Benidipine-loaded nanoflower-likemagnesium silicate improves bone regeneration

Regeneration and reconstruction of bone tissue is always a challenge for clinicians due to the uncertainty of bone repair materials in terms of long-term and efficient effects on osteoblasts.Here,we propose a novel strategy combining benidipine,an antihypertensive drug and nanoparticles to synergistically promote the healing of bone defects.Loose and porous benidipine-loaded magnesium silicate nanoparticles were prepared and validated for their biosafety.The nanoparticles were efficiently taken up by preosteoblasts and uniformly distributed around the nucleus.After internalization into cells,the nanosystem is degraded by lysosomes,and the effect of promoting osteogenic differentiation is reflected by the continuous release of benidipine,silicon and magnesium ions.Our results clearly evaluated that the nanoflower-like magnesium silicate delivering benidipine tends to be more appropriate for the bone regeneration in preosteoblasts,indicating that it might be a potential approach in guiding bone repair in clinical applications.

Recent advances in bone regeneration using adult stem cells

Bone is a highly vascularized tissue reliant on the close spatial and temporal association between bloodvessels and bone cells. Therefore, cells that participate in vasculogenesis and osteogenesis play a pivotal role in bone formation during prenatal and postnatal periods. Nevertheless, spontaneous healing of bone fracture is occasionally impaired due to insufficient blood and cellular supply to the site of injury. In these cases, bone regeneration process is interrupted, which might result in delayed union or even nonunion of the fracture. Nonunion fracture is difficult to treat and have a high financial impact. In the last decade, numerous technological advancements in bone tissue engineering and cell-therapy opened new horizon in the field of bone regeneration. This review starts with presentation of the biological processes involved in bone development, bone remodeling, fracture healing process and the microenvironment at bone healing sites. Then, we discuss the rationale for using adult stem cells and listed the characteristics of the available cells for bone regeneration. The mechanism of action and epigenetic regulations for osteogenic differentiation are also described. Finally, we review the literature for translational and clinical trials that investigated the use of adult stem cells(mesenchymal stem cells, endothelial progenitor cells and CD34+ blood progenitors) for bone regeneration.

Dynamic culture of a thermosensitive collagen hydrogel as an extracellular matrix improves the construction of tissue-engineered peripheral nerve

Tissue engineering technologies offer new treatment strategies for the repair of peripheral nerve injury, hut cell loss between seeding and adhesion to the scaffold remains inevitable. A thermosensitive collagen hydrogel was used as an extracellular matrix in this study and combined with bone marrow mesenchymal stem cells to construct tissue-engineered peripheral nerve composites in vitro. Dynamic culture was performed at an oscillating frequency of 0.5 Hz and 35° swing angle above and below the horizontal plane. The results demonstrated that bone marrow mesenchymal stem cells formed membrane-like structures around the poly-L-lactic acid scaffolds and exhibited regular alignment on the composite surface. Collagen was used to fill in the pores, and seeded cells adhered onto the poly-L-lactic acid fibers. The DNA content of the bone marrow mesenchymal stem cells was higher in the composites constructed with a thermosensitive collagen hydrogel compared with that in collagen I scaffold controls. The cellular DNA content was also higher in the thermosensitive collagen hydrogel composites constructed with the thermosensitive collagen hydrogel in dynamic culture than that in static culture. These results indicate that tissue-engineered composites formed with thermosensitive collagen hydrogel in dynamic culture can maintain larger numbers of seeded cells by avoiding cell loss during the initial adhe-sion stage. Moreover, seeded cells were distributed throughout the material.

Vital roles of stem cells and biomaterials in skin tissue engineering

Tissue engineering essentially refers to technology for growing new human tissue and is distinct from regenerative medicine. Currently, pieces of skin are already being fabricated for clinical use and many other tissue types may be fabricated in the future.Tissue engineering was first defined in 1987 by the United States National Science Foundation which critically discussed the future targets of bioengineering research and its consequences. The principles of tissue engineering are to initiate cell cultures in vitro, grow them on scaffolds in situ and transplant the composite into a recipient in vivo. From the beginning, scaffolds have been necessary in tissue engineering applications. Regardless, the latest technology has redirected established approaches by omitting scaffolds. Currently, scientists from diverse research institutes are engineering skin without scaffolds. Due to their advantageous properties, stem cells have robustly transformed the tissue engineering field as part of an engineered bilayered skin substitute that will later be discussed in detail. Additionally, utilizing biomaterials or skin replacement products in skin tissue engineering as strategy to successfully direct cell proliferation and differentiation as well as to optimize the safety of handling during grafting is beneficial. This approach has also led to the cells' application in developing the novel skin substitute that will be briefly explained in this review.

Perinatal stem cells: A promising cell resource for tissue engineering of craniofacial bone

In facing the mounting clinical challenge and suboptimal techniques of craniofacial bone defects resulting from various conditions, such as congenital malformations, osteomyelitis, trauma and tumor resection, the ongoing research of regenerative medicine using stem cells and concurrent advancement in biotechnology have shifted the focus from surgical reconstruction to a novel stem cell-based tissue engineering strategy for customized and functional craniofacial bone regeneration. Given the unique ontogenetical and cell biological properties of perinatal stem cells, emerging evidence has suggested these extraembryonic tissue-derived stem cells to be a promising cell source for extensive use in regenerative medicine and tissue engineering. In this review, we summarize the current achievements and obstacles in stem cell-based craniofacial bone regeneration and subsequently we address the characteristics of various types of perinatal stem cells and their novel application in tissue engineering of craniofacial bone. We propose the promising feasibility and scope of perinatal stem cell-based craniofacial bone tissue engineering for future clinical application.

