Understanding the multi-functionality and tissue-specificity of decellularized dental pulp matrix hydrogels for endodontic regeneration

Dental pulp is the only soft tissue in the tooth which plays a crucial role in maintaining intrinsic multi-functional behaviors of the dentin-pulp complex. Nevertheless, the restoration of fully functional pulps after pulpitis or pulp necrosis, termed endodontic regeneration, remained a major challenge for decades. Therefore, a bioactive and in-situ injectable biomaterial is highly desired for tissue-engineered pulp regeneration. Herein, a decellularized matrix hydrogel derived from porcine dental pulps (pDDPM-G) was prepared and characterized through systematic comparison against the porcine decellularized nerve matrix hydrogel (pDNM-G). The pDDPM-G not only exhibited superior capabilities in facilitating multi-directional differentiation of dental pulp stem cells (DPSCs) during 3D culture, but also promoted regeneration of pulp-like tissues after DPSCs encapsulation and transplantation. Further comparative proteomic and transcriptome analyses revealed the differential compositions and potential mechanisms that endow the pDDPM-G with highly tissue-specific properties. Finally, it was realized that the abundant tenascin C (TNC) in pDDPM served as key factor responsible for the activation of Notch signaling cascades and promoted DPSCs odontoblastic differentiation. Overall, it is believed that pDDPM-G is a sort of multi-functional and tissue-specific hydrogel-based material that holds great promise in endodontic regeneration and clinical translation. STATEMENT OF SIGNIFICANCE: Functional hydrogel-based biomaterials are highly desirable for endodontic regeneration treatments. Decellularized extracellular matrix (dECM) preserves most extracellular matrix components of its native tissue, exhibiting unique advantages in promoting tissue regeneration and functional restoration. In this study, we prepared a porcine dental pulp-derived dECM hydrogel (pDDPM-G), which exhibited superior performance in promoting odontogenesis, angiogenesis, and neurogenesis of the regenerating pulp-like tissue, further showed its tissue-specificity compared to the peripheral nerve-derived dECM hydrogel. In-depth proteomic and transcriptomic analyses revealed that the activation of tenascin C-Notch axis played an important role in facilitating odontogenic regeneration. This biomaterial-based study validated the great potential of the dental pulp-specific pDDPM-G for clinical applications, and provides a springboard for research strategies in ECM-related regenerative medicine.

[Enhancing survival outcomes in stage Ⅲ gastric/esophagogastric junction cancer: a retrospective study of immune checkpoint inhibitors and adjuvant chemotherapy based on real-world data]

Objective: To explore the efficacy of immune checkpoint inhibitors combined with adjuvant chemotherapy in patients with phase III gastric cancer and esophagogastric junction cancer. Methods: This study used a retrospective cohort study method based on real-world data. Clinical data of 403 patients with stage III gastric/esophagogastric junction cancer who underwent gastrectomy followed by adjuvant therapy in the Department of Gastric Surgery at Sun Yat-sen University Cancer Center from January 2020 to December 2023 were retrospectively collected. The study cohort comprised 147 (36.5%) patients with stage IIIA, 130 (32.3%) with stage IIIB, and 126 (31.3%) with stage IIIC gastric/esophagogastric junction cancer. Of them, 15 (3.7%) were HER-2 positive, 25 (6.2%) dMMR, and 22 (5.5%) patients Epstein-Barr virus encoding RNA (EBER) positive. Based on treatment plans, the patients were divided into immune checkpoint inhibitor combined with chemotherapy group (immune therapy group, n=110, 71 males and 39 females, median age 59 years old) and chemotherapy alone group (chemotherapy group, n=293, 186 males and 107 females, median age 60 years old). All patients in the immunotherapy group received immune checkpoint inhibitors targeting the programmed cell death protein-1 (PD-1) and its ligand (PD-L1). Of them, 85 received pembrolizumab, 10 received sintilimab, 8 received tislelizumab, 4 received camrelizumab, 2 received toripalimab, and 1 received pabocizumab. The adjuvant chemotherapy regimens used among the chemotherapy alone group includes SOX regimen (132 cases), XELOX (102 cases), S-1 monotherapy (44 cases), and other regimens (15 cases). The 3-year DFS rate of the two groups was compared, and subgroup analysis was conducted based on different ages, molecular phenotypes, pTNM staging, extranodal infiltration, and tumor length. Results: The median follow-up was 20.5 months (range 3.1~46.3), with a 3-year overall DFS rate of 61.4% for the entire 403 patients. The 3-year DFS rate for the immunotherapy group was 82.7%, higher than the chemotherapy alone group (58.8%), with a statistically significant difference (P=0.021). Multivariate analysis showed that postoperative immunotherapy was a protective factor for DFS (HR=0.352, 95%CI: 0.180~0.685). Subgroup analysis showed that stage IIIC (HR=0.416, 95%CI: 0.184~0.940), aged ≥60 years (HR=0.336, 95%CI: 0.121~0.934) and extranodal invasion (HR=0.378, 95%CI: 0.170~0.839) were associated with benefit from the combined immune adjuvant chemotherapy, while no association was observed for MMR, HER-2 or EBER status. Conclusion: Stage III gastric/esophagogastric junction cancer patients may benefite from postoperative immune checkpoint inhibitor combined with adjuvant chemotherapy in real-world settings.

Enzymatically Bioactive Nucleus Pulposus Matrix Hydrogel Microspheres for Exogenous Stem Cells Therapy and Endogenous Repair Strategy to Achieve Disc Regeneration

Exogenous stem cell therapy and endogenous repair has shown great potential in intervertebral disc regeneration. However, limited nutrients and accumulation of lactate largely impair the survival and regenerative capacity of implanted stem cells and endogenous nucleus pulposus cells (NPCs). Herein, an injectable hydrogel microsphere (LMGDNPs) have been developed by immersing lactate oxidase (LOX)-manganese dioxide (MnO2 ) nanozyme (LM) into glucose-enriched decellularized nucleus pulposus hydrogel microspheres (GDNPs) through a microfluidic system. LMGDNPs showed a delayed release profile of LOX and satisfactory enzymatic capacity in consuming lactate. Mesenchymal stem cells (MSCs) plated on LMGDNPs exhibited better cell viability than cells on GelMA and decellularized nucleus pulposus microspheres (DNP) and showed a obviously increased NPCs phenotype. LMGDNPs prevented MSCs and NPCs death and promoted extracellular matrix synthesis by exhausting lactate. It is determined that LMGDNPs promoted NPCs autophagy by activating transforming growth factor β2 overlapping transcript 1 (TGFB2-OT1), relying on the nanozyme. MSCs-loaded LMGDNPs largely preserved disc hydration and alleviated matrix degradation in vivo. Summarily, LMGDNPs promoted cell survival and matrix regeneration by providing a nutrient supply, exhausting lactate, and activating autophagy via TGFB2-OT1 and its downstream pathway and may serve as an ideal delivery system for exogenous stem cell therapy and endogenous repair.

