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

Mechanistic insights into the spontaneous induction of bone formation

The grand discovery of morphogens, or "form-generating substances", revealed that tissue morphogenesis is initiated by soluble molecular signals or morphogens primarily belonging to the transforming growth factor-β (TGF-β) supergene family. The regenerative potential of bone rests on its extracellular matrix, which is the repository of several morphogens that tightly control cellular differentiating pathways, cellular matrix deposition and remodeling. Alluringly, the matrix also contains specific factors transferred from the heterotopic implanted bone matrices initiating "Tissue Induction", as provocatively described in Nature in 1945. Later, it was found that selected genes and gene products of the TGF-β supergene family singly, synchronously, and synergistically mastermind the induction of bone formation. This review describes the phenomenon of the spontaneous and/or intrinsic osteoinductivity of calcium phosphate-based biomaterials and titanium' constructs without the applications of soluble osteogenetic molecular signals. The review shows the spontaneous induction of bone formation initiated by Ca++ activating stem cell differentiation and up-regulation of bone morphogenetic proteins genes. Expressed gene products are embedded into the concavities of the calcium phosphate-based substrata, initiating bone formation as a secondary response. Pure titanium's substrata do not initiate the spontaneous induction of bone formation. The induction of bone is solely dependent on acid, alkali and heat treatments to form apatite layers on the treated titanium surfaces. The induction of bone formation is achieved exclusively by apatite-based biomaterial surfaces. The hydroxyapatite, in its various forms and geometric configurations, finely tunes the induction of bone formation in heterotopic sites. Cellular differentiation by fine-tuning of the cellular molecular machinery is initiated by specific geometric modularity of the hydroxyapatite substrata that push cellular buttons that start the ripple-like cascade of "Tissue Induction", generating newly formed ossicles with bone marrow in heterotopic extraskeletal sites. The highlighted mechanistic insights into the spontaneous induction of bone formation are a research platform invocating selected molecular elements to construct the induction of bone formation.

Exercise-Induced Myokines can Explain the Importance of Physical Activity in the Elderly: An Overview

Physical activity has been found to aid the maintenance of health in the elderly. Exercise-induced skeletal muscle contractions lead to the production and secretion of many small proteins and proteoglycan peptides called myokines. Thus, studies on myokines are necessary for ensuring the maintenance of skeletal muscle health in the elderly. This review summarizes 13 myokines regulated by physical activity that are affected by aging and aims to understand their potential roles in metabolic diseases. We categorized myokines into two groups based on regulation by aerobic and anaerobic exercise. With aging, the secretion of apelin, β-aminoisobutyric acid (BAIBA), bone morphogenetic protein 7 (BMP-7), decorin, insulin-like growth factor 1 (IGF-1), interleukin-15 (IL-15), irisin, stromal cell-derived factor 1 (SDF-1), sestrin, secreted protein acidic rich in cysteine (SPARC), and vascular endothelial growth factor A (VEGF-A) decreased, while that of IL-6 and myostatin increased. Aerobic exercise upregulates apelin, BAIBA, IL-15, IL-6, irisin, SDF-1, sestrin, SPARC, and VEGF-A expression, while anaerobic exercise upregulates BMP-7, decorin, IGF-1, IL-15, IL-6, irisin, and VEGF-A expression. Myostatin is downregulated by both aerobic and anaerobic exercise. This review provides a rationale for developing exercise programs or interventions that maintain a balance between aerobic and anaerobic exercise in the elderly.

Elevated activity levels do not influence extrinsic fiber attachment morphology on the surface of muscle-attachment sites

Extrinsic fibers (EFs) are a type of penetrating collagenous fiber, closely related to the periodontal ligament, which help anchor soft tissue into bone. These fibers are associated with muscle attachment sites (entheses). Their size and grouping patterns are thought to be indicative of the loading history of the muscle. EFs are of particular significance in anthropology as potential tools for the reconstruction of behavior from skeletal remains and, specifically, entheses. In this study, we used a mouse model to experimentally test how activity level alters the morphology of EF insertion sites on the bone surface of a fibrocartilaginous enthesis, the biceps brachii insertion. Further, we adapted surface metrological techniques from studies of dental wear to perform automated, quantitative and non-destructive analysis of bone surface histology. Our results show that experimentally increased activity had no significant effect on the quantity or density of EF insertions at the enthesis, nor on the size of those insertions. Although EF presence does indicate muscle attachment, activity did not have an observable effect on EF morphology.

Microporous Bio-orthogonally Annealed Particle Hydrogels for Tissue Engineering and Regenerative Medicine

Microporous annealed particle (MAP) hydrogels are an emerging class of biomaterials with the potential to improve outcomes in tissue repair and regeneration. Here, a new MAP hydrogel platform comprising poly(ethylene) glycol (PEG) hydrogel microparticles that are annealed in situ using bio-orthogonal tetrazine click chemistry is reported (i.e., TzMAP hydrogels). Briefly, clickable PEG-peptide hydrogel microparticles with extracellular matrix mimetic peptides to permit cell adhesion and enzymatic degradation were fabricated via submerged electrospraying and stoichiometrically controlled thiol-norbornene click chemistry. Subsequently, unreacted norbornene groups in the microparticles were leveraged for functionalization with bioactive proteins as well as annealing into TzMAP hydrogels via the tetrazine-norbornene click reaction, which is highly selective and proceeds spontaneously without requiring an initiator or catalyst. The results demonstrate that the clickable particles can be easily applied to a tissue-like defect and then annealed into an inherently microporous structure in situ. In addition, the ability to produce TzMAP hydrogels with heterogeneous properties by incorporating multiple types of hydrogel microspheres is demonstrated, first with fluorophore-functionalized hydrogel microparticles and then with protein-functionalized hydrogel microparticles. For the latter, tetrazine-modified alkaline phosphatase was conjugated to PEG hydrogel microparticles, which were mixed with nonfunctionalized microparticles and used to produce TzMAP hydrogels. A biomimetic mineralized/nonmineralized interface was then produced upon incubation in calcium glycerophosphate. Finally, platelet-derived growth factor-BB (PDGF-BB) and human periodontal ligament stem cells (PDLSC) were incorporated into the TzMAP hydrogels during the annealing step to demonstrate their potential for delivering regenerative therapeutics, specifically for periodontal tissue regeneration. In vitro characterization revealed excellent PDGF-BB retention as well as PDLSC growth and spreading. Moreover, PDGF-BB loading increased PDLSC proliferation within hydrogels by 90% and more than doubled the average volume per cell. Overall, these results demonstrate that TzMAP hydrogels are a versatile new platform for the delivery of stem cells and regenerative factors.

