Effects of low oxygen tension on gene profile of soluble growth factors in co-cultured adipose-derived stromal cells and chondrocytes

Dihydrocapsaicin suppresses the STING-mediated accumulation of ROS and NLRP3 inflammasome and alleviates apoptosis after ischemia-reperfusion injury of perforator skin flap

Avascular necrosis frequently occurs as a complication following surgery involving the distal perforator flap. Dihydrocapsaicin (DHC) can protect tissue from ischemia-reperfusion (I/R) injury, but its specific role in multizone perforator flaps remains unclear. In this study, the prospective target of DHC in the context of I/R injury was predicted using network pharmacology analysis. Flap viability was determined through survival area analysis, laser Doppler blood flow, angiograms, and histological examination. The expressions of angiogenesis, apoptosis, NLR family pyrin domain containing 3 (NLRP3) inflammasome, oxidative stress, and molecules related to cyclic guanosine monophosphate (GMP)-adenosine monophosphate synthase (cGAS)-interferon gene stimulant (STING) pathway were assessed using western blotting, immunofluorescence, TUNEL staining, and dihydroethidium (DHE) staining. Our finding revealed that DHC promoted the perforator flap survival, which involves the cGAS-STING pathway, oxidative stress, NLRP3 inflammasome, apoptosis, and angiogenesis. DHC induced oxidative stress resistance and suppressed the NLRP3 inflammasome, preventing apoptosis in vascular endothelial cells. Through regulation of STING pathway, DHC controlled oxidative stress in endothelial cells and NLRP3 levels in ischemic flaps. However, activation of the cGAS-STING pathway led to the accumulation of reactive oxygen species (ROS) and NLRP3 inflammasome, thereby diminishing the protective role of DHC. DHC enhanced the survival of multidomain perforator flaps by suppressing the cGAS-STING pathway, oxidative stress, and the formation of NLRP3 inflammasome. These findings unveil a potentially novel mechanism with clinical significance for promoting the survival of multidomain perforator flaps.

Hypoxia Promotes Cartilage Regeneration in Cell-Seeded 3D-Printed Bioscaffolds Cultured with a Bespoke 3D Culture Device

In this study, we investigated the effect of oxygen tension on the expansion of ADMSCs and on their differentiation toward their chondrocytic phenotype, regenerating a lab-based cartilaginous tissue with superior characteristics. Controversial results with reference to MSCs that were cultured under different hypoxic levels, mainly in 2D culturing settings combined with or without other biochemical stimulus factors, prompted our team to study the role of hypoxia on MSCs chondrogenic differentiation within an absolute 3D environment. Specifically, we used 3D-printed honeycomb-like PCL matrices seeded with ADMSCs in the presence or absence of TGF and cultured with a prototype 3D cell culture device, which was previously shown to favor nutrient/oxygen supply, cell adhesion, and infiltration within scaffolds. These conditions resulted in high-quality hyaline cartilage that was distributed uniformly within scaffolds. The presence of the TGF medium was necessary to successfully produce cartilaginous tissues with superior molecular and increased biomechanical properties. Despite hypoxia's beneficial effect, it was overall not enough to fully differentiate ADMSCs or even promote cell expansion within 3D scaffolds alone.

Cartilage 3D bioprinting for rhinoplasty using adipose-derived stem cells as seed cells: Review and recent advances

Nasal deformities due to various causes affect the aesthetics and use of the nose, in which case rhinoplasty is necessary. However, the lack of cartilage for grafting has been a major problem and tissue engineering seems to be a promising solution. 3D bioprinting has become one of the most advanced tissue engineering methods. To construct ideal cartilage, bio-ink, seed cells, growth factors and other methods to promote chondrogenesis should be considered and weighed carefully. With continuous progress in the field, bio-ink choices are becoming increasingly abundant, from a single hydrogel to a combination of hydrogels with various characteristics, and more 3D bioprinting methods are also emerging. Adipose-derived stem cells (ADSCs) have become one of the most popular seed cells in cartilage 3D bioprinting, owing to their abundance, excellent proliferative potential, minimal morbidity during harvest and lack of ethical considerations limitations. In addition, the co-culture of ADSCs and chondrocytes is commonly used to achieve better chondrogenesis. To promote chondrogenic differentiation of ADSCs and construct ideal highly bionic tissue-engineered cartilage, researchers have used a variety of methods, including adding appropriate growth factors, applying biomechanical stimuli and reducing oxygen tension. According to the process and sequence of cartilage 3D bioprinting, this review summarizes and discusses the selection of hydrogel and seed cells (centered on ADSCs), the design of printing, and methods for inducing the chondrogenesis of ADSCs.

Protein kinase D1 promotes the survival of random-pattern skin flaps in rats

BACKGROUND

In reconstructive surgery, random skin flaps are commonly used tools to cover skin defects, however, their applicability and size are limited by post-operative complications such as marginal ischemia-reperfusion injury and flap necrosis. Protein kinase D1 (PKD1), a calcium/calmodulin-dependent serine/threonine kinase, is known to induce angiogenesis and has been shown to mitigate ischemia in cardiovascular diseases. However, the role of PKD1 has not been investigated in skin flaps.

