Enhanced survival of transplanted human adipose-derived stem cells by co-delivery with liposomal apoptosome inhibitor in fibrin gel matrix

External cold atmospheric plasma-responsive on-site hydrogel for remodeling tumor immune microenvironment

Although immunotherapy has recently emerged as a promising anti-tumor approach, it remains limited by the immunosuppressive tumor microenvironment. Cold atmospheric plasma irradiation can generate reactive oxygen species and trigger the presentation of tumor-associated antigens. Here, we exploited cold atmospheric plasma for on-site hydrogel application in the tumor environment, aiming to facilitate the sustainable uptake of tumor-associated antigens and nanoadjuvants by dendritic cells. Hyaluronic acid-tyramine conjugate was intratumorally injected as a liquid and formed an on-site hydrogel under irradiation with cold atmospheric plasma. Intratumoral delivery of hyaluronic acid-tyramine conjugate with transforming growth factor β-blocking nanoadjuvant (TLN) followed by cold atmospheric plasma irradiation yielded a micro-network of TLN-loaded hydrogel (TLN@CHG). In vivo intratumoral injection of TLN@CHG promoted the activation of dendritic cells and more effectively increased the proportion of CD4 T cells and CD8 T cells in the tumor microenvironment, compared to the groups receiving TLN or hydrogel alone. Moreover, in CT26 tumor model mice, cold atmospheric plasma-induced TLN@CHG therapy ablated the primary tumor and provided 100% survival among mice rechallenged with CT26 cells. Taken together, our findings suggest that an on-site hydrogel-based micro-network of TLN has the potential to remodel the tumor immune microenvironment. Although we used TLN in this study, the concept could be extended to support the sustained action of other nanoadjuvants in a hydrogel micro-network.

Too much death can kill you: inhibiting intrinsic apoptosis to treat disease

Apoptotic cell death is implicated in both physiological and pathological processes. Since many types of cancerous cells intrinsically evade apoptotic elimination, induction of apoptosis has become an attractive and often necessary cancer therapeutic approach. Conversely, some cells are extremely sensitive to apoptotic stimuli leading to neurodegenerative disease and immune pathologies. However, due to several challenges, pharmacological inhibition of apoptosis is still only a recently emerging strategy to combat pathological cell loss. Here, we describe several key steps in the intrinsic (mitochondrial) apoptosis pathway that represent potential targets for inhibitors in disease contexts. We also discuss the mechanisms of action, advantages and limitations of small-molecule and peptide-based inhibitors that have been developed to date. These inhibitors serve as important research tools to dissect apoptotic signalling and may foster new treatments to reduce unwanted cell loss.

A Reciprocal Role of the Smad4-Taz Axis in Osteogenesis and Adipogenesis of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into mature cells of various cell types. Although the differentiation process of MSCs requires lineage-specific transcription factors, the exact molecular mechanism that determines MSCs differentiation is not clearly addressed. Here, we demonstrate a Smad4-Taz axis as a new intrinsic regulator for adipo-osteogenic differentiation of MSCs and show that this function of Smad4 is independent of the transforming growth factor-β signal. Smad4 directly bound to the Taz protein and facilitated nuclear localization of Taz through its nuclear localization signal. Nuclear retention of Taz by direct binding to Smad4 increased expression of osteogenic genes through enhancing Taz-runt-related transcription factor 2 (Runx2) interactions in the C3H10T1/2 MSC cell line and preosteoblastic MC3T3-E1 cells, whereas it suppressed expression of adipogenic genes through promoting Taz-peroxisome proliferator-activated receptor-γ (PPARγ) interaction in C3H10T1/2 and preadipogenic 3T3-L1 cells. A reciprocal role of the Smad4 in osteogenic and adipogenic differentiation was also observed in human adipose tissue-derived stem cells (hASCs). Consequently, Smad4 depletion in C3H10T1/2 and hASCs reduced nuclear retention of Taz and thus caused the decreased interaction with Runx2 or PPARγ, resulting in delayed osteogenesis or enhanced adipogenesis of the MSC. Therefore, these findings provide insight into a novel function of Smad4 to regulate the balance of MSC lineage commitment through reciprocal targeting of the Taz protein in osteogenic and adipogenic differentiation pathways. Stem Cells 2019;37:368-381.