Recombinant Human Bone Morphogenetic Protein 7 Exerts Osteo-Catabolic Effects on Bone Grafts That Outweigh Its Osteo-Anabolic Capacity

This study aimed to investigate the effects of recombinant human bone morphogenetic protein (rhBMP-7) on human cancellous bone grafts (BGs) while differentiating between anabolic and catabolic events. Human BGs alone or supplemented with rhBMP-7 were harvested 14 weeks after subcutaneous implantation into NOD/Scid mice, and studied via micro-CT, histomorphometry, immunohistochemistry and flow cytometry. Immunohistochemical staining for human-specific proteins made it possible to differentiate between grafted human bone and newly formed murine bone. Only BGs implanted with rhBMP-7 formed an ossicle containing a functional hematopoietic compartment. The total ossicle volume in the BMP⁺ group was higher than in the BMP^- group (835 mm³ vs. 365 mm³, respectively, p < 0.001). The BMP⁺ group showed larger BM spaces (0.47 mm vs. 0.28 mm, p = 0.002) and lower bone volume-to-total volume ratio (31% vs. 47%, p = 0.002). Immunohistochemical staining for human-specific proteins confirmed a higher ratio of newly formed bone area (murine) to total area (0.12 vs. 0.001, p < 0.001) in the BMP+ group, while the ratio of grafted bone (human) area to total area was smaller (0.14 vs. 0.34, p = 0.004). The results demonstrate that rhBMP-7 induces BG resorption at a higher rate than new bone formation while creating a haematopoietic niche. Clinicians therefore need to consider the net catabolic effect when rhBMP-7 is used with BGs. Overall, this model indicates its promising application to further decipher BMPs action on BGs and its potential in complex bone tissue regeneration.

BMP4 and Neuregulin regulate the direction of mouse neural crest cell differentiation

The neural crest is a transient embryonic tissue that initially generates neural crest stem cells, which then migrate throughout the body to give rise to a variety of mature tissues. It was proposed that the fate of neural crest cells is gradually determined via environmental cues from the surrounding tissues. In the present study, neural crest cells were isolated and identified from mouse embryos. Bone morphogenetic protein 4 (BMP4) and Neuregulin (NRG) were employed to induce the differentiation of neural crest cells. Treatment with BMP4 revealed neuron-associated differentiation; cells treated with NRG exhibited differentiation into the Schwann cell lineage, a type of glia. Soft agar clonogenic and neurosphere formation assays were conducted to investigate the effects of N-Myc (MYCN) overexpression in neural crest cells; the number of colonies and neurospheres notably increased after 14 days. These findings demonstrated that the direction of cell differentiation may be affected by altering the factors present in the surrounding environment. In addition, MYCN may serve a key role in regulating neural crest cell differentiation.

Signals in Stem Cell Differentiation on Fluorapatite-Modified Scaffolds

Previously, we reported that the fluorapatite (FA)-modified polycaprolactone (PCL) nanofiber could be an odontogenic/osteogenic inductive tissue-engineering scaffold by inducing stem cell differentiation and mineralization. The present study aimed to explore which of the signal pathways affected this differentiation and mineralization process. The Human Signal Transduction PathwayFinder RT2 Profiler PCR Array was used to analyze the involvement of potential signal transduction pathways during human dental pulp stem cell (DPSCs) osteogenic differentiation induced by FA-modified PCL nanofiber scaffolds. Based on the results, perturbation studies of the signaling pathways hedgehog, insulin, and Wnt were performed. Moreover, the autophagy process was studied, as indicated by the expression of the microtubule-associated protein 1 light chain 3A/B-II (LC3-II) and the cell osteogenic phenotypic changes. In a comparison of the cells grown on PCL + FA scaffolds and those on PCL-only scaffolds, the transcript expression of BMP2, BMP4, FOXA2, PTCH1, WNT1, and WNT2 (PCR array-labeled signal proteins of the hedgehog pathway); CEBPB, FASN, and HK2 (PCR array-labeled signal proteins of the insulin pathway); and CCND1, JUN, MYC, TCF7, and WISP1 (PCR array-labeled signal proteins of the Wnt pathway) doubled at day 14 when obvious cell osteogenic differentiation occurred. Phenotypically, in all the perturbation groups at day 14, ALP activity, OPN, and autophagy marker LC3-II expression were coincidently decreased. Consistently, no positive alizarin red staining or von Kossa staining was observed in the specimens from these perturbation groups at day 28. The results showed that when obvious cell differentiation occurred at day 14 on PCL + FA control groups, the inhibition of the hedgehog, insulin, and Wnt pathways significantly decreased DPSC osteogenic differentiation and mineralization. The osteogenic differentiation of DPSCs grown on FA-modified PCL scaffolds appeared to be positively modulated by the hedgehog, insulin, and Wnt signal pathways, which were coordinated with and/or mediated by the cell autophagy process.

Nanoscale and Macroscale Scaffolds with Controlled-Release Polymeric Systems for Dental Craniomaxillofacial Tissue Engineering

Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed biological responses. Better understanding of extracellular matrix functions is ensuring optimal adhesive substrates to promote cell mobility and a suitable physical niche to direct stem cell responses. Further, appreciation of the roles of matrix constituents as morphogen cues, termed matrikines or matricryptins, are also now being directly exploited in biomaterial design. These insoluble topological cues can be presented at both micro- and nanoscales with specific fabrication techniques. Progress in development and molecular biology has described key roles for a range of biological molecules, such as proteins, lipids, and nucleic acids, to serve as morphogens promoting directed behavior in stem cells. Controlled-release systems involving encapsulation of bioactive agents within polymeric carriers are enabling utilization of soluble cues. Using our efforts at dental craniofacial tissue engineering, this narrative review focuses on outlining specific biomaterial fabrication techniques, such as electrospinning, gas foaming, and 3D printing used in combination with polymeric nano- or microspheres. These avenues are providing unprecedented therapeutic opportunities for precision bioengineering for regenerative applications.