Multifunctional annulus fibrosus matrix prevents disc-related pain via inhibiting neuroinflammation and sensitization

Chronic low back pain mainly attributed to intervertebral disc (IVD) degeneration. Endogenous damage-associated molecular patterns (DAMPs) in the injured IVD, particularly mitochondria-derived nucleic acid molecules (CpG DNA), play a primary role in the inflammatory responses in macrophages. M1-type macrophages form a chronic inflammatory microenvironment by releasing pro-inflammatory factors and nerve growth factor (NGF) that induce nerve growth into the inner annulus fibrosus, resulting in persistent hyperalgesia. We fabricated an amphiphilic polycarbonate that naturally forms cationic nanoparticles (cNP) in aqueous solutions, with the hydrophobic core loaded with TrkA-IN-1, an antagonist against the NGF receptor (TrkA). The drug delivery nanoparticles were denoted as TI-cNP. TrkA-IN-1 and TI-cNP were added to the decellularized annulus fibrosus matrix (DAF) hydrogel to form hybrid hydrogels, denoted as TI-DAF and TI-cNP-DAF, respectively. As a result, TrkA-IN-1 showed a delayed release profile both in TI-DAF and TI-cNP-DAF. Each mole of cNP could bind approximately 3 mol of CpG DNA to inhibit inflammation. cNP-DAF and TI-cNP-DAF significantly inhibited the M1 phenotype induced by CpG DNA. TI-DAF and TI-cNP-DAF reduced neurite branching and axon length, and inhibited the expression of neurogenic mediators (CGRP and substance P) in the presence of NGF. Besides, TI-cNP-DAF relieved mechanical hyperalgesia, reduced CGRP and substance P expression in the dorsal root ganglion, and downregulated GFAP and c-FOS signaling in the spinal cord in the rat disc herniation model. Summarily, TI-cNP-DAF, a novel composite IVD hydrogel, efficiently mediated the inflammatory environment, inhibited nerve ingrowth and sensitization, and could be clinically applied for treating discogenic pain. STATEMENT OF SIGNIFICANCE: Discogenic lower back pain, related to intervertebral disc degeneration (IDD), imposes a tremendous health and economic burden globally. M1-type macrophages release pro-inflammatory factors and nerve growth factor (NGF) that induce nerve growth into the inner annulus fibrosus, resulting in persistent hyperalgesia and discogenic pain. Reconstructing matrix integrity and modulating the inflammatory microenvironment are promising strategies for preventing the ingrowth and activation of neurites. The TI-cNP-DAF hydrogel recovers tissue integrity, alleviates inflammation, and delivers the TrkA antagonist to inhibit the activity of NGF, thus restraining hyperinnervation and nociceptive input. Due to its simple production process, injectability, and acellular strategy, the hydrogel is operable and holds great potential for treating discogenic lower back pain.

Injectable decellularized extracellular matrix hydrogel promotes salivary gland regeneration via endogenous stem cell recruitment and suppression of fibrogenesis

Saliva is key to the maintenance of oral homeostasis. However, several forms of salivary gland (SG) disorders, followed by hyposalivation, often result in dental caries, oral infection, and decreased taste, which dramatically affect the quality of patient's life. Functional biomaterials hold great potential for tissue regeneration in damaged or dysfunctional SGs and maintaining the good health of oral cavity. Herein, we prepared an injectable hydrogel derived from decellularized porcine submandibular glands (pDSG-gel), the material and biological properties of the hydrogel were systematically investigated. First, good biocompatibility and bioactivities of the pDSG-gel were validated in 2D and 3D cultures of primary submandibular gland mesenchymal stem cells (SGMSCs). Especially, the pDSG-gel effectively facilitated SGMSCs migration and recruitment through the activation of PI3K/AKT signaling pathway, suggested by transcriptomic analysis and immunoblotting. Furthermore, proteomic analysis of the pDSG revealed that many extracellular matrix components and secreted factors were preserved, which may contribute to stem cell homing. The recruitment of endogenous SG cells was confirmed in vivo, upon in situ injection of the pDSG-gel into the defective SGs in rats. Acinar and ductal-like structures were evident in the injury sites after pDSG-gel treatment, suggesting the reconstruction of functional SG units. Meanwhile, histological characterizations showed that the administration of the pDSG-gel also significantly suppressed fibrogenesis within the injured SG tissues. Taken together, this tissue-specific hydrogel provides a pro-regenerative microenvironment for endogenous SG regeneration and holds great promise as a powerful and bioactive material for future treatments of SG diseases. STATEMENT OF SIGNIFICANCE: Decellularized extracellular matrix (dECM) has been acknowledged as one of the most promising biomaterials that recapitalizes the microenvironment in native tissues. Hydrogel derived from the dECM allows in situ administration for tissue repair. Herein, a tissue-specific dECM hydrogel derived from porcine salivary glands (pDSG-gel) was successfully prepared and developed for functional reconstruction of defective salivary gland (SG) tissues. The pDSG-gel effectively accelerated endogenous SG stem cells migration and their recruitment for acinar- and ductal-like regeneration, which was attributed to the activation of PI3K/AKT signaling pathway. Additionally, the introduction of the pDSG-gel resulted in highly suppressed fibrogenesis in the defective tissues. These outcomes indicated that the pDSG-gel holds great potential in clinical translation toward SG regeneration through cell-free treatments.

A comparative study of human and porcine-derived decellularised nerve matrices

Decellularised extracellular matrix (dECM) biomaterials originating from allogeneic and xenogeneic tissues have been broadly studied in the field of regenerative medicine and have already been used in clinical treatments. Allogeneic dECMs are considered more compatible, but they have the drawback of extremely limited human tissue sources. Their availability is also restricted by the health and age of the donors. To investigate the viability of xenogeneic tissues as a substitute for human tissues, we fabricated both porcine decellularised nerve matrix (pDNM) and human decellularised nerve matrix for a comprehensive comparison. Photomicrographs showed that both dECM scaffolds retained the ECM microstructures of native human nerve tissues. Proteomic analysis demonstrated that the protein compositions of both dECMs were also very similar to each other. Their functional ECM contents effectively promoted the proliferation, migration, and maturation of primary human Schwann cells in vitro. However, pDNM contained a few antigens that induced severe host immune responses in humanised mice. Interestingly, after removing the α-galactosidase antigen, the immune responses were highly alleviated and the pre-treated pDNM maintained a human decellularised nerve matrix-like pro-regenerative phenotype. Therefore, we believe that an α-galactosidase-free pDNM may serve as a viable substitute for human decellularised nerve matrix in future clinical applications.

Decellularised spinal cord matrix manipulates glial niche into repairing phase via serglycin-mediated signalling pathway

Astrocytes are the most abundant and widespread glial cells in the central nervous system. The heterogeneity of astrocytes plays an essential role in spinal cord injury (SCI) repair. Decellularised spinal cord matrix (DSCM) is advantageous for repairing SCI, but little is known regarding the exact mechanisms and niche alterations. Here, we investigated the DSCM regulatory mechanism of glial niche in the neuro-glial-vascular unit using single-cell RNA sequencing. Our single cell sequencing, molecular and biochemical experiments validated that DSCM facilitated the differentiation of neural progenitor cells through increasing the number of immature astrocytes. Upregulation of mesenchyme-related genes, which maintained astrocyte immaturity, causing insensitivity to inflammatory stimuli. Subsequently, we identified serglycin (SRGN) as a functional component of DSCM, which involves inducing CD44-AKT signalling to trigger human spinal cord-derived primary astrocytes (hspASCs) proliferation and upregulation of genes related to epithelial-mesenchymal transition, thus impeding astrocyte maturation. Finally, we verified that SRGN-COLI and DSCM had similar functions in the human primary cell co-culture system to mimic the glia niche. In conclusion, our work revealed that DSCM reverted astrocyte maturation and altered the glia niche into the repairing phase through the SRGN-mediated signalling pathway.

