Intervertebral disc human nucleus pulposus cells associated with back pain trigger neurite outgrowth in vitro and pain behaviors in rats.

Low back pain (LBP) is often associated with the degeneration of human intervertebral discs (IVDs). However, the pain-inducing mechanism in degenerating discs remains to be elucidated. Here, we identified a subtype of locally residing human nucleus pulposus cells (NPCs), generated by certain conditions in degenerating discs, that was associated with the onset of discogenic back pain. Single-cell transcriptomic analysis of human tissues showed a strong correlation between a specific cell subtype and the pain condition associated with the human degenerated disc, suggesting that they are pain-triggering. The application of IVD degeneration-associated exogenous stimuli to healthy NPCs in vitro recreated a pain-associated phenotype. These stimulated NPCs activated functional human iPSC-derived sensory neuron responses in an in vitro organ-chip model. Injection of stimulated NPCs into the healthy rat IVD induced local inflammatory responses and increased cold sensitivity and mechanical hypersensitivity. Our findings reveal a previously uncharacterized pain-inducing mechanism mediated by NPCs in degenerating IVDs. These findings could aid in the development of NPC-targeted therapeutic strategies for the clinically unmet need to attenuate discogenic LBP.

Single Cell Transcriptomics-Informed Induced Pluripotent Stem Cells Differentiation to Tenogenic Lineage.

During vertebrate embryogenesis, axial tendons develop from the paraxial mesoderm and differentiate through specific developmental stages to reach the syndetome stage. While the main roles of signaling pathways in the earlier stages of the differentiation have been well established, pathway nuances in syndetome specification from the sclerotome stage have yet to be explored. Here, we show stepwise differentiation of human iPSCs to the syndetome stage using chemically defined media and small molecules that were modified based on single cell RNA-sequencing and pathway analysis. We identified a significant population of branching off-target cells differentiating towards a neural phenotype overexpressing Wnt. Further transcriptomics post-addition of a WNT inhibitor at the somite stage and onwards revealed not only total removal of the neural off-target cells, but also increased syndetome induction efficiency. Fine-tuning tendon differentiation in vitro is essential to address the current challenges in developing a successful cell-based tendon therapy.

Predicting Best-Selling New Products in a Major Promotion Campaign Through Graph Convolutional Networks.

Many e-commerce platforms, such as AliExpress, run major promotion campaigns regularly. Before such a promotion, it is important to predict potential best sellers and their respective sales volumes so that the platform can arrange their supply chains and logistics accordingly. For items with a sufficiently long sales history, accurate sales forecast can be achieved through the traditional statistical forecasting techniques. Accurately predicting the sales volume of a new item, however, is rather challenging with existing methods; time series models tend to overfit due to the very limited historical sales records of the new item, whereas models that do not utilize historical information often fail to make accurate predictions, due to the lack of strong indicators of sales volume among the item's basic attributes. This article presents the solution deployed at Alibaba in 2019, which had been used in production to prepare for its annual "Double 11" promotion event whose total sales amount exceeded U.S. $ 38 billion in a single day. The main idea of the proposed solution is to predict the sales volume of each new item through its connections with older products with sufficiently long sales history. In other words, our solution considers the cross-selling effects between different products, which has been largely neglected in previous methods. Specifically, the proposed solution first constructs an item graph, in which each new item is connected to relevant older items. Then, a novel multitask graph convolutional neural network (GCN) is trained by a multiobjective optimization-based gradient surgery technique to predict the expected sales volumes of new items. The designs of both the item graph and the GCN exploit the fact that we only need to perform accurate sales forecasts for potential best-selling items in a major promotion, which helps reduce computational overhead. Extensive experiments on both proprietary AliExpress data and a public dataset demonstrate that the proposed solution achieves consistent performance gains compared to existing methods for sales forecast.

iPSC-neural crest derived cells embedded in 3D printable bio-ink promote cranial bone defect repair.

