Periodontal ligament stem cells (PDLSCs), a new population of mesenchymal stem cells (MSCs), have been isolated from the periodontal ligament (PDL). The capacity of multipotency and self-renewal makes them an excellent cell source for bone regeneration and repair. However, their bone-regeneration ability could be awakened in inflammatory microenvironments, which may be the result of changes in their differentiation potential. Recently, genetic evidences has shown that the Wnt pathway plays an important role in bone homeostasis. In this study we have determined the specific role of b-catenin in osteogenic differentiation of PDLSCs obtained from inflammatory microenvironments (P-PDLSCs). The inflammatory microenvironment, while inhibiting osteogenic differentiation potential, promotes proliferation of MSCs. A higher the level of b-catenin in P-PDLSCs than in H-PDLSCs (PDLSCs obtained from a healthy microenvironment) resulted in the same disparity in canonical Wnt signaling pathway activation between each cell type. Here we show that activation of bcatenin suppresses the noncanonical Wnt/Ca 2þ pathway, leading to increased proliferation but reduced osteogenic differentiation of PPDLSCs. Downregulation of the levels of b-catenin by treatment with dickkopf-1 (DKK-1) leads to activation of the noncanonical Wnt/ Ca 2þ pathway, which, in turn, results in the promotion of osteogenic differentiation in P-PDLSCs. Interestingly, b-catenin can affect both the canonical Wnt/b-catenin pathway and the noncanonical Wnt/Ca 2þ pathway. Our data indicate that b-catenin plays a central role in regulating osteogenic differentiation of MSCs in inflammatory microenvironments. Given the important role of Wnt signaling in osteogenic differentiation, it is possible that agents that can modify this pathway may be of value in bone regeneration by MSCs in chronic inflammatory microenvironments. ß

Bioink optimization is considered as one of main challenges in cell-laden 3D bioprinting. Alginate-Gelatin (Alg-Gel) hydrogel have been extensively used as bioink. However, its properties could be influenced by various parameters, and little is known about the evidence featuring the impact of solvent. Here we investigated four Alg-Gel bioink by varying solvent ionic strength (named B-1, B-2, B-3 and B-4). Mechanical properties and printability of bioink samples and their impacts on behaviors of encapsulated epidermal stem cells (ESCs) were tested. Bioink with increased ionic strength of solvent showed decreased stiffness and viscosity, and increased swelling and degradation by printability and mechanical property tests. Due to the increased swelling and degradation was associated with shape-maintenance of post-printing constructs, B-3 and B-4 were hardly observable after 14 days. Cellular behaviors were assessed through viability, proliferation, aggregation and differentiation tests. B-2 with optimal properties resulted in higher viability and proliferation of ESCs, and further facilitated cellular aggregation and lineage differentiation. We demonstrated that the solvent can be tuned by ionic strength to control the properties of Alg-Gel bioink and post-printing constructs, which represented a promising avenue for promotion of therapeutic stem cell behaviors in 3D bioprinting.

No abstract

The cutaneous wound-healing process can lead to hypertrophic scar formation, during which exaggerated inflammation has been demonstrated to have an important role. Therefore, an exploration of strategies designed to regulate this inflammatory process is warranted. Mesenchymal stem cells (MSCs) have recently been demonstrated to regulate inflammation in various diseases. In this regard, using a rabbit model, we locally injected human mesenchymal stem cells (hMSCs) derived from bone marrow to treat hypertrophic scar formation, and explored their underlying mechanisms. We found that hMSC therapy efficiently regulated inflammation and prevented scar formation. We attributed the therapeutic effects of hMSCs to their secretion of an anti-inflammatory protein, TNF-alpha-stimulated gene/protein 6 (TSG-6). Unexpectedly, after injection, the number of surviving hMSCs decreased markedly and the hMSCs underwent extensive apoptosis, which was demonstrated to promote their secretion of TSG-6, partially through the activation of caspase-3. Moreover, H2O2-induced apoptotic hMSCs showed higher inflammatory regulatory abilities. The inhibition of caspase-3 decreased the inflammatory regulatory abilities of hMSCs and attenuated their therapeutic effects. Our results demonstrate that hMSCs can efficiently prevent hypertrophic scar formation via inflammatory regulation. In addition, we found that apoptosis has an important role in the activation of the inflammatory regulatory abilities of hMSCs.

