Effect of Hypoxia on the Differentiation and the Self-Renewal of Metanephrogenic Mesenchymal Stem Cells

Hederagenin ameliorates cisplatin-induced acute kidney injury via inhibiting long non-coding RNA A330074k22Rik/Axin2/β-catenin signalling pathway

BACKGROUND

Acute kidney injury (AKI), a kidney disease with high morbidity and mortality, is characterized by a dramatic decline in renal function. Hederagenin (HDG), a pentacyclic triterpenoid saponin isolated from astragalus membranaceus, has been shown to have significant anti-inflammatory effects on various diseases. However, the effects of HDG on renal injury and inflammation in AKI has not been elucidated.

METHODS

In this research, mice model of AKI was established by intraperitoneal injection of cisplatin in vivo, the inflammatory model of renal tubular epithelial cells was established by LPS stimulation in vitro, and HDG was used to intervene in vitro and in vivo models. Transcriptome sequencing was used to analyze the alterations of LncRNA and mRNA expression in AKI model and LncRNA-A330074k22Rik (A33) knockdown cells, respectively. Renal in situ electrotransfer knockdown plasmid was used to establish mice model of AKI with low expression of A33 in kidney.

RESULTS

The results showed that HDG effectively alleviate cisplatin-induced kidney injury and inflammation in mice. Transcriptome sequencing results showed that multiple LncRNAs in kidney of AKI model exhibited significant changes, among which LncRNA-A33 had the most obvious change trend. Subsequent results showed that A33 was highly expressed in kidney of AKI mice and LPS-induced renal tubular cells. After in situ renal electroporation knockdown plasmid down-regulated A33 in kidney of AKI mice, it was found that inhibition of A33 could significantly relieve cisplatin-induced kidney injury and inflammation of AKI, while HDG could effectively suppress the expression of A33 in vitro and in vivo, respectively. Subsequently, transcriptome sequencing was again used to analyze the changes in mRNA expression of renal tubular cells after A33 knockdown by siRNA. The results showed that a large number of inflammation-related signaling pathways were down-regulated, Axin2 and its downstream β-catenin signal were significantly inhibited. Cell recovery test showed that HDG inhibited Axin2/β-catenin signal by down-regulating A33, and improved kidney injury and inflammation of AKI.

CONCLUSION

Taken together, HDG significantly ameliorated cisplatin-induced kidney injury through LncRNA-A330074k22Rik/Axin2/β-catenin signal axis, which providing a potential therapeutic approach for the treatment of AKI.

Therapeutic Effect of Pericytes for Diabetic Wound Healing

Objective

Numerous attempts have been made to devise treatments for ischemic foot ulcer (IFU), which is one of the most severe and fatal consequences of diabetes mellitus (DM). Pericytes, which are perivascular multipotent cells, are of interest as a treatment option for IFU because they play a critical role in forming and repairing various tissues. In this study, we want to clarify the angiogenic potential of pericytes in DM-induced wounds.

Methods

We evaluated pericyte stimulation capability for tube formation, angiogenesis, and wound healing (cell migration) in human umbilical vein endothelial cells (HUVECs) with in-vivo and in-vitro models of high glucose conditions.

Results

When HUVECs were co-cultured with pericytes, their tube-forming capacity and cell migration were enhanced. Our diabetic mouse model showed that pericytes promote wound healing via increased vascularization.

Conclusion

The findings of this study indicate that pericytes may enhance wound healing in high glucose conditions, consequently making pericyte transplantation suitable for treating IFUs.

Insight into Hypoxia Stemness Control

Recently, the research on stemness and multilineage differentiation mechanisms has greatly increased its value due to the potential therapeutic impact of stem cell-based approaches. Stem cells modulate their self-renewing and differentiation capacities in response to endogenous and/or extrinsic factors that can control stem cell fate. One key factor controlling stem cell phenotype is oxygen (O₂). Several pieces of evidence demonstrated that the complexity of reproducing O₂ physiological tensions and gradients in culture is responsible for defective stem cell behavior in vitro and after transplantation. This evidence is still worsened by considering that stem cells are conventionally incubated under non-physiological air O₂ tension (21%). Therefore, the study of mechanisms and signaling activated at lower O₂ tension, such as those existing under native microenvironments (referred to as hypoxia), represent an effective strategy to define if O₂ is essential in preserving naïve stemness potential as well as in modulating their differentiation. Starting from this premise, the goal of the present review is to report the status of the art about the link existing between hypoxia and stemness providing insight into the factors/molecules involved, to design targeted strategies that, recapitulating naïve O₂ signals, enable towards the therapeutic use of stem cell for tissue engineering and regenerative medicine.