Cranial bone loss presents a major clinical challenge and new regenerative approaches to address craniofacial reconstruction are in great demand. Induced pluripotent stem cell (iPSC) differentiation is a powerful tool to generate mesenchymal stromal cells (MSCs). Prior research demonstrated the potential of bone marrow-derived MSCs (BM-MSCs) and iPSC-derived mesenchymal progenitor cells via the neural crest (NCC-MPCs) or mesodermal lineages (iMSCs) to be promising cell source for bone regeneration. Overexpression of human recombinant bone morphogenetic protein (BMP)6 efficiently stimulates bone formation. The study aimed to evaluate the potential of iPSC-derived cells via neural crest or mesoderm overexpressing BMP6 and embedded in 3D printable bio-ink to generate viable bone graft alternatives for cranial reconstruction. Cell viability, osteogenic potential of cells, and bio-ink (Ink-Bone or GelXa) combinations were investigated in vitro using bioluminescent imaging. The osteogenic potential of bio-ink-cell constructs were evaluated in osteogenic media or nucleofected with BMP6 using qRT-PCR and in vitro µCT. For in vivo testing, two 2 mm circular defects were created in the frontal and parietal bones of NOD/SCID mice and treated with Ink-Bone, Ink-Bone + BM-MSC-BMP6, Ink-Bone + iMSC-BMP6, Ink-Bone + iNCC-MPC-BMP6, or left untreated. For follow-up, µCT was performed at weeks 0, 4, and 8 weeks. At the time of sacrifice (week 8), histological and immunofluorescent analyses were performed. Both bio-inks supported cell survival and promoted osteogenic differentiation of iNCC-MPCs and BM-MSCs in vitro. At 4 weeks, cell viability of both BM-MSCs and iNCC-MPCs were increased in Ink-Bone compared to GelXA. The combination of Ink-Bone with iNCC-MPC-BMP6 resulted in an increased bone volume in the frontal bone compared to the other groups at 4 weeks post-surgery. At 8 weeks, both iNCC-MPC-BMP6 and iMSC-MSC-BMP6 resulted in an increased bone volume and partial bone bridging between the implant and host bone compared to the other groups. The results of this study show the potential of NCC-MPC-incorporated bio-ink to regenerate frontal cranial defects. Therefore, this bio-ink-cell combination should be further investigated for its therapeutic potential in large animal models with larger cranial defects, allowing for 3D printing of the cell-incorporated material.

Single-cell atlas unveils cellular heterogeneity and novel markers in human neonatal and adult intervertebral discs.

The origin, composition, distribution, and function of cells in the human intervertebral disc (IVD) have not been fully understood. Here, cell atlases of both human neonatal and adult IVDs have been generated and further assessed by gene ontology pathway enrichment, pseudo-time trajectory, histology, and immunofluorescence. Comparison of cell atlases revealed the presence of two subpopulations of notochordal cells (NCs) and their associated markers in both the neonatal and adult IVDs. Developmental trajectories predicted 7 different cell states that describe the developmental process from neonatal to adult cells in IVD and analyzed the NC's role in the IVD development. A high heterogeneity and gradual transition of annulus fibrosus cells (AFCs) in the neonatal IVD was detected and their potential relevance in IVD development assessed. Collectively, comparing single-cell atlases between neonatal and adult IVDs delineates the landscape of IVD cell biology and may help discover novel therapeutic targets for IVD degeneration.

Engineering Nano-to-Micron-Patterned Polymer Coatings on Bioresorbable Magnesium for Controlling Human Endothelial Cell Adhesion and Morphology.