Elevated Pentraxin 3 in Obese Adipose Tissue Promotes Adipogenic Differentiation by Activating Neuropeptide Y Signaling

Obesity is accompanied by chronic systemic inflammation characterized by macrophage infiltration of obese tissues, an elevated plasma level of inflammatory substances, and excessive accumulation of lipids. The pro-inflammatory factor pentraxin 3 (PTX3) is also elevated in obese tissues, suggesting its potential role in adipogenesis. We found by analyzing murine preadipocyte 3T3-L1 cells, and human adipocytes derived from mesenchymal stem cells, which locally elevated PTX3 in obese adipose tissue augments adipocyte differentiation and subsequent lipid accumulation. This occurs via the upregulation of adipogenesis-related transcription factors. PTX3 enhanced lipid accumulation in murine 3T3-L1 cells by upregulating the expression of neuropeptide Y (NPY)/NPY receptor (NPYR) expression in preadipocytes. Pharmacological inhibition by NPYR antagonists abolished these effects. NPY also promoted the production of reactive oxygen species (ROS), a known trigger of adipogenesis. NPYR antagonists as well as antioxidant N-acetylcysteine showed anti-adipogenic effects by reducing the ROS levels, indicating that PTX3 mediates adipogenesis through NPY-dependent ROS production. These findings suggest that PTX3 plays a key role in the development of obesity by enhancing adipocyte differentiation and lipid synthesis via NPY/NPYR signaling. These observations provide a mechanistic explanation for the adipogenesis mediated by PTX3.

Small molecule-based lineage switch of human adipose-derived stem cells into neural stem cells and functional GABAergic neurons

Cellular reprogramming using small molecules (SMs) without genetic modification provides a promising strategy for generating target cells for cell-based therapy. Human adipose-derived stem cells (hADSCs) are a desirable cell source for clinical application due to their self-renewal capacity, easy obtainability and the lack of safety concerns, such as tumor formation. However, methods to convert hADSCs into neural cells, such as neural stem cells (NSCs), are inefficient, and few if any studies have achieved efficient reprogramming of hADSCs into functional neurons. Here, we developed highly efficient induction protocols to generate NSC-like cells (iNSCs), neuron-like cells (iNs) and GABAergic neuron-like cells (iGNs) from hADSCs via SM-mediated inhibition of SMAD signaling without genetic manipulation. All induced cells adopted morphological, molecular and functional features of their bona fide counterparts. Electrophysiological data demonstrated that iNs and iGNs exhibited electrophysiological properties of neurons and formed neural networks in vitro. Microarray analysis further confirmed that iNSCs and iGNs underwent lineage switch toward a neural fate. Together, these studies provide rapid, reproducible and robust protocols for efficient generation of functional iNSCs, iNs and iGNs from hADSCs, which have utility for modeling disease pathophysiology and providing cell-therapy sources of neurological disorders.

Metabolic reprogramming by HIF-1 activation enhances survivability of human adipose-derived stem cells in ischaemic microenvironments

OBJECTIVES

Poor cell survival severely limits the beneficial effect of adipose-derived stem cell (ADSC)-based therapy for disease treatment and tissue regeneration, which might be caused by the attenuated level of hypoxia-inducible factor-1 (HIF-1) in these cells after having been cultured in 21% ambient oxygen in vitro for weeks. In this study, we explored the role of pre-incubation in dimethyloxalylglycine (DMOG, HIF-1 activator) in the survivability of human ADSCs in a simulated ischaemic microenvironment in vitro and in vivo. The underlying mechanism and angiogenesis were also studied.

MATERIALS AND METHODS

Survivability of ADSCs was determined in a simulated ischaemic model in vitro and a nude mouse model in vivo. Cell metabolism and angiogenesis were investigated by tube formation assay, flow cytometry, fluorescence staining and real-time polymerase chain reaction (RT-PCR) after DMOG treatment.

RESULTS

The results of the experimental groups showed significant enhancement of ADSC survivability in a simulated ischaemic microenvironment in vitro and transplanted model in vivo. Study of the underlying mechanisms suggested that the improved cell survival was regulated by HIF-1-induced metabolic reprogramming including decreased reactive oxygen species, increased intracellular pH, enhanced glucose uptake and increased glycogen synthesis. Tube formation assay revealed higher angiogenic ability in the DMOG-treated group than that in control group.

CONCLUSIONS

The promotion of HIF-1 level in ADSCs induced by DMOG preconditioning suggests a potential strategy for improving the outcome of cell therapy due to increased survival and angiogenic ability.

Fibrin matrices: The versatile therapeutic delivery systems

Fibrin sealants, that have been employed for over a century by surgeons to stop post surgery bleeding, are finding novel applications in the controlled delivery of antibiotics and several other therapeutics. Fibrinogen can be easily purified from blood plasma and converted by thrombolysis to fibrin that undergoes spontaneous aggregation to form insoluble clot. During the gelling, fibrin can be formulated into films, clots, threads, microbeads, nanoconstructs and nanoparticles. Whole plasma clots in the form of beads and microparticles can also be prepared by activating endogenous thrombin, for possible drug delivery. Fibrin formulations offer remarkable scope for controlling the porosity as well as in vivo degradability and hence the release of the associated therapeutics. Binding/covalent-linking of therapeutics to the fibrin matrix, crosslinking of the matrix with bifunctional reagents and coentrapment of protease inhibitors have been successful in regulating both in vitro and in vivo release of the therapeutics. The release rates can also be remarkably lowered by preentrapment of therapeutics in insoluble particles like liposomes or by anchoring them to the matrix via molecules that bind them as well as fibrin.