METHOD

Seventy-five male Sprague-Dawley rats with skin flaps were randomly divided into three groups: control, PKD1, and CID755673. Seven days following surgery, we assessed the general view and survival rate of the flap using histological analysis. Laser Doppler and lead oxide/gelatin angiography were used to evaluate microcirculation blood flow. Histopathological changes, neovascularization and microvascular density (MVD). were examined and calculated using microscopy after H&E staining. Protein expression levels were determined using immunoblotting and immunohistochemistry techniques.

RESULT

PKD1 significantly improved flap survival by upregulating angiogenic factors VEGF and cadherin5 and increasing antioxidant enzymes SOD, eNOS, and HO1, as well as reducing caspase 3, cytochrome c, and Bax expression, and attenuating IL-1β, IL-6, and TNF-α. In the PKD1 group, PKD1 increased neovascularization, and blood flow and flap survival areas were larger as compared to the control and CID755673 groups.

CONCLUSION

These findings show that PKD1 accelerates angiogenesis, reduces oxidative stress, and impedes apoptosis and inflammation, thus resulting in improved flap survival. Our observations indicated that PKD1 could be a therapeutic target for flap failure treatment.

Characterization of Scleraxis and SRY-Box 9 from Adipose-Derived Stem Cells Culture Seeded with Enthesis Scaffold in Hypoxic Condition

The use of mesenchymal stem cells can add local improvements potential to enthesis tissue regeneration based on tropical activity through secretions of growth factors, cytokines, and vesicles (e.g. exosomes), collectively known as secretomes. This study aims to analyze secretomes characterization from adipose-derived mesenchymal stem cells seeded with enthesis tissue scaffold in hypoxic conditions and to analyze the influence of hypoxic environment to the characterization of secretomes. This is an in-vitro study using a Randomized Control Group Post-Test Only design. This study using Adipose Stem Cells (ASCs) were cultured in hypoxia (Oxygen 5%) and Normoxia (21%) condition. The scaffolds are fresh-frozen enthesis tissue and was seeded in the treatment group and compared to control. The evaluation of Scleraxis (Scx) and SRY-box (Sox9) was measured using ELISA on the 2nd, 4th, and 6th days. Comparison of Scx levels between each evaluation time showed a positive trend in a group with scaffold in hypoxia condition although it has no significant differences (p=0.085), with the highest level on day 6, that is 13,568 ng/ml. Conversely, the comparison of Sox9 showed significant differences (p=0.02) in a group with scaffold in hypoxia condition, with the highest level on day 4, that is 28,250 ng/ml. The use of enthesis scaffold seeded in adipose-derived mesenchymal stem cells in hypoxic conditions shows a positive trend as regenerative effort of injured enthesis tissue through Scleraxis and Sox9 secretomes induction.

The Application of Bioreactors for Cartilage Tissue Engineering: Advances, Limitations, and Future Perspectives

Tissue engineering (TE) has brought new hope for articular cartilage regeneration, as TE can provide structural and functional substitutes for native tissues. The basic elements of TE involve scaffolds, seeded cells, and biochemical and biomechanical stimuli. However, there are some limitations of TE; what most important is that static cell culture on scaffolds cannot simulate the physiological environment required for the development of natural cartilage. Recently, bioreactors have been used to simulate the physical and mechanical environment during the development of articular cartilage. This review aims to provide an overview of the concepts, categories, and applications of bioreactors for cartilage TE with emphasis on the design of various bioreactor systems.

Co-culture and Mechanical Stimulation on Mesenchymal Stem Cells and Chondrocytes for Cartilage Tissue Engineering

Defects in articular cartilage injury and chronic osteoarthritis are very widespread and common, and the ability of injured cartilage to repair itself is limited. Stem cell-based cartilage tissue engineering provides a promising therapeutic option for articular cartilage damage. However, the application of the technique is limited by the number, source, proliferation, and differentiation of stem cells. The co-culture of mesenchymal stem cells and chondrocytes is available for cartilage tissue engineering, and mechanical stimulation is an important factor that should not be ignored. A combination of these two approaches, i.e., co-culture of mesenchymal stem cells and chondrocytes under mechanical stimulation, can provide sufficient quantity and quality of cells for cartilage tissue engineering, and when combined with scaffold materials and cytokines, this approach ultimately achieves the purpose of cartilage repair and reconstruction. In this review, we focus on the effects of co-culture and mechanical stimulation on mesenchymal stem cells and chondrocytes for articular cartilage tissue engineering. An in-depth understanding of the impact of co-culture and mechanical stimulation of mesenchymal stem cells and chondrocytes can facilitate the development of additional strategies for articular cartilage tissue engineering.

Effect of low oxygen tension on transcriptional factor OCT4 and SOX2 expression in New Zealand rabbit bone marrow-derived mesenchymal stem cells

Background and Aim:

Octamer-binding transcription factor 4 (OCT4) and sex-determining region Y-box 2 (SOX2) are transcription factors whose functions are essential to maintain the pluripotency of embryonic stem cells. The purpose of this study was to derive stem cells for in vitro culture and to maintain their viability and pluripotency, with the goal to obtain a cell line for transplantation in patients with degenerative diseases or injuries. This research focused on examining the effect of low oxygen tension on the ability of bone marrow-derived mesenchymal stem cells (BM-MSCs) to express OCT4 and SOX2 in vitro.

