Yi Sun's research while affiliated with Shanghai Jiao Tong University and other places

Excessive neuroinflammation after spinal cord injury (SCI) is a major hurdle during nerve repair. Although proinflammatory macrophage/microglia-mediated neuroinflammation plays important roles, the underlying mechanism that triggers neuroinflammation and aggravating factors remain unclear. The present study identified a proinflammatory role of semaphorin3C (SEMA3C) in immunoregulation after SCI. SEMA3C expression level peaked 7 days post-injury (dpi) and decreased by 14 dpi. In vivo and in vitro studies revealed that macrophages/microglia expressed SEMA3C in the local microenvironment, which induced neuroinflammation and conversion of proinflammatory macrophage/microglia. Mechanistic experiments revealed that RAGE/NF-κB was downstream target of SEMA3C. Inhibiting SEMA3C-mediated RAGE signaling considerably suppressed proinflammatory cytokine production, reversed polarization of macrophages/microglia shortly after SCI. In addition, inhibition of SEMA3C-mediated RAGE signaling suggested that the SEMA3C/RAGE axis is a feasible target to preserve axons from neuroinflammation. Taken together, our study provides the first experimental evidence of an immunoregulatory role for SEMA3C in SCI via an autocrine mechanism.

Cutaneous wound healing affecting millions of people worldwide represents an unsolvable clinical issue that is frequently challenged by scar formation with dramatical pain, impaired mobility and disfigurement. Herein, we prepared a kind of light-sensitive decellularized dermal extracellular matrix-derived hydrogel with fast gelling performance, biomimetic porous microstructure and abundant bioactive functions. On account of its excellent cell biocompatibility, this ECM-derived hydrogel could induce a marked cellular infiltration and enhance the tube formation of HUVECs. In vivo experiments based upon excisional wound splinting model showed that the hydrogel prominently imparted skin wound healing, as evidenced by notably increased skin appendages and well-organized collagen expression, coupled with significantly enhanced angiogenesis. Moreover, the skin regeneration mediated by this bioactive hydrogel was promoted by an accelerated M1-to-M2 macrophage phenotype transition. Consequently, the decellularized dermal matrix-derived bioactive hydrogel orchestrates the entire skin healing microenvironment to promote wound healing and will be of high value in treatment of cutaneous wound healing. As such, this biomimetic ddECMMA hydrogel provides a promising versatile opinion for the clinical translation.

Cutaneous wounds remain a major clinical challenge that urgently requires the development of advanced and functional wound dressings. During the wound healing process, macrophages are well known to exhibit temporal dynamics with a pro-inflammatory phenotype at early stages and a pro-healing phenotype at late stages, thus playing an important role in regulating inflammatory responses and tissue regeneration. Meanwhile, disrupted temporal dynamics of macrophages caused by poor wound local conditions and deficiency of macrophage function always impair the wound-healing progression. Here in this work, we proposed a novel controllable strategy to construct a spatiotemporal dynamical immune-microenvironment for the treatment of cutaneous wounds. To achieve this goal, a concentric decellularized dermal hydrogel was constructed with the combination of type 1 and type 2 macrophage-associated cytokine complexes in the sheath portion and core portion, respectively. The in vitro degradation experiment exhibited a sequential cascade release of pro-inflammatory cytokines and pro-healing cytokines. The enhanced cell biocompatibility and tube formation of HUVECs were confirmed. A full-thickness skin defect model of rats was developed to analyze the effect of the spatiotemporal dynamical bioactive hydrogels on wound healing. Remarkable angiogenesis, rapid wound restoration, moderate extracellular matrix deposition and obvious skin appendage neogenesis were identified at different time points after treatment with the macrophage cytokine-based decellularized hydrogels. Consequently, the concentric decellularized hydrogels with spatiotemporal dynamics of immune cytokines have considerable potential for cell-free therapy for wound healing.

Background The extensive functional and structural remodeling that occurs in the brain after amputation often results in phantom limb pain (PLP). These closely related phenomena are still not fully understood. Methods Using magnetic resonance imaging (MRI) and graph theoretical analysis (GTA), we explored how alterations in brain cortical thickness (CTh) and structural covariance networks (SCNs) in upper limb amputees (ULAs) relate to PLP. In all, 45 ULAs and 45 healthy controls (HCs) underwent structural MRI. Regional network properties, including nodal degree, betweenness centrality (BC), and node efficiency, were analyzed with GTA. Similarly, global network properties, including global efficiency (Eglob), local efficiency (Eloc), clustering coefficient (Cp), characteristic path length (Lp), and the small‐worldness index, were evaluated. Results Compared with HCs, ULAs had reduced CThs in the postcentral and precentral gyri contralateral to the amputated limb; this decrease in CTh was negatively correlated with PLP intensity in ULAs. ULAs showed varying degrees of change in node efficiency in regional network properties compared to HCs (p < 0.005). There were no group differences in Eglob, Eloc, Cp, and Lp properties (all p > 0.05). The real‐worldness SCN of ULAs showed a small‐world topology ranging from 2% to 34%, and the area under the curve of the small‐worldness index in ULAs was significantly different compared to HCs (p < 0.001). Conclusion These results suggest that the topological organization of human CNS functional networks is altered after amputation of the upper limb, providing further support for the cortical remapping theory of PLP.

