Nanoclay-Modified Hyaluronic Acid Microspheres for Bone Induction by Sustained rhBMP-2 Delivery.

Microspheres (MSs) are ideal candidates as biological scaffolds loading with growth factors or cells for bone tissue engineering to repair irregular alveolar bone defects by minimally invasive injection. However, the high initial burst release of growth factor and low cell attachment limit the application of microspheres. The modification of microspheres often needs expensive experiments facility or complex chemical reactions, which is difficult to achieve and may bring other problems. In this study, a sol-grade nanoclay, laponite XLS is used to modify the surface of MSs to enhance its affinity to either positively or negatively charged proteins and cells without changing the interior structure of the MSs. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is used as a representation of growth factor to check the osteoinduction ability of laponite XLS-modified MSs. By modification, the protein sustained release, cell loading, and osteoinduction ability of MSs are improved. Modified by 1% laponite XLS, the MSs can not only promote osteogenic differentiation of MC3T3-E1 cells by themselves, but also enhance the effect of the rhBMP-2 below the effective dose. Collectively, the study provides an easy and viable method to modify the biological behavior of microspheres for bone tissue regeneration.

ß-Tricalcium Phosphate as Alveolar Bone Grafting in Cleft Lip/Palate: A Systematic Review.

The aim of this systematic review is to describe and identify the prospects of ß-Tricalcium Phosphate (ß-TCP) as an alveolar bone grafting (ABG) material in cleft lip/palate (CL/P) or alveolar bone cleft defects. A systematic review protocol based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) was drafted. The literature search was conducted using MEDLINE/PubMed, Web of Science/ISI Web of Knowledge, Scopus, and the Cochrane Library, with English as the inclusion criterion and no publication year limits. The keywords yielded a total of 5824 publications. After removing duplicates and non-English articles, there were 3196 suitable articles available for evaluation. Subsequently, 1315 studies remained after reviewing titles and abstracts. Furthermore, 85 full articles were assessed for eligibility. After reading the complete texts of those papers, 20 were eventually selected that matched the inclusion requirements. Thirteen out of the twenty studies included in this systematic review were deemed to have a low risk of bias; one had a high risk of bias; and six had a moderate risk of bias due to not reporting randomization. ß-TCP, when used as an ABG material, is biocompatible, visible, practical, offers a less invasive procedure, and does not interfere with orthodontic treatment. Synthetic ß-TCP for ABG can be an alternative to autologous bone grafts under certain terms and conditions. The efficacy of ß-TCP for ABG in CL/P or alveolar bone cleft defects can be enhanced through a tissue engineering approach that combines ß-TCP with growth factors, mesenchymal stem cells, or other graft materials, along with modifications to ß-TCP's physical properties.

Zn-Incorporated TiO2 Nanotube Surface Improves Osteogenesis Ability Through Influencing Immunomodulatory Function of Macrophages.

PURPOSE: Zinc (Zn), an essential trace element in the body, has stable chemical properties, excellent osteogenic ability and moderate immunomodulatory property. In the present study, a Zn-incorporated TiO2 nanotube (TNT) was fabricated on titanium (Ti) implant material. We aimed to evaluate the influence of nano-scale topography and Zn on behaviors of murine RAW 264.7 macrophages. Moreover, the effects of Zn-incorporated TNT surface-regulated macrophages on the behaviors and osteogenic differentiation of murine MC3T3-E1 osteoblasts were also investigated. METHODS: TNT coatings were firstly fabricated on a pure Ti surface using anodic oxidation, and then nano-scale Zn particles were incorporated onto TNTs by the hydrothermal method. Surface topography, chemical composition, roughness, hydrophilicity, Zn release pattern and protein adsorption ability of the Zn-incorporated TiO2 nanotube surface were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), surface profiler, contact angle test, Zn release test and protein adsorption test. The cell behaviors and both pro-inflammatory (M1) and pro-regenerative (M2) marker gene and protein levels in macrophages cultured on Zn-incorporated TNTs surfaces with different TNT diameters were detected. The supernatants of macrophages were extracted and preserved as conditioned medium (CM). Furthermore, the behaviors and osteogenic properties of osteoblasts cultured in CM on various surfaces were evaluated. RESULTS: The release profile of Zn on Zn-incorporated TNT surfaces revealed a controlled release pattern. Macrophages cultured on Zn-incorporated TNT surfaces displayed enhanced gene and protein expression of M2 markers, and M1 markers were moderately inhibited, compared with the LPS group (the inflammation model). When cultured in CM, osteoblasts cultured on Zn-incorporated TNTs showed strengthened cell proliferation, adhesion, osteogenesis-related gene expression, alkaline phosphatase activity and extracellular mineralization, compared with their TNT counterparts and the Ti group. CONCLUSION: This study suggests that the application of Zn-incorporated TNT surfaces may establish an osteogenic microenvironment and accelerate bone formation. It provided a promising strategy of Ti surface modification for a better applicable prospect.