Wnt and BMP Signaling Crosstalk in Regulating Dental Stem Cells: Implications in Dental Tissue Engineering

Tooth is a complex hard tissue organ and consists of multiple cell types that are regulated by important signaling pathways such as Wnt and BMP signaling. Serious injuries and/or loss of tooth or periodontal tissues may significantly impact aesthetic appearance, essential oral functions and the quality of life. Regenerative dentistry holds great promise in treating oral/dental disorders. The past decade has witnessed a rapid expansion of our understanding of the biological features of dental stem cells, along with the signaling mechanisms governing stem cell self-renewal and differentiation. In this review, we first summarize the biological characteristics of seven types of dental stem cells, including dental pulp stem cells, stem cells from apical papilla, stem cells from human exfoliated deciduous teeth, dental follicle precursor cells, periodontal ligament stem cells, alveolar bone-derived mesenchymal stem cells (MSCs), and MSCs from gingiva. We then focus on how these stem cells are regulated by bone morphogenetic protein (BMP) and/or Wnt signaling by examining the interplays between these pathways. Lastly, we analyze the current status of dental tissue engineering strategies that utilize oral/dental stem cells by harnessing the interplays between BMP and Wnt pathways. We also highlight the challenges that must be addressed before the dental stem cells may reach any clinical applications. Thus, we can expect to witness significant progresses to be made in regenerative dentistry in the coming decade.

A Putative Association of a Single Nucleotide Polymorphism in GPR126 with Aggressive Periodontitis in a Japanese Population

Periodontitis is an inflammatory disease causing loss of tooth-supporting periodontal tissue. Disease susceptibility to the rapidly progressive form of periodontitis, aggressive periodontitis (AgP), appears to be influenced by genetic risk factors. To identify these in a Japanese population, we performed whole exome sequencing of 41 unrelated generalized or localized AgP patients. We found that AgP is putatively associated with single nucleotide polymorphism (SNP) rs536714306 in the G-protein coupled receptor 126 gene, GPR126 [c.3086 G>A (p.Arg1029Gln)]. Since GPR126 activates the cAMP/PKA signaling pathway, we performed cAMP ELISA analysis of cAMP concentrations, and found that rs536714306 impaired the signal transactivation of GPR126. Moreover, transfection of human periodontal ligament (HPDL) cells with wild-type or mutant GPR126 containing rs536714306 showed that wild-type GPR126 significantly increased the mRNA expression of bone sialoprotein, osteopontin, and Runx2 genes, while mutant GPR126 had no effect on the expression of these calcification-related genes. The increase in expression of these genes was through the GPR126-induced increase of bone morphogenic protein-2, inhibitor of DNA binding (ID) 2, and ID4 expression. These data indicate that GPR126 might be important in maintaining the homeostasis of periodontal ligament tissues through regulating the cytodifferentiation of HPDL cells. The GPR126 SNP rs536714306 negatively influences this homeostasis, leading to the development of AgP, suggesting that it is a candidate genetic risk factor for AgP in the Japanese population.

The remodeling pattern of human mandibular alveolar bone during prenatal formation from 19 to 270mm CRL

The underlying mechanisms of human bone morphogenesis leading to a topologically specific shape remain unknown, despite increasing knowledge of the basic molecular aspects of bone formation and its regulation. The formation of the alveolar bone, which houses the dental primordia, and later the dental roots, may serve as a model to approach general questions of bone formation. Twenty-five heads of human embryos and fetuses (Radlanski-Collection, Berlin) ranging from 19mm to 270mm (crown-rump-length) CRL were prepared as histological serial sections. For each stage, virtual 3D-reconstructions were made in order to study the morphogenesis of the mandibular molar primordia with their surrounding bone. Special focus was given to recording the bone-remodeling pattern, as diagnosed from the histological sections. In early stages (19-31mm CRL) developing bone was characterized by appositional only. At 41, in the canine region, mm CRL bony extensions were found forming on the bottom of the trough. Besides general apposition, regions with resting surfaces were also found. At a fetal size of 53mm CRL, septa have developed and led to a compartment for canine development. Furthermore, one shared compartment for the incisor primordia and another shared compartment for the molars also developed. Moreover, the inner surfaces of the dental crypts showed resorption of bone. From this stage on, a general pattern became established such that the compartmentalizing ridges and septa between all of the dental primordia and the brims of the crypts were noted, and were due to appositional growth of bone, while the crypts enlarged on their inner surfaces by resorption. By 160mm CRL, the dental primordia were larger, and all of the bony septa had become reduced in size. The primordia for the permanent teeth became visible at 225mm CRL and shared the crypts of their corresponding deciduous primordia.

Redefining the induction of periodontal tissue regeneration in primates by the osteogenic proteins of the transforming growth factor-β supergene family

The molecular bases of periodontal tissue induction and regeneration are the osteogenic proteins of the transforming growth factor-β (TGF-β) supergene family. These morphogens act as soluble mediators for the induction of tissues morphogenesis sculpting the multicellular mineralized structures of the periodontal tissues with functionally oriented ligament fibers into newly formed cementum. Human TGF-β₃ (hTGF-β₃ ) in growth factor-reduced Matrigel^® matrix induces cementogenesis when implanted in class II mandibular furcation defects surgically prepared in the non-human primate Chacma baboon, Papio ursinus. The newly formed periodontal ligament space is characterized by running fibers tightly attached to the cementoid surface penetrating as mineralized constructs within the newly formed cementum assembling and initiating within the mineralized dentine. Angiogenesis heralds the newly formed periodontal ligament space, and newly sprouting capillaries are lined by cellular elements with condensed chromatin interpreted as angioblasts responsible for the rapid and sustained induction of angiogenesis. The inductive activity of hTGF-β₃ in Matrigel^® matrix is enhanced by the addition of autogenous morcellated fragments of the rectus abdominis muscle potentially providing myoblastic, pericytic/perivascular stem cells for continuous tissue induction and morphogenesis. The striated rectus abdominis muscle is endowed with stem cell niches in para/perivascular location, which can be dominant, thus imposing stem cell features or stemness to the surrounding cells. This capacity to impose stemness is morphologically shown by greater alveolar bone induction and cementogenesis when hTGF-β₃ in Matrigel^® matrix is combined with morcellated fragments of autogenous rectus abdominis muscle. The induction of periodontal tissue morphogenesis develops as a mosaic structure in which the osteogenic proteins of the TGF-β supergene family singly, synergistically and synchronously initiate and maintain tissue induction and morphogenesis. In primates, the presence of several homologous yet molecularly different isoforms with osteogenic activity highlights the biological significance of this apparent redundancy and indicates multiple interactions during embryonic development and bone regeneration in postnatal life. Molecular redundancy with associated different biological functionalities in primate tissues may simply represent the fine-tuning of speciation-related molecular evolution in anthropoid apes at the early Pliocene boundary, which resulted in finer tuning of the bone induction cascade.