Materials and Methods:

BM-MSCs were obtained from femurs of 2000 to 3000 g New Zealand male rabbits. BM-MSCs were divided into three groups to test different culture conditions: A control group under hyperoxia condition (21% O₂) and two treatment groups with low oxygen tension (1% and 3% O₂). We characterized the BM-MSCs using flow cytometric measurement of cluster differentiation 44 (CD44) and cluster differentiation 90 (CD90) expression. The expression of OCT4 and SOX2 was measured by immunofluorescence staining after 48 h of incubation in chambers with normal or low oxygen tension with controlled internal atmosphere consisting of 95% N₂, 5% CO₂, and 1% O₂ (T1) and 3% O₂ (T2). We considered OCT4 and SOX2 as two markers of pluripotency induction. All immunofluorescence data were subjected to a post hoc normality Tukey’s honestly significant difference test; all differences with p<5% were considered significant.

Results:

BM-MSCs were positive for CD44 and CD90 expression after isolation. Oxygen tension culture conditions of 1% and 3% O₂ led to OCT4 and SOX2 expression on culture days 2 and 4 (p<0.05), respectively, as compared to the hyperoxia condition (21% O₂).

Conclusion:

Based on the OCT4 and SOX2 immunofluorescence data, we conclude that the stem cells were pluripotent at low O₂ tension (at 1% O₂ on day 2 and at 3% O₂ on day 4), whereas under 21% O₂ the OCT4 and SOX2 were not expressed.

Detrimental Effect of Sitagliptin Induced Autophagy on Multiterritory Perforator Flap Survival

Multiterritory perforator flap survival is commonly applied in surgical tissue reconstructions and covering of large skin defects. However, multiple risk factors such as ischemia, reperfusion injury, and apoptosis after reconstructive surgeries cause necrosis in distal parts with outcomes ranging from poor aesthetic appearance to reconstructive failure. A few studies have reported that sitagliptin (Sit) promotes angiogenesis and inhibits apoptosis. However, little is known about Sit-induced autophagy especially on the flap model. Therefore, our study investigated the effect of Sit and its induced autophagy on the perforator flap survival. Ninety male Sprague-Dawley rats were randomly separated into control, Sit, and Sit+3-methyladenine group. Results revealed that Sit significantly promoted flap survival by enhancing angiogenesis, reducing oxidative stress, and attenuating apoptosis. In addition, flap survival was further improved after co-administration with 3-methyladenine to inhibit autophagy. Overall, our results established that Sit has positive effects in promoting survival of multiterritory perforator flap. Sit-induced autophagy was detrimental for flap survival and its inhibition may further improve flap survival.

Pegylated carbon nitride nanosheets for enhanced reactive oxygen species generation and photodynamic therapy under hypoxic conditions

The application of photodynamic therapy (PDT) is of ever-increasing importance in the treatment of malignant tumors; however, there are several major constraints that make it impossible to achieve optimal therapeutic effects. Our objective is to develop a novel photosensitizing drug for skin cancer. In the experiment, we fabricated four-arm-poly ethylene glycol modified amino-rich graphite phase carbon nitride nanosheets (AGCN-PEG), which have good stability in physiological solution and show selective accumulation in tumor cells. Under hypoxic conditions, the AGCN-PEG induced PDT can effectively inhibit growth on A431 human epidermoid carcinoma cells in vivo and in vitro. What's more, after being combined with TMPyP4, the therapeutic effect of AGCN-PEG was greatly improved.

Trehalose promotes the survival of random-pattern skin flaps by TFEB mediated autophagy enhancement

Random-pattern skin flaps are commonly used and valuable tools in reconstructive surgery, however, post-operative random skin flap necrosis remains a major and common complication. Previous studies have suggested that activating autophagy, a major pathway for degradation of intracellular waste, may improve flap survival. In this study, we investigated whether trehalose, a novel and potent autophagy activator, improves random skin flap viability. Our results demonstrated that trehalose significantly improves viability, augments blood flow, and decreases tissue edema. Furthermore, we found that trehalose leads to increased angiogenesis, decreased apoptosis, and reduced oxidative stress. Using immunohistochestry and western blot, we demonstrated that trehalose augments autophagy, and that inhibition of autophagy augmentation using 3MA significantly blunted the aforementioned benefits of trehalose therapy. Mechanistically, we showed that trehalose’s autophagy augmentation is mediated by activation and nuclear translocation of TFEB, which may be due to inhibition of Akt and activation of the AMPK-SKP2-CARM1 signaling pathway. Altogether, our results established that trehalose is a potent agent capable for significantly increasing random-pattern skin flap survival by augmenting autophagy and subsequently promoting angiogenesis, reducing oxidative stress, and inhibiting cell death.