Harnessing decellularised extracellular matrix microgels into modular bioinks for extrusion-based bioprinting with good printability and high post-printing cell viability

The printability of bioink and post-printing cell viability is crucial for extrusion-based bioprinting. A proper bioink not only provides mechanical support for structural fidelity, but also serves as suitable three-dimensional (3D) microenvironment for cell encapsulation and protection. In this study, a hydrogel-based composite bioink was developed consisting of gelatin methacryloyl (GelMA) as the continuous phase and decellularised extracellular matrix microgels (DMs) as the discrete phase. A flow-focusing microfluidic system was employed for the fabrication of cell-laden DMs in a high-throughput manner. After gentle mixing of the DMs and GelMA, both rheological characterisations and 3D printing tests showed that the resulting DM-GelMA hydrogel preserved the shear-thinning nature, mechanical properties, and good printability from GelMA. The integration of DMs not only provided an extracellular matrix-like microenvironment for cell encapsulation, but also considerable shear-resistance for high post-printing cell viability. The DM sizes and inner diameters of the 3D printer needles were correlated and optimised for nozzle-based extrusion. Furthermore, a proof-of-concept bioink composedg of RSC96 Schwann cells encapsulated DMs and human umbilical vein endothelial cell-laden GelMA was successfully bioprinted into 3D constructs, resulting in a modular co-culture system with distinct cells/materials distribution. Overall, the modular DM-GelMA bioink provides a springboard for future precision biofabrication and will serve in numerous biomedical applications such as tissue engineering and drug screening.

Dual-crosslinked regenerative hydrogel for sutureless long-term repair of corneal defect

Corneal transplantation is the most effective clinical treatment for corneal defects, but it requires precise size of donor corneas, surgical sutures, and overcoming other technical challenges. Postoperative patients may suffer graft rejection and complications caused by sutures. Ophthalmic glues that can long-term integrate with the corneal tissue and effectively repair the focal corneal damage are highly desirable. Herein, a hybrid hydrogel consisting of porcine decellularized corneal stroma matrix (pDCSM) and methacrylated hyaluronic acid (HAMA) was developed through a non-competitive dual-crosslinking process. It can be directly filled into corneal defects with various shapes. More importantly, through formation of interpenetrating network and stable amide bonds between the hydrogel and adjacent tissue, the hydrogel manifested excellent adhesion properties to achieve suture-free repair. Meanwhile, the hybrid hydrogel not only preserved bioactive components from pDCSM, but also exhibited cornea-matching transparency, low swelling ratio, slow degradation, and enhanced mechanical properties, which was capable of withstanding superhigh intraocular pressure. The combinatorial hydrogel greatly improved the poor cell adhesion performance of HAMA, supported the viability, proliferation of corneal cells, and preservation of keratocyte phenotype. In a rabbit corneal stromal defect model, the experimental eyes treated with the hybrid hydrogel remained transparent and adhered intimately to the stroma bed with long-term retention, accelerated corneal re-epithelialization and wound healing. Giving the advantages of high bioactivity, low-cost, and good practicality, the dual-crosslinked hybrid hydrogel served effectively for long-term suture-free treatment and tissue regeneration after corneal defect.

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Double-network hydrogel contains regenerative decellularized corneal stroma matrix.

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Suture-free easy operation, high transparency, strong attachment to stroma bed.

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Long-term retention on corneal defect with excellent force and pressure resistance.

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Rapid re-epithelialization, minimal scar formation, sustained cornea regeneration.

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A functional biomaterial-based strategy for in situ corneal wound healing.

Biomaterial-Based Schwann Cell Transplantation and Schwann Cell-Derived Biomaterials for Nerve Regeneration

Schwann cells (SCs) dominate the regenerative behaviors after peripheral nerve injury by supporting axonal regrowth and remyelination. Previous reports also demonstrated that the existence of SCs is beneficial for nerve regeneration after traumatic injuries in central nervous system. Therefore, the transplantation of SCs/SC-like cells serves as a feasible cell therapy to reconstruct the microenvironment and promote nerve functional recovery for both peripheral and central nerve injury repair. However, direct cell transplantation often leads to low efficacy, due to injection induced cell damage and rapid loss in the circulatory system. In recent years, biomaterials have received great attention as functional carriers for effective cell transplantation. To better mimic the extracellular matrix (ECM), many biodegradable materials have been engineered with compositional and/or topological cues to maintain the biological properties of the SCs/SCs-like cells. In addition, ECM components or factors secreted by SCs also actively contribute to nerve regeneration. Such cell-free transplantation approaches may provide great promise in clinical translation. In this review, we first present the current bio-scaffolds engineered for SC transplantation and their achievement in animal models and clinical applications. To this end, we focus on the physical and biological properties of different biomaterials and highlight how these properties affect the biological behaviors of the SCs/SC-like cells. Second, the SC-derived biomaterials are also reviewed and discussed. Finally, the relationship between SCs and functional biomaterials is summarized, and the trends of their future development are predicted toward clinical applications.

Bioactive Decellularized Extracellular Matrix Hydrogel Microspheres Fabricated Using a Temperature-Controlling Microfluidic System

Hydrogel microspheres have drawn great attention as functional three-dimensional (3D) microcarriers for cell attachment and growth, which have shown great potential in cell-based therapies and biomedical research. Hydrogels derived from a decellularized extracellular matrix (dECM) retain the intrinsic physical and biological cues from the native tissues, which often exhibit high bioactivity and tissue-specificity in promoting tissue regeneration. Herein, a novel two-stage temperature-controlling microfluidic system was developed which enabled production of pristine dECM hydrogel microspheres in a high-throughput manner. Porcine decellularized peripheral nerve matrix (pDNM) was used as the model raw dECM material for continuous generation of pDNM microgels without additional supporting materials or chemical crosslinking. The sizes of the microspheres were well-controlled by tuning the feed ratios of water/oil phases into the microfluidic device. The resulting pDNM microspheres (pDNM-MSs) were relatively stable, which maintained a spherical shape and a nanofibrous ultrastructure for at least 14 days. Schwann cells and PC12 cells preseeded on the pDNM-MSs not only showed excellent viability and an adhesive property, but also promoted cell extension compared to the commercially available gelatin microspheres. Moreover, primary neural stem/progenitor cells attached well to the pDNM-MSs, which further facilitated their proliferation. The successfully fabricated dECM hydrogel microspheres provided a highly bioactive microenvironment for 3D cell culture and functionalization, which showed promising potential in versatile biomedical applications.

Corrigendum to 'Decellularized disc hydrogels for hBMSC tissue-specific differentiation and tissue regeneration' [Bioactive Materials 6 (2021) 3541-3556]

[This corrects the article DOI: 10.1016/j.bioactmat.2021.03.014.].

