Guowei Feng

Molecular imaging for assessment of mesenchymal stem cells mediated breast cancer therapy

The tumor tropism of mesenchymal stem cells (MSCs) makes them an excellent delivery vehicle used in anticancer therapy. However, the exact mechanisms of MSCs involved in tumor microenvironment are still not well defined. Molecular imaging technologies with the versatility in monitoring the therapeutic effects, as well as basic molecular and cellular processes in real time, offer tangible options to better guide MSCs mediated cancer therapy. In this study, an in situ breast cancer model was developed with MDA-MB-231 cells carrying a reporter system encoding a double fusion (DF) reporter gene consisting of firefly luciferase (Fluc) and enhanced green fluorescent protein (eGFP). In mice breast cancer model, we injected human umbilical cord-derived MSCs (hUC-MSCs) armed with a triple fusion (TF) gene containing the herpes simplex virus truncated thymidine kinase (HSV-ttk), renilla luciferase (Rluc) and red fluorescent protein (RFP) into tumor on day 13, 18, 23 after MDA-MB-231 cells injection. Bioluminescence imaging of Fluc and Rluc provided the real time monitor of tumor cells and hUC-MSCs simultaneously. We found that tumors were significantly inhibited by hUC-MSCs administration, and this effect was enhanced by ganciclovir (GCV) application. To further demonstrate the effect of hUC-MSCs on tumor cells in vivo, we employed the near infrared (NIR) imaging and the results showed that hUC-MSCs could inhibit tumor angiogenesis and increased apoptosis to a certain degree. In conclusion, hUC-MSCs can inhibit breast cancer progression by inducing tumor cell death and suppressing angiogenesis. Moreover, molecular imaging is an invaluable tool in tracking cell delivery and tumor response to hUC-MSCs therapies as well as cellular and molecular processes in tumor.

Bone marrow-derived cells can acquire renal stem cells properties and ameliorate ischemia-reperfusion induced acute renal injury.

BackgroundBone marrow (BM) stem cells have been reported to contribute to tissue repair after kidney injury model. However, there is no direct evidence so far that BM cells can trans-differentiate into renal stem cells.MethodsTo investigate whether BM stem cells contribute to repopulate the renal stem cell pool, we transplanted BM cells from transgenic mice, expressing enhanced green fluorescent protein (EGFP) into wild-type irradiated recipients. Following hematological reconstitution and ischemia-reperfusion (I/R), Sca-1 and c-Kit positive renal stem cells in kidney were evaluated by immunostaining and flow cytometry analysis. Moreover, granulocyte colony stimulating factor (G-CSF) was administrated to further explore if G-CSF can mobilize BM cells and enhance trans-differentiation efficiency of BM cells into renal stem cells.ResultsBM-derived cells can contribute to the Sca-1+ or c-Kit+ renal progenitor cells population, although most renal stem cells came from indigenous cells. Furthermore, G-CSF administration nearly doubled the frequency of Sca-1+ BM-derived renal stem cells and increased capillary density of I/R injured kidneys.ConclusionsThese findings indicate that BM derived stem cells can give rise to cells that share properties of renal resident stem cell. Moreover, G-CSF mobilization can enhance this effect.

IGF-1 C Domain–Modified Hydrogel Enhances Cell Therapy for AKI

Low cell retention and engraftment after transplantation limit the successful application of stem cell therapy for AKI. Engineered microenvironments consisting of a hydrogel matrix and growth factors have been increasingly successful in controlling stem cell fate by mimicking native stem cell niche components. Here, we synthesized a bioactive hydrogel by immobilizing the C domain peptide of IGF-1 (IGF-1C) on chitosan, and we hypothesized that this hydrogel could provide a favorable niche for adipose-derived mesenchymal stem cells (ADSCs) and thereby enhance cell survival in an AKI model. In vitro studies demonstrated that compared with no hydrogel or chitosan hydrogel only, the chitosan-IGF-1C hydrogel increased cell viability through paracrine effects. In vivo, cotransplantation of the chitosan-IGF-1C hydrogel and ADSCs in ischemic kidneys ameliorated renal function, likely by the observed promotion of stem cell survival and angiogenesis, as visualized by bioluminescence imaging and attenuation of fibrosis. In conclusion, IGF-1C immobilized on a chitosan hydrogel provides an artificial microenvironment for ADSCs and may be a promising therapeutic approach for AKI.

