Rat adipose tissue-derived stem cells attenuate peritoneal injuries in rat zymosan-induced peritonitis accompanied by complement activation

Advances in stem cell therapy for peritoneal fibrosis: from mechanisms to therapeutics

Peritoneal fibrosis (PF) is a pathophysiological condition caused by a variety of pathogenic factors. The most important features of PF are mesothelial-mesenchymal transition and accumulation of activated (myo-)fibroblasts, which hinder effective treatment; thus, it is critical to identify other practical approaches. Recently, stem cell (SC) therapy has been indicated to be a potential strategy for this disease. Increasing evidence suggests that many kinds of SCs alleviate PF mainly by differentiating into mesothelial cells; secreting cytokines and extracellular vesicles; or modulating immune cells, particularly macrophages. However, there are relatively few articles summarizing research in this direction. In this review, we summarize the risk factors for PF and discuss the therapeutic roles of SCs from different sources. In addition, we outline effective approaches and potential mechanisms of SC therapy for PF. We hope that our review of articles in this area will provide further inspiration for research on the use of SCs in PF treatment.

Peritoneal Expression of Membrane Complement Regulators Is Decreased in Peritoneal Dialysis Patients with Infected Peritonitis

In peritoneal dialysis (PD) patients, fungi and Pseudomonas aeruginosa are considered important causative microorganisms for peritonitis with poor prognosis. Our objective was to explore expressions of membrane complement (C) regulators (CRegs) and tissue injuries in the peritoneum of patients with PD-related peritonitis, including fungal and Pseudomonas aeruginosa peritonitis. In peritoneal biopsy tissues obtained at PD catheter removal, we investigated the severity of peritonitis-associated peritoneal injuries and the expression of CRegs, CD46, CD55, and CD59 against peritoneal tissues without any episode of peritonitis. In addition, we evaluated peritoneal injuries among fungal and Pseudomonas aeruginosa-peritonitis (P1) and Gram-positive bacterial peritonitis (P2). We also observed deposition of C activation products such as activated C and C5b-9 and measured sC5b-9 in the PD fluid of patients. As a result, the severity of peritoneal injuries correlated inversely with the expression of peritoneal CRegs. Peritoneal CReg expression in peritonitis was significantly reduced compared to no peritonitis. Peritoneal injuries were more severe in P1 than in P2. CReg expression was further decreased and C5b-9 further increased in P1 than in P2. In conclusion, severe peritoneal injuries due to fungal and Pseudomonas aeruginosa-peritonitis decreased CReg expression and increased deposition of activated C3 and C5b-9 in the peritoneum, suggesting that peritonitis, particularly fungal and Pseudomonas aeruginosa-peritonitis, might induce susceptibility to further peritoneal injuries due to excessive C activation.

Potential of Autologous Adipose-Derived Mesenchymal Stem Cells in Peritoneal Fibrosis: A Pilot Study

BACKGROUND

We aimed to determine the effects of systemic therapy with autologous adipose tissue derived mesenchymal stem cells (AD-MSCs) on different parameters of peritoneal function and inflammation in peritoneal dialysis (PD) patients.

METHODS

We enrolled nine PD patients with ultrafiltration failure (UFF). Patients received 1.2±0.1×106 cell/kg of AD-MSCs via cubital vein and were then followed for six months at time points of baseline, 3, 6, 12, 16 and 24 weeks after infusion. UNI-PET was performed for assessment of peritoneal characteristics at baseline and weeks 12 and 24. Systemic and peritoneal levels of tumor necrosis factor α (TNF-α), interleukin-6(IL-6), IL-2 and CA125 (by ELISA) and gene expression levels of transforming growth factor beta (TGF-β), smooth muscle actin (𝛼-SMA) and fibroblast-specific protein-1 (FSP-1) in PD effluent derived cells (by quantitative real-time PCR) were measured at baseline and weeks 3, 6, 12, 16 and 24.

RESULTS

Slight improvement was observed in the following UF capacity indices: free water transport (FWT, 32%), ultrafiltration - small pore (UFSP, 18%), ultrafiltration total (UFT, 25%), osmotic conductance to glucose (OCG, 25%), D/P creatinine (0.75 to 0.70), and Dt/D0 glucose (0.23 to 0.26). There was a slight increase in systemic and peritoneal levels of CA125 and a slight decrease in gene expression levels of TGF-β, α-SMA and FSP-1 that was more prominent at week 12 and vanished by the end of the study.

