Shear Stress Induces Differentiation of Endothelial Lineage Cells to Protect Neonatal Brain from Hypoxic-Ischemic Injury through NRP1 and VEGFR2 Signaling

Adipose-derived stem cells transplantation improves survival and alleviates contraction of skin grafts via promoting macrophages M2 polarization

BACKGROUND

Full-thickness skin grafts are widely used in plastic and reconstructive surgery. The main limitation of skin grafting is the poor textural durability and associated contracture, which often needs further corrective surgery. Excessive inflammation is the main reason for skin graft contractions, which involve overactivation of myofibroblasts. These problems have prompted the development of new therapeutic approaches, including macrophage polarization modulation and stem cell-based therapies. Currently, adipose-derived stem cells (ASCs) have shown promise in promoting skin grafts survival and regulating macrophage phenotypes. However, the roles of ASCs on macrophages in decreasing skin grafts contraction remain unknown.

MATERIALS AND METHODS

Rat adipose-derived stem cells (rASCs) were isolated from rat inguinal adipose tissues. Full-thickness skin graft model was constructed on male rats divided into control group and rASCs treatment group. Skin graft was assessed for concentration, elasticity modulus and stiffness. Rat bone marrow-derived macrophages (rBMDMs) were isolated from rat femurs, and subsequent RT-qPCR and coculture assays were carried out to explore the cellular mechanisms. Immunohistochemical and immunofluorescence staining were used to verify mechanisms in vivo.

RESULTS

In vivo results showed that after injection of ASCs, improved texture, increased survival and inhibited contraction of skin grafts were seen. Vascularization was also improved as illustrated by laser perfusion image and vascular endothelial growth factor (VEGF) concentration. Histological analysis revealed that ASCs injection significantly reduced expression of pro-inflammatory cytokines (TNF-a, IL-1β) and increased expression of anti-inflammatory (IL-10) and pro-healing cytokines (IGF-1). At cellular level, after co-culturing with rASCs, rat bone marrow derived macrophages (rBMDMs) favored M2 polarization even under inflammatory stimulus.

CONCLUSION

ASCs treatment enhanced vascularization via angiogenic cytokines secretion and alleviated inflammatory environment in skin grafts by driving M2 macrophages polarization, which improved survival and decreased skin grafts contraction. Our work showed that ASCs transplantation can be harnessed to enhance therapeutic efficacy of skin grafting in cutaneous defects treatment.

Sodium phenylbutyrate inhibits Schwann cell inflammation via HDAC and NFκB to promote axonal regeneration and remyelination

Background

Epigenetic regulation by histone deacetylases (HDACs) in Schwann cells (SCs) after injury facilitates them to undergo de- and redifferentiation processes necessary to support various stages of nerve repair. Although de-differentiation activates the synthesis and secretion of inflammatory cytokines by SCs to initiate an immune response during nerve repair, changes in either the timing or duration of prolonged inflammation mediated by SCs can affect later processes associated with repair and regeneration. Limited studies have investigated the regulatory processes through which HDACs in SCs control inflammatory cytokines to provide a favorable environment for peripheral nerve regeneration.

Methods

We employed the HDAC inhibitor (HDACi) sodium phenylbutyrate (PBA) to address this question in an in vitro RT4 SC inflammation model and an in vivo sciatic nerve transection injury model to examine the effects of HDAC inhibition on the expression of pro-inflammatory cytokines. Furthermore, we assessed the outcomes of suppression of extended inflammation on the regenerative potential of nerves by assessing axonal regeneration, remyelination, and reinnervation.

Results

Significant reductions in lipopolysaccharide (LPS)-induced pro-inflammatory cytokine (tumor necrosis factor-α [TNFα]) expression and secretion were observed in vitro following PBA treatment. PBA treatment also affected the transient changes in nuclear factor κB (NFκB)-p65 phosphorylation and translocation in response to LPS induction in RT4 SCs. Similarly, PBA mediated long-term suppressive effects on HDAC3 expression and activity. PBA administration resulted in marked inhibition of pro-inflammatory cytokine secretion at the site of transection injury when compared with that in the hydrogel control group at 6-week post-injury. A conducive microenvironment for axonal regrowth and remyelination was generated by increasing expression levels of protein gene product 9.5 (PGP9.5) and myelin basic protein (MBP) in regenerating nerve tissues. PBA administration increased the relative gastrocnemius muscle weight percentage and maintained the intactness of muscle bundles when compared with those in the hydrogel control group.

Conclusions

Suppressing the lengthened state of inflammation using PBA treatment favors axonal regrowth and remyelination following nerve transection injury. PBA treatment also regulates pro-inflammatory cytokine expression by inhibiting the transcriptional activation of NFκB-p65 and HDAC3 in SCs in vitro.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02273-1.

Reduction in MicroRNA-4488 Expression Induces NFκB Translocation in Venous Endothelial Cells Under Arterial Flow

PURPOSE

Little is known about the molecular interactions among inflammatory responses that damage venous endothelial cells (vECs) during venous-to-arterial flow transition in vein graft diseases. Because arterial flow triggers excessive autophagy and inflammation in vECs, this study aimed to investigate the mediator of inflammation and methods to prevent vEC damage.

METHODS

Arterial laminar shear stress (ALSS; 12 dynes/cm²) was applied to vECs via in vitro and ex vivo perfusion systems. Inflammation in vECs was measured using inflammatory protein markers, NFκB translocation, cyclooxygenase-2 (COX-2) and COX-2 and NFκB promoter assays. The involvement of microRNA-4488 (miR-4488) was measured and confirmed by altering the specific miR using a miR-4488 mimic or inhibitor. The potential anti-inflammatory drugs and/or nitric oxide (NO) donor L-arginine (L-Arg) to prevent damage to vECs under ALSS was investigated.