Properties Regulation and Biological Applications of Decellularized Peripheral Nerve Matrix Hydrogel

Decellularized peripheral nerve matrix hydrogel (DNM-G) has drawn increasing attention in the field of neural tissue engineering, owing to its high tissue-specific bioactivity, drug/cell delivery capability, and multifunctional processability. However, the mechanisms and influencing factors of DNM-G formation have been rarely reported. To enable potential biological applications, the relationship between gelation conditions (including digestion time and gel concentration) and mechanical properties/stability (sol-gel transition temperature, gelation time, nanotopology, and storage modulus) of the DNM-G were systematically investigated in this study. The adequate-digested decellularized nerve matrix solution exhibited higher mechanical property, shorter gelation time, and a lower gelation temperature. A noteworthy increase of β-sheet proportion was identified through Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD) characterizations, which suggested the possible major secondary structure formation during the phase transition. Besides, the DNM-G degraded fast that over 70% mass loss was noted after 4 weeks when immersing in PBS. A natural cross-linking agent, genipin, was gently introduced into DNM-G to enhance its mechanical properties and stability without changing its microstructure and biological performance. As a prefabricated scaffold, DNM-G remarkably increased the length and penetration depth of dorsal root ganglion (DRG) neurites compared to collagen gel. Furthermore, the DNM-G promoted the myelination and facilitated the formation of the morphological neural network. Finally, we demonstrated the feasibility of applying DNM-G in support-free extrusion-based 3D printing. Overall, the mechanical and biological performance of DNM-G can be manipulated by tuning the processing parameters, which is key to the versatile applications of DNM-G in regenerative medicine.

Tissue-Specific Hydrogels for 3D Printing and Potential Application in Peripheral Nerve Regeneration

Decellularized extracellular matrix hydrogel (dECM-G) has demonstrated its significant tissue-specificity, high biocompatibility, and versatile utilities in tissue engineering. However, the low mechanical stability and fast degradation are major drawbacks for its application in 3D printing. Herein, we report a hybrid hydrogel system consisting of dECM-Gs and photocrosslinkable gelatin methacrylate (GelMA), which resulted in significantly improved printability and structural fidelity. These pre-mixed hydrogels retained high bioactivity and tissue-specificity due to their containing dECM-Gs. More specifically, it was realized that the hydrogel containing dECM-G derived from porcine peripheral nerves (GelMA/pDNM-G) effectively facilitated neurite growth and Schwann cell migration from 2D cultured dorsal root ganglion explants. The nerve cells were also encapsulated in the GelMA/pDNM-G hydrogel for 3D culture or underwent cell-laden bioprinting with high cell viability. The preparation of such GelMA/dECM-G hydrogels enabled the recapitulation of functional tissues through extrusion-based bioprinting, which holds great potential for applications in regenerative medicine.

Decellularized Disc Hydrogels for hBMSCs tissue-specific differentiation and tissue regeneration

Tissue specificity, a key factor in the decellularized tissue matrix (DTM), has shown bioactive functionalities in tuning cell fate-e.g., the differentiation of mesenchymal stem cells. Notably, cell fate is also determined by the living microenvironment, including material composition and spatial characteristics. Herein, two neighboring tissues within intervertebral discs, the nucleus pulposus (NP) and annulus fibrosus (AF), were carefully processed into DTM hydrogels (abbreviated DNP-G and DAF-G, respectively) to determine the tissue-specific effects on stem cell fate, such as specific components and different culturing methods, as well as in vivo regeneration. Distinct differences in their protein compositions were identified by proteomic analysis. Interestingly, the fate of human bone marrow mesenchymal stem cells (hBMSCs) also responds to both culturing methods and composition. Generally, hBMSCs cultured with DNP-G (3D) differentiated into NP-like cells, while hBMSCs cultured with DAF-G (2D) underwent AF-like differentiation, indicating a close correlation with the native microenvironments of NP and AF cells, respectively. Furthermore, we found that the integrin-mediated RhoA/LATS/YAP1 signaling pathway was activated in DAF-G (2D)-induced AF-specific differentiation. Additionally, the activation of YAP1 determined the tendency of NP- or AF-specific differentiation and played opposite regulatory effects. Finally, DNP-G and DAF-G specifically promoted tissue regeneration in NP degeneration and AF defect rat models, respectively. In conclusion, DNP-G and DAF-G can specifically determine the fate of stem cells through the integrin-mediated RhoA/LATS/YAP1 signaling pathway, and this tissue specificity is both compositional and spatial, supporting the utilization of tissue-specific DTM in advanced treatments of intervertebral disc degeneration.

Nanofibrous nerve guidance conduits decorated with decellularized matrix hydrogel facilitate peripheral nerve injury repair

Rationale: Peripheral nerve injury (PNI) is a great challenge for regenerative medicine. Nerve autograft is the gold standard for clinical PNI repair. Due to its significant drawbacks, artificial nerve guidance conduits (NGCs) have drawn much attention as replacement therapies. We developed a combinatorial NGC consisting of longitudinally aligned electrospun nanofibers and porcine decellularized nerve matrix hydrogel (pDNM gel). The in vivo capacity for facilitating nerve tissue regeneration and functional recovery was evaluated in a rat sciatic nerve defect model.

Methods: Poly (L-lactic acid) (PLLA) was electrospun into randomly oriented (PLLA-random) and longitudinally aligned (PLLA-aligned) nanofibers. PLLA-aligned were further coated with pDNM gel at concentrations of 0.25% (PLLA-aligned/0.25% pDNM gel) and 1% (PLLA-aligned/1% pDNM gel). Axonal extension and Schwann cells migration were evaluated by immunofluorescence staining of dorsal root ganglia cultured on the scaffolds. To fabricate implantable NGCs, the nanofibrous scaffolds were rolled and covered with an electrospun protection tube. The fabricated NGCs were then implanted into a 5 mm sciatic nerve defect model in adult male Sprague-Dawley rats. Nerves treated with NGCs were compared to contralateral uninjured nerves (control group), injured but untreated nerves (unstitched group), and autografted nerves. Nerve regeneration was monitored by an established set of assays, including T2 values and diffusion tensor imaging (DTI) derived from multiparametric magnetic resonance imaging (MRI), histological assessments, and immunostaining. Nerve functional recovery was evaluated by walking track analysis.

Results: PLLA-aligned/0.25% pDNM gel scaffold exhibited the best performance in facilitating directed axonal extension and Schwann cells migration in vitro due to the combined effects of the topological cues provided by the aligned nanofibers and the biochemical cues retained in the pDNM gel. Consistent results were obtained in animal experiments with the fabricated NGCs. Both the T2 and fractional anisotropy values of the PLLA-aligned/0.25% pDNM gel group were the closest to those of the autografted group, and returned to normal much faster than those of the other NGCs groups. Histological assessment indicated that the implanted PLLA-aligned/0.25% pDNM gel NGC resulted in the largest number of axons and the most extensive myelination among all fabricated NGCs. Further, the PLLA-aligned/0.25% pDNM gel group exhibited the highest sciatic nerve function index, which was comparable to that of the autografted group, at 8 weeks post-surgery.