Fabrication of a Bi-layer Tubular Scaffold Consisted of a Dense Nanofibrous Inner Layer and a Porous Nanoyarn Outer Layer for Vascular Tissue Engineering

Recent years, it has attracted more attentions to increase the porosity and pore size of nanofibrous scaffolds to provide the for the cells to grow into the small-diameter vascular grafts. In this study, a novel bi-layer tubular scaffold with an inner layer and an outer layer was fabricated. The inner layer was random collagen/poly （ L-lactide-co-caprolactone ） I P （ LLA- CL） ] nanofibrous mat fabricated by conventional electrospinning and the outer layer was aligned collagen/P （LLA-CL） nanoyarns prepared by a dynamic liquid dectrospinning method. Fourier transform infrared spectroscopy （FTIR） was used to characterize the chemical structure. Scanning electron microscopy （ SEM ） was employed to observe the morphology of the layers and the cross- sectioned bi-layer tubular scaffold. A liquid displacement method was employed to measure the porosities of the inner and outer layers. Stress-strain curves were obtained to evaluate the mechanical properties of the two different layers and the bi-layer membrane. The diameters of the nanofibers and the nanoyarns were （480 ± 197 ） nm and （ 19.66 ± 4.05 ） μm, respectively. The outer layer had a significantly higher porosity and a larger pore size than those of the inner layer. Furthermore, the bi-layer membrane showed a good mechanical property which was suitable as small-diameter vascular graft. The results indicated that the bi-layer tubular scaffold had a great potential application in small vascular tissue engineering.

Characterization of decellularized scaffold derived from porcine meniscus for tissue engineering applications

Menisci are fundamental fibrocartilaginous organs in knee joints. The injury in meniscus can impair normal knee function and predisposes patients to osteoarthritis. This study prepared decellularized meniscus scaffolds using a 1% （w/w） sodium dodecyl sulfate solution and sufficient rinsing steps. Complete cell removal was verified by hematoxylin and eosin staining and DNA content assay. Decellularized menisci had accordant tension properties to intact ones, but with declined compression properties. This occurred because the collagen fiber was not damaged but glycosami- noglycans was significantly lost during the decellularization process, which was confirmed by biochemical assay and histology staining. In vitro cytotoxicity assay demonstrated that decellularized meniscus scaffolds have no toxicity on L929 murine fibroblasts and porcine chondrocytes. Further experiment showed that porcine chondrocytes could adhere and proliferate on the scaffold surface, and some cells even could infiltrate into the scaffold. All results showed the potential of this decellularized meniscus to be the scaffolds in tissue engineering.

Novel crosslinked alginate/hyaluronic acid hydrogels for nerve tissue engineering

CT： Artificial tissue engineering scaffods can potentially provide supportand guidance for the regrowth of severed axons following nerve injury. In this study a hybrid biomaterial composed of alginate and hyaluronic acid （HA） was synthesized characterized in terms of its suitability for covalent modification, biocompatibility fir living Schwann cells and feasibility to construct three dimensional （3D） Carbodiimide mediated amide formation for the purpose of covalent crosslinking of the HA was carried out in the presence of calcium ions that ionically crosslink alginate.Amide formation was found to be dependent on the concentrations of cabodiimide and calclum chloride. The double-crosslinked composite hydrogels display blocompatibllity that is comparable to simple HA hydrogels, allowing for Schwann cell survival and significant difference was found between composite hydrogels made from different of alginate and HA. A 3D BioPIotterTM rapid prototyping system was used to fabricats 3D scaffolds. The result indicated that combining HA with alginate facilitated the fabrication process and that 3D scaffolds with porous inner structure can be fabricated ;from the composite hydrogels, but not from HA alone. This information provides a basis for continuing in vitro and in vivo tests of the suitability of alginate/HA hydrogel as a biomaterial to create living cell scaffolds to support nerve regeneration.

Novel pre-vascularized tissue-engineered dermis based on stem cell sheet technique used for dermis-defect healing

Insufficient donor dermis and the shortage of three-dimensional vascular networks are the main limitations in the tissue-engineered dermis(TED).To solve these problems,we initially constructed pre-vascularized bone marrow mesenchymal stem cell sheet(PBMCS)and pre-vascularized fibroblasts cell sheet(PFCS)by cell sheet technology,and then superimposed or folded them together to construct a pre-vascularized TED(PTED),aiming to mimic the real dermis structure.The constructed PTED was implanted in nude mice dorsal dermis-defect wound and the wound-healing effect was quantified at Days 1,7 and 14 via the methods of histochemistry and immunohistochemistry.The results showed that PTED could rapidly promote the wound closure,especially at Day 14,and the wound-healing rate of three-layer PTED could reach 97.2%(P<0.01),which was faster than the blank control group(89.1%),PBMCS(92.4%),PFCS(93.8%)and six-layer PTED(92.3%).In addition,the vessel density in the PTED group was higher than the other groups on the 14th day.Taken together,it is proved that the PTED,especially three-layer PTED,is more conducive to the fullthickness dermis-defect repair and the construction of the three-dimensional vascular networks,indicating its potential application in dermis-defect repair.