Fibrin Hydrogel Based Bone Substitute Tethered with BMP-2 and BMP-2/7 Heterodimers

Current clinically used delivery methods for bone morphogenetic proteins (BMPs) are collagen based and require large concentrations that can lead to dangerous side effects. Fibrin hydrogels can serve as osteoinductive bone substitute materials in non-load bearing bone defects in combination with BMPs. Two strategies to even further optimize such a fibrin based system include employing more potent BMP heterodimers and engineering growth factors that can be covalently tethered to and slowly released from a fibrin matrix. Here we present an engineered BMP-2/BMP-7 heterodimer where an N-terminal transglutaminase substrate domain in the BMP-2 portion provides covalent attachment to fibrin together with a central plasmin substrate domain, a cleavage site for local release of the attached BMP-2/BMP-7 heterodimer under the influence of cell-activated plasmin. In vitro and in vivo results revealed that the engineered BMP-2/BMP-7 heterodimer induces significantly more alkaline phosphatase activity in pluripotent cells and bone formation in a rat calvarial model than the engineered BMP-2 homodimer. Therefore, the engineered BMP-2/BMP-7 heterodimer could be used to reduce the amount of BMP needed for clinical effect.

N-methyl pyrrolidone/bone morphogenetic protein-2 double delivery with in situ forming implants

Bone morphogenetic proteins (BMPs) are growth and differentiation factors involved during development in morphogenesis, organogenesis and later mainly in regeneration processes, in particular in bone where they are responsible for osteoinduction. For more than a decade, recombinant human (rh)BMP-2 has been used in the clinic for lumbar spinal fusion at non-physiological high dosages that appear to be causative for side effects, like male sterility. A possible strategy to reduce the effective amount of rhBMP-2 in the clinic is the co-delivery with an enhancer of BMPs' activity. In an earlier study, we showed that N-methylpyrrolidone (NMP) enhances BMP activity in vitro and in vivo. Here we report on the development of a slow and sustained double delivery of rhBMP-2 and NMP via an in situ forming implant based on poly(lactide-co-glycolide). The results showed that the release of NMP can be adjusted by varying the lactide/glycolide ratio and the polymer's molecular weight. The same applied to rhBMP-2, with release rates that could be sustained from two to three weeks. In the in vivo model of a critical size defect in the calvarial bone of rabbits, the implant containing 50mol% lactide performed better than the one having 75mol% lactide in terms of defect bridging and extent of bony regenerated area. In situ forming implants for the double delivery of the BMP enhancer NMP and rhBMP-2 appear to be promising delivery systems in bone regeneration.

Morphogenesis of the compartmentalizing bone around the molar primordia in the mouse mandible during dental developmental stages between lamina, bell-stage, and root formation (E13-P20)

Despite increasing knowledge of the basic molecular aspects of bone formation and its regulation, the mechanisms of bone morphogenesis leading to a topologically specific shape remain unknown. The formation of the alveolar bone, which houses the dental primordia and later, the dental roots, may serve as a model to understand the formation of bone form in general. Thirty-eight heads of mice (C57 Bl/6J) ranging from stages E13-P20 were used to prepare histological serial sections. For each stage, virtual 3D-reconstructions were made in order to study the morphogenesis of the mandibular molar primordia concomitantly with their surrounding bone. Special focus was given to recording the remodeling pattern. It has been shown that, in early stages (E13, E14), bone formation is characterized by apposition only. In stage E15, the bony crypt around the dental primordia is remodeled mostly by resorption of bone. In stage E18, the bone remodeling pattern shows resorption all along the bony gutter, which houses the molar primordia. The medial and lateral margins are characterized by apposition. At birth (stage P0), a bony septum has begun to form between the primordium m1 and of m2, arising from both sides and characterized by pure apposition of bone. In stage P4, the crypts of m1 and m2, and also that of m3, show bone resorption inside, while the medial and lateral bony margins show apposition of bone throughout. Generally, during development, the bone gradually encapsulates the dental primordia, in such a way that the bone reaches over the dental primordia and leaves only a continuous longish opening of about 200μm width. The opening at the occlusal surface of m1, at the time of eruption, starting at stage P14, appears to have increased in size again. The distance between bone and dental primordium undergoes change during development. In erupted molars, it is around 100μm, during early developmental stages, it may be as less as 20μm. These data show the inevitability of bone remodeling.

Fluorapatite-modified scaffold on dental pulp stem cell mineralization

In previous studies, fluorapatite (FA) crystal-coated surfaces have been shown to stimulate the differentiation and mineralization of human dental pulp stem cells (DPSCs) in two-dimensional cell culture. However, whether the FA surface can recapitulate these properties in three-dimensional culture is still unknown. This study examined the differences in behavior of human DPSCs cultured on electrospun polycaprolactone (PCL) NanoECM nanofibers with or without the FA crystals. Under near-physiologic conditions, the FA crystals were synthesized on the PCL nanofiber scaffolds. The FA crystals were evenly distributed on the scaffolds. DPSCs were cultured on the PCL+FA or the PCL scaffolds for up to 28 days. Scanning electron microscope images showed that DPSCs attached well to both scaffolds after the initial seeding. However, it appeared that more multicellular aggregates formed on the PCL+FA scaffolds. After 14 days, the cell proliferation on the PCL+FA was slower than that on the PCL-only scaffolds. Interestingly, even without any induction of mineralization, from day 7, the upregulation of several pro-osteogenic molecules (dmp1, dspp, runx2, ocn, spp1, col1a1) was detected in cells seeded on the PCL+FA scaffolds. A significant increase in alkaline phosphatase activity was also seen on FA-coated scaffolds compared with the PCL-only scaffolds at days 14 and 21. At the protein level, osteocalcin expression was induced only in the DPSCs on the PCL+FA surfaces at day 21 and then significantly enhanced at day 28. A similar pattern was observed in those specimens stained with Alizarin red and Von Kossa after 21 and 28 days. These data suggest that the incorporation of FA crystals within the three-dimensional PCL nanofiber scaffolds provided a favorable extracellular matrix microenvironment for the growth, differentiation, and mineralization of human DPSCs. This FA-modified PCL nanofiber scaffold shows promising potential for future bone, dental, and orthopedic regenerative applications.

Bone morphogenetic proteins: periodontal regeneration

Periodontitis is an infectious inflammatory disease that results in attachment loss and bone loss. Regeneration of the periodontal tissues entails de novo formation of cementum, periodontal ligament, and alveolar bone. Several different approaches are currently being explored to achieve complete, reliable, and reproducible regeneration of periodontal tissues. The therapeutic management of new bone formation is one of the key issues in successful periodontal regeneration. Bone morphogenetic proteins form a unique group of proteins within the transforming growth factor superfamily of genes and have a vital role in the regulation in the bone induction and maintenance. The activity of bone morphogenetic proteins was first identified in the 1960s, but the proteins responsible for bone induction were unknown until the purification and cloning of human bone morphogenetic proteins in the 1980s, because of their osteoinductive potential. Bone morphogenetic proteins have gained a lot of interest as therapeutic agents for treating periodontal defects. A systematic search for data related to the use of bone morphogenetic proteins for the regeneration of periodontal defects was performed to recognize studies on animals and human (PUBMED, MEDLINE, COCHRANE, and Google search). All the studies included showed noticeable regeneration of periodontal tissues with the use of BMP.

