Catechins: Therapeutic Perspectives in COVID-19-Associated Acute Kidney Injury

Data obtained from several intensive care units around the world have provided substantial evidence of the strong association between impairment of the renal function and in-hospital deaths of critically ill COVID-19 patients, especially those with comorbidities and requiring renal replacement therapy (RRT). Acute kidney injury (AKI) is a common renal disorder of various etiologies characterized by a sudden and sustained decrease of renal function. Studies have shown that 5–46% of COVID-19 patients develop AKI during hospital stay, and the mortality of those patients may reach up to 100% depending on various factors, such as organ failures and RRT requirement. Catechins are natural products that have multiple pharmacological activities, including anti-coronavirus and reno-protective activities against kidney injury induced by nephrotoxic agents, obstructive nephropathies and AKI accompanying metabolic and cardiovascular disorders. Therefore, in this review, we discuss the anti-SARS-CoV-2 and reno-protective effects of catechins from a mechanistic perspective. We believe that catechins may serve as promising therapeutics in COVID-19-associated AKI due to their well-recognized anti-SARS-CoV-2, and antioxidant and anti-inflammatory properties that mediate their reno-protective activities.     

间充质干细胞扩增载体材料

间充质干细胞(MSCs)具有高度自我更新能力、多分化潜能、体外易分离和培养的特性,是细胞治疗和组织工程重要的种子细胞来源,但如何大规模地获得具有可再生活性的MSCs一直是限制其临床应用的关键因素,近几年发展起来的贴壁动物细胞动态培养技术为MSCs的大规模体外扩增提供了一条重要的途径。本综述结合动物细胞扩增载体的发展现状,主要介绍了用于间充质干细胞三维动态培养的明胶载体、海藻酸盐载体、壳聚糖载体和其他多糖载体等常规载体及其表面修饰和改性方法,并进一步介绍了以非酶解途径回收扩 增细胞的新型干细胞载体的研究进展。随着新型载体材料的涌现以及人们对干细胞生长和扩增特点的了解,采用三维动态培养技术安全而有效地大规模体外扩增MSCs的必要性将得到进一步的确认。     

Mimicking Nanofibrous Hybrid Bone Substitute for Mesenchymal Stem Cells Differentiation into Osteogenesis

Mimicking hybrid extracellular matrix is one of the main challenges for bone tissue engineering (BTE). Biocompatible polycaprolactone/poly(α,β)‐DL ‐aspartic acid/collagen nanofibrous scaffolds were fabricated by electrospinning and nanohydroxyapatite (n‐HA) was deposited by calcium phosphate dipping method for BTE. Human mesenchymal stem cells (hMSCs) were cultured on these hybrid scaffolds to investigate the cell proliferation, osteogenic differentiation by alkaline phosphatase activity, mineralization, double immunofluorescent staining using CD90 and expression of osteocalcin. The present study indicated that the PCL/PAA/collagen/n‐HA scaffolds promoted greater osteogenic differentiation of hMSCs, proving to be a potential hybrid scaffolds for BTE.

     

Restraint of the Differentiation of Mesenchymal Stem Cells by a Nonfouling Zwitterionic Hydrogel

The success of human mesenchymal stem cell (hMSC) therapies is largely dependent on the ability to maintain the multipotency of cells and control their differentiation. External biochemical and biophysical cues can readily trigger hMSCs to spontaneously differentiate, thus resulting in a rapid decrease in the multipotent cell population and compromising their regenerative capacity. Herein, we demonstrate that nonfouling hydrogels composed of pure poly(carboxybetaine) (PCB) enable hMSCs to retain their stem‐cell phenotype and multipotency, independent of differentiation‐promoting media, cytoskeletal‐manipulation agents, and the stiffness of the hydrogel matrix. Moreover, encapsulated hMSCs can be specifically induced to differentiate down osteogenic or adipogenic pathways by controlling the content of fouling moieties in the PCB hydrogel. This study examines the critical role of nonspecific interactions in stem‐cell differentiation and highlights the importance of materials chemistry in maintaining stem‐cell multipotency and controlling differentiation.     