RESULTS

ALSS triggered reactive oxygen species production, excessive autophagy, COX-2 protein expression, and NFκB translocation during vEC inflammation. Reduction in miR-4488 expression was detected in inflamed vECs treated with LPS, lipopolysaccharide (LPS) TNFα, and ALSS. Transfection of miR-4488 mimic (50 nM) prior to ALSS application inhibited the accumulation of inflammatory proteins as well as the translocation of NFκB. Combined treatment of vECs with COX-2-specific inhibitor (SC-236) and L-Arg alleviated the ALSS-induced inflammatory responses. Protective effects of the combined treatment on vECs against ALSS-induced damage were abolished by the application of miR-4488 inhibitor.

CONCLUSION

We showed that ALSS triggered the COX-2/NFκB pathway to induce vEC inflammation with a reduction in miR-4488. Combination of SC-236 and L-Arg prevented ALSS-induced vEC damage, thus, shows high potential for preventing vein graft diseases.

FGF9 induces functional differentiation to Schwann cells from human adipose derived stem cells

Rationale: The formation of adipose-derived stem cells (ASCs) into spheres on a chitosan-coated microenvironment promoted ASCs differentiation into a mixed population of neural lineage-like cells (NLCs), but the underline mechanism is still unknown. Since the fibroblast growth factor 9 (FGF9) and fibroblast growth factor receptors (FGFRs) play as key regulators of neural cell fate during embryo development and stem cell differentiation, the current study aims to reveal the interplay of FGF9 and FGFRs for promoting peripheral nerve regeneration.

Methods: Different concentration of FGF9 peptide (10, 25, 50, 100 ng/mL) were added during NLCs induction (FGF9-NLCs). The FGFR expressions and potential signaling were studied by gene and protein expressions as well as knocking down by specific FGFR siRNA or commercial inhibitors. FGF9-NLCs were fluorescent labeled and applied into a nerve conduit upon the injured sciatic nerves of experimental rats.

Results: The FGFR2 and FGFR4 were significantly increased during NLCs induction. The FGF9 treated FGF9-NLCs spheres became smaller and changed into Schwann cells (SCs) which expressed S100β and GFAP. The specific silencing of FGFR2 diminished FGF9-induced Akt phosphorylation and inhibited the differentiation of SCs. Transplanted FGF9-NLCs participated in myelin sheath formation, enhanced axonal regrowth and promoted innervated muscle regeneration. The knockdown of FGFR2 in FGF9-NLCs led to the abolishment of nerve regeneration.

Conclusions: Our data therefore demonstrate the importance of FGF9 in the determination of SC fate via the FGF9-FGFR2-Akt pathway and reveal the therapeutic benefit of FGF9-NLCs.

The Influence of AGEs Environment on Proliferation, Apoptosis, Homeostasis, and Endothelial Cell Differentiation of Human Adipose Stem Cells

The aim of this study was to evaluate the changes of proliferation, apoptosis, homeostasis, and differentiation of human adipose-derived stem cells (hASCs) in the simulated diabetic microenvironment and discuss the potential of the mesenchymal stem cell in the treatment of chronic diabetic wound. We simulated diabetic microenvironment with glycation end products (AGEs) in vitro and studied the changes of hASCs in proliferation and apoptosis. We found that AGEs inhibited the proliferation and lead to hASCs apoptosis, and the endothelial cell directed differentiation was also inhibited. AGEs upregulated growth-related oncogene and monocyte chemoattractant protein-1 and downregulated urokinase-type plasminogen activator receptor, which may inhibit the proliferation and transference of endothelial cells. The simulated diabetic microenvironment affects the proliferation, apoptosis, and homeostasis of hASCs, the endothelial cell migration, and the synthesis of collagen protein, leading to delayed wound healing.

Endothelial differentiation of bone marrow mesenchyme stem cells applicable to hypoxia and increased migration through Akt and NFκB signals

BACKGROUND

Bone marrow mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) are used to repair hypoxic or ischemic tissue. However, the underlining mechanism of resistance in the hypoxic microenvironment and the efficacy of migration to the injured tissue are still unknown. The current study aims to understand the hypoxia resistance and migration ability of MSCs during differentiation toward endothelial lineages by biochemical and mechanical stimuli.

METHOD

MSCs were harvested from the bone marrow of 6-8-week-old Sprague-Dawley rats. The endothelial growth medium (EGM) was added to MSCs for 3 days to initiate endothelial differentiation. Laminar shear stress was used as the fluid mechanical stimulation.

RESULTS

Application of EGM facilitated the early endothelial lineage cells (eELCs) to express EPC markers. When treating the hypoxic mimetic desferrioxamine, both MSCs and eELCs showed resistance to hypoxia as compared with the occurrence of apoptosis in rat fibroblasts. The eELCs under hypoxia increased the wound closure and C-X-C chemokine receptor type 4 (CXCR4) gene expression. Although the shear stress promoted eELC maturation and aligned cells parallel to the flow direction, their migration ability was not superior to that of eELCs either under normoxia or hypoxia. The eELCs showed higher protein expressions of CXCR4, phosphorylated Akt (pAkt), and endogenous NFκB and IκBα than MSCs under both normoxia and hypoxia conditions. The potential migratory signals were discovered by inhibiting either Akt or NFκB using specific inhibitors and revealed decreases of wound closure and transmigration ability in eELCs.

CONCLUSION

The Akt and NFκB pathways are important to regulate the early endothelial differentiation and its migratory ability under a hypoxic microenvironment.