CONCLUSION

Our results for the first time showed the potential of MSCs for treatment of peritoneal damage in a clinical trial. Our results could be regarded as hypothesis suggestion and will need confirmation in future studies.

Comparison of mesenchymal stromal cells from peritoneal dialysis effluent with those from umbilical cords: characteristics and therapeutic effects on chronic peritoneal dialysis in uremic rats

Background

A long-term of peritoneal dialysis (PD) using a hypertonic PD solution (PDS) leads to patient’s peritoneal membrane (PM) injury, resulting in ultrafiltration failure (UFF) and PD drop-out. Our previous study shows that PD effluent-derived mesenchymal stromal cells (pMSCs) prevent the PM injury in normal rats after repeated exposure of the peritoneal cavity to a PDS. This study was designed to compare the cytoprotection between pMSCs and umbilical cord-derived MSCs (UC-MSCs) in the treatment of both PM and kidney injury in uremic rats with chronic PD.

Methods

5/6 nephrectomized (5/6Nx) Sprague Dawley rats were intraperitoneally (IP) injected Dianeal (4.25% dextrose, 10 mL/rat/day) and were treated with pMSCs or umbilical cord (UC)-MSCs (approximately 2 × 10⁶/rat/week, IP). Ultrafiltration was determined by IP injection of 30 mL of Dianeal (4.25% dextrose) with 1.5-h dewell time, and kidney failure by serum creatinine (SCr) and blood urea nitrogen (BUN). The structure of the PM and kidneys was assessed using histology. Gene expression was examined using quantitative reverse transcription PCR, and protein levels using flow cytometric and Western blot analyses.

Results

We showed a slight difference in the morphology between pMSCs and UC-MSCs in plastic dishes, and significantly higher expression levels of stemness-related genes (NANOG, OCT4, SOX2, CCNA2, RAD21, and EXO1) and MSCs surface markers (CD29, CD44, CD90 and CD105) in UC-MSCs than those in pMSCs, but no difference in the differentiation to chondrocytes, osteocytes or adipocytes. pMSC treatment was more effective than UC-MSCs in the protection of the MP and remnant kidneys in 5/6Nx rats from PDS-induced injury, which was associated with higher resistance of pMSCs than UC-MSCs to uremic toxins in culture, and more reduction of peritoneal mesothelial cell death by the secretome from pMSCs than from UC-MSCs in response to PDS exposure. The secretome from both pMSCs and UC-MSCs similarly inactivated NOS2 in activated THP1 cells.

Conclusions

As compared to UC-MSCs, pMSCs may more potently prevent PDS-induced PM and remnant kidney injury in this uremic rat model of chronic PD, suggesting that autotransplantation of ex vivo-expanded pMSCs may become a promising therapy for UFF and deterioration of remnant kidney function in PD patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02473-9.

Induced neural stem cell grafts exert neuroprotection through an interaction between Crry and Akt in a mouse model of closed head injury

Background

Recently, growing evidence has indicated an important role of the complement system, a crucial component of immunity, in mediating neuroinflammation and promoting neuronal apoptosis following closed head injury (CHI). We previously reported that transplanted induced neural stem cells (iNSCs) pre-treated with CHI mouse serum could enhance complement receptor type 1-related protein y (Crry) expression and ameliorate complement-mediated damage in mouse CHI models. However, the mechanism underlying the elevated levels of Crry expression remains elusive.

Methods

CHI models were established using a standardized weight-drop device. We collected CHI mouse serum at 12 h post-trauma. RT-QPCR assay, western blot analysis, complement deposition assay, Akt inhibition assay, flow cytometry, cell transplantation, and functional assay were utilized to clarify the mechanism of Crry expression in iNSCs receiving CHI mouse serum treatment.