中国小型猪骨髓间充质干细胞的蛋白质组研究

报道了骨髓间充质干细胞(MSCs)的蛋白质组表达研究。从体外培养的MSCs提取细胞蛋白,经二维电泳分离后用银染方法可检出蛋白点约1600个,选取48个蛋白点进行胶内酶解及质谱分析,经数据库检索成功鉴定了37个蛋白,并对蛋白功能进行初步分析。本实验数据为进一步分析MSCs增殖、分化或凋亡的分子机理提供相关信息。     

Hispidulin Ameliorates Endotoxin-Induced Acute Kidney Injury in Mice

Lipopolysaccharide (LPS) is an endotoxin that plays a crucial role in septic acute kidney injury (AKI). Hispidulin is a natural flavonoid that possesses various biological activities. Recent studies have shown that hispidulin administration alleviates various inflammatory diseases in animal models. This study aimed to investigate the renoprotective effect of hispidulin on LPS-induced AKI. Male C57BL/6 mice were administered LPS (10 mg/kg) with or without hispidulin (50 mg/kg). Hispidulin administration attenuated renal dysfunction, histological alterations, and the upregulation of neutrophil gelatinase-associated lipocalin. This flavonoid also reduced cytokine production and Toll-like receptor 4 expression, inhibited nuclear factor-κB and mitogen-activated protein kinase cascades, and alleviated immune cell infiltration. The oxidation of lipids and DNA was also inhibited by hispidulin administration. This antioxidant effect of hispidulin was associated with the downregulation of NADPH oxidase 4, the activation of catalase and superoxide dismutase activities, and the restoration of glutathione levels. Moreover, hispidulin administration attenuated tubular cell apoptosis by inhibiting caspase-3 pathway. These data suggest that hispidulin ameliorates endotoxin-induced kidney injury by suppressing inflammation, oxidative stress, and tubular cell death.     

干细胞迁移机理的近场扫描光学显微术研究

将内皮细胞生长因子(VEGF)置于甲基纤维素碟中形成VEGF的浓度梯度分布,并将人脐带间充质干细胞(Mesenchymal stem cells,MSCs)于此浓度梯度中培养,观察VEGF能否诱导MSCs定向迁移。应用近场扫描光学显微术(Near-field scanning optical microscopy,NSOM)同时获取了VEGF诱导前后的MSCs的形貌和光学信息。结果表明,近场光学图观测到形貌图上所没有的黑色斑点,分析认为这些黑斑为细胞的黏着斑。近场光学图显示经过VEGF诱导后细胞的黏着斑数量明显增加。同时,对诱导前后干细胞的骨架蛋白进行免疫荧光标记并用共聚焦显微镜进行观察,结果表明细胞骨架由诱导前的无序状态转变为诱导后的有序状态,说明诱导后的干细胞处于迁移状态。光学超微结构图则显示了诱导后干细胞表面的光学细节比诱导前细胞大量增加,出现了大量直径约200 nm的光斑,这是由于细胞表面大量分泌黏附分子等蛋白分子引起的,这些结果为VEGF能够诱导MSCs进行定向迁移提供了实验依据和可视化证明。也表明NSOM不但能提供高分辨的光学分辨率,还可提供生物细胞精细结构的更深层次的光学信息。     

Photocontrolled Multidirectional Differentiation of Mesenchymal Stem Cells on an Upconversion Substrate

The effective guidance of mesenchymal stem cell (MSC) differentiation on a substrate by near‐infrared (NIR) light is particularly attractive for tissue engineering and regenerative medicine. However, most of current substrates cannot control multidirectional differentiation of MSCs like natural tissues. Herein, a photocontrolled upconversion‐based substrate was designed and constructed for guiding multidirectional differentiation of MSCs. The substrate enables MSCs to maintain their stem‐cell characteristics due to the anti‐adhesive effect of 4‐(hydroxymethyl)‐3‐nitrobenzoic acid modified poly(ethylene glycol) (P1) attached on the upconversion substrate. Upon NIR irradiation, the P1 is released from the substrate by photocleavage. The detachment of P1 can change cell–matrix interactions dynamically. Moreover, MSCs cultured on the upconversion substrate can be specifically induced to differentiate to adipocytes or osteoblasts by adjusting the NIR laser. Our work provides a new way of using NIR‐based upconversion substrate to modulate the multidirectional differentiation of MSCs.     

大鼠骨髓间充质干细胞分化过程的比较蛋白质组学研究

从蛋白质组学角度分析大鼠骨髓间充质干细胞(MSCs)体外定向分化为心肌细胞过程中蛋白表达情况, 采用二维电泳分离蛋白, 用PDQuest软件分析蛋白表达差异, 并采用质谱(MALDI-TOF-MS)进行鉴定, 得到了54个蛋白点, 对蛋白的生物功能分析表明, 部分蛋白通过不同的信号途径参与了MSCs的分化过程.     