Exogenous bone morphogenetic protein-7 reduces hepatic fibrosis in Schistosoma japonicum-infected mice via transforming growth factor-β/Smad signaling

AIM: To investigate the antifibrotic effects of bone morphogenetic protein-7 (BMP-7) on Schistosoma japonicum (S. japonicum)-induced hepatic fibrosis in BALB/C mice.

METHODS: Sixty BALB/C mice were randomly divided into three groups, including a control group (group A, n = 20), model group (group B, n = 20) and BMP-7 treated group (group C, n = 20). The mice in group B and group C were abdominally infected with S. japonicum cercariae to induce a schistosomal hepatic fibrosis model. The mice in group C were administered human recombinant BMP-7. Liver samples were extracted from mice sacrificed at 9 and 15 wk after modeling. Hepatic histopathological changes were assessed using Masson’s staining. Transforming growth factor-beta 1 (TGF-β1), alpha-smooth muscle actin (α-SMA), phosphorylated Smad2/3 (pSmad2/3) and Smad7 protein levels and localization were measured by Western blotting and immunohistochemistry, respectively, and their mRNA expressions were detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: The schistosomal hepatic fibrosis mouse model was successfully established, as the livers of mice in group B and group C showed varying degrees of typical schistosomal hepatopathologic changes such as egg granuloma and collagen deposition. The degree of collagen deposition in group C was higher than that in group A (week 9: 22.95 ± 6.66 vs 2.02 ± 0.76; week 15: 12.84 ± 4.36 vs 1.74 ± 0.80; P < 0.05), but significantly lower than that in group B (week 9: 22.95 ± 6.66 vs 34.43 ± 6.96; week 15: 12.84 ± 4.36 vs 18.90 ± 5.07; P < 0.05) at both time points. According to immunohistochemistry data, the expressions of α-SMA, TGF-β1 and pSmad2/3 protein in group C were higher than those in group A (α-SMA: week 9: 21.24 ± 5.73 vs 0.33 ± 0.20; week 15: 12.42 ± 4.88 vs 0.34 ± 0.27; TGF-β1: week 9: 37.00 ± 13.74 vs 3.73 ± 2.14; week 15: 16.71 ± 9.80 vs 3.08 ± 2.35; pSmad2/3: week 9: 12.92 ± 4.81 vs 0.83 ± 0.48; week 15: 7.87 ± 4.09 vs 0.90 ± 0.45; P < 0.05), but significantly lower than those in group B (α-SMA: week 9: 21.24 ± 5.73 vs 34.39 ± 5.74; week 15: 12.42 ± 4.88 vs 25.90 ± 7.01; TGF-β1: week 9: 37.00 ± 13.74 vs 55.66 ± 14.88; week 15: 16.71 ± 9.80 vs 37.10 ± 12.51; pSmad2/3: week 9: 12.92 ± 4.81 vs 19.41 ± 6.87; week 15: 7.87 ± 4.09 vs 13.00 ± 4.98; P < 0.05) at both time points; the expression of Smad7 protein in group B was higher than that in group A and group C at week 9 (8.46 ± 3.95 vs 1.00 ± 0.40 and 8.46 ± 3.95 vs 0.77 ± 0.42; P < 0.05), while there were no differences in Smad7 expression between the three groups at week 15 (1.09 ± 0.38 vs 0.97 ± 0.42 vs 0.89 ± 0.39; P > 0.05). Although minor discrepancies were observed, the results of RT-PCR and Western blotting were mainly consistent with the immunohistochemical results.

CONCLUSION: Exogenous BMP-7 significantly decreased the degree of hepatic fibrosis in both the acute and chronic stages of hepato-schistosomiasis, and the regulatory mechanism may involve the TGF-β/Smad signaling pathway.

Bone repair cells for craniofacial regeneration

Reconstruction of complex craniofacial deformities is a clinical challenge in situations of injury, congenital defects or disease. The use of cell-based therapies represents one of the most advanced methods for enhancing the regenerative response for craniofacial wound healing. Both somatic and stem cells have been adopted in the treatment of complex osseous defects and advances have been made in finding the most adequate scaffold for the delivery of cell therapies in human regenerative medicine. As an example of such approaches for clinical application for craniofacial regeneration, Ixmyelocel-T or bone repair cells are a source of bone marrow derived stem and progenitor cells. They are produced through the use of single pass perfusion bioreactors for CD90+ mesenchymal stem cells and CD14+ monocyte/macrophage progenitor cells. The application of ixmyelocel-T has shown potential in the regeneration of muscular, vascular, nervous and osseous tissue. The purpose of this manuscript is to highlight cell therapies used to repair bony and soft tissue defects in the oral and craniofacial complex. The field at this point remains at an early stage, however this review will provide insights into the progress being made using cell therapies for eventual development into clinical practice.

Effect of grafting BMP2-derived peptide to nanoparticles on osteogenic and vasculogenic expression of stromal cells

Bone morphogenetic protein-2 (BMP2) plays a major role in initiating the cascade of osteogenesis. However, high doses of exogenous BMP2 coupled with diffusion away from the intended site cause adverse side-effects. An alternative is to use biodegradable polymeric nanoparticles (NPs) grafted with peptides of the active domains of BMP2. NPs present a multivalent form of the peptide for stronger interaction with cell surface receptors, leading to a stronger activation of osteogenic signalling pathways. The objective of this work was to compare osteogenic activity of the BMP2 peptide (BMP2Pe), corresponding to residues 73-92 of BMP2 protein (BMP2Pr), grafted to biodegradable NPs with that of BMP2 protein (BMP2Pr). BMP2Pe was functionalized with a cysteine residue and grafted to poly(lactide fumarate) and poly(lactide-co-ethylene oxide fumarate) (PLAF/PLEOF) NPs via a thioether link. The calcium content of bone marrow stromal (BMS) cells cultured in osteogenic medium supplemented with BMP2 peptide/protein-grafted NPs (BMP2Pe-gNP and BMP2Pr-gNP) was slightly higher than other BMP2-treated groups, but all osteogenic groups showed similar levels of mineralization after 21 days. The expression pattern of master transcription factors Dlx5 and Runx2 indicated that BMP2 protein induced faster osteogenic signalling than the BMP peptide. The expression level of Osteopontin (OP), Osteocalcin (OC) and PECAM-1 in the NP-grafted BMP2 groups was significantly higher than those of ungrafted BMP2Pr and BMP2Pe groups, which may be due to a more effective presentation of the peptide/protein to cell surface receptors, thus leading to a stronger interaction of the peptide/protein with clustered cell surface receptors.