Synthesis of an ethyleneimine/tetrahedral DNA nanostructure complex and its potential application as a multi-functional delivery vehicle

Nowadays, DNA nanostructures are extensively researched for their biocompatibility, editable functionality, and structural stability. Tetrahedral DNA nanostructures (TDNs), widely known for their membrane permeability, are regarded as potential candidates for drug delivery. However, the stability and membrane permeability of TDNs call for further enhancement if in vivo usage is ascribed. To overcome the drawbacks of TDNs, ethylene imine (PEI, 25 kDa, branched)-a classic cationic polymer in the field of gene delivery-was applied. Via a facile one-pot synthesis method, a PEI/TDNs complex was formed. Subsequently, a DNase protection assay, a cytotoxicity assay, endocytosis-related experiments, and lysosome staining were performed to examine the potential of PEI/TDNs as a delivery vehicle. The combination of PEI and TDNs not only overcame the drawbacks of each substance but also retained their individual merits. Traditionally, drug-delivery vehicles that enable enhanced cell entry and lysosome escape are often compromised by their toxicity and poor multifunctionality. We believe this novel PEI/TDNs complex with enhanced systemic stability, biocompatibility, cell-entry ability, and lysosome-escape ability and unsurpassed editable functionality could be a powerful tool as a multi-functional delivery vehicle in targeted drug delivery, in vivo imaging, and other related fields.

Total Flavonoids in Caragana (TFC) Promotes Angiogenesis and Enhances Cerebral Perfusion in a Rat Model of Ischemic Stroke

Previous studies have demonstrated that total flavonoid extracts from Caragana sinica (TFC) exert multiple therapeutic effects, promote blood flow, and exhibit anti-inflammatory and antioxidant properties. The present study aimed to investigate whether TFC promotes angiogenesis and exerts neuroprotective effects in a rat model of transient middle cerebral artery occlusion (tMCAO). Male Wistar rats were subjected to tMCAO for 1.5 h, followed by 24 h of reperfusion. TFC (15, 30, 60 mg/kg) was administered for 14 days. Evaluations of neurological function were performed following reperfusion, and infarct volumes were assessed in brain slices stained with 2,3,5-triphenyltetrazolium chloride (TTC). Our results indicated that TFC significantly attenuated cerebral infarct volume and neurological deficits following tMCAO. Laser Doppler, micro-PET/CT, and MRI analyses further demonstrated that TFC reduced infarct volume and enhanced cerebral blood flow in a dose-dependent manner, with the most significant effects occurring at a concentration of 60 mg/kg. Significant up-regulation of CD31, VEGF, Ang-1, HIF-1α, delta-like 4 (Dll4), and Notch1 expression was also observed in the experimental groups, relative to that in the vehicle group. In summary, the results of the present study indicate that TFC (15, 30, 60 mg/kg) attenuates neurological deficits, reduces infarct volume, and promotes angiogenesis following MCAO in a concentration-dependent manner, likely via increases in the expression of CD31, VEGF, Ang-1, HIF-1α, Dll4, and Notch1. Further studies are required to determine the clinical usefulness and potential mechanisms of TFC in patients with cerebral focal ischemic stroke.

Magnesium enhances the chondrogenic differentiation of mesenchymal stem cells by inhibiting activated macrophage-induced inflammation

Magnesium deficiency increases the generation of pro-inflammatory cytokines, which is consistently accompanied by the sensitization of cells such as neutrophils, macrophages and endothelial cells. We investigated the potential of magnesium to regulate macrophage polarization and macrophage-induced inflammation with or without lipopolysaccharide (LPS) and interferon-γ (IFN-γ) activation and further elucidated whether these effects impact the inhibitory functions of activated macrophage-induced inflammation on cartilage regeneration. The results showed that magnesium inhibited the activation of macrophages, as indicated by a significant reduction in the percentage of CCR7-positive cells, while the percentage of CD206-positive cells decreased to a lesser degree. After activation, both pro-inflammatory and anti-inflammatory cytokines were down-regulated at the mRNA level and certain cytokines (IL-1β, IL-6 and IL-10) were decreased in the cell supernatant with the addition of magnesium. Moreover, magnesium decreased the nuclear translocation and phosphorylation of nuclear factor-κB (NF-κB) to impede its activation. A modified micromass culture system was applied to assess the effects of activated macrophage-conditioned medium with or without magnesium treatment on the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). Magnesium enhanced the chondrogenic differentiation of hBMSCs by reversing the adverse effects of activated macrophage-induced inflammation.

Effect of tetrahedral DNA nanostructures on proliferation and osteo/odontogenic differentiation of dental pulp stem cells via activation of the notch signaling pathway

Dental pulp stem cells (DPSCs) derived from the human dental pulp tissue have multiple differentiation capabilities, such as osteo/odontogenic differentiation. Therefore, DPSCs are deemed as ideal stem cell sources for tissue regeneration. As new nanomaterials based on DNA, tetrahedral DNA nanostructures (TDNs) have tremendous potential for biomedical applications. Here, the authors aimed to explore the part played by TDNs in proliferation and osteo/odontogenic differentiation of DPSCs, and attempted to investigate if these cellular responses could be driven by activating the canonical Notch signaling pathway. Upon exposure to TDNs, proliferation and osteo/odontogenic differentiation of DPSCs were dramatically enhanced, accompanied by up regulation of Notch signaling. In general, our study suggested that TDNs can significantly promote proliferation and osteo/odontogenic differentiation of DPSCs, and this remarkable discovery can be applied in tissue engineering and regenerative medicine to develop a significant and novel method for bone and dental tissue regeneration.

