Background
Nonresorbable membranes promote bone formation during guided bone regeneration (GBR), yet the relationships between membrane properties and molecular changes in the surrounding tissue are ...largely unknown.
Aim
To compare the molecular events in the overlying soft tissue, the membrane, and the underlying bone defect during GBR using dual‐layered expanded membranes versus dense polytetrafluoroethylene (PTFE) membranes.
Materials and Methods
Rat femur defects were treated with either dense PTFE (d‐PTFE) or dual‐layered expanded PTFE (dual e‐PTFE) or left untreated as a sham. Samples were collected after 6 and 28 days for gene expression, histology, and histomorphometry analyses.
Results
The two membranes promoted the overall bone formation compared to sham. Defects treated with dual e‐PTFE exhibited a significantly higher proportion of new bone in the top central region after 28 days. Compared to that in the sham, the soft tissue in the dual e‐PTFE group showed 2‐fold higher expression of genes related to regeneration (FGF‐2 and FOXO1) and vascularization (VEGF). Furthermore, compared to cells in the d‐PTFE group, cells in the dual e‐PTFE showed 2.5‐fold higher expression of genes related to osteogenic differentiation (BMP‐2), regeneration (FGF‐2 and COL1A1), and vascularization (VEGF), in parallel with lower expression of proinflammatory cytokines (IL‐6 and TNF‐α). Multiple correlations were found between the molecular activities in membrane‐adherent cells and those in the soft tissue.
Conclusion
Selective surface modification of the two sides of the e‐PTFE membrane constitutes a novel means of modulating the tissue response and promoting bone regeneration.
Epoxyeicosatrienoic acids (EETs), lipid mediators produced by cytochrome P450 epoxygenases, regulate inflammation, angiogenesis, and vascular tone. Despite pleiotropic effects on cells, the role of ...these epoxyeicosanoids in normal organ and tissue regeneration remains unknown. EETs are produced predominantly in the endothelium. Normal organ and tissue regeneration require an active paracrine role of the microvascular endothelium, which in turn depends on angiogenic growth factors. Thus, we hypothesize that endothelial cells stimulate organ and tissue regeneration via production of bioactive EETs. To determine whether endothelial-derived EETs affect physiologic tissue growth in vivo, we used genetic and pharmacological tools to manipulate endogenous EET levels. We show that endothelial-derived EETs play a critical role in accelerating tissue growth in vivo, including liver regeneration, kidney compensatory growth, lung compensatory growth, wound healing, corneal neovascularization, and retinal vascularization. Administration of synthetic EETs recapitulated these results, whereas lowering EET levels, either genetically or pharmacologically, delayed tissue regeneration, demonstrating that pharmacological modulation of EETs can affect normal organ and tissue growth. We also show that soluble epoxide hydrolase inhibitors, which elevate endogenous EET levels, promote liver and lung regeneration. Thus, our observations indicate a central role for EETs in organ and tissue regeneration and their contribution to tissue homeostasis.
Objective
To test whether the use of (i) particulated bone substitute + collagen membrane used for guided bone regeneration (GBR) of peri‐implant bone defects renders different results from (ii) ...particulated bone substitute + collagen membrane + fixation pins and from (iii) block bone substitute + collagen membrane with respect to the volume stability of the augmented region during suturing of mucosal flaps.
Material and methods
Twenty peri‐implant box‐shaped bone defects were created in 10 pig mandibles. Every bone defect was augmented once with each of the following GBR procedures: Granulate (particulated xenograft + collagen membrane), Granulate + Pins (particulated xenograft + collagen membrane + fixation pins), and Block (block xenograft + collagen membrane). Cone‐beam computed tomography scans were obtained prior and after blinded wound closure. The horizontal thickness (HT) of the augmented region (bone substitute + membrane) was assessed at the implant shoulder (HT0 mm) and at 1–5 mm apical to the implant shoulder (HT1 mm–HT5 mm). The changes of HT during flap suturing were calculated as absolute (mm) and relative values (%). Repeated‐measures ANOVA was used for statistical analysis.
Results
Wound closure induced a statistically significant change of HT0 mm and of HT1 mm in all the treatment groups (P ≤ 0.05). The change in HT0 mm measured −42.8 ± 17.9% (SD) for Granulate, −22.9 ± 21.2% (SD) for Granulate + Pins, and −20.2 ± 18.9% (SD) for Block. The reduction in HT0 mm, HT1 mm, HT2 mm, and HT3 mm for the Granulate procedure was significantly higher as compared to the Granulate + Pins and the Block procedures (P ≤ 0.05). There were no statistically significant differences in the change of HT between the Granulate + Pins and the Block procedures (P > 0.05).
Conclusion
Wound closure induced displacement of the bone substitute resulting in a partial collapse of the collagen membrane in the coronal portion of the augmented site. The stability of the bone substitute and collagen membrane was enhanced by the application of fixation pins and by the use of block bone substitute instead of particulated bone substitute.