Osteoblast-like cell response to calcium phosphate coating chemistry and morphology on etched silicon surfaces

Being able to control the behaviour of osteoblast-like cells on a surface may provide a genuine insight into the material surface characteristics and help in creating a successful coating/cell interface. The possibility of creating a micro-environment that can induce proliferation, differentiation and mineralisation of bone cells in vitro, by successfully combining both chemistry and topography of a micro-fabricated substrate is an area that requires a multi-disciplinary approach. Utilising sputter deposition, a process that lends itself to high processability, in conjunction with photolithography allowing for the creation of highly repeatable etched surfaces, we aim to provide a successful combination of chemistry and topography. Correlating the substrate conditions with resultant osteoblast biological function and activity can ultimately be used with a view to modulating the behavior of osteoblast-like cells in vitro.

Bone morphogenetic protein-9 induces osteogenic differentiation of rat dental follicle stem cells in P38 and ERK1/2 MAPK dependent manner

Dental follicle stem cells are a group of cells possessing osteogenic, adipogenetic and neurogenic differentiations, but the specific mechanism underlying the multilineage differentiation remains still unclear. Great attention has been paid to bone morphogenetic protein-9 (BMP-9) due to its potent osteogenic activity. In the present study, rat dental follicle stem cells were isolated and purified, and cells of passage 3 underwent adenovirus mediated BMP-9 gene transfection to prepare dental follicle stem cells with stable BMP-9 expression. Detection of alkaline phosphatase (ALP) and calcium deposition showed dental follicle stem cells transfected with BMP-9 gene could significantly promote the osteogenesis. In addition, SB203580 and PD98059 were employed to block the p38 mitogen-activated protein kinase (p38MAPK) and extracellular signal-regulated kinase (ERK1/2), respectively. Detection of ALP and calcium deposition revealed the BMP-9 induced osteogenic differentiation of dental follicle stem cells depended on MAPK signaling pathway.

[Oro-maxillofacial bone tissue engineering combining biomaterials, stem cells, and gene therapy]

Improvements have been made in regenerative medicine, due to the development of tissue engineering and cellular therapy. Bone regeneration is an ambitious project, leading to many applications involving skull, maxillofacial, and orthopaedic surgery. Scaffolds, stem cells, and signals support bone tissue engineering. The scaffold physical and chemical properties promote cell invasion, guide their differentiation, and enable signal transmission. Scaffold may be inorganic or organic. Their conception was improved by the use of new techniques: self-assembled nanofibres, electrospinning, solution-phase separation, micropatterned hydrogels, bioprinting, and rapid prototyping. Cellular biology processes allow us to choose between embryonic stem cells or adult stem cells for regenerative medicine. Finally, communication between cells and their environment is essential; they use various signals to do so. The study of signals and their transmission led to the discovery and the use of Bone Morphogenetic Protein (BMP). The development of cellular therapy led to the emergence of a specific field: gene therapy. It relies on viral vectors, which include: retroviruses, adenoviruses and adeno-associated vectors (AAV). Non-viral vectors include plasmids and lipoplex. Some BMP genes have successfully been transfected. The ability to control transfected cells and the capacity to combine and transfect many genes involved in osseous healing will improve gene therapy.

Ectopic study of tissue-engineered bone complex with enamel matrix proteins, bone marrow stromal cells in porous calcium phosphate cement scaffolds, in nude mice

OBJECTIVE

This study aimed to investigate the potential of enamel matrix proteins (EMPs) on promoting osteogenic differentiation of porcine bone marrow stromal cells (pBMSCs), as well as new bone formation capabilities, in a tissue-engineered bone complex scaffold of EMPs, pBMSCs and porous calcium phosphate cement (CPC).

MATERIALS AND METHODS

Effects of EMPs on pBMSCs in vitro was first determined by alkaline phosphatase (ALP) activity, von Kossa staining assay and mRNA expression of ALP, bone sialoprotein (BSP) and osteocalcin (OCN) genes. Next, an ectopic new bone formation test was performed in a nude mouse model with four groups: CPC scaffold alone; CPC scaffold + EMPs; CPC scaffold + pBMSCs; and CPC scaffold + EMPs + pBMSCs, for 2 or 4 weeks.

RESULTS

ALP activity, von Kossa assay and mRNA expressions of ALP, BSP and OCN genes were all significantly higher with 150 μg/ml EMP treatment in vitro. In nude mice, new bone formation was detected only in the CPC scaffold + EMPs + pBMSCs group at 2 weeks. At 4 weeks, in the tissue-engineered construct there was significantly higher bone formation ability than other groups.

CONCLUSIONS

EMPs promoted osteogenic differentiation of pBMSCs, and the tissue-engineered complex of EMPs, pBMSCs and CPC scaffold may be a valuable alternative to be used in periodontal bone tissue engineering and regeneration.

Future of local bone regeneration - Protein versus gene therapy

The most promising attempts to achieve bone regeneration artificially are based on the application of mediators such as bone morphogenetic proteins (BMPs) directly to the deficient tissue site. BMPs, as promoters of the regenerative process, have the ability to induce de novo bone formation in various tissues, and many animal models have demonstrated their high potential for ectopic and orthotopic bone formation. However, the biological activity of the soluble factors that promote bone formation in vivo is limited by diffusion and degradation, leading to a short half-life. Local delivery remains a problem in clinical applications. Several materials, including hydroxyapatite, tricalcium phosphate, demineralised bone matrices, poly-lactic acid homo- and heterodimers, and collagen have been tested as carriers and delivery systems for these factors in a sustained and appropriate manner. Unfortunately these delivery vehicles often have limitations in terms of biodegradability, inflammatory and immunological rejection, disease transmission, and most importantly, an inability to provide a sustained, continuous release of these factors at the region of interest. In coping with these problems, new approaches have been established: genes encoding these growth factor proteins can be delivered to the target cells. In this way the transfected cells serve as local "bioreactors", as they express the exogenous genes and secrete the synthesised proteins into their vicinity. The purpose of this review is to present the different methods of gene versus growth factor delivery in tissue engineering. Our review focuses on these promising and innovative methods that are defined as regional gene therapy and provide an alternative to the direct application of growth factors. Various advantages and disadvantages of non-viral and viral vectors are discussed. This review identifies potential candidate genes and target cells, and in vivo as well as ex vivo approaches for cell transduction and transfection. In explaining the biological basis, this paper also refers to current experimental and clinical applications.