Bacterial contamination of soft tissue in open fractures leads to high infection rates. Pathogens and their resistance against therapeutic agents change with time and vary in different regions. The purpose of this study was to characterize the bacterial spectrum present in open fractures and analyze the bacterial resistance to antibiotic agents based on five trauma centers in East China. A retrospective multicenter cohort study was conducted in six major trauma centers in East China from January 2015 to December 2017. Patients who sustained open fractures of the lower extremities were included. The data collected included the mechanism of injury, the Gustilo-Anderson classification, the isolated pathogens and their resistance against therapeutic agents, as well as the prophylactic antibiotics administered. In total, 1348 patients were included in our study, all of whom received antibiotic prophylaxis (cefotiam or cefuroxime) during the first debridement at the emergency room. Wound cultures were taken in 1187 patients (85.8%); the results showed that the positive rate of open fracture was 54.8% (651/1187), and 59% of the bacterial detections occurred in grade III fractures. Most pathogens (72.7%) were sensitive to prophylactic antibiotics, according to the EAST guideline. Quinolones and cotrimoxazole showed the lowest rates of resistance. The updated EAST guidelines for antibiotic prophylaxis in open fracture (2011) have been proven to be adequate for a large portion of patients, and we would like to suggest additional Gram-negative coverage for patients with grade II open fractures based on the results obtained in this setting in East China.

Hydrogel-based chondrocyte implantation presents a promising tissue engineering strategy for cartilage repair. However, the widely used elastic hydrogels usually restrict cell volume expansion and induce the dedifferentiation of encapsulated chondrocytes. To address this limitation, a photoannealed granular hydrogel (GH) composed of hyaluronic acid, polyethylene glycol, and gelatin was formulated for cartilage regeneration in this study. The unannealed GH prepared by Diels-Alder cross-linked microgels could be mixed with chondrocytes and delivered to cartilage defects by injection, after which light was introduced to anneal the scaffold, leading to the formation of a stable and microporous chondrocyte deploying scaffold. The in vitro studies showed that GH could promote the volume expansion and morphology recovery of chondrocytes and significantly improve their chondrogenic phenotype compared to the nongranular hydrogel (nGH) with similar compositions. Further in vivo studies of subcutaneous culture and the rat full-thickness cartilage defect model proved that chondrocyte loaded GH could significantly stimulate hyaline cartilage matrix deposition and connection, therefore facilitating hyaline-like cartilage regeneration. Finally, the mechanistic study revealed that GH might improve chondrogenic phenotype via activating the AMP-activated protein kinase/glycolysis axis. This study proves the great feasibility of GHs as in situ chondrocyte deploying scaffolds for cartilage regeneration and brings new insights in designing hydrogel scaffold for cartilage tissue engineering.

Background Insufficient staff of cytology limited the spread of on-site rapid cytology evaluation (ROSE). Therefore, trained endosonographers performing ROSE became an option. To explore the effect of visualization aids memory in cytology learning, we assessed the impact of image-associative teaching versus traditional didactic teaching of cytopathology for novice endosonographers in a limited time. Methods EUS trainees without previous training in cytopathology were invited to participate in this study. Participants in period 1 attended traditional didactic learning, and trainees in period 2 received images-associative teaching. The images in the period 2 tutorial were cytopathology images combined with their simulation images. Whereas in period 1, cytopathologic images were described in pathological terminology only. After the theoretical study, trainees received a knowledge quiz and an assessment for real smear interpretation. Results Seventeen trainees attended traditional didactic learning. Whereas the other eight participated in image-associative learning. In the theory test, the correct overall rate of trainees in period 2 was higher than that of the trainees in period 1 (76.92% vs. 53.85%). In the evaluation of real smear reviews, the performance of trainees in period 2 was still better than that of the trainees in period 1 (the median correct rate 100% versus 75%). Conclusion The use of image-associative tutorials allows more efficient use of time and is then feasible for the study of ROSE.