Conclusions: NGCs composed of aligned PLLA nanofibers decorated with 0.25% pDNM gel provided both topological and biochemical guidance for directing and promoting axonal extension, nerve fiber myelination, and functional recovery. Moreover, T2-mapping and DTI metrics were found to be useful non-invasive monitoring techniques for PNI treatment.

Decellularized nerve matrix hydrogel scaffolds with longitudinally oriented and size-tunable microchannels for peripheral nerve regeneration

The scaffolding biomaterials and their internal structures are crucial in constructing growth-permissive microenvironment for tissue regeneration. A functional bioscaffold not only requires sufficient extracellular matrix components, but also provides topological guidance by mimicry of the ultrastructure of the native tissue. In our laboratory, a decellularized nerve matrix hydrogel derived from porcine sciatic nerve (pDNM-G) is successfully prepared, which shows great promise for peripheral nerve regeneration. Herein, longitudinally oriented microchannel structures were introduced into pDNM-G bioscaffolds (A-pDNM-G) through controlled unidirectional freeze-drying. The axially aligned microchannels effectively directed and significantly promoted neurite extension and Schwann cell migration, assessed by culturing dorsal root ganglion explants on the longitudinal sections of A-pDNM-G scaffolds. Such regenerative cellular responses can be further optimized by tuning the channel sizes. In vivo studies confirmed that the implanted nerve guidance conduits containing A-pDNM-G scaffolds significantly facilitated axonal extension, myelination, and reached considerable functional recovery in 15-mm rat sciatic nerve defects. The incorporation of nerve growth factor further improved the overall performance in the grafted nerve. The bioactive pDNM-G enables controlled release of neurotrophic factor and easy integration of topological cue provided by the axially aligned microchannels into implantable bioscaffolds, which may serve in future clinical treatments of peripheral nerve injury.

Facilitate Angiogenesis and Neurogenesis by Growth Factors Integrated Decellularized Matrix Hydrogel

Neurological functional recovery depends on the synergistic interaction between angiogenesis and neurogenesis after peripheral nerve injury (PNI). Decellularized nerve matrix hydrogels have drawn much attention and been considered as potential therapeutic biomaterials for neurovascularization, due to their intrinsic advantages in construction of a growth-permissive microenvironment, strong affinity to multiple growth factors (GFs), and promotion of neurite outgrowth. In the present study, nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) were incorporated into porcine decellularized nerve matrix hydrogel (pDNM-gel) for PNI treatment. Both GFs bound strongly to pDNM-gel and underwent a controlled release manner, which showed facilitated axonal extension and vascular-like tube formation in vitro. Especially, a companion growth was identified when human umbilical vein endothelial cells and neurons were cocultured on the GFs containing pDNM-gel. In a crushed rat sciatic nerve model, the incorporated NGF and VEGF appeared to contribute for axonal growth and neovascularization correspondingly but separately. Both GFs were equally important in improving nerve functional recovery after in situ administration. These findings indicate that pDNM-gel is not only a bioactive hydrogel-based material that can be used alone, but also serves as suitable carrier of multiple GFs for promoting an effective PNI repair. Impact statement Decellularized matrix hydrogel derived from nerve tissue has demonstrated its effectiveness in promoting nerve reinnervation, remyelination, and functionalization. Meanwhile, angiogenesis is highly desirable for treatment of long-distance peripheral nerve defects. To this end, we incorporated both vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) into porcine decellularized nerve matrix hydrogel (pDNM-gel) to induce neovascularization and neuroregeneration. At the cellular level, the pDNM-gel with both growth factors (GFs) exhibited significant capability in promoting axonal elongation, Schwann cell proliferation and migration, as well as vessel/nerve interaction. In crushed peripheral nerve injury (PNI) rat model, the integrated VEGF was more favorable for angiogenesis, whereas NGF mainly contributed to neurogenesis. However, the combination of both GFs in pDNM-gel highly facilitated motor functional recovery, highlighting the therapeutic promise of decellularized matrix hydrogel for growth factor delivery toward neuroprotection and neuroregeneration after PNI.

Decellularized nerve matrix hydrogel and glial-derived neurotrophic factor modifications assisted nerve repair with decellularized nerve matrix scaffolds

Nerve defects are challenging to address clinically without satisfactory treatments. As a reliable alternative to autografts, decellularized nerve matrix scaffolds (DNM-S) have been widely used in clinics for surgical nerve repair. However, DNM-S remain inferior to autografts in their ability to support nerve regeneration for long nerve defects. In this study, we systematically and clearly presented the nano-architecture of nerve-specific structures, including the endoneurium, basement membrane and perineurium/epineurium in DNM-S. Furthermore, we modified the DNM-S by supplementing decellularized nerve matrix hydrogel (DNMG) and glial-derived neurotrophic factor (GDNF) and then bridged a 50-mm sciatic nerve defect in a beagle model. Fifteen beagles were randomly divided into three groups (five per group): an autograft group, DNM-S group and GDNF-DNMG-modified DNM-S (DNM-S/GDNF@DNMG) group. DNM-S/GDNF@DNMG, as optimized nerve grafts, were used to bridge nerve defects in the same manner as in the DNM-S group. The repair outcome was evaluated by behavioural observations, electrophysiological assessments, regenerated nerve tissue histology and reinnervated target muscle examinations. Compared with the DNM-S group, limb function, electrophysiological responses and histological findings were improved in the DNM-S/GDNF@DNMG group 6 months after grafting, reflecting a narrower gap between the effects of DNM-S and autografts. In conclusion, modification of DNM-S with DNMG and GDNF enhanced nerve regeneration and functional recovery, indicating that noncellular modification of DNM-S is a promising method for treating long nerve defects.

Promoting Neurite Growth and Schwann Cell Migration by the Harnessing Decellularized Nerve Matrix onto Nanofibrous Guidance

Synergistic intercellular interactions have been widely acknowledged in tuning functional cell behaviors in vivo, and these interactions have inspired the development of a variety of scaffolds for regenerative medicine. In this paper, the promotion of Schwann cell (SC)-neurite interactions through the use of a nerve extracellular matrix-coated nanofiber composite in vitro was demonstrated using a cell culturing platform consisting of either random or aligned electrospun poly(l-lactic acid) nanofibers and decellularized peripheral nerve matrix gel (pDNM gel) from porcine peripheral nervous tissue. The pDNM-coated nanofiber platform served as a superior substrate for dorsal root ganglion culturing. Furthermore, SC migration was facilitated by pDNM gel coating on the nanofibers, accompanied with much faster axonal extension, in comparison with the effect of topographical guidance from the aligned electrospun fibers only. Finally, the decellularized nerve matrix promoted the ability of SCs to wrap around bundled neurites, triggering axonal remyelination toward nerve fiber functionalization.