Extracellular Matrix can Recover the Downregulation of Adhesion Molecules after Cell Detachment and Enhance Endothelial Cell Engraftment

The low cell engraftment after transplantation limits the successful application of stem cell therapy and the exact pathway leading to acute donor cell death following transplantation is still unknown. Here we investigated if processes involved in cell preparation could initiate downregulation of adhesion-related survival signals, and further affect cell engraftment after transplantation. Human embryonic stem cell-derived endothelial cells (hESC-ECs) were suspended in PBS or Matrigel and kept at 4 °C. Quantitative RT-PCR analysis was used to test the adhesion and apoptosis genes’ expression of hESC-ECs. We demonstrated that cell detachment can cause downregulation of cell adhesion and extracellular matrix (ECM) molecules, but no obvious cell anoikis, a form of apoptosis after cell detachment, was observed. The downregulation of adhesion and ECM molecules could be regained in the presence of Matrigel. Finally, we transplanted hESC-ECs into a mouse myocardial ischemia model. When transplanted with Matrigel, the long-term engraftment of hESC-ECs was increased through promoting angiogenesis and inhibiting apoptosis, and this was confirmed by bioluminescence imaging. In conclusion, ECM could rescue the functional genes expression after cell detached from culture dish, and this finding highlights the importance of increasing stem cell engraftment by mimicking stem cell niches through ECM application.

Activation of mesenchymal stem cells by macrophages promotes tumor progression through immune suppressive effects

Cancer development and progression is linked to tumor-associated macrophages (TAMs). Distinct TAMs subsets perform either protective or pathogenic effects in cancer. A protective role in carcinogenesis has been described for M1 macrophages, which activate antitumor mechanisms. By comparison, TAMs isolated from solid and metastatic tumors have a suppressive M2-like phenotype, which could support multiple aspects of tumor progression. Currently, it has not been clearly understood how macrophages in tumor-associated stroma could be hijacked to support tumor growth. Mesenchymal stem cells (MSCs) actively interact with components of the innate immune system and display both anti-inflammatory and pro-inflammatory effects. Here, we tested whether MSCs could favor the tumor to escape from immunologic surveillance in the presence of M1 macrophages. We found that MSCs educated by M1 condition medium (cMSCs) possessed a greatly enhanced ability in promoting tumor growth in vivo. Examination of cytokines/chemokines showed that the cMSCs acquired a regulatory profile, which expressed high levels of iNOS and MCP1. Consistent with an elevated MCP1 expression in cMSCs, the tumor-promoting effect of the cMSCs depended on MCP1 mediated macrophage recruitment to tumor sites. Furthermore, IL-6 secreted by the cMSCs could polarize infiltrated TAMs into M2-like macrophages. Therefore, when macrophages changed into M1 pro-inflammation type in tumor microenvironment, the MSCs would act as poor sensors and switchers to accelerate tumor growth.

Embryonic stem cell preconditioned microenvironment suppresses tumorigenic properties in breast cancer

BackgroundMicroenvironment is being increasingly recognized as a critical determinant in tumor progression and metastasis. However, the appropriate regulatory mechanism to maintain the normal balance between differentiation and self-renewal of the cancer cell in microenvironment is not well known.Methods4T1 breast cancer cells were treated with embryonic stem (ES) cell conditioned medium which was collected from mouse ES cells. Inhibition of tumor cell growth was based on the reduction of cell proliferation and viability, and inhibition of aggressive properties of tumor cells were examined using the wound-healing and mammosphere assays. The expression of stem cell-associated genes was detected by quantitative RT-PCR.ResultsWe used a real-time imaging system to investigate the effect of the mouse ES cell microenvironment on aggressive breast cancer cells in vitro and in vivo. Exposure of breast cancer cells in mouse ES cell conditioned medium resulted in inhibition of growth, migration, metastasis, and angiogenesis of cancer cells. For many tumors, aggressive properties were tightly related to Stat3 signaling activation. We specifically discovered that the ES cell microenvironment sufficiently suppressed Stat3 signaling pathway activation in aggressive tumor cells, leading to a reduction in tumorigenesis and invasiveness.ConclusionsWe identified important functions of Stat3 and their implications for antitumor effects of ES cell conditioned medium. Some factors secreted by ES cells could efficiently suppress Stat3 pathway activation in breast cancer cells, and were then involved in cancer cell growth, survival, invasion, and migration. This study may act as a platform to understand tumor cell plasticity and may offer new therapeutic strategies to inhibit breast cancer progression.