Low oxygen tension potentiates proliferation and stemness but not multilineage differentiation of caprine male germline stem cells

The milieu of male germline stem cells (mGSCs) is characterized as a low-oxygen (O₂) environment, whereas, their in-vitro expansion is typically performed under normoxia (20-21% O₂). The comparative information about the effects of low and normal O₂ levels on the growth and differentiation of caprine mGSCs (cmGSCs) is lacking. Thus, we aimed to investigate the functional and multilineage differentiation characteristics of enriched cmGSCs, when grown under hypoxia and normoxia. After enrichment of cmGSCs through multiple methods (differential platting and Percoll-density gradient centrifugation), the growth characteristics of cells [population-doubling time (PDT), viability, proliferation, and senescence], and expression of key-markers of adhesion (β-integrin and E-Cadherin) and stemness (OCT-4, THY-1 and UCHL-1) were evaluated under hypoxia (5% O₂) and normoxia (21% O₂). Furthermore, the extent of multilineage differentiation (neurogenic, adipogenic, and chondrogenic differentiation) under different culture conditions was assessed. The survival, viability, and proliferation were significantly (p < 0.05) improved, thus, yielding a significantly (p < 0.05) higher number of viable cells with larger colonies under hypoxia. Furthermore, the expression of stemness and adhesion markers were distinctly upregulated under lowered O₂ conditions. Conversely, the differentiated regions and expression of differentiation-specific genes [C/EBPα (adipogenic), nestin and β-tubulin (neurogenic), and COL2A1 (chondrogenic)] were significantly (p < 0.05) reduced under hypoxia. Overall, the results demonstrate that culturing cmGSCs under hypoxia augments the growth characteristics and stemness but not the multilineage differentiation of cmGSCs, as compared with normoxia. These data are important to develop robust methodologies for ex-vivo expansion and lineage-committed differentiation of cmGSCs for clinical applications.

Hypoxia further exacerbates woody breast myopathy in broilers via alteration of satellite cell fate

Woody breast (WB) condition has created a variety of challenges for the global poultry industry. To date, there are no effective treatments or preventative measures due to its unknown (undefined) etiology. Several potential mechanisms including oxidative stress, fiber-type switching, cellular damage, and altered intracellular calcium levels have been proposed to play a key role in the progression of the WB myopathy. In a previous study, we have shown that WB is associated with hypoxia-like status and dysregulated oxygen homeostasis. As satellite cells (SC) play a pivotal role in muscle fiber repair and remodeling under stress conditions, we undertook the present study to determine satellite cell fate in WB-affected birds when reared in either normoxic or hypoxic conditions. Modern random bred broilers from 2015 (n = 200) were wing banded and reared under standard brooding practices for the first 2 wk post-hatch. At 15 d, chicks were divided in 2 body weight-matched groups and reared to 6 wk in either control local altitude or hypobaric chambers with simulated altitude of 6,000 ft. Birds were provided ad libitum access to water and feed, according to the Cobb recommendations. At 6 wk of age, birds were processed and scored for WB, and breast samples were collected from WB-affected and unaffected birds for molecular analyses (n = 10/group). SCs were isolated from normal breast muscle, cultured in vitro, and exposed to normoxia or hypoxia for 2 h. The expression of target genes was determined by qPCR using 2^−∆∆Ct method. Protein distribution and expression were determined by immunofluorescence staining and immunoblot, respectively. Data were analyzed by the Student's t test with significance set at P < 0.05. Multiple satellite cell markers, myogenic factor (Myf)-5 and paired box (PAX)-7 were significantly decreased at the mRNA and protein levels in the breast muscle from WB-affected birds compared to their unaffected counterparts. Lipogenic-and adipogenic-associated factors (acetyl-CoA carboxylase, ACCα; fatty acid synthase, FASN, malic enzyme, ME; and ATP citrate lyase, ACLY) were activated in WB-affected birds. These data were supported by an in vitro study where hypoxia decreased the expression of Myf5 and Pax7, and increased that of ACCα, FASN, ME, and ACLY. Together, these data indicate that under hypoxic condition, SC change fate by switching from a myogenic to an adipogenic program, which explains at least partly, the etiology of the WB myopathy.

