influence of Smad-6 and Smad-7 down-stream antagonists of the TGF-β signalling pathway. RT-PCR, Western and Northern blot analyses of tissue specimens generated by the TGF-β₃ isoform demonstrate robust expression of Smad-6 and Smad-7 in orthotopic calvarial sites with limited expression in heterotopic rectus abdominis sites. Smad-6 and -7 overexpression in hTGF-β₃/treated and untreated calvarial defects may be due to the vascular endothelial tissue of the arachnoids expressing signalling proteins modulating the expression of the inhibitory Smads in pre-osteoblastic and osteoblastic calvarial cell lines controlling the induction of bone in the primate calvarium.

Periodontal tissue regeneration by recombinant human transforming growth factor-beta 3 in Papio ursinus

BACKGROUND AND OBJECTIVE

Osteogenic proteins of the transforming growth factor-beta superfamily induce periodontal tissue regeneration in animal models, including primates. To our knowledge, no studies have been performed in periodontal regeneration using the transforming growth factor-beta 3 isoform. In the present study, recombinant human transforming growth factor-beta 3 was examined for its ability to induce periodontal tissue regeneration in the nonhuman primate, Papio ursinus.

MATERIAL AND METHODS

Class II furcation defects were surgically created bilaterally in the maxillary and mandibular molars of four adult baboons. Heterotopic ossicles, for transplantation to selected furcation defects, were induced within the rectus abdominis muscle by recombinant human transforming growth factor-beta 3. Forty days later, the periodontal defects were implanted with recombinant human transforming growth factor-beta 3 in Matrigel as the delivery system, with recombinant human transforming growth factor-beta 3 plus minced muscle tissue in Matrigel, or with the harvested recombinant human transforming growth factor-beta 3-induced ossicles. Sixty days after periodontal implantation, the animals were killed and the specimens harvested. Histological analysis on undecalcified sections measured the area and volume of new alveolar bone and the coronal extension of newly formed alveolar bone and cementum.

RESULTS

Morphometric analyses showed pronounced periodontal regeneration in experimental defects compared with controls. Substantial regeneration was observed in defects implanted with fragments of heterotopically induced ossicles and with recombinant human transforming growth factor-beta 3 plus minced muscle tissue.

CONCLUSION

Recombinant human transforming growth factor-beta 3 in Matrigel significantly enhanced periodontal tissue regeneration in the nonhuman primate, P. ursinus.

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.

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.

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.

Glucocorticoids, antioxidants and staurosporine modulate the adherence between monocytes and malaria infected erythrocytes

OBJECTIVE AND DESIGN

Adherence interactions involving monocytes are important for cell-cell interaction as an integral component of immune function. The adherence of malaria parasitised red cells to monocytes was determined after monocytes were treated with dexamethasone, cortisol, ambroxol, danazol, probucol and staurosporine.

MATERIALS

Human peripheral blood monocytes isolated by density gradient centrifugation and adherence to glass cover slips.

METHODS

The adherence of malaria parasitised red cells to monocytes was determined after the monocytes were incubated for 24 h in the presence of each of the 6 drugs.

RESULTS

The two glucocorticoids and staurosporine reduced the adherence of malaria infected erythrocytes to monocytes in a dose dependent manner at concentrations from 10(-10) M and above and ambroxol, danazol, and probucol at 10(-5) M. Staurosporine was the most effective of the drugs studied, completely abolishing adherence at 10(-6) M.

CONCLUSION

The adherence of malaria infected erythrocytes to monocytes is reduced in response to glucocorticoids (dexamethasone and cortisol), anti-oxidants (probucol and ambroxol), danazol and staurosporine.

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.