Results

We observed dramatic increases in the levels of Crry expression and Akt activation in iNSCs receiving CHI mouse serum treatment. Remarkably, Akt inhibition led to the reduction of Crry expression in iNSCs. Intriguingly, the treatment of iNSC-derived neurons with recombinant complement receptor 2-conjugated Crry (CR2-Crry), which inhibits all complement pathways, substantially enhanced Crry expression and Akt activation in neurons after CHI mouse serum treatment. In subsequent in vitro experiments of pre-treatment of iNSCs with CR2-Crry, we observed significant increases in the levels of Crry expression and Akt activation in iNSCs and iNSC-derived astrocytes and neurons post-treatment with CHI mouse serum. Additionally, an in vivo study showed that intracerebral-transplanted iNSCs pre-treated with CR2-Crry markedly enhanced Crry expression in neurons and protected neurons from complement-dependent damage in the brains of CHI mice.

Conclusion

INSCs receiving CR2-Crry pre-treatment increased the levels of Crry expression in iNSCs and iNSC-derived astrocytes and neurons and attenuated complement-mediated injury following CHI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02186-z.

Mesenchymal stem cells reduce alcoholic hepatitis in mice via suppression of hepatic neutrophil and macrophage infiltration, and of oxidative stress

Mesenchymal stem cells (MSCs) are a population of pluripotent cells that have been tested for the treatment of many inflammatory diseases. It remains unclear whether MSCs were effective in treating mice with alcoholic hepatitis (AH) and its underlying mechanism. In the present study, MSCs were isolated from bone marrow of 4-6 week-old C57BL/6N male mice. AH was induced in female mice by chronic-binge ethanol feeding for 10 days. Intraperitoneal (i.p.) transplantation of MSCs or saline were performed in mice on day 10. Blood samples and hepatic tissues were harvested on day 11. Biochemical, liver histological and flow cytometric analyses were performed. Compared to the control mice, the AH mice had significantly increased liver/body weight ratio, serum alanine aminotransferase (ALT) and aspartate aminotransferases (AST), hepatic total cholesterol (TC), triglyceride (TG), malondialdehyde (MDA), hepatic neutrophil and macrophage infiltration (P<0.001), which were markedly reduced by i.p. transplantation of MSCs (P<0.01). Compared to the control mice, the hepatic glutathione (GSH) was prominently lower in the AH mice (P<0.001), which was markedly enhanced after i.p. injection of MSCs (P<0.001). MSCs were effective for the treatment of AH mice, which might be associated with their ability in inhibiting hepatic neutrophil and macrophage infiltration, and alleviating oxidative stress.

The Complement System Is Essential for the Phagocytosis of Mesenchymal Stromal Cells by Monocytes

Mesenchymal stromal cell (MSC) therapy is a promising tool in the treatment of chronic inflammatory diseases. This has been ascribed to the capacity of MSC to release a large variety of immune-modulatory factors. However, all aspects of the mode of therapeutic MSC action in different diseases remain unresolved, mainly because most of the infused MSC are undetectable in the circulation within hours after infusion. The aim of this study was to elucidate the fate of MSC after contact with plasma. We found that upon contact with blood, complement proteins including C3b/iC3b are deposited on MSC. Importantly, we also found that complement bound to MSC enhanced their phagocytosis by classical and intermediate monocytes via a mechanism that involves C3 but not C5. Thus, we describe for the first time a mechanism which might explain, at least partly, why MSC are not found in the blood circulation after infusion. Our results indicate that MSC immune-modulatory effects could be mediated by monocytes that have phagocytosed them.

Protection of the Peritoneal Membrane by Peritoneal Dialysis Effluent-Derived Mesenchymal Stromal Cells in a Rat Model of Chronic Peritoneal Dialysis