Angiogenesis in a 3D model containing adipose tissue stem cells and endothelial cells is mediated by canonical Wnt signaling

Adipose-derived stromal cells (ASCs) have gained great attention in regenerative medicine. Progress in our understanding of adult neovascularization further suggests the potential of ASCs in promoting vascular regeneration, although the specific cues that stimulate their angiogenic behavior remain controversial. In this study, we established a three-dimensional (3D) angiogenesis model by co-culturing ASCs and endothelial cells (ECs) in collagen gel and found that ASC-EC-instructed angiogenesis was regulated by the canonical Wnt pathway. Furthermore, the angiogenesis that occurred in implants collected after injections of our collagen gel-based 3D angiogenesis model into nude mice was confirmed to be functional and also regulated by the canonical Wnt pathway. Wnt regulation of angiogenesis involving changes in vessel length, vessel density, vessel sprout, and connection numbers occurred in our system. Wnt signaling was then shown to regulate ASC-mediated paracrine signaling during angiogenesis through the nuclear translocation of β-catenin after its cytoplasmic accumulation in both ASCs and ECs. This translocation enhanced the expression of nuclear co-factor Lef-1 and cyclin D1 and activated the angiogenic transcription of vascular endothelial growth factor A (VEGFA), basic fibroblast growth factor (bFGF), and insulin-like growth factor 1 (IGF-1). The angiogenesis process in the 3D collagen model appeared to follow canonical Wnt signaling, and this model can help us understand the importance of the canonical Wnt pathway in the use of ASCs in vascular regeneration.

All-trans retinoic acid induces mitochondria-mediated apoptosis of human adipose-derived stem cells and affects the balance of the adipogenic differentiation

The all-trans-retinoic acid (ATRA) is the most active form of vitamin A that helps to regulate the proliferation, differentiation and apoptosis of several types of cells, mainly the adipocytes, and causes weight loss through the reduction of adipogenesis and lipogenesis. In this present study we demonstrated that ATRA concentrations of 20.75, 50 and 100 μM decreased the cell viability in vitro of human adipose-derived stem cells (ADSCs), and in ADSCs during adipogenic differentiation. The cells cycle assessment showed that ATRA increased the cell frequency in Sub-G1 at 4.02x and decreased it in G1 in 2.54x. Moreover, the membrane integrity loss increased by 4.66x and apoptosis increased by 33.56x in ATRA-treated cultures. The gene expression assay suggested that the treatment using ATRA leads to mitochondrial membrane permeabilization and to consequent release of proapoptotic BAK and BAX molecules (increased expression 5.5 and 5.4x respectively); in addition, it increased CASP3 expression (by 8.8x). These events may activate the Bcl-2 (4.1x increase), GADD45 (increase 3.14x) and PPAR-γ (16x increase) expressions, as well as, to reduce the p53 (by -1.38x) expression; therefore, these events should be further mediated by increased RARα expression (by 3.8x). The results evidenced that ATRA may be a good proposal for mesotherapy strategies in order to control the development of subcutaneous adipose tissue; as this tissue have a higher development in some specific areas and ATRA interferes not only in the ADSCs differentiation but also in the apoptosis of ADSCs, preadipocytes and adipocytes.

Substrate stiffness regulated migration and angiogenesis potential of A549 cells and HUVECs

Tumor tissue tends to stiffen during solid tumor progression. Substrate stiffness is known to alter cell behaviors, such as proliferation and migration, during which angiogenesis is requisite. Mono- and co-culture systems of lung cancer cell line A549 and human umbilical vein endothelial cells (HUVECs), on polydimethylsiloxane substrates (PDMS) with varying stiffness, were used for investigating the effects of substrate stiffness on the migration and angiogenesis of lung cancer. The expressions of matrix metalloproteinases (MMPs) and angiogenesis-related growth factors were up-regulated with the increase of substrate stiffness, whereas that of tissue inhibitor of matrix metalloproteinase (TIMPs) were down-regulated with increasing substrate stiffness. Our data not only suggested that stiff substrate may promote the migration and angiogenesis capacities of lung cancer, but also suggested that therapeutically targeting lung tumor stiffness or response of ECs to lung tumor stiffness may help reduce migration and angiogenesis of lung tumor.

Aptamer-Modified Tetrahedral DNA Nanostructure for Tumor-Targeted Drug Delivery

Tetrahedral DNA nanostructures (TDNs) are considered promising drug delivery carriers because they are able to permeate cellular membrane and are biocompatible and biodegradable. Furthermore, they can be modified by functional groups. To improve the drug-delivering ability of TDNs, we chose anticancer aptamer AS1411 to modify TDNs for tumor-targeted drug delivery. AS1411 can specifically bind to nucleolin, which is overexpressed on the cell membrane of tumor cells. Furthermore, AS1411 can inhibit NF-κB signaling and reduce the expression of bcl-2. In this study, we compared the intracellular localization of AS1411-modified TDNs (Apt-TDNs) with that of TDNs in different cells under hypoxic condition. Furthermore, we compared the effects of Apt-TDNs and TDNs on cell growth and cell cycle under hypoxic condition. A substantial amount of Apt-TDNs entered and accumulated in the nucleus of MCF-7 cells; however, the amount of Apt-TDNs that entered L929 cells was comparatively less. TDNs entered in much lower quantity in MCF-7 cells than Apt-TDNs. Moreover, there was little difference in the amount of TDNs that entered L929 cells and MCF-7 cells. Apt-TDNs can inhibit MCF-7 cell growth and promote L929 cell growth, while TDNs can promote both MCF-7 and L929 cell growth. Thus, the results indicate that Apt-TDNs are more effective tumor-targeted drug delivery vehicles than TDNs, with the ability to specifically inhibit tumor cell growth.

