Enhanced activity of demineralised bone matrix augmented with xenogeneic bone morphogenetic protein complex in rats

INTRODUCTION: Demineralised bone matrix (DBM) is an allograft material widely used as a bone filler and bone graft substitute. DBM contains bone morphogenetic proteins (BMPs), which induce and regulate bone formation during embryogenesis and in postnatal life. AIMS AND OBJECTIVES: To investigate the osteoinductivity of DBM augmented with xenogeneic BMP-complex at different doses. MATERIALS AND METHODS: Rat DBM was augmented with BMP-complex purified from porcine diaphyseal bone. RESULTS: Dorsal subcutaneous implantation of 25 mg rat allogeneic DBM augmented with 0, 3, 6 and 12 mg BMPcomplex per gram of DBM resulted in dose dependant upregulation of bone formation on day 21, as scored histologically and biochemically. CONCLUSIONS: Allogeneic DBM can be augmented with xenogeneically sourced BMP-complex to improve DBM performance in vivo. This work demonstrates the potential of BMP-complex augmented DBM to induce new bone formation with improved parameters of bone formation.http://www.sadanet.co.zaam2013ay201

Physicochemical modification of kafirin microparticles and their ability to bind bone morphogenetic protein-2 (BMP-2), for application as a biomaterial

Vacuolated spherical kafirin microparticles with a mean diameter of 5 μm can be formed from an acidic solution with water addition. Three-dimensional scaffolds for hard tissue repair require large structures with a high degree of interconnected porosity. Cross-linking the formed kafirin microparticles using wet heat or glutaraldehyde treatment resulted in larger structures (approximately 20 μm), which, while similar in size and external morphology, were apparently formed by further assisted assembly by two significantly different mechanisms. Heat treatment, which increased the vacuole size, involved kafirin polymerization by disulfide bonding with the microparticles being formed from round, coalesced nanostructures, as shown by atomic force microscopy (AFM). Kafirin polymerization of glutaraldehyde-treated microparticles was not by disulfide bonding, and the nanostructures, as revealed by AFM, were spindle shaped. Both treatments enhanced BMP-2 binding to the microparticles, probably due to their increased size. Thus, these modified kafirin microparticles have potential as natural, nonanimal protein bioactive scaffolds.University of Pretoria Postgraduate Research Support Bursaryhttp://pubs.acs.org/JAF

Materials in particulate form for tissue engineering. 2 Applications in bone

Materials in particulate form have been the subjects of intensive research in view of their use as drug delivery systems. While within this application there are still issues to be addressed, these systems are now being regarded as having a great potential for tissue engineering applications. Bone repair is a very demanding task, due to the specific characteristics of skeletal tissues, and the design of scaffolds for bone tissue engineering presents several difficulties. Materials in particulate form are now seen as a means of achieving higher control over parameters such as porosity, pore size, surface area and the mechanical properties of the scaffold. These materials also have the potential to incorporate biologically active molecules for release and to serve as carriers for cells. It is believed that the combination of these features would create a more efficient approach towards regeneration. This review focuses on the application ofmaterials in particulate formfor bone tissue engineering. A brief overview of bone biology and the healing process is also provided in order to place the application in its broader context. An original compilation of molecules with a documented role in bone tissue biology is listed, as they have the potential to be used in bone tissue engineering strategies. To sum up this review, examples of works addressing the above aspects are presented

Synergistic interaction of bone morphogenetic protein and transforming growth factor-β in bone induction and regeneration