Surface Immobilization of TiO2 Nanotubes with Bone Morphogenetic Protein-2 Synergistically Enhances Initial Preosteoblast Adhesion and Osseointegration.

Although titanium (Ti) alloys have been widely used as implant materials, the bioinertness of pristine Ti impairs their bioactivity and early osseointegration. In the present work, we prepared TiO2 nanotubes (TNT) layer on the titanium (Ti) surface by anodic oxidation. The anodized surface was functionalized with human bone morphogenetic protein-2 coating to form the hBMP-2/TNT surface. The release behavior of hBMP-2 on the hBMP-2/TNT surface displayed a controlled and sustained pattern, compared to that on the hBMP-2/Ti surface, which showed a rapid release. In vitro cellular activity tests demonstrated that both TNT and hBMP-2/Ti surfaces, particularly the hBMP-2/TNT surface, enhanced adhesion, proliferation, and differentiation of osteoblast cells. Increased cell adhesion, improved cytoskeleton organization, and immunofluorescence staining of vinculin were observed on the modified surfaces. The TNT, hBMP-2/Ti, and hBMP-2/TNT surfaces, especially the hBMP-2/TNT surface, further displayed an upregulated gene expression of adhesion and osteogenic markers vinculin, collagen type 1, osteopontin, and osteocalcin, compared to the pristine Ti surface. In vivo experiments using a rat model demonstrated that the TNT and hBMP-2/Ti surfaces, in particular the hBMP-2/TNT surface, improved osseointegration and showed a superior bone bonding ability compared to Ti. Our study revealed a synergistic role played by TiO2 nanotubes nanotopography and hBMP-2 in promoting initial osteoblast adhesion, proliferation, differentiation, and osseointegration, thus suggesting a promising method for better modifying the implant surface.

Improved osteoblast adhesion and osseointegration on TiO2 nanotubes surface with hydroxyapatite coating.

To improve initial osteoblast adhesion and subsequent osseointegration, TiO2 nanotubes layer was constructed on the titanium (Ti) surface by anodic oxidation (AO), with an additional hydroxyapatite (HA) coating to form the AO/HA surface. Tests on in vitro cellular activity displayed that the AO surface, especially the AO/HA surface, promoted initial adhesion, proliferation and differentiation of osteoblast cells. The modified AO and AO/HA surfaces further presented an up-regulated gene expression of osteogenic and adhesion markers collagen type 1 (COL), osteopontin (OPN), osteocalcin (OCN) and vinculin. In addition, in vivo experiments with a rat model demonstrated that the AO surface, particularly the AO/HA surface, achieved earlier osseointegration and a superior bone bonding ability compared with Ti. Our study shed light on a synergistic role played by nanotopography and HA in promoting osteoblast adhesion, proliferation, differentiation and osseointegration, thus suggesting a promising method for better modifying the implant surface.

Loading icariin on titanium surfaces by phase-transited lysozyme priming and layer-by-layer self-assembly of hyaluronic acid/chitosan to improve surface osteogenesis ability.

PURPOSE: Icariin (ICA) is one of the main active constituents of Herba Epimedii for improving osteogenesis. It is necessary to create a simple and efficient method to load ICA onto the surface of titanium (Ti) implant. The purpose of this study was to establish a local ICA delivery system via a layer-by-layer (LbL) self-assembly system on phase-transited lysozyme (PTL)-primed Ti surface. MATERIALS AND METHODS: A PTL nanofilm was first firmly coated on the pristine Ti. Then, the ICA-loaded hyaluronic acid/chitosan (HA/CS) multilayer was applied via the LbL system to form the HA/CS-ICA surface. This established HA/CS-ICA surface was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The ICA release pattern of the HA/CS-ICA surface was also examined. MC3T3-E1 osteoblast culture test and a rat model were used to evaluate the effects of the HA/CS-ICA surface in vitro and in vivo. RESULTS: SEM, XPS and contact angle measurement demonstrated successful fabrication of the HA/CS-ICA surface. The HA/CS-ICA surfaces with different ICA concentrations revealed a controlled release profile of ICA during a 2-week monitoring span. Osteoblasts grown on the coated substrates displayed higher adhesion, viability, proliferation and ALP activity than those on the polished Ti surface. Furthermore, in vivo histological evaluation revealed much obvious bone formation in the ICA-coated group by histological staining and double fluorescent labeling at 2 weeks after implantation. CONCLUSION: The present study demonstrated that ICA-immobilized HA/CS multilayer on the PTL-primed Ti surface had a sustained release pattern of ICA which could promote the osteogenesis of osteoblasts in vitro and improve early osseointegration in vivo. This study provides a novel method for creating a sustained ICA delivery system to improve osteoblast response and osseointegration.