Simulation for the smooth muscle layer of blood vessel plays a key role in tubular tissue engineering. However, fabrication of biocompatible tube with defined inner nano/micro-structure remains a challenge. Here, we show that a biocompatible polymer tube from poly(l-lactide) (PLLA) and polydimethylsiloxane (PDMS) can be prepared by using electrospinning technique, with assistance of rotating collector and parallel auxiliary electrode. The tube has circumferentially aligned PLLA fibers in the inner surface for cell growth regulation and has a PDMS coating for better compressive property. MTT assay showed the composite PLLA/PDMS tube was suitable for various cells growth. In vitro smooth muscle cells (SMCs) cultured in the tube showed that the aligned PLLA fibers could induce SMCs' orientation, and different expression of α-SMA and OPN genes were observed on the aligned and random PLLA fibers, respectively. The successful fabrication of composite PLLA/PDMS tubular scaffold for regulating smooth muscle cells outgrowth has important implications for tissue-engineered blood vessels.

Positively-charged surfaces on implants have a similar potential to upregulate osteogenesis of bone marrow-derived mesenchymal stem cells (BMSCs) as electromagnetic therapy approved for bone regeneration. Generally, their osteogenesis functions are generally considered to stem from the charge-induced adhesion of extracellular matrix (ECM) proteins without exploring the underlying surface charge/cell signaling molecule pathways. Herein, a positively-charged surface with controllable tertiary amines is produced on a polymer implant by plasma surface modification. In addition to inhibiting the TNF-α expression, the positively-charged surface with tertiary amines exhibits excellent cytocompatibility as well as remarkably upregulated osteogenesis-related gene/protein expressions and calcification of the contacted BMSCs. Stimulated by the charged surface, these BMSCs display high iNOS expressions among the three NOS isoforms. Meanwhile, downregulation of the iNOS by L-Can or siRNA inhibit osteogenic differentiation in the BMSCs. These findings suggest that a positively-charged surface with tertiary amines induces osteogenesis of BMSCs via the surface charge/iNOS signaling pathway in addition to elevated ECM protein adhesion. Therefore, creating a positively-charged surface with tertiary amines is a promising approach to promote osseointegration with bone tissues.

Multifunctionalization is an important development direction of electromagnetic interference (EMI)-shielding materials. However, it is still a huge challenge to effectively integrate multiple functions into materials. Herein, we reported a facile method to fabricate multifunctional EMI-shielding materials, which were assembled with multidimensional components consisting of a 3D melamine–formaldehyde (MF) foam skeleton, 0D ferroferric oxide (Fe3O4) nanoparticles, and 1D silver nanowires (AgNWs) via coprecipitation and dip-coating processes. Due to the coaction of conductive AgNWs and magnetic Fe3O4 nanoparticles, the resultant hybrid foam showed excellent absorption-dominant EMI-shielding performances with a high specific EMI-shielding effectiveness value of 12,704 dB cm2 g–1. Moreover, thanks to the multilayer porous micro-/nanostructure and the nonflammability of functional coatings, the hybrid foam shows excellent flame retardancy and heat insulation, making it attractive for the functions of infrared stealth and heat insulation. The corresponding mechanism is discussed in detail. Combined with the advantages of high thermal insulation, flame retardancy, elasticity, and excellent absorption-dominant EMI-shielding performances, the hybrid foam showed great applications in the fields of both military and civilian. This work provides new inspiration and insights for the design of multifunctional high-performance EMI-absorbing materials.

Diabetes mellitus involves metabolic changes that can impair bone repair. Bone mesenchymal stem cells (BMSCs) play an important role in bone regeneration. However, the bone regeneration ability of BMSCs is inhibited in high glucose microenvironments. It can be speculated that this effect is due to changes in BMSCs' proliferation and migration ability, because the recruitment of factors with an adequate number of MSCs and the microenvironment around the site of bone injury are required for effective bone repair. Recent genetic evidence has shown that the Cyclin D1 and the CXC receptor 4 (CXCR-4) play important roles in the proliferation and migration of BMSCs. In this study we determined the specific role of glycogen synthase kinase-3β (GSK3β) in the proliferation and migration of BMSCs in high glucose microenvironments. The proliferation and migration ability of BMSCs were suppressed under high glucose conditions. We showed that high glucose activates GSK3β but suppresses CXCR-4, β-catenin, LEF-1, and cyclin D1. Inhibition of GSK3β by LiCl led to increased levels of β-catenin, LEF-1, cyclin D1, and CXCR-4 expression. Our data indicate that GSK3β plays an important role in regulating the proliferation and migration of BMSCs by inhibiting cyclin D1 and CXCR-4 under high glucose conditions.