Surface patterning is an attractive approach to modify the surface of biomaterials for modulating cell activities and enhancing the performance of medical implants without involving typical chemical changes to the implants such as adding growth factors, antibiotics, and drugs. In this study, nano-to-micron patterns were engineered on thermoplastic and thermoset polymer coatings on bioresorbable magnesium (Mg) substrates to control the cellular responses and material degradation for vascular applications. Capillary force lithography (CFL) was modified and integrated with spray coating to fabricate well-aligned nano-to-micron patterns on the thermoplastic poly(lactic-co-glycolic acid) (PLGA) and thermoset poly(glycerol sebacate) (PGS) coatings on Mg substrates. Specifically, a new process of molding-curing CFL was revised from the conventional CFL to successfully create nano-to-submicron patterns on thermoset PGS for the first time. The nano-to-micron-patterned polymer coatings of PLGA and PGS on Mg were carefully characterized, and their effects on cell adhesion and morphology were investigated through direct culture with human umbilical vein endothelial cells (HUVECs) in vitro. The results showed that the 3000 nm parallel grooves could effectively elongate the HUVECs, while the 740 nm parallel grooves tended to reduce the spreading of HUVECs. The PLGA coatings reduced the degradation of Mg substrates more than that of the PGS coatings in the direct culture with HUVECs in vitro. CFL-based methods coupled with spray coating should be further studied as a nonchemical approach for creating nano-to-micron-patterned polymer coatings on Mg-based substrates of various sizes and shapes, which may present a new direction for improving the performance of Mg-based bioresorbable vascular devices toward potential clinical translation.

Photo-assisted green synthesis of silver doped silk fibroin/carboxymethyl cellulose nanocomposite hydrogels for biomedical applications.

Silver nanoparticles (AgNPs) and regenerated silk fibroin (RSF) have recently attracted significant interests for their potential applications in preventing wound-related infections and in tissue engineering. Indeed, nano-silver has long been recognized as one of the most effective antimicrobial agents, and silk fibroin is well known for its capability of stimulating cell activities and facilitating tissue regeneration. In this study, a green synthesis approach was used to create a composite hydrogel (CoHy) of RSF stabilized with CarboxymethylCellulose-Na (CMC-Na) and loaded with AgNPs. Their swelling ratios were up to 59 g/g when tested in different physiologically relevant fluids. Material characterizations by Scanning electron microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), and X-Ray Diffraction (XRD) confirmed the presence of AgNPs on the surface. Antimicrobial properties of the CoHy samples were evaluated using agar diffusion tests. The results showed distinct inhibition zones against major microorganisms found in wound infections, including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis), Methicillin Resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa (P. aeruginosa), Candida albicans (C. albicans) and Fluconazole-resistant Candida albicans (FRCA). Cytocompatibility studies with rat bone marrow derived mesenchymal stem cells (BMSCs) in vitro showed that the adhesion density of BMScs on the CoHy loaded with 1 mg/mL was similar to the cell-only control group for the first 24 h of culture; moreover, higher cell proliferation was observed on the CoHy without AgNPs, indicating the regenerative potentials of the RSF/CMC composite hydrogels.

A portable device for studying the effects of fluid flow on degradation properties of biomaterials inside cell incubators.

A portable device was designed and constructed for studying the properties of biomaterials in physiologically relevant fluids under controllable flow conditions that closely simulate fluid flow inside the body. The device can fit entirely inside a cell incubator; and, thus, it can be used directly under standard cell culture conditions. An impedance-driven pump was built in the sterile flow loop to control the flow rates of fluids, which made the device small and portable for easy deployment in the incubator. To demonstrate the device functions, magnesium (Mg) as a representative biodegradable material was tested in the flow device for immersion degradation under flow versus static conditions, while the flow module was placed inside a standard cell incubator. The flow rate was controlled at 0.17 ± 0.06 ml/s for this study; and, the flow rate is adjustable through the controller module outside of incubators for simulating the flow rates in the ranges of blood flow in human artery (0.05 ∼0.43 ml/s) and vein (0.02 ∼0.08 ml/s). Degradation of Mg under flow versus static conditions was characterized by measuring the changes of sample mass and thickness, and Mg2+ ion concentrations in the immersion media. Surface chemistry and morphology of Mg after immersion under flow versus static conditions were compared. The portable impedance-driven flow device is easy to fit inside an incubator and much smaller than a peristaltic pump, providing a valuable solution for studying biomaterials and implants (e.g. vascular or ureteral stents) in body fluids under flow versus static conditions with or without cells.