IGF-1 promotes angiogenesis in endothelial cells/adipose-derived stem cells co-culture system with activation of PI3K/Akt signal pathway

OBJECTIVES

The aim of this study was to investigate the role of insulin-like growth factor-1 (IGF-1) and crosstalk between endothelial cells (ECs) and adipose-derived stem cells (ASCs) in the process of angiogenesis.

METHODS

A three-dimensional collagen gel used to culture mouse ASCs and mouse ECs in vitro was established. The effects of angiogenesis after exposure to IGF-1 were observed by confocal laser scanning microscopy. Western blotting and qPCR were performed to elucidate the underlying mechanisms.

RESULTS

IGF-1 treatment promoted the formation of vessel-like structures and the recruitment of ASCs in the three-dimensional collagen gel. The angiogenic genes and proteins in ECs were up-regulated by IGF-1 and in co-culture. Similar changes in the genes and in the proteins were detected in ASCs after exposure to IGF-1 and co-culture. p-Akt expression levels were high in ECs and ASCs after exposure to IGF-1 and co-culture.

CONCLUSIONS

IGF-1 and co-culture between cells facilitate the process of angiogenesis via the PI3-kinase/Akt signalling pathway. In ECs, IGF-1 stimulates the expression of angiogenesis-related growth factors with the activation of the PI3-kinase/Akt signalling pathway. Co-cultured ECs exposed to excess VEGF-A and other angiogenesis-related growth factors para-secreted from ASCs exhibit high expression of angiogenesis-related genes and proteins. In ASCs, IGF-1 induces the recruitment and function of ASCs by up-regulating the expression of PDGFB, MMPs and α-SMA. Crosstalk with ECs further facilitates changes in ASCs.

MMP-2 and Notch signal pathway regulate migration of adipose-derived stem cells and chondrocytes in co-culture systems

OBJECTIVES

The crosstalk between chondrocytes and adipose-derived stem cells (ADSCs) could regulate the secretion of multiple growth factors. However, it is not clear how the paracrine action in co-culture systems affect cell migration. This study focused on the changes of cell migration of ADSCs and chondrocytes in co-culture conditions.

MATERIALS AND METHODS

Primary ADSCs and chondrocytes were isolated from Sprague-Dawley rat. Transwell co-culture systems, inoculated with ADSCs and chondrocytes, were established in vitro. The morphology of the cells was observed 7 days post-seeding by inverted phase-contrast microscope. Additionally, the cytoskeleton changes were investigated by immunofluorescence staining. To detect the abundance of Vinculin, we used immunofluorescence and Western blotting. Additionally, the expression level of MMP-2, Hey1 and Hes1 was examined to determine the mechanisms of co-culture-induced cell migration changes.

RESULTS

The migration of ADSCs and chondrocytes in co-culture conditions significantly decreased compared with that in mono-culture groups, accompanied by the decrease of filopodia and the expression level of MMP-2.

CONCLUSIONS

The overall study showed that the migration of ADSCs and chondrocytes differs significantly depending on culture conditions. Moreover, the Notch signalling pathway may be involved in this process. Accordingly, by studying changes in migration caused by co-culture, we obtained new insight into the crosstalk between ADSCs and chondrocytes.

Injectable and thermosensitive TGF-β1-loaded PCEC hydrogel system for in vivo cartilage repair

Chondral defects pose a great challenge for clinicians to manage owing to the limited capacity for self-healing. Various traditional approaches have been adopted for the repair of these defects with unsatisfactory results. Cartilage tissue engineering techniques have emerged as promising strategies to enhance regeneration and overcome these traditional shortcomings. The cell-homing based technique is considered the most promising owing to its unique advantages. Thermosensitive hydrogels have been applied as scaffolds for biomedical applications with smart sol-gel response for altering environmental temperature. Transforming growth factor (TGF)-β1 is considered to be capable of promoting chondrogenesis. In this study, a novel TGF-β1-loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCEC) hydrogel was fabricated using simple procedures. Hydrogel characterization, rheological testing, component analysis, and assessment of sol-gel transition, in vitro degradation, and TGF-β1 release confirmed that this material possesses a porous microstructure with favorable injectability and sustained drug release. Full-thickness cartilage defects were induced on rat knees for in vivo cartilage repair for eight weeks. Micro-CT and histological evaluation provided further evidence of the optimal capacity of this novel hydrogel for cartilage regeneration with respect to that of other methods. Moreover, our results demonstrated that the cell-free hydrogel is thermosensitive, injectable, biodegradable, and capable of in vivo cartilage repair and possesses high potential and benefits for acellular cartilage tissue engineering and clinical application in the future.

Modulation of chondrocyte motility by tetrahedral DNA nanostructures

OBJECTIVES

Contemporarily, a highly increasing attention was paid to nanoconstructs, particularly DNA nanostructures possessing precise organization, functional manipulation, biocompatibility and biodegradability. Amongst these DNA nanomaterials, tetrahedral DNA nanostructures (TDNs) are a significantly ideal bionanomaterials with focusing on the property that can be internalized into cytoplasm in the absence of transfection. Therefore, the focus of this study was on investigating the influence of TDNs on the chondrocytes locomotion.