Acid-sensing ion channel 1a is involved in ischaemia/reperfusion induced kidney injury by increasing renal epithelia cell apoptosis

Acidic microenvironment is commonly observed in ischaemic tissue. In the kidney, extracellular pH dropped from 7.4 to 6.5 within 10 minutes initiation of ischaemia. Acid‐sensing ion channels (ASICs) can be activated by pH drops from 7.4 to 7.0 or lower and permeates to Ca²⁺entrance. Thus, activation of ASIC1a can mediate the intracellular Ca²⁺ accumulation and play crucial roles in apoptosis of cells. However, the role of ASICs in renal ischaemic injury is unclear. The aim of the present study was to test the hypothesis that ischaemia increases renal epithelia cell apoptosis through ASIC1a‐mediated calcium entry. The results show that ASIC1a distributed in the proximal tubule with higher level in the renal tubule ischaemic injury both in vivo and in vitro. In vivo, Injection of ASIC1a inhibitor PcTx‐1 previous to ischaemia/reperfusion (I/R) operation attenuated renal ischaemic injury. In vitro, HK‐2 cells were pre‐treated with PcTx‐1 before hypoxia, the intracellular concentration of Ca²⁺, mitochondrial transmembrane potential (∆ψm) and apoptosis was measured. Blocking ASIC1a attenuated I/R induced Ca²⁺ overflow, loss of ∆ψm and apoptosis in HK‐2 cells. The results revealed that ASIC1a localized in the proximal tubular and contributed to I/R induced kidney injury. Consequently, targeting the ASIC1a may prove to be a novel strategy for AKI patients.

Role of miRNAs in hypoxia-related disorders

Hypoxia is a complex pathophysiological condition. The physiological and molecular responses to this stress have been extensively studied. However, the management of its ill effects still poses a challenge to clinicians. MicroRNAs (miRNAs) are short non-coding RNA molecules that control post-transcriptional gene expression. The regulatory role of miRNAs in hypoxic environments has been studied in many hypoxia-related disorders, however a comprehensive compilation and analysis of all data and the significance of miRNAs in hypoxia adaption is still lacking. This review summarizes the miRNAs related to various hypoxia-related disorders and highlights the computational approaches to study them. This would help in designing novel strategies toward efficient management of hypoxia-related disorders.

Establishment of Insulin-Producing Cells From Human Embryonic Stem Cells Underhypoxic Condition for Cell Based Therapy

Diabetes mellitus (DM) is a group of diseases characterized by abnormally high levels of glucose in the blood stream. In developing a potential therapy for diabetic patients, pancreatic cells transplantation has drawn great attention. However, the hinder of cell transplantation for diabetes treatment is insufficient sources of insulin-producing cells. Therefore, new cell based therapy need to be developed. In this regard, human embryonic stem cells (hESCs) may serve as good candidates for this based on their capability of differentiation into various cell types. In this study, we designed a new differentiation protocol that can generate hESC-derived insulin-producing cells (hES-DIPCs) in a hypoxic condition. We also emphasized on the induction of definitive endoderm during embryoid bodies (EBs) formation. After induction of hESCs differentiation into insulin-producing cells (IPCs), the cells obtained from the cultures exhibited pancreas-related genes such as Pdx1, Ngn3, Nkx6.1, GLUT2, and insulin. These cells also showed positive for DTZ-stained cellular clusters and contained ability of insulin secretion in a glucose-dependent manner. After achievement to generated functional hES-DIPCs in vitro, some of the hES-DIPCs were then encapsulated named encapsulated hES-DIPCs. The data showed that the encapsulated cells could possess the function of insulin secretion in a time-dependent manner. The hES-DIPCs and encapsulated hES-DIPCs were then separately transplanted into STZ-induced diabetic mice. The findings showed the significant blood glucose levels regulation capacity and declination of IL-1β concentration in all transplanted mice. These results indicated that both hES-DIPCs and encapsulated hES-DIPCs contained the ability to sustain hyperglycemia condition as well as decrease inflammatory cytokine level in vivo. The findings of this study may apply for generation of a large number of hES-DIPCs in vitro. In addition, the implication of this work is therapeutic value in type I diabetes treatment in the future. The application for type II diabetes treatment remain to be investigated.