Ex Vitro Expansion of Human Placenta-Derived Mesenchymal Stem Cells in Stirred Bioreactor

The high demand of human placenta-derived mesenchymal stem cells (hPDMSCs) for therapeutic applications requires reproducible production of large numbers of well-characterized cells under well-controlled conditions. However, no method for fast hPDMSCs proliferation has yet been reported. In the present study, the feasibility of using a stirred bioreactor system to expand hPDMSCs was examined. hPDMSCs were cultured either in stirred bioreactors or in tissue culture flasks (T-flasks) for 5 days. Total cell density and several parameters of physical microenvironments were monitored in the two culture systems every 24 h. The maintenance of the antigenic phenotype of hPDMSCs before and after culturing in the stirred bioreactor system was cytometrically assessed. Data suggested that the physical microenvironment in the stirred bioreactors was much more favorable than that of the T-flasks. At the end of 144 h culturing, the total cell number was increased 1.73 times from the T-flasks to the stirred bioreactors. In addition, hPDMSCs could maintain their antigenic phenotype when cultured in stirred bioreactors. These results provide the initial assessment for large-scale hPDMSCs production using suspension culture bioreactors.     

Osmolyte Type and the Osmolarity Level Affect Chondrogenesis of Mesenchymal Stem Cells

The inductive effects of increased osmolarity on chondrogenesis are well approved. However, the effects of the osmolyte agent invoked to induce hyperosmolarity are largely neglected. Herein, we scrutinized how hyperosmotic conditions acquired by addition of different osmolytes would impact chondrogenesis. We briefly assessed whether such conditions would differentially affect hypertrophy and angiogenesis during MSC chondrogenesis. Chondrogenic and hypertrophic marker expression along with VEGF secretion during adipose-derived (AD)-MSC chondrogenesis under three osmolarity levels (350, 450, and 550 mOsm) using three different osmolytes (NaCl, sorbitol, and PEG) were assessed. MTT assay, qRT-PCR, immunocytochemistry, Alcian Blue staining, ELISA, and ALP assays proved osmolyte-type dependent effects of hyperosmolarity on chondrogenesis, hypertrophy, and angiogenesis. At same osmolarity level, PEG had least cytotoxic/cytostatic effect and most prohibitive effects on angiogenesis. As expected, all hyperosmolar conditions led to enhanced chondrogenesis with slightly varying degrees. PEG and sorbitol had higher chondro-promotive and hypertrophy-suppressive effects compared to NaCl, while NaCl had exacerbated hypertrophy. We observed that TonEBP was involved in osmoadaptation of all treatments in varying degrees. Of importance, we highlighted differential effects of hyperosmolarity obtained by different osmolytes on the efficacy of chondrogenesis and more remarkably on the induction/suppression of cartilage pathologic markers. Our study underlies the need for a more vigilant exploitation of physicobiochemical inducers in order to maximize chondrogenesis while restraining unwanted hypertrophy and angiogenesis.     

Mineralized Synthetic Matrices as an Instructive Microenvironment for Osteogenic Differentiation of Human Mesenchymal Stem Cells

The effect of substrate‐mediated signals on osteogenic differentiation of hMSCs is studied using a synthetic bone‐like material comprising both organic and inorganic components that supports adhesion, spreading, and proliferation of hMSCs. hMSCs undergo osteogenic differentiation even in the absence of osteogenesis‐inducing supplements. They exhibit higher expressions of Runx2, BSP, and OCN compared to their matrix‐rigidity‐matched, non‐mineralized hydrogel counterparts. The mineralized‐hydrogel‐assisted osteogenic differentiation of hMSCs could be attributed to their exposure to high local concentrations of calcium and phosphate ions in conjunction with chemical and topological cues arising from the hydrogel‐bound calcium phosphate mineral layer.

     

Polyphenol Oxidase as a Promising Alternative Therapeutic Agent for Cancer Therapy