Hydrogel derived from porcine decellularized nerve tissue as a promising biomaterial for repairing peripheral nerve defects

Decellularized matrix hydrogels derived from tissues or organs have been used for tissue repair due to their biocompatibility, tunability, and tissue-specific extracellular matrix (ECM) components. However, the preparation of decellularized peripheral nerve matrix hydrogels and their use to repair nerve defects have not been reported. Here, we developed a hydrogel from porcine decellularized nerve matrix (pDNM-G), which was confirmed to have minimal DNA content and retain collagen and glycosaminoglycans content, thereby allowing gelatinization. The pDNM-G exhibited a nanofibrous structure similar to that of natural ECM, and a ∼280-Pa storage modulus at 10 mg/mL similar to that of native neural tissues. Western blot and liquid chromatography tandem mass spectrometry analysis revealed that the pDNM-G consisted mostly of ECM proteins and contained primary ECM-related proteins, including fibronectin and collagen I and IV). In vitro experiments showed that pDNM-G supported Schwann cell proliferation and preserved cell morphology. Additionally, in a 15-mm rat sciatic nerve defect model, pDNM-G was combined with electrospun poly(lactic-acid)-co-poly(trimethylene-carbonate)conduits to bridge the defect, which did not elicit an adverse immune response and promoted the activation of M2 macrophages associated with a constructive remodeling response. Morphological analyses and electrophysiological and functional examinations revealed that the regenerative outcomes achieved by pDNM-G were superior to those by empty conduits and closed to those using rat decellularized nerve matrix allograft scaffolds. These findings indicated that pDNM-G, with its preserved ECM composition and nanofibrous structure, represents a promising biomaterial for peripheral nerve regeneration.

STATEMENT OF SIGNIFICANCE

Decellularized nerve allografts have been widely used to treat peripheral nerve injury. However, given their limited availability and lack of bioactive factors, efforts have been made to improve the efficacy of decellularized nerve allograft for nerve regeneration, with limited success. Xenogeneic decellularized tissue matrices or hydrogels have been widely used for surgical applications owing to their ease of harvesting and low immunogenicity. Moreover, decellularized tissue matrix hydrogels show good biocompatibility and are highly tunable. In this study, we prepared a porcine decellularized nerve matrix (pDNM-G) and evaluated its potential for promoting nerve regeneration. Our results demonstrate that pDNM-G can support Schwann cell proliferation and peripheral nerve regeneration by means of residual primary extracellular matrix components and nano-fibrous structure features.

Comparison of Both Sides for Retroperitoneal Laparoscopic Donor Nephrectomy: Experience From a Single Center in China

BACKGROUND

Laparoscopic donor nephrectomy (LDN) has gradually become the main approach to obtain live donor kidneys. However, the shorter right renal vein limits its wider application. The aim of this study was to compare the outcomes of left- and right-side retroperitoneal LDN.

METHODS

We reviewed the perioperative data of 527 consecutive donors receiving retroperitoneal pure LDN with a new method at our center between April 2009 and April 2014. The patients were divided into group A (the first 100 patients) and group B (the remaining 427 patients). A total of 423 cases of left donor surgery and 104 cases of right donor surgery were compared. The comparison of the laterality of LDN was also performed between group A and group B.

RESULTS

This is currently the largest case series of LDN in our country. Although right-side LDN patients had longer operation time and a slightly higher incidence of intraoperative complications compared with left-side LDN patients, the operation time was shorter in both the groups compared with previous reports. In group B, patients undergoing right-side LDN had longer operation time and more frequent complications. Once the learning curve of 100 cases was completed, the incidence of complications and operation time were greatly reduced in both sides for LDN. There was no significant difference in the serum creatinine levels in recipients at 6 months of follow-up.

CONCLUSIONS

Despite a slightly higher incidence of complications and longer operation time, right-side LDN can achieve equally safe and effective transplantation outcomes. This expands the source of potential donor kidneys.

High On-Treatment Platelet Reactivity to Adenosine Diphosphate Predicts Ischemic Events of Minor Stroke and Transient Ischemic Attack

BACKGROUND

This study aimed to evaluate the relationship between thromboelastography adenosine diphosphate maximum amplitude (TEG-ADP_MA) and recurrent ischemic events in patients with minor ischemic stroke or high-risk transient ischemic attack (TIA).

METHODS

A total of 265 patients received dual antiplatelet therapy were consecutively enrolled. High on-treatment platelet reactivity (HTPR) to ADP was assessed by TEG-ADP_MA and detected the CYP2C19 genotype; recurrent ischemic events were followed up for 90 days after onset. The difference of recurrent ischemic events was analyzed with or without HTPR to ADP by the Kaplan-Meier, and further to determine the difference of recurrent ischemic events in each group according to TEG-ADP_MA-based tertile distribution.

RESULTS

A total of 23 (8.6%) patients had recurrent ischemic events. TEG-ADP_MA greater than or equal to 48 mm had good predictive value. Whether these patients were divided into 2 groups or 3 groups, the HTPR to ADP group had higher risk of recurrent ischemic events than the normal on-treatment platelet reactivity to ADP group by the Kaplan-Meier (all, P < .05). The tertile distribution map showed that the results of recurrent ischemic events were statistically significant in the third tertile group compared with the other two groups (all, P < .03); also, the third tertile group had a higher rate of carriers of at least 1 CYP2C19 reduced-function allele than the other two groups (P < .05).

CONCLUSIONS

In patients with minor ischemic stroke and high-risk TIA, the TEG-ADP_MA could predict recurrent ischemic events and has auxiliary effect on clinical decision-making.

Efficient androst-1,4-diene-3,17-dione production by co-expressing 3-ketosteroid-Δ1 -dehydrogenase and catalase in Bacillus subtilis

AIMS

3-ketosteroid-Δ¹ -dehydrogenase (KSDD), a flavin adenine dinucleotide (FAD)-dependent enzyme involved in sterol metabolism, specifically catalyses the conversion of androst-4-ene-3,17-dione (AD) to androst-1,4-diene-3,17-dione (ADD). However, the low KSDD activity and the toxic effects of hydrogen peroxide (H₂ O₂ ) generated during the biotransformation of AD to ADD with FAD regeneration hinder its application on AD conversion. The aim of this work was to improve KSDD activity and eliminate the toxic effects of the generated H₂ O₂ to enhance ADD production.

METHODS AND RESULTS

The ksdd gene obtained from Mycobacterium neoaurum JC-12 was codon-optimized to increase its expression level in Bacillus subtilis, and the KSDD activity reached 12·3 U mg^-1 , which was sevenfold of that of codon-unoptimized gene. To improve AD conversion, catalase was co-expressed with KSDD in B. subtilis 168/pMA5-ksdd^opt -katA to eliminate the toxic effects of H₂ O₂ generated during AD conversion. Finally, under optimized bioconversion conditions, fed-batch strategy was carried out and the ADD yield improved to 8·76 g l^-1 .

CONCLUSIONS

This work demonstrates the potential to improve enzyme activity by codon-optimization and eliminate the toxic effects of H₂ O₂ by co-expressing catalase.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study showed the highest ADD productivity ever reported and provides a promising strain for efficient ADD production in the pharmaceutical industry.

Conversion From Calcineurin Inhibitors to Mammalian Target-of-Rapamycin Inhibitors in Heart Transplant Recipients: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

Conversion from calcineurin inhibitors (CNIs) to mammalian target-of-rapamycin inhibitors (mTORi) was systematically evaluated in heart transplant recipients (HTRs) for the first time.

METHODS

MEDLINE (PUBMED), EMBASE, Cochrane Library, and clinical trial registries were searched comprehensively. After screening for eligibility, the randomized controlled trials (RCTs) comparing continuation of CNI with conversion to mTORi therapy underwent review, quality assessment, and data extraction. Outcomes analyzed including creatinine clearance, serum creatinine level, rejection, adverse effects, and triglyceride levels were expressed as mean differences (MDs) or as risk ratios (RRs) with 95% confidence intervals (CIs).