Several members of the bone moirphogenetic protein and osteogenic protein (BMP/OP) and transforming growth factor-13 (TGF-J3) families are molecular regulators of cartilage and bone regeneration, although their precise mode of signal transduction and combined interactions 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 postfoetal life. Heterotopic and orthotopic implantation o f BMPs/OPs elicit the local differentiation of new bone in a number of animal models studied, whereas reports to date show that implantation o f TGF-Bs in heterotopic sites of the rat results in fibrovascular tissue formation, without evidence of bone formation.Instead, TGF-Bs show limited osteo-chondrogenic activity only when applied orthotopically in some, and not all of the animal models studied. Here, data are presented that show for the first time that, in contrast to previously described animal models, implantation of TGF-13i with a collagenous matrix carrier in the rectus abdominis of the baboon (Papio ursinus) results in de novo bone formation, as evidenced radiographically, histologically and biochemically. TGF-Bj induced endochondral bone at heterotopic sites o f the baboon at doses of 5 jug/lOO mg collagenous matrix as carrier, with an inductive efficiency comparable to single applications of 5 and 25 fig recombinant human osteogenic protein-1 (rhOP-1), a morphogen whose osteoinductive activity has previously been demonstrated in a number of animal models. It was shown further, that rhOP-1 and TGF-Bi (of porcine or recombinant source), interact synergistically to induce massive ossicles in extraskeletal sites of the primate as early as 14 or 15 days after implantation. Binary combinations of the morphogens induced ossicles with indeces of bone formation which were greater than the sum of indeces of single application of each respective morphogen. By applying isobolographic analysis, a well established pharmacological mathematical model previously developed for the study of interactions between pharmacologic agents, it was shown that the interaction between rhOP-1 and TGF-Bi in bone induction was of the type defined as synergism. The level of tissue induced by single applications of rhOP-1 (5, 25 and 125 pg/100 mg collagenous matrix) was raised several-fold by the simultaneous addition of comparatively low doses of TGF- 13i (0.5,1.5 and 5 |ig), which by itself induced bone formation at doses of 5gg/100 mg collagenous matrix. Combinations of rhOP-1 and TGF-Bi yielded a 2- to 3-fold increase in cross-sectional area of the newly generated ossicles, with markedly elevated parameters of bone formation, and corticalisation of the newly formed bone by day 15, culminating in marrow generation by day 30. The tissue generated by the combined application of rhOP-1 and TGF-Bi showed distinct morphological differences when compared with rhOP-1-treated specimens, with large zones of endochondral development and extensive bone marrow formation. Heterotopic tissue generated on day 30 by single application o f rhOP-1 or TGF-Bi expressed comparable levels of OP-1, BMP-3 and type IV collagen mRNA transcripts, whereas TGF-Bi and type II collagen mRNA expression was 2- to 3-fold higher in TGF-Bi-treated impants, as determined by Northern analysis. In ossicles generated by rhOP-1 in combination with TGF-B], mRNA for type II collagen, a marker of chondrogenesis, was increased in a TGF-13 dose-dependent manner. Type IV collagen mRNA, a marker of angiogenesis, was synergistically upregulated with a 3- to 4-fold increase compared to ossicles generated by single application of rhOP-1 or TGF-13j. Since angiogenesis is a prerequisite for osteogenesis, increased angiogenesis may be at least part of the mechanism whereby moiphogen combinations interact synergistically in endochondral bone formation. Single application of pTGF-Bi induced ossicles expressing mRNA for OP-1, BMP-3 and TGF-Bi, showing that osteogenesis elicited by pTGF-Bi proceeds, at least in part, -via the expression of genes of the BMP/OP family. Single applications of rhOP-1 and pTGF-Bi induced ossicles expressing high levels of their own mRNA, suggesting an autoinductive effect of these morphogens in the initiation of the bone differentiation cascade. A t the doses tested, synergy was optimal at a ratio of 1:20 by weight of TGF-B, and rhOP-1 respectively.expressing mRNA for OP-1, BMP-3 and TGF-Bi, showing that osteogenesis elicited by pTGF-Bi proceeds, at least in part, -via the expression of genes of the BMP/OP family. Single applications of rhOP-1 and pTGF-Bi induced ossicles expressing high levels of their own mRNA, suggesting an autoinductive effect of these morphogens in the initiation of the bone differentiation cascade. A t the doses tested, synergy was optimal at a ratio of 1:20 by weight of TGF-B, and rhOP-1 respectively. Morphogen combinations (5 ug pTGF-Bi with 20 pg rhOP-1, and 5 and 15 jig pTGFBi with 100 with 100 pg rhOP-1 per gram o f collagenous matrix as carrier) induced exuberant tissue formation and greater amounts o f osteoid than rhOP-1 alone when implanted in calvarial defects o f the baboon as evaluated on day 30 and 90, with displacement of the temporalis muscle above the defects. Since single application o f TGF-Bi in the primate did not induce bone formation in calvarial defects, whilst it induces endochondral bone differentiation in heterotopic sites, the data indicate that that the bone inductive activity of TGF-Bj is site and tissue specific. The findings presented may provide the basis for synergistic molecular therapeutics for cartilage and bone regeneration in clinical contexts

Total cardiovascular risk approach to improve efficiency of cardiovascular prevention in resource constrain settings

Objectives: To determine the population distribution of cardiovascular risk in eight low- and middle-income countries and compare the cost of drug treatment based on cardiovascular risk (cardiovascular risk thresholds ≥30%/≥40%) with single risk fact