Effect of coating Straumann Bone Ceramic with Emdogain on mesenchymal stromal cell hard tissue formation

Periodontal tissue engineering requires a suitable biocompatible scaffold, cells with regenerative capacity, and instructional molecules. In this study, we investigated the capacity of Straumann Bone Ceramic coated with Straumann Emdogain, a clinical preparation of enamel matrix protein (EMP), to aid in hard tissue formation by post-natal mesenchymal stromal cells (MSCs) including bone marrow stromal cells (BMSCs) and periodontal ligament fibroblasts (PDLFs). MSCs were isolated and ex vivo-expanded from human bone marrow and periodontal ligament and, in culture, allowed to attach to Bone Ceramic in the presence or absence of Emdogain. Gene expression of bone-related proteins was investigated by real time RT-PCR for 72 h, and ectopic bone formation was assessed histologically in subcutaneous implants of Bone Ceramic containing MSCs with or without Emdogain in NOD/SCID mice. Alkaline phosphatase activity was also assessed in vitro, in the presence or absence of Emdogain. Collagen-I mRNA was up-regulated in both MSC populations over the 72-h time course with Emdogain. Expression of BMP-2 and the osteogenic transcription factor Cbfa-1 showed early stimulation in both MSC types after 24 h. In contrast, expression of BMP-4 was consistently down-regulated in both MSC types with Emdogain. Up-regulation of osteopontin and periostin mRNA was restricted to BMSCs, while higher levels of bone sialoprotein-II were observed in PDLFs with Emdogain. Furthermore, alkaline phosphatase activity levels were reduced in both BMSCs and PDLFs in the presence of Emdogain. Very little evidence was found for ectopic bone formation following subcutaneous implantation of MSCs with Emdogain-coated or -uncoated Bone Ceramic in NOD/SCID mice. The early up-regulation of several important bone-related genes suggests that Emdogain may have a significant stimulatory effect in the commitment of mesenchymal cells to osteogenic differentiation in vitro. While Emdogain inhibited AP activity and appeared not to induce ectopic bone formation, longer-term studies are required to determine whether it promotes the final stages of osteoblast formation and mineralization at gene and protein levels. While used in clinical applications, whether Emdogain and other commercial preparations of EMPs truly possess the capacity to induce the regeneration of bone or other components of the periodontium remains to be established.

Autologous periodontal ligament cells in the treatment of class II furcation defects: a study in dogs

AIM

The goal of this study was to histologically investigate the use of periodontal ligament cells (PDL cells) in tissue engineering to regenerate class II furcation defects.

MATERIAL AND METHODS

PDL cells were obtained from the mandibular tooth extracted from each dog (seven), cultured in vitro and phenotypically characterized with regard to their biological properties. Following, bilateral class II furcation lesions were created at maxillary 3rd premolars and were randomly assigned to the test group [PDL cells+guided tissue regeneration (GTR)] or the control group (GTR). After 3 months, the animals were euthanized to evaluate the histometric parameters.

RESULTS

In vitro, PDL cells were able to promote mineral nodule formation and to express bone sialoprotein, type I collagen and alkaline phosphatase. Histometrically, data analysis demonstrated that the cell-treated group presented a superior length of new cementum (6.00 ± 1.50 and 8.08 ± 1.08 mm), a greater extension of periodontal regeneration (3.94 ± 1.20 and 7.28 ± 1.00 mm), a lower formation of connective tissue/epithelium (2.15 ± 1.92 and 0.60 ± 0.99 mm), a larger area of new bone (7.01 ± 0.61 and 9.02 ± 2.30 mm(2)) and a smaller area of connective tissue/epithelium (5.90 ± 1.67 and 4.22 ± 0.95 mm(2)), when compared with control group.

CONCLUSION

PDL cells in association with GTR may significantly promote periodontal regeneration in class II furcation defects in dog.

Preparation of mineralized nanofibers: collagen fibrils containing calcium phosphate

We report a straightforward, bottom-up, scalable process for preparing mineralized nanofibers. Our procedure is based on flowing feed solution, containing both inorganic cations and polymeric molecules, through a nanoporous membrane into a receiver solution with anions, which leads to the formation of mineralized nanofibers at the exit of the pores. With this strategy, we were able to achieve size control of the nanofiber diameters. We illustrate this approach by producing collagen fibrils with calcium phosphate incorporated inside the fibrils. This structure, which resembles the basic constituent of bones, assembles itself without the addition of noncollagenous proteins or their polymeric substitutes. Rheological experiments demonstrated that the stiffness of gels derived from these fibrils is enhanced by mineralization. Growth experiments of human adipose derived stem cells on these gels showed the compatibility of the fibrils in a tissue-regeneration context.

Evaluation of osteoinduction properties of the demineralized bovine foetal growth plate powder as a new xenogenic biomaterial in rat

The aim of this study was evaluation of osteoinductive properties of demineralized bovine foetal growth plate in submuscular transplantation (ectopic osteoinduction) as a new xenogenic biomaterial in rat model. Demineralized bovine foetal growth plate was ectopically implanted in 18 male Sprague-Dawley rats. In 18 of the animals under aseptic conditions two submuscular pouches were created between external and internal oblique abdominal muscles in the two flanks: the right was left empty (sham) and the left was filled with 20mg of demineralized bovine foetal growth plate powder. Radiographs were taken in 2, 4 and 6 weeks after the surgery, then six animals were pharmacologically euthanized after 2, 4 and 6 weeks for histopathological evaluation. Results showed: (1) osteoinductivity of xenogenic demineralized bovine foetal growth plate powder, and (2) earlier mineralization of ectopically implanted demineralized bovine foetal growth plate in the submuscular implanted area. Our results show that submuscular implantation of xenogenic demineralized bovine foetal growth plate has osteoinductive properties in a rat model.