RESULTS

This is the first systematic review evaluating converting from CNI to mTORi therapy in HTRs. A total of 4 RCTs (231 HTRs, 117 vs 114) were included in our analysis. Patients converted to mTORi had a higher creatinine clearance (MD, 19.31; 95% CI [11.16, 27.46]; P < .00001) and lower serum creatinine levels (MD, -0.15; 95% CI [-0.25, -0.05]; P = .002). Patients converted to mTORi had a significantly higher occurrence of adverse effects, which included skin diseases, gastrointestinal side effects, bone marrow suppression, and infections. There was no significant difference between the 2 groups regarding graft rejection and triglyceride levels (RR, 2.61; 95% CI [0.08, 81.25]; P = .58; MD, 22.89; 95% CI [-21.86, 67.63]; P = .32).

CONCLUSIONS

Conversion from CNI to mTORi therapy may improve the renal function in HTRs, but the patients may suffer from a high incidence of mTORi-associated adverse events. Therefore, conversion to mTORi must be carefully assessed for the benefits and risks.

Identification and characterization of a novel 2,3-butanediol dehydrogenase/acetoin reductase from Corynebacterium crenatum SYPA5-5

Acetoin and 2,3-butanediol are widely used in the chemical and pharmaceutical industries. The enzyme, 2,3-butanediol dehydrogenase/acetoin reductase (2,3-BDH/AR), plays a significant role in the microbial production of acetoin and 2,3-butanediol by catalysing a reversible reaction between acetoin and 2,3-butanediol. To date, a 2,3-BDH has not been characterized from Corynebacterium crenatum. 2,3-BDH was cloned from Coryne. crenatum SYPA5-5 and expressed in Escherichia coli BL21. Sequence analysis suggested that the 2,3-BDH from Coryne. crenatum SYPA5-5 belongs to the short-chain dehydrogenase/reductase superfamily. Its maximum specific activity was obtained at 35°C, however, it became very unstable when the temperature was above 35°C. Its optimal pH was 4·0 for reduction reaction and 10·0 for oxidation reaction. The 2,3-BDH activity was increased to some extent by Ca(2+) , Mg(2+) , Zn(2+) and Mn(2+) ions. In particular, Ca(2+) induced about 1·5-fold increase. The value of kcat /Km for diacetyl and acetoin are higher than for 2,3-butanediol indicating that 2,3-BDH can easily reduce diacetyl or acetoin to 2,3-butanediol under lower pH conditions. The characteristics of 2,3-BDH from Coryne. crenatum SYPA5-5 will give guide to further studies for the production of acetoin and 2,3-butanediol with engineered Coryne. crenatum SYPA5-5.

SIGNIFICANCE AND IMPACT OF THE STUDY

Acetoin and 2,3-butanediol are commonly used as platform chemicals and widely used in pharmaceutical industries. 2,3-butanediol dehydrogenase/acetoin reductase (2,3-BDH/AR) plays a significant role in the microbial production of acetoin and 2,3-butanediol. In this study, 2,3-BDH was cloned from Corynebacterium crenatum SYPA5-5, was expressed in Escherichia coli BL21 and characterized with respect to the optimal temperature, pH, substrate specificity and kinetics. The results will guide further studies in Coryne. crenatum SYPA5-5 for the production of acetoin and 2,3-butanediol.

Short-term therapeutic drug monitoring of mycophenolic acid reduces infection: a prospective, single-center cohort study in Chinese living-related kidney transplantation

BACKGROUND

The role of therapeutic drug monitoring (TDM) of mycophenolic acid (MPA) in kidney transplant recipients (KTRs) is not clear. We performed a prospective cohort study to evaluate the efficiency of MPA TDM in the Chinese population.

METHODS

A total of 183 living-related KTRs were studied; 101 KTRs received controlled-dose mycophenolate mofetil (MMF) (the CD group), and 82 patients received fixed-dose MMF (the FD group). MPA exposure was measured at days 3, 7, 14, and 30 in the CD group, and at day 30 in the FD group. The primary endpoint was treatment failure (a composite of acute rejection, graft loss, death, or MMF discontinuation) at 12 months post transplantation.

RESULTS

In the CD group, with a starting MMF dose of 2 g/day, approximately 35% of patients had high MPA levels, which were >60 mg × h/L, and mean MPA levels were 59.17 mg × h/L and 61.38 mg × h/L for the CD and FD groups, respectively (P = 0.588). After adjusting MMF dose, MPA exposures in the CD group at day 30 were lower than those in the FD group at day 30 (54.06 vs. 61.38, P = 0.004). At month 12, the CD group had fewer infections (16.8% vs. 31.7%, P = 0.018) with no difference in treatment failure, acute rejection, diarrhea, or anemia.

CONCLUSIONS

KTRs can benefit from short-term TDM of MPA in reducing infection, without increasing acute rejection.

Clinicopathological and prognostic significance of α5β1-integrin and MMP-14 expressions in colorectal cancer

The purpose of this study was to evaluate the association of expression level of α5β1-integrin and MMP-14 with clinicopathologic features and prognosis in colorectal cancer (CRC). The expressions of α5β1-integrin and MMP-14 in normal colorectal mucosa and CRC tissue were detected with immunohistochemistry. We estimated the five-year survival rate by the Kaplan-Meier method. The positive expressions rates of α5β1-integrin and MMP-14 in CRC tissue were 60.6% and 63.3% respectively, and there were significant differences on their positive expression rates between in CRC tissue and in normal colorectal mucosa(P<0.05). The expression rates of α5β1-integrin and MMP-14 in patients with poor histological differentiation, lymph node metastasis and high clinical staging were heightened. There was a significant difference (P<0.05) on the five-year survival rate for α5β1-integrin expression, which was 44.6% in positive groups and 75.5% in negative groups. And there was a significant difference (P<0.05) on the five-year survival rate for MMP-14 expression, which was 48.2% in positive group and 73.1% in negative group. The expression of α5β1-integrin and MMP-14 is correlated with the progression and metastasis of CRC, and α5β1-integrin and MMP-14 may be used as prognostic markers in CRC.

Ubiquitin pathway and ovarian cancer

The ubiquitin-proteasome pathway is a common cellular process in eukaryotic tissue. Ubiquitin binds to proteins and tags them for destruction; this tagging directs proteins to the proteosome in the cell that degrades and recycles unneeded proteins. The ubiquitin-proteasome pathway plays an important role in the regulation of cellular proteins with respect to cell cycle control, transcription, apoptosis, cell adhesion, angiogenesis, and tumour growth. This review article discusses the various ways that the ubiquitin pathway is involved in ovarian cancer, such as modulating the ovarian-cancer-related gene BRCA1 and tumour suppressor p53, and interfering with the erk pathway, the cyclin-dependent cell cycle regulation process, and ERBB2 gene expression.