Microsurgical techniques for the treatment of large peripheral nerve injuries (such as the gold standard autograft) and its main clinically approved alternative—hollow nerve guidance conduits ...(NGCs)—have a number of limitations that need to be addressed. NGCs, in particular, are limited to treating a relatively short nerve gap (4 cm in length) and are often associated with poor functional recovery. Recent advances in biomaterials and tissue engineering approaches are seeking to overcome the limitations associated with these treatment methods. This review critically discusses the advances in biomaterial-based NGCs, their limitations and where future improvements may be required. Recent developments include the incorporation of topographical guidance features and/or intraluminal structures, which attempt to guide Schwann cell (SC) migration and axonal regrowth towards their distal targets. The use of such strategies requires consideration of the size and distribution of these topographical features, as well as a suitable surface for cell–material interactions. Likewise, cellular and molecular-based therapies are being considered for the creation of a more conductive nerve microenvironment. For example, hurdles associated with the short half-lives and low stability of molecular therapies are being surmounted through the use of controlled delivery systems. Similarly, cells (SCs, stem cells and genetically modified cells) are being delivered with biomaterial matrices in attempts to control their dispersion and to facilitate their incorporation within the host regeneration process. Despite recent advances in peripheral nerve repair, there are a number of key factors that need to be considered in order for these new technologies to reach the clinic.
For a successful clinical outcome, periodontal regeneration requires the coordinated response of multiple soft and hard tissues (periodontal ligament, gingiva, cementum, and bone) during the ...wound-healing process. Tissue-engineered constructs for regeneration of the periodontium must be of a complex 3-dimensional shape and adequate size and demonstrate biomechanical stability over time. A critical requirement is the ability to promote the formation of functional periodontal attachment between regenerated alveolar bone, and newly formed cementum on the root surface. This review outlines the current advances in multiphasic scaffold fabrication and how these scaffolds can be combined with cell- and growth factor–based approaches to form tissue-engineered constructs capable of recapitulating the complex temporal and spatial wound-healing events that will lead to predictable periodontal regeneration. This can be achieved through a variety of approaches, with promising strategies characterized by the use of scaffolds that can deliver and stabilize cells capable of cementogenesis onto the root surface, provide biomechanical cues that encourage perpendicular alignment of periodontal fibers to the root surface, and provide osteogenic cues and appropriate space to facilitate bone regeneration. Progress on the development of multiphasic constructs for periodontal tissue engineering is in the early stages of development, and these constructs need to be tested in large animal models and, ultimately, human clinical trials.
In general, bone fractures are able of healing by itself. However, in critical situations such as large bone defects, poor blood supply or even infections, the biological capacity of repair can be ...impaired, resulting in a delay of the consolidation process or even in non‐union fractures. Thus, technologies able of improving the process of bone regeneration are of high demand. In this context, ceramic biomaterials‐based bone substitutes and photobiomodulation (PBM) have been emerging as promising alternatives. Thus, the present study performed a systematic review targeting to analyze studies in the literature which investigated the effects of the association of ceramic based bone substitutes and PBM in the process of bone healing using animal models of bone defects. The search was conducted from March and April of 2019 in PubMed, Web of Science and Scopus databases. After the eligibility analyses, 16 studies were included in this review. The results showed that the most common material used was hydroxyapatite (HA) followed by Biosilicate associated with infrared PBM. Furthermore, 75% of the studies demonstrated positive effects to stimulate bone regeneration from association of ceramic biomaterials and PBM. All studies used low‐level laser therapy (LLLT) device and the most studies used LLLT infrared. The evidence synthesis was moderate for all experimental studies for the variable histological analysis demonstrating the efficacy of techniques on the process of bone repair stimulation. In conclusion, this review demonstrates that the association of ceramic biomaterials and PBM presented positive effects for bone repair in experimental models of bone defects.
Tissue regenerative potential displays striking divergence across phylogeny and ontogeny, but the underlying mechanisms remain enigmatic. Loss of mammalian cardiac regenerative potential correlates ...with cardiomyocyte cell-cycle arrest and polyploidization as well as the development of postnatal endothermy. We reveal that diploid cardiomyocyte abundance across 41 species conforms to Kleiber's law-the ¾-power law scaling of metabolism with bodyweight-and inversely correlates with standard metabolic rate, body temperature, and serum thyroxine level. Inactivation of thyroid hormone signaling reduces mouse cardiomyocyte polyploidization, delays cell-cycle exit, and retains cardiac regenerative potential in adults. Conversely, exogenous thyroid hormones inhibit zebrafish heart regeneration. Thus, our findings suggest that loss of heart regenerative capacity in adult mammals is triggered by increasing thyroid hormones and may be a trade-off for the acquisition of endothermy.
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