The expression of bone matrix proteins induced by different bioimplants in a rabbit sinus lift model

This study aimed to analyze the expression of bone matrix proteins and CD31 by immunohistochemistry after maxillary sinus grafting with different bioimplants in a rabbit model. Rabbit demineralized bone matrix (DBM), partially purified bovine bone morphogenetic proteins (BMP), a mixture of BMP with DBM (BMP/DBM), or particulated autogenous bone was grafted into the maxillary sinuses of 42 rabbits. Animals were sacrificed at 2 and 8 weeks. Immunohistochemistry was used to investigate the expression of type 1 collagen (COL1), osteonectin (ON), osteocalcin (OC), bone sialoprotein (BSP), osteopontin (OPN), and CD31. Sinuses grafted with BMP were filled with trabeculae of woven bone that was strongly immunoreactive for COL1, OC, ON, and BSP. BMP/DBM showed strongly positive immunoreactivity for these proteins within the newly formed bone, but weak immunoreactivity in the DBM particles. Immunoreactivity for COL1, OC, ON, and BSP in DBM sinuses was only seen in the osteoblasts rimming the grafted bone particles. The staining of autogenous bone graft sinuses was similar to those grafted with DBM. OPN staining was detected in autogenous bone graft, BMP/DBM, and BMP bioimplants. CD31 staining was strongest in BMP and BMP/noncollagenous matrix proteins sinuses. These results suggest that exogenous BMP enhances not only osteogenesis but also angiogenesis, an important part of bone repair.

Periodontal tissue engineering and regeneration: current approaches and expanding opportunities

The management of periodontal tissue defects that result from periodontitis represents a medical and socioeconomic challenge. Concerted efforts have been and still are being made to accelerate and augment periodontal tissue and bone regeneration, including a range of regenerative surgical procedures, the development of a variety of grafting materials, and the use of recombinant growth factors. More recently, tissue-engineering strategies, including new cell- and/or matrix-based dimensions, are also being developed, analyzed, and employed for periodontal regenerative therapies. Tissue engineering in periodontology applies the principles of engineering and life sciences toward the development of biological techniques that can restore lost alveolar bone, periodontal ligament, and root cementum. It is based on an understanding of the role of periodontal formation and aims to grow new functional tissues rather than to build new replacements of periodontium. Although tissue engineering has merged to create more opportunities for predictable and optimal periodontal tissue regeneration, the technique and design for preclinical and clinical studies remain in their early stages. To date, the reconstruction of small- to moderate-sized periodontal bone defects using engineered cell-scaffold constructs is technically feasible, and some of the currently developed concepts may represent alternatives for certain ideal clinical scenarios. However, the predictable reconstruction of the normal structure and functionality of a tooth-supporting apparatus remains challenging. This review summarizes current regenerative procedures for periodontal healing and regeneration and explores their progress and difficulties in clinical practice, with particular emphasis placed upon current challenges and future possibilities associated with tissue-engineering strategies in periodontal regenerative medicine.

Emdogain in carcinogenesis: a systematic review of in vitro studies

Emdogain is a commercial product of unknown composition and is clinically used to induce periodontal regeneration. This study aims to review current knowledge of the in vitro effects of Emdogain on oral tissues and, in particular, factors related to carcinoma. A systematic approach was used to review studies from the Embase and Pubmed databases; a total of 76 studies were included. These comprised in vitro studies of the cytokines in, or regulated by, Emdogain and assays designed to study the effects of EMD on human cells in oral tissues or malignant cells. Several studies have shown that EMD regulates the proliferation, migration, adhesion, gene expression, and cytokine production of (pre-)osteoblasts, periodontal fibroblasts, and gingival fibroblasts. However, the effects of EMD on malignant oral cells are not well understood. EMD seems to have broad regulatory effects on malignant cells and on several carcinoma-related factors. Evidence suggests that patients with premalignant or malignant mucosal lesions should not be treated with EMD.

Biodegradable poly(alpha-hydroxy acid) polymer scaffolds for bone tissue engineering

Synthetic graft materials are emerging as a viable alternative to autogenous bone graft and bone allograft for the treatment of critical-sized bone defects. These materials can be osteoconductive but are rarely intrinsically osteogenic, although this can be greatly enhanced by the application of bone morphogenetic proteins (BMPs). This review will discuss the versatility of biodegradable poly(alpha-hydroxy acids) for the delivery of BMPs for bone tissue engineering. Poly(alpha-hydroxy acids) have a considerable potential for customization and adaptability via modification of design parameters, including scaffold architecture, composition, and biodegradability. Different fabrication techniques will also be discussed.

The effects of one-step self-etch adhesives on the induction of oxidative stress and production of TGF-beta1 and BMP-2 by human gingival fibroblasts

The aim of this study was to evaluate and compare the effects of two self-etch adhesive materials on the induction of oxidative stress and production of transforming growth factor-beta1 (TGF-beta1) and bone morphogenetic protein-2 (BMP-2) by cultured human gingival fibroblasts (HGF). Inflammation-free attached gingiva was obtained from healthy donors under informed consent. Following 24- and 72-h exposure of HGF to two different elutes of the test materials, cell viability was determined using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Lipid peroxidation, a major indicator of oxidative stress, was measured by the thiobarbituric acid reactive substance (TBARS) assay. TGF-beta1 and BMP-2 levels in cell-free culture media were determined by enzyme-linked immunosorbent assay (ELISA). Cell viability of the test groups was significantly lower than those of control at 24 and 72 h (P < 0.001), but showed an increase at 72 h (P < 0.001). The TBARS levels of both test groups were significantly greater than that of control (P < 0.05), and displayed similar values at 72 h (P > 0.05). For both materials, the levels of TGF-beta1 and BMP-2 were significantly greater than that of control (P < 0.05). Both test groups showed increased TGF-beta1 levels. These results indicate that the tested self-etch adhesives might be capable of inducing production of TGF-beta1 and BMP-2 in cultured HGF, despite their cytotoxic and oxidative stress-producing potential.

Targeted delivery with peptidomimetic conjugated self-assembled nanoparticles

Peptides produce specific nanostructures, making them useful for targeting in biological systems but they have low bioavailability, potential immunogenicity and poor metabolic stability. Peptidomimetic self-assembled NPs can possess biological recognition motifs as well as providing desired engineering properties. Inorganic NPs, coated with self-assembled macromers for stability and anti-fouling, and conjugated with target-specific ligands, are advancing imaging from the anatomy-based level to the molecular level. Ligand conjugated NPs are attractive for cell-selective tumor drug delivery, since this process has high transport capacity as well as ligand dependent cell specificity. Peptidomimetic NPs can provide stronger interaction with surface receptors on tumor cells, resulting in higher uptake and reduced drug resistance. Self-assembled NPs conjugated with peptidomimetic antigens are ideal for sustained presentation of vaccine antigens to dendritic cells and subsequent activation of T cell mediated adaptive immune response. Self-assembled NPs are a viable alternative to encapsulation for sustained delivery of proteins in tissue engineering. Cell penetrating peptides conjugated to NPs are used as intracellular delivery vectors for gene expression and as transfection agents for plasmid delivery. In this work, synthesis, characterization, properties, immunogenicity, and medical applications of peptidomimetic NPs in imaging, tumor delivery, vaccination, tissue engineering, and intracellular delivery are reviewed.