The Phenotypic Fate of Bone Marrow-Derived Stem Cells in Acute Kidney Injury

Background: Despite increasing attention on the role of bone marrow derived stem cells in repair or rejuvenation of tissues and organs, cellular mechanisms of such cell-based therapy remain poorly understood. Methods: We reconstituted hematopoiesis in recipient C57BL/6J mice by transplanting syngeneic GFP+ bone marrow (BM) cells. Subsequently, the recipients received subcutaneous injection of granulocyte-colony stimulating factor (G-CSF) and were subjected to acute renal ischemic injury. Flow cytometry and immunostaining were performed at various time points to assess engraftment and phenotype of BM derived stem cells. Results: Administration of G-CSF increased the release of BM derived stem cells into circulation and enhanced the ensuing recruitment of BM derived stem cells into injured kidney. During the second month post injury, migrated BM derived stem cells lost hematopoietic phenotype (CD45) but maintained the expression of other markers (Sca-1, CD133 and CD44), suggesting their potential of transdifferentiation into renal stem cells. Moreover, G-CSF treatment enhanced the phenotypic conversion. Conclusion: Our work depicted a time-course dependent transition of phenotypic characteristics of BM derived stem cells, demonstrated the existence of BM derived stem cells in damaged kidney and revealed the effects of G-CSF on cell transdifferentiation.

Differential effects of tumor necrosis factor-α on matrix metalloproteinase-2 expression in human myometrial and uterine leiomyoma smooth muscle cells.

STUDY QUESTION Does tumor necrosis factor-α (TNF-α) differentially regulate matrix metalloproteinase-2 (MMP-2) expression in leiomyomas compared with normal myometrium? SUMMARY ANSWER TNF-α up-regulates MMP-2 expression and stimulates cell migration through the activation of extracellular signal-regulated kinase (ERK) signaling pathway in leiomyoma smooth muscle cells (SMCs), but not in normal myometrial SMCs. WHAT IS KNOWN ALREADY Uterine leiomyoma, the benign smooth muscle cell tumor, is the single most common indication for hysterectomy. High expression of MMPs or TNF-α has been reported in uterine leiomyomas; however, the molecular mechanism underlying these observations remains unknown. STUDY DESIGN, SIZE, DURATION Samples were obtained between 2009 and 2013 from 12 women of reproductive age at the proliferative phase of the menstrual cycle by hysterectomy. Leiomyomas and matched normal myometrium from each woman were analyzed in vitro. PARTICIPANTS/MATERIALS, SETTING, METHODS Western blot, RT-qPCR and a wound-healing assay were used to investigate the effects of TNF-α on MMP-2 expression and intracellular signal transduction in cultured SMCs from leiomyomas and matched myometrium. MAIN RESULTS AND THE ROLE OF CHANCE Western blot and RT-qPCR analyses using tissues from clinical patients showed that the levels of MMP-2 protein (P = 0.008) and mRNA (P = 0.009) were significantly higher in uterine leiomyomas compared with their matched myometrium. Treatment with TNF-α significantly up-regulated the protein (P = 0.039) and mRNA (P = 0.037) levels of MMP-2 in cultured leiomyoma SMCs but not in matched myometrial SMCs. The extracellular signal-regulated kinase (ERK) and nuclear factor-kappa B (NF-κB) pathways were activated by TNF-α in leiomyoma SMCs. Specific inhibitors of the ERK or NF-κB pathway (PD98059 or Bay11-7082) suppressed TNF-α-induced MMP-2 expression in leiomyoma SMCs. The wound-healing assay revealed that TNF-α promoted the migration of cultured leiomyoma SMCs (P = 0.036); however, PD98059 compromised the cell migration triggered by TNF-α. LIMITATIONS, REASONS FOR CAUTION This study is descriptive and although we observed clear differential regulation of MMP-2 by TNF-α at mRNA and protein levels in leiomyoma, future studies are needed to identify why the difference in TNF-α response exists between human leiomyoma tissue and normal myometrium. Including some of the experiments such as transfection studies for TNF-α and MMP-2 promoter mapping could have added more insight as to why this difference exists. In addition, further studies in vivo are needed to verify the results obtained from primary cultured SMCs. WIDER IMPLICATIONS OF THE FINDINGS Considering the positive effect of TNF-α on leiomyoma SMC migration, strategies targeting TNF-α, in parallel with the production of more specific inhibitors of MMPs, may provide alternative therapeutic approaches for the treatment of leiomyoma. STUDY FUNDING/COMPETING INTERESTS This work was partially supported by grants from the Program for New Century Excellent Talents in University (NCET-12-0282), National Natural Science Foundation of China (81371620) and Tianjin Natural Science Foundation (12JCZDJC24900). The authors have no conflicts of interest to declare.