Ideal Characteristics of a Laser-Protected Endotracheal Tube: ABEA and AHNS Member Survey and Biomechanical Testing.

OBJECTIVES: To determine the characteristics of laser-protected endotracheal tubes (LPETs) valued by otolaryngologists performing transoral laser surgery in the head and neck and to measure LPET stiffness. METHODS: An online questionnaire was completed by American Broncho-Esophagological Association (ABEA) and American Head and Neck Society (AHNS) members. LPET distal end compliance was measured in a biomechanics laboratory. RESULTS: A total of 228 out of 2109 combined ABEA and AHNS members completed the survey. The following LPET characteristics, which were properties of the Medtronic Laser-Shield II tube (MLST), were highly valued: softness and flexibility, surface smoothness, and a tight-to-shaft balloon (all P < .01). Prior to industry-driven discontinuation of the MLST, 52% of surgeons (78% of fellowship-trained laryngologists [FTLs]) reported using it; afterward, 58% reported using the stainless steel, Mallinckrodt Laser-Flex tube (MLFT). Forty-six percent of all respondents (69% of FTLs) did not consider cost being a factor in LPET choice. Biomechanical testing revealed the distal end of the MLST to be 3.45 times more compliant than the MLFT ( P < .01). CONCLUSION: Members of the ABEA and AHNS, particularly FTLs, highly value distinguishing properties of the now discontinued MLST. Manufacturers should consider this in the design of new LPETs.

Microphthalmia-associated transcription factor acts through PEDF to regulate RPE cell migration.

Cells of the retinal pigment epithelium (RPE) play major roles in metabolic functions, maintenance of photoreceptor function, and photoreceptor survival in the retina. They normally form a stable monolayer, but migrate during disease states. Although growth factors produced by the RPE cells primarily control these cellular events, how these factors are regulated in RPE cells remain largely unknown. Here we show that the basic-helix-loop-helix-leucine zipper microphthalmia-associated transcription factor (MITF), which plays central roles in the development and function of a variety of cell types including RPE cells, upregulates the expression of a multifunctional factor PEDF in RPE cells. Consequently, the upregulation of PEDF impairs microtubule assembly and thus inhibits RPE cell migration. Conversely, specific knockdown of PEDF partially rescues the impairment of microtubule assembly and cell migration proceeds in MITF overexpressing stable cells. We conclude that MITF acts through PEDF to inhibit RPE cell migration and to play a significant role in regulating RPE cellular function. We suggest that MITF has a novel and important role in maintaining RPE cells as a stable monolayer and the down-regulation of PEDF that may contribute to retinal degenerative diseases.

Allele-specific genetic interactions between Mitf and Kit affect melanocyte development.

The tyrosine kinase receptor KIT and the transcription factor MITF, each required for melanocyte development, have been shown to interact functionally both in vitro and in vivo. In vitro, KIT signaling leads to MITF phosphorylation, affecting MITF activity and stability. In vivo, the presence of the Mitf (Mi-wh) allele exacerbates the spotting phenotype associated with heterozygosity for Kit mutations. Here, we show that among a series of other Mitf alleles, only the recessive Mitf (mi-bws) mimics the effect of Mitf (Mi-wh) on Kit. Intriguingly, Mitf (mi-bws) is characterized by a splice defect that leads to a reduction of RNAs containing MITF exon 2B which encodes serine-73, a serine phosphorylated upon KIT signaling. Nevertheless, other Mitf alleles that generally affect Mitf RNA levels, or carry a serine-73-to-alanine mutation that specifically reduces exon 2B-containing RNAs, do not show similar interactions with Kit in vivo. We conclude that the recessive Mitf (mi-bws) is a complex allele that can display a semi-dominant effect when present in a Kit-sensitized background. We suggest that human disease variability may equally be due to complex, allele-specific interactions between different genes.