Engineered Saccharomyces cerevisiae that produces 1,3-propanediol from D-glucose

AIMS

Saccharomyces cerevisiae is a safe micro-organism used in fermentation industry. 1,3-Propanediol is an important chemical widely used in polymer production, but its availability is being restricted owing to its expensively chemical synthesis. The aim of this study is to engineer a S. cerevisiae strain that can produce 1,3-propanediol at low cost.

METHODS AND RESULTS

By using D-glucose as a feedstock, S. cerevisiae could produce glycerol, but not 1,3-propanediol. In this study, we have cloned two genes yqhD and dhaB required for the production of 1,3-propanediol from glycerol, and integrated them into the chromosome of S. cerevisiae W303-1A by Agrobacterium tumefaciens-mediated transformation. Both genes yqhD and dhaB functioned in the engineered S. cerevisiae and led to the production of 1,3-propanediol from D-glucose.

CONCLUSION

Saccharomyces cerevisiae can be engineered to produce 1,3-propanediol from low-cost feedstock D-glucose.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, this is the first report on developing S. cerevisiae to produce 1,3-propanediol by using A. tumefaciens-mediated transformation. This study might lead to a safe and cost-efficient method for industrial production of 1,3-propanediol.

Human 8-oxoguanine DNA glycosylase increases resistance to hyperoxic cytotoxicity in lung epithelial cells and involvement with altered MAPK activity

It is unknown whether base excision DNA repair (BER) proteins interact with mitogen-activated protein kinases (MAPK) under oxidation. Here, we explored roles of BER proteins in signaling transduction involving MAPK during hyperoxia. We demonstrated that ERK1/2 phosphorylation in A549 cells was increased in 95% O₂. p38 activity in A549 cells was also increased by exposure to 95% O₂. To evaluate regulatory roles of MAPK, we have transduced A549 cells and primary alveolar epithelial type II cells (AECII) to overexpress 8-oxoguanine DNA glycosylase (hOgg1). Overexpression of hOgg1 reduced hyperoxic toxicity in A549 and AECII cells. Furthermore, protection by BER against hyperoxia appeared to involve an upregulation of ERK1/2 and downregulation of p38. These observations demonstrate, for the first time, that reduction of hyperoxic toxicity by BER proteins may be involved with MAPK activity, thereby impacting cell survival. Furthermore, our studies suggest that modulation of MAPK may be used in combination with BER proteins to counteract hyperoxic toxicity.

Crystallization of a calcium-binding EGF-like domain

Crystals of a calcium-binding epidermal growth factor (EGF)-like domain of human clotting factor IX suitable for X-ray diffraction analysis have been obtained by vapour diffusion (sitting drop) against 48% PEG 400. The crystals belong to the tetragonal space group P4(3)2(1)2, with unit-cell dimensions a = b = 40.3, c = 98.2 A. The crystals diffract beyond 1.5 A resolution and are relatively stable in the X-ray beam. This is the first reported crystallization of a calcium-binding EGF-like domain.

Purification, crystallization and preliminary X-ray analysis of human pirin

Pirin is a novel highly conserved nuclear protein, but very little is known about its cellular function. Human pirin has been cloned, expressed, purified and crystallized using PEG as precipitant. The crystal belongs to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 42.3, b = 67.0, c = 107.3 A, alpha = beta = gamma = 90 A. It contains one molecule per asymmetric unit and diffracts to 2.0 A under cryoconditions (100 K) using an in-house Cu rotating-anode X-ray generator.

Biochemical and biophysical analysis of heptad repeat regions from the fusion protein of Menangle virus, a newly emergent paramyxovirus

Menangle virus is a novel paramyxovirus isolated in Australia in 1997, but its classification position has not yet been finally settled. Here by using a computational program, LearnCoil-VMF, we determined the heptad repeat (HR) regions (HR1 and HR2) of Menangle virus F protein. Subsequently the HR1 and HR2 peptides were expressed as a single chain (named 2-Helix) connected by a six amino-acid linker as a GST fusion protein with an E. coli in vitro expression system. The GST-removed purified 2-Helix protein could form a stable trimer in vitro judging by gel-filtration and chemical cross-linking. CD spectra showed that the 2-Helix protein had a high percentage of alpha-helix and was very thermo-stable. Crystals of the 2-Helix protein preparations have been obtained in many conditions with hanging-drop diffusion method. These results indicated that Menangle virus has the common features of the fusion protein for other paramyxoviruses and should adopt a similar fusion mechanism to other members. As the HR regions of Menangle virus F protein could form stable six-helix bundle coiled coil structure, they should be used as drug target for the design of fusion inhibitors, as successfully used for other parmyxoviruses. This is especially relevant to such a newly emergent virus with zoonotic potentials.

Engineering substrate recognition in catalysis by cytochrome P450cam

We have a continuing interest in applying the current knowledge of cytochrome P450cam substrate recognition to engineer the enzyme for the biotransformation of unnatural substrates with the long-term aim of applications in the synthesis of fine chemicals and bioremediation of environmental contaminants. Comparisons of the structure of target substrates with that of camphor, the natural substrate, led to the design of active-site mutants with greatly enhanced activity for the oxidation of chlorinated benzenes and selectivity of (+)-alpha-pinene oxidation. The crystal structures of the F87W/Y96F/V247L mutant with 1,3,5-trichlorobenzene or (+)-alpha-pinene bound have revealed the enzyme-substrate contacts and provided insights into the activity and selectivity patterns. The structures have also provided a novel basis for further engineering of P450cam for increased activity in the oxidation of the highly inert pentachlorobenzene and hexachlorobenzene, and increased selectivity of (+)-alpha-pinene oxidation.

Crystallization of the N-terminal domain of DFF45: the mutual chaperone mechanism is challenged

DNA fragmentation factor 45 (DFF45) regulates DNase DFF40 as its inhibitor and chaperone. It was reported that the N-terminal domain (NTD) of DFF45 alone is disordered and DFF40 is necessary as a mutual chaperone for the folding of NTD. However, here we reported the crystallization of DFF45 NTD. These crystals diffract to 9A using a synchrotron radiation source. In spite of the low resolution, the demonstration of crystal formation indicates that DFF45 NTD itself is not unstructured, which strongly questions the mutual chaperone speculation about DFF45 and DFF40.

Purification, crystallization and X-ray analysis of swine vesicular disease virus

Swine vesicular disease virus (SVDV) is the etiological agent of swine vesicular disease, a highly contagious disease in pigs, and is related to coxsackie B virus. Crystalline arrays of SVDV can be observed in the cytoplasm of cells 4.5 h after inoculation to porcine kidney cells (IBRS-2 cells). Crystals of the JX/78 strain of SVDV were obtained from virus in two wells of crystallization conditions and present preliminary X-ray data to 3.6 A resolution.

Crystallization and preliminary x-ray crystallographic studies of trichosanthin delta C7

Trichosanthin (TCS) is a type I ribosome-inactivating protein (RIP) which possesses rRNA N-glycosidase activity. TCS has various pharmacological properties. It is possible to reduce the antigenicity of TCS by deleting up to seven C-terminal residues of TCS (TCS-C7) with minimal effect on its activity. TCS-C7 has been crystallized and the crystal diffracted to 1.8 A. It belongs to space group P2(1), with unit-cell parameters a=71.6A, b=74.4A, c=87.6A, beta=97.0 degrees. It is given that there are four molecules per asymmetric unit.