In vitro evaluation of MgSr and MgCaSr alloys via direct culture with bone marrow derived mesenchymal stem cells.

Magnesium (Mg) and its alloys have been widely investigated as the most promising biodegradable metals to replace conventional non-degradable metals for temporary medical implant applications. New Mg alloys have been developed for medical applications in recent years; and the concept of alloying Mg with less-toxic elements have aroused tremendous interests due to the promise to address the problems associated with rapid degradation of Mg without compromising its cytocompatibility and biocompatibility. Of particular interests for orthopedic/spinal implant applications are the additions of calcium (Ca) and strontium (Sr) into Mg matrix because of their beneficial properties for bone regeneration. In this study, degradation and cytocompatibility of four binary MgSr alloys (Mg-xSr, x = 0.2, 0.5, 1 and 2 wt%) and four ternary MgCaSr alloys (Mg-1Ca-xSr, x = 0.2, 0.5, 1 and 2 wt%) were investigated and compared via direct culture with bone marrow-derived mesenchymal stem cells (BMSCs). The influence of the alloy composition on the degradation rates were studied and compared. Moreover, the cellular responses to the binary MgSr alloys and the ternary MgCaSr alloys were comparatively evaluated; and the critical factors influencing BMSC behaviors were discussed. This study screened the degradability and in vitro cytocompatibility of the binary MgSr alloys and the ternary MgCaSr alloys. Mg-1Sr, Mg-1Ca-0.5Sr and Mg-1Ca-1Sr alloys are recommended for further in vivo studies toward clinical translation due to their best overall performances in terms of degradation and cytocompatibility among all the alloys studied in the present work. STATEMENT OF SIGNIFICANCE: Traditional Mg alloys with slower degradation often contain aluminum or rare earth elements as alloying components, which raised safety and regulatory concerns. To circumvent unsafe elements, nutrient elements such as calcium (Ca) and strontium (Sr) were selected to create Mg-Sr binary alloys and Mg-Ca-Sr ternary alloys to improve the safety and biocompatibility of bioresorbable Mg alloys for medical implant applications. In this study, in vitro degradation and cellular responses to four binary Mg-xSr alloys and four ternary Mg-1Ca-xSr alloys with increasing Sr content (up to 2 wt%) were evaluated in direct culture with bone marrow derived mesenchymal stem cells (BMSCs). The roles of Sr and Ca in tuning the alloy microstructure, degradation behaviors, and BMSC responses were collectively compared in the BMSC direct culture system for the first time. The most promising alloys were identified and recommended for further in vivo studies toward clinical translation.

Electrochemical deposition of conductive polymers onto magnesium microwires for neural electrode applications.

Metals are widely used in electrode design for recording neural activities because of their excellent electrical conductivity and mechanical strength. However, there are still serious problems related to these currently used metallic electrodes, including tissue damage due to the mechanical mismatch between metals and neural tissues, fibrosis, and electrode fouling and encapsulation that lead to the loss of signal and eventual failure. In this study, a biocompatible, biodegradable, and conductive electrode was created. Specifically, pure magnesium (Mg) microwire with a diameter of 127 µm was used as the electrode substrate and the conductive polymer, that is, poly(3,4-ethylenedioxythiophene) (PEDOT), was electrochemically deposited onto Mg microwires to decrease corrosion rate and improve biocompatibility of the electrodes for potential neural electrode applications. Both chronopotentiometry and cyclic voltammetry (CV) methods and the associated parameters for electrochemical deposition of PEDOT onto Mg microwires were investigated, such as deposition current, deposition temperature, voltage, sweep rate, cycle number, and duration. The CV method from -2.0 to 1.25 V for 1 cycle at a cycle duration of 600 s with a sweep rate of 5 mV/s at 65°C led to a consistent, uniform, and complete PEDOT coating on Mg microwires. The surface conditions of Mg microwires also affected the quality of PEDOT coating. The corrosion rate of PEDOT-coated Mg microwire was 0.75 mm/year, much slower than the noncoated Mg microwire that showed a corrosion rate of 1.78 mm/year. The optimal Mg microwires with PEDOT coating could potentially serve as biodegradable electrodes for neural recording and stimulation applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1887-1895, 2018.