Background In traumatic spinal cord injury (SCI), secondary injuries, including vascular injury, cellular death, mitochondrial dysfunction, and vascular injury, have been considered as important causes of impaired functional recovery after SCI. Postinjury angiogenesis has been considered to be a potential strategy for SCI treatment. New-born vessels may play a key role in nerve regeneration, which indicates the importance of angiogenesis in nerve regeneration. Recent studies have revealed the crosstalk between reactive oxygen species (ROS) and angiogenesis. As the main source of cellular ROS, mitochondria have been proven to be essential to the angiogenesis process. Methods SCI was established in a T10 clip-compression animal model. Then, the animals received an intraperitoneal injection of MitoQ (1 mg/ml) on Days 0, 1, and 2 after surgery. The Basso Mouse Scale (BMS) score and footprint analysis (CatWalk analysis) were performed to evaluate functional recovery after SCI. Immunofluorescence assay (LEL-FITC/CD31/Iba-1/Neurofilament) was performed to evaluate angiogenesis, microglia activation and neural regeneration. RT-qPCR (VEGFR-1, VEGFR-2 and VEGFA) was performed to evaluate angiogenesis-related factor in injured spinal cord. ATP production assay and western-blotting assay (Mfn-1 and Drp-1) were performed to evaluate mitochondrial function in the injured spinal cord. BV2 cells were used as in vitro cell models. After receiving TBHP or TBHP-MitoQ treatment, ELISA and immunofluorescence assays were used to evaluate the level of VEGFA secretion from BV2 cells. A coculture system of HUVECs and BV2 cells was established. Tube formation assays and immunofluorescence assays (CD31) were performed on HUVECs in a coculture system to evaluate angiogenesis promotion. ATP production assays were performed to evaluate mitochondrial function in BV2 cells. MitoSOX Red and DCFH-DA staining were performed to evaluate mitochondrial and cellular ROS. Results In vitro MitoQ promoted the secretion of VEGFA from BV2 cells, which was verified through ELISA and immunofluorescence assays. The angiogenic promotion of MitoQ-treated BV2 cells was evaluated by tube formation and immunofluorescence assays (CD31) in a coculture system of BV2 cells and HUVECs. MitoQ inhibited cellular and mitochondrial-derived ROS in TBHP-treated BV2 cells. ATP production was increased in MitoQ-treated BV2 cells. To verify MitoQ’s effect in vivo, a T10 clip-compression animal model was established successfully. MitoQ significantly promoted functional recovery, as shown by the BMS assay and gait analyser. The promotion of neural regeneration was identified through immunofluorescence assay of neurofilament. Immunofluorescence assay (LEL-FITC/CD31/Iba-1) and RT-qPCR (VEGFR-1, VEGFR-2 and VEGFA) indicated that MitoQ could promote angiogenesis and inhibit macrophage/microglia activation in lesion-site after SCI. Enhanced ATP production and increased Mfn-1 with decreased Drp-1 protein expression showed MitoQ could promote mitochondrial function in SCI. Conclusion The mitochondrial-specific antioxidant MitoQ promotes functional recovery and tissue preservation through the enhancement of angiogenesis with the modification of mitochondrial function after SCI.

Inhibitors that target diabetes pathology-related signaling pathways have great therapeutic potential for diabetic wound healing. Metal—organic frameworks (MOFs) are increasingly popular drug delivery systems that have high loading capacity and can release their intrinsic metal ions to act as bioactive agents. In light of this, a receptor for advanced glycation end products (RAGE) inhibitor, 4-chloro-N-cyclohexyl-N-(phenylmethyl)-benzamide (FPS-ZM1), was loaded into a cobalt (Co)-based MOF (zeolitic imidazolate framework-67, ZIF-67) to fabricate FPS-ZM1 encapsulated ZIF-67 (FZ@ZIF-67) nanoparticles (NPs). As a result, FZ@ZIF-67 NPs could dually deliver Co ions and FPS-ZM1 in a controlled manner for over 14 days. Our in vitro study showed that FZ@ZIF-67 NPs not only enhanced angiogenesis by delivering Co ions but also released FPS-ZM1 to promote M2 macrophage polarization and attenuated high glucose (HG)- and/or inflammation-induced impairment of angiogenesis through RAGE inhibition. Moreover, in an in vivo study, FZ@ZIF-67 NPs markedly improved re-epithelialization, collagen deposition, neovascularization, and relieved inflammation in diabetic wounds in rats. This study not only provides a low-cost, effective, and synergistic proangiogenic bioactive agent but also demonstrates that targeting diabetes-related pathological signaling pathways is necessary to ameliorate vascularization impairment during diabetic wound healing.