Skin-Derived Precursor Cells Promote Angiogenesis and Stimulate Proliferation of Endogenous Neural Stem Cells after Cerebral Infarction

Stroke is one of the most common diseases that caused high mortality and has become burden to the health care systems. Stem cell transplantation has shown therapeutic effect in ameliorating ischemic damage after cerebral artery occlusion mainly due to their neurogenesis, immune regulation, or effects on the plasticity, proliferation, and survival of host cells. Recent studies demonstrated that skin-derived precursor cells (SKPs) could promote central nervous system regeneration in spinal cord injury model or the neonatal peripheral neuron. Here, we investigated the therapeutic potential of SKPs in a rat model of cerebral ischemia. SKPs were isolated, expanded, and transplanted into rat cortex and striatum after transient middle cerebral artery occlusion. Our results revealed that SKPs transplantation could improve the behavioral measures of neurological deficit. Moreover, immunohistology confirmed that SKPs could secrete basic FGF and VEGF in the ischemic region and further markedly increase the proliferation of endogenous nestin+ and βIII-tubulin+ neural stem cells. Furthermore, increased angiogenesis induced by SKPs was observed by vWF and α-SMA staining. These data suggest that SKPs induced endogenous neurogenesis and angiogenesis and protected neuron from hypoxic-ischemic environment. In conclusion, SKPs transplantation may be a promising approach in treatment of stroke.

Nitric Oxide-Releasing Biomaterials for Biomedical Applications

Nitric oxide (NO), as an essential signaling molecule, participates in various physiological processes such as cardiovascular homeostasis, neuronal transmission, immunomodulation, and tumor growth. The multiple role of NO in physiology and pathophysiology has triggered a massive interest in the strategies of delivering exogenous NO for biomedical applications. Hence, different kinds of NO prodrugs have been developed up to date, including diazeniumdiolates, S-nitrosothiol, metal-nitrosyl, nitrobenzene, and so on. However, the clinical application of these low molecular weight NO donors has been restricted due to the problems of burst release, low payloads, and untargeted delivery. The delivery of NO by biomaterialbased carrier offers a beneficial strategy to realize the controlled and sustained delivery of NO to the targeted tissues or organs. In detail, NO-donor prodrugs have been attached and loaded to diverse biomaterials to fabricate nanoparticles, hydrogels, and coating platforms by means of physical, chemical, or supramolecular techniques. These NO-releasing biomaterials hold promise for a number of biomedical applications ranging from therapy of the ischemic disease and several types of cancer to cardiovascular devices and wound dressing. First, surface coating with NO-releasing biomaterials could mimic the physiological function of vascular endothelium, therefore promoting vascularization and improving the patency of cardiovascular implants. Next, because NO also mediates many important processes that take place after cutaneous injury, NO-releasing biomaterials could serve as ideal wound dressing to accelerate tissue regeneration. Finally, biomaterials enable localized delivery of high dose of NO to tumors in a sustained manner, thus generating potent tumoricidal effect. In this review, we will summarize the progress of different NO-releasing biomaterials, and highlight their biomedical applications with a hope to inspire new perspectives in the area of biomaterial-based NO-delivery systems.