The Effects of Serum Proteins on Magnesium Alloy Degradation in Vitro.

Magnesium (Mg) alloys are promising materials for biodegradable implants, but their clinical translation requires improved control over their degradation rates. Proteins may be a major contributing factor to Mg alloy degradation, but are not yet fully understood. This article reports the effects of fetal bovine serum (FBS), a physiologically relevant mixture of proteins, on Mg and Mg alloy degradation. FBS had little impact on mass loss of pure Mg during immersion degradation, regardless of whether or not a native oxide layer was present on the sample surface. FBS reduced the mass loss of Mg-Yttrium (MgY) alloy with an oxidized surface during immersion degradation, but increased the mass loss for the same alloy with a metallic surface (surface oxides were removed). FBS also influenced the mode of degradation by limiting the depth of pit formation during degradation processes on commercially pure Mg with metallic or oxidized surfaces and on MgY alloy with oxidized surfaces. The results demonstrated that serum proteins had significant interactions with Mg-based biodegradable metals, and these interactions may be modified by alloy composition and processing. Therefore, proteins should be taken into account when designing experiments to assess degradation of Mg-based implants.

Comparison Study on Four Biodegradable Polymer Coatings for Controlling Magnesium Degradation and Human Endothelial Cell Adhesion and Spreading.

Magnesium (Mg)-based bioresorbable cardiovascular scaffold (BCS) is a promising alternative to conventional permanent cardiovascular stents, but it faces the challenges of rapid degradation and poor endothelium recovery after device degradation. To address these challenges, we investigated poly(l-lactic acid) (PLLA), poly(lactic-co-glycolic acid) (PLGA) (90:10), PLGA (50:50), and polycaprolactone (PCL) coatings on Mg, respectively, and evaluated their surface and biological properties. Intact polymer coatings with complete coverage on Mg substrate were achieved. The biological performance of the materials was evaluated by culturing with human umbilical vein endothelial cells (HUVECs) in vitro using the direct culture method. The pH of the culture media and Mg2+ and Ca2+ ion concentrations in the media were measured after culture to characterize the degradation rate of the materials in vitro. The results showed that the PLGA (50:50) coating improved the adhesion and spreading of HUVECs the most among the four polymer coatings. Moreover, we found three possible factors that promoted HUVECs directly attached on the surface of PLGA (50:50)-coated Mg: (1) the higher concentration of Mg2+ ions released into culture media with a concentration range of 9-15 mM; (2) the lower Ca2+ ion concentration in culture media at 1.3-1.6 mM; and (3) the favorable surface conditions of PLGA (50:50), when compared with the other sample groups. This in vitro study provided the first evidence that the PLGA (50:50) is a promising coating material for Mg-based biodegradable metals toward potential cardiovascular or neurovascular applications.

Nanomaterials for treating cardiovascular diseases: A review.

Nanomaterials such as nanostructured surfaces, nanoparticles, and nanocomposites represent new viable sources for future therapeutics for cardiovascular diseases. The special properties of nanomaterials such as their intrinsic physiochemical properties, surface energy and surface topographies could actively enhance desirable cellular responses within the cardiovascular system, projecting a growing potential for clinical translation. Recent progress on nanomaterials opened up new opportunities for treating cardiovascular diseases. Successful translation of nanomaterials into cardiovascular applications requires a comprehensive understanding of both nanomaterials and biomedicine, and, thus, it is critical to stress current advancements on both sides. In this review, the authors introduced crucial fabrication techniques for promising nanomaterials for cardiovascular applications. This review highlighted the key elements to consider for their fabrication, properties and applications. The important concerns relevant to cardiovascular nanomaterials, such as cellular responses to nanomaterials and the toxicity of nanomaterials, are also discussed. This review provided an overview of necessary knowledge and key concerns on nanomaterials specific for treating cardiovascular diseases, from the perspectives of both material science and biomedicine.