MATERIALS AND METHODS

Tetrahedral DNA nanostructures was confirmed by 6% polyacrylamide gel electrophoresis (PAGE) and dynamic light scattering (DLS). Subsequently, the effect of TDNs on chondrocyte locomotion was investigated by real-time cell analysis (RTCA) and wound healing assay. The variation of relevant genes and proteins was detected by quantitative polymerase chain reaction (qPCR), western blotting and immunofluorescence respectively.

RESULTS

We demonstrated that tetrahedral DNA nanostructures have positive influence on chondrocytes locomotion and promoted the expression of RhoA, ROCK2 and vinculin. Additionally, upon exposure to TDNs with the concentration of 250 nmol L^-1 , the chondrocytes were showed the highest motility via both RTCA and wound healing assay. Meanwhile, the mRNA and protein expression of RhoA, ROCK2 and vinculin were also significantly enhanced with the same concentration.

CONCLUSIONS

It can be concluded that the TDNs with the optimal concentration of 250 nmol L^-1 could extremely promoted the chondrocytes locomotion through facilitating the expression of RhoA, ROCK2 and vinculin. These results seemed to reveal that this special three-dimensional DNA tetrahedral nanostructures may be applied to cartilage repair and treatment in the future.

Curved microstructures promote osteogenesis of mesenchymal stem cells via the RhoA/ROCK pathway

OBJECTIVES

Cells in the osteon reside in a curved space, accordingly, the curvature of the microenvironment is an important geometric feature in bone formation. However, it is not clear how curved microstructures affect cellular behaviour in bone tissue.

MATERIALS AND METHODS

Rat primary bone marrow mesenchymal stem cells (BMSCs) on wavy microgrooves were exposed to PDMS substrates with various curvatures to investigate alterations in cellular morphology and osteogenic differentiation. Additionally, the expression levels of RhoA and its effectors were examined by immunofluorescence and quantitative PCR to determine the mechanisms of curvature-dependent osteogenic differentiation.

RESULTS

Wavy microgrooves caused dramatic nuclear distortion and cytoskeletal remodelling. We detected a noticeable increase in the expression of osteogenic-related genes in BMSCs in wavy microgroove groups, and the maximum expression was observed in the high curvature group. Moreover, immunofluorescent staining and quantitative RT-PCR results for RhoA and its effectors showed that the RhoA/ROCK signalling pathway is associated with curvature-dependent osteogenic differentiation.

CONCLUSIONS

Our results illustrated that curved microstructures could promote BMSC differentiation to the osteogenic lineage, and the osteogenic effects of higher curvature are more obvious. Wavy microstructures could also influence the RhoA/ROCK pathway. Accordingly, curved microstructures may be useful in bone tissue engineering.

Morphological, Immunocytochemical, and Biochemical Studies of Rat Costal Chondrocytes Exposed to IL-1β and TGF-β1

This study was undertaken to determine the effects of IL-1β and TGF-β1 on the expression of differentiation-associated genes in chondrocytes in vitro. Rat costal chondrocytes were exposed to different concentrations of IL-1β and TGF-β1 for 48 h and tested for gene expression. IL-1β increased the expression of aggrecanase-1 and aggrecanase-2 and decreased the content of aggrecan and collagen II. Low concentration of TGF-β1 decreased the expression of aggrecan and collagen II and increased the expression of aggrecanase-2. However, the level of aggrecanase-1 was significantly elevated in the presence of high concentration of TGF-β1. IL-1β and TGF-β1 show the ability to modulate the production of aggrecan and collagen II in chondrocytes in vitro.

The fabrication of biomimetic biphasic CAN-PAC hydrogel with a seamless interfacial layer applied in osteochondral defect repair

Cartilage tissue engineering based on biomimetic scaffolds has become a rapidly developing strategy for repairing cartilage defects. In this study, a biphasic CAN-PAC hydrogel for osteochondral defect (OCD) regeneration was fabricated based on the density difference between the two layers via a thermally reactive, rapid cross-linking method. The upper hydrogel was cross-linked by CSMA and NIPAm, and the lower hydrogel was composed of PECDA, AAm and PEGDA. The interface between the two layers was first grafted by the physical cross-linking of calcium gluconate and alginate, followed by the chemical cross-linking of the carbon-carbon double bonds in the other components. The pore sizes of the upper and lower hydrogels were ~187.4 and ~112.6 μm, respectively. The moduli of the upper and lower hydrogels were ~0.065 and ~0.261 MPa. This prepared bilayer hydrogel exhibited the characteristics of mimetic composition, mimetic structure and mimetic stiffness, which provided a microenvironment for sustaining cell attachment and viability. Meanwhile, the biodegradability and biocompatibility of the CAN-PAC hydrogel were examined in vivo. Furthermore, an osteochondral defect model was developed in rabbits, and the bilayer hydrogels were implanted into the defect. The regenerated tissues in the bilayer hydrogel group exhibited new translucent cartilage and repaired subchondral bone, indicating that the hydrogel can enhance the repair of osteochondral defects.