Cancers have always been the most difficult to fight, the treatment of cancer is still not considered. Thus, exploring new anticancer drugs is still imminent. Traditional Chinese medicine has played an important role in the treatment of cancer. Polyphenol oxidase (PPO) extracted from Edible mushroom has many related reports on its characteristics, but its role in cancer treatment is still unclear. This study aims to investigate the effects of PPO extracted from Edible mushroom on the proliferation, migration, invasion, and apoptosis of cancer cells in vitro and explore the therapeutic effects of PPO on tumors in vivo. A cell counting kit-8 (CCK8) assay was used to detect the effect of PPO on the proliferation of cancer cells. The effect of PPO on cancer cell migration ability was detected by scratch test. The effect of PPO on the invasion ability of cancer cells was detected by a transwell assay. The effect of PPO on the apoptosis of cancer cells was detected by flow cytometry. Female BALB/c mice (18–25 g, 6–8 weeks) were used for in vivo experiments. The experiments were divided into control group, model group, low-dose group (25 mg/kg), and high-dose group (50 mg/kg). In vitro, PPO extracted from Edible mushroom significantly inhibited the proliferation, migration, and invasion capability of breast cancer cell 4T1, lung cancer cell A549, and prostate cancer cell C4-2, and significantly promoted the apoptosis of 4T1, A549, and C4-2. In vivo experiments showed PPO inhibitory effect on tumor growth. Collectively, the edible fungus extract PPO could play an effective role in treating various cancers, and it may potentially be a promising agent for treating cancers.     

Electrical Stimulation of Human Mesenchymal Stem Cells on Conductive Substrates Promotes Neural Priming

Electrical stimulation (ES) within a conductive scaffold is potentially beneficial in encouraging the differentiation of stem cells toward a neuronal phenotype. To improve stem cell-based regenerative therapies, it is essential to use electroconductive scaffolds with appropriate stiffnesses to regulate the amount and location of ES delivery. Herein, biodegradable electroconductive substrates with different stiffnesses are fabricated from chitosan-grafted-polyaniline (CS-g-PANI) copolymers. Human mesenchymal stem cells (hMSCs) cultured on soft conductive scaffolds show a morphological change with significant filopodial elongation after electrically stimulated culture along with upregulation of neuronal markers and downregulation of glial markers. Compared to stiff conductive scaffolds and non-conductive CS scaffolds, soft conductive CS-g-PANI scaffolds promote increased expression of microtubule-associated protein 2 (MAP2) and neurofilament heavy chain (NF-H) after application of ES. At the same time, there is a decrease in the expression of the glial markers glial fibrillary acidic protein (GFAP) and vimentin after ES. Furthermore, the elevation of intracellular calcium [Ca²⁺] during spontaneous, cell-generated Ca²⁺ transients further suggests that electric field stimulation of hMSCs cultured on conductive substrates can promote a neural-like phenotype. The findings suggest that the combination of the soft conductive CS-g-PANI substrate and ES is a promising new tool for enhancing neuronal tissue engineering outcomes.     

Scaffold Effects on Osteogenic Differentiation of Equine Mesenchymal Stem Cells: An In Vitro Comparative Study

The in vitro viability, osteogenic differentiation, and mineralization of four different equine mesenchymal stem cells (MSCs) from bone marrow, periosteum, muscle, and adipose tissue are compared, when they are cultured with different collagen‐based scaffolds or with fibrin glue. The results indicate that bone marrow cells are the best source of MSCs for osteogenic differentiation, and that an electrochemically aggregated collagen gives the highest cell viability and best osteogenic differentiation among the four kinds of scaffolds studied.

     

Molecular Mobility of Polyrotaxane Surfaces Alleviates Oxidative Stress-Induced Senescence in Mesenchymal Stem Cells

Polyrotaxane is a supramolecular assembly consisting of multiple cyclic molecules threaded by a linear polymer. One of the unique properties of polyrotaxane is molecular mobility, cyclic molecules moving along the linear polymer. Molecular mobility of polyrotaxane surfaces affects cell spreading, differentiation, and other cell-related aspects through changing subcellular localization of yes-associated proteins (YAPs). Subcellular YAP localization is also related to cell senescence derived from oxidative stress, which is known to cause cancer, diabetes, and heart disease. Herein, the effects of polyrotaxane surface molecular mobility on subcellular YAP localization and cell senescence following H₂O₂-induced oxidative stress are evaluated in human mesenchymal stem cells (HMSCs) cultured on polyrotaxane surfaces with different molecular mobilities. Oxidative stress promotes cytoplasmic YAP localization in HMSCs on high-mobility polyrotaxane surfaces; however, low-mobility polyrotaxane surfaces more effectively maintain nuclear YAP localization, exhibiting lower senescence-associated β-galactosidase activity and senescence-related gene expression and DNA damage than that seen with the high-mobility surfaces. These results suggest that the molecular mobility of polyrotaxane surfaces regulates subcellular YAP localization, thereby protecting HMSCs from oxidative stress-induced cell senescence. Applying the molecular mobility of polyrotaxane surfaces to implantable scaffolds can provide insights into the prevention and treatment of diseases caused by oxidative stress.