The Effect of shape on Cellular Uptake of Gold Nanoparticles in the forms of Stars, Rods, and Triangles

Gold nanomaterials have attracted considerable interest as vehicles for intracellular drug delivery. In our study, we synthesized three different shapes of methylpolyethylene glycol coated-anisotropic gold nanoparticles: stars, rods, and triangles. The cellular internalization of these nanoparticles by RAW264.7 cells was analyzed, providing a parametric evaluation of the effect of shape. The efficiency of cellular uptake of the gold nanoparticles was found to rank in the following order from lowest to highest: stars, rods, and triangles. The possible mechanisms of cellular uptake for the three types of gold nanoparticles were examined, and it was found that different shapes tended to use the various endocytosis pathways in different proportions. Our study, which has demonstrated that shape can modulate the uptake of nanoparticles into RAW264.7 cells and that triangles were the shape with the most efficient cellular uptake, provides useful guidance toward the design of nanomaterials for drug delivery.

* Hypoxia for Mesenchymal Stem Cell Expansion and Differentiation: The Best Way for Enhancing TGFß-Induced Chondrogenesis and Preventing Calcifications in Alginate Beads

We examined the respective influence of a sequential or a continuous hypoxia during expansion and transforming growth factor beta 1-driven chondrogenic differentiation of human bone marrow mesenchymal stem cells (MSCs). The differentiation was performed within alginate beads, a classical tool for the implantation of MSCs within the joint. The standard normoxic 2D (expansion) and 3D (differentiation) MSCs cultures served as reference. To determine the quality of chondrogenesis, we analyzed typical markers such as type II and X collagens, SOX9, COMP, versican, and aggrecan mRNAs using polymerase chain reaction and we assessed the production of type II collagen and hypoxia-inducible factor (HIF)-1α by histological stainings. We simultaneously assessed the expression of osteogenic mRNAs (Alkaline Phosphatase, RUNX2, and Osteocalcin) and the presence of micro-calcifications by Alizarin red and Raman spectroscopy. Chondrogenic differentiation is clearly improved by hypoxia in 3D. Best results were obtained when the entire process, that is, 2D expansion and 3D differentiation, was performed under continuous 5% hypoxic condition. In addition, no calcification (hydroxyapatite, proved by RAMAN) was observed after 2D hypoxic expansion even in the case of a normoxic differentiation, in contrast with controls. Finally, a better chondrogenic differentiation of human MSCs is achieved when a reduced oxygen tension is applied during both expansion and differentiation times, avoiding in vitro osteogenic commitment of cells and subsequently the calcification deposition.

Notch Signaling Pathway Regulates Angiogenesis via Endothelial Cell in 3D Co-Culture Model

This study aimed to investigate the role of Notch signaling pathway for angiogenesis in a three-dimensional (3D) collagen gel model with co-culture of adipose-derived stromal cells (ASCs) and endothelial cells (ECs). A 3D collagen gel model was established in vitro by implanting both ASCs from green fluorescent protein-labeled mouse and ECs from red fluorescent protein-labeled mouse, and the phenomena of angiogenesis with Notch signaling inducer Jagged1, inhibitor DAPT and PBS, respectively were observed by confocal laser scanning microscopy. Semi-quantitative PCR and immunofluorescent staining were conducted to detect expressions of angiogenesis-related genes and proteins. Angiogenesis in the co-culture gels was promoted by Jagged1 treatment while attenuated by DAPT treatment, compared to control group. In co-culture system of ASCs and ECs, the gene expressions of VEGFA, VEGFB, Notch1, Notch2, Hes1, Hey1, VEGFR1,and the protein expression of VEGFA, VEGFB, Notch1, Hes1, Hey1 were increased by Jagged1 treatment and decreased by DAPT treatment in ECs. And the result of VEGFR3 was the opposite. However, the same results did not appear completely in ASCs. These results revealed the VEGFA/B-Notch1/2-Hes1/Hey1- VEGFR1/3 signal axis played an important role in angiogenesis when ASCs and ECs were co-cultured in a 3D collagen gel model. J. Cell. Physiol. 232: 1548-1558, 2017. © 2016 Wiley Periodicals, Inc.

PCL-PEG-PCL film promotes cartilage regeneration in vivo

OBJECTIVE

Management of chondral defects has long been a challenge due to poor self-healing capacity of articular cartilage. Many approaches, ranging from symptomatic treatment to structural cartilage regeneration, have obtained very limited satisfactory results. Cartilage tissue engineering, which involves optimized combination of novel scaffolds, cell sources and growth factors, has emerged as a promising strategy for cartilage regeneration and repair. In this study, the aim was to investigate the role of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) PCEC scaffold in cartilage repair.

MATERIALS AND METHODS

First, PCEC film was fabricated, and its characteristics were tested using SEM and AFM. Cell (rASC - rat adipose-derived stem cells, and mASCs - green fluorescent mouse adipose-derived stem cells) morphologies on PCEC film were observed using SEM and fluorescence microscopy, after cell seeding. Tests of cell viability on PCEC film were conducted using the CCK-8 assay. Furthermore, full cartilage defects in rats were created, and PCEC films were implanted, to evaluate their healing effects, over 8 weeks.

RESULTS

It was found that PCEC film, as a biomaterial implant, possessed good in vitro properties for cell adhesion, migration and proliferation. Importantly, in the in vivo experiment, PCEC film exhibited desirable healing outcomes.

CONCLUSIONS

These results demonstrated that PCEC film was a good scaffold for cartilage tissue engineering for improving cell proliferation and adhesion and could lead to excellent repair of cartilage defects.