Peritoneal dialysis (PD) is a renal replacement option for patients with end-stage renal disease. However, a long-term exposure to hypertonic PD solutions leads to peritoneal membrane (PM) injury, resulting in ultrafiltration (UF) failure. This study was designed to primarily evaluate efficacy of PD effluent-derived mesenchymal stromal cells (pMSCs) in the prevention of PM injury in rats. The pMSCs were isolated from PD effluent. Male Wistar rats received daily intraperitoneal (IP) injection of 10 mL of Dianeal (4.25% dextrose) and were treated with pMSCs (1.2‐1.5 × 10⁶/rat/wk, IP). UF was determined by IP injection of 30 mL of Dianeal (4.25% dextrose) with dwell time of 1.5 h, and PM injury was examined by histology. Apoptosis was quantitated by using flow cytometric analysis, and gene expression by using the PCR array and Western blot. Here, we showed that as compared to naive control, daily IP injection of the Dianeal PD solution for 6 weeks without pMSC treatment significantly reduced UF, which was associated with an increase in both PM thickness and blood vessel, while pMSC treatment prevented the UF loss and reduced PM injury and blood vessels. In vitro incubation with pMSC-conditioned medium prevented cell death in cultured human peritoneal mesothelial cells (HPMCs) and downregulated proinflammatory (i.e., CXCL6, NOS2, IL1RN, CCL5, and NR3C1) while upregulated anti-inflammatory (i.e., CCR1, CCR4, IL9, and IL-10) gene expression in activated THP1 cells. In conclusion, pMSCs prevent bioincompatible PD solution-induced PM injury and UF decline, suggesting that infusing back ex vivo-expanded pMSCs intraperitoneally may have therapeutic potential for reduction of UF failure in PD patients.

Induced neural stem cell-derived astrocytes modulate complement activation and mediate neuroprotection following closed head injury

The complement system is a crucial component of immunity, and its activation has critical roles in neuroinflammatory response and cellular damage following closed head injury (CHI). We previously demonstrated that systemically injected induced neural stem cells (iNSCs) could modulate complement activation to ameliorate neuronal apoptosis in mouse CHI models. However, it remains unknown whether iNSC derivatives can regulate complement activation. In the present study, after CHI mouse serum treatment, we found dramatic decreases in the cellular viabilities of differentiated iNSCs. Interestingly, following CHI mouse serum treatment, the death of astrocytes derived from iNSCs which were pre-treated with CHI mouse serum was significantly decreased. Meanwhile, the deposition of C3 (C3d) and C5b-9 in these astrocytes was substantially reduced. Remarkably, we detected increased expression of complement receptor type 1-related protein y (Crry) in these astrocytes. Moreover, these astrocytes could reduce the numbers of apoptotic neurons via Crry expression post-CHI mouse serum treatment. Additionally, intracerebral-transplanted iNSCs, pre-treated with CHI mouse serum, significantly increased the levels of Crry expression in astrocytes to reduce the accumulation of C3d and C9 and the death of neurons in the brains of CHI mice. In summary, iNSCs receiving CHI mouse serum pre-treatment could enhance the expression of Crry in iNSC-derived astrocytes to modulate complement activation and mediate neuroprotection following CHI.

Systemic Administration of Induced Neural Stem Cells Regulates Complement Activation in Mouse Closed Head Injury Models

Complement activation plays important roles in the pathogenesis of central nervous system (CNS) diseases. Patients face neurological disorders due to the development of complement activation, which contributes to cell apoptosis, brain edema, blood-brain barrier dysfunction and inflammatory infiltration. We previously reported that induced neural stem cells (iNSCs) can promote neurological functional recovery in closed head injury (CHI) animals. Remarkably, we discovered that local iNSC grafts have the potential to modulate CNS inflammation post-CHI. In this study, we aimed to explore the role of systemically delivered iNSCs in complement activation following CNS injury. Our data showed that iNSC grafts decreased the levels of sera C3a and C5a and down-regulated the expression of C3d, C9, active Caspase-3 and Bax in the brain, kidney and lung tissues of CHI mice. Furthermore, iNSC grafts decreased the levels of C3d⁺/NeuN⁺, C5b-9⁺/NeuN⁺, C3d⁺/Map2⁺ and C5b-9⁺/Map2⁺ neurons in the injured cortices of CHI mice. Subsequently, we explored the mechanisms underlying these effects. With flow cytometry analysis, we observed a dramatic increase in complement receptor type 1-related protein y (Crry) expression in iNSCs after CHI mouse serum treatment. Moreover, both in vitro and in vivo loss-of-function studies revealed that iNSCs could modulate complement activation via Crry expression.

Rat Models of Acute and/or Chronic Peritoneal Injuries Including Peritoneal Fibrosis and Peritoneal Dialysis Complications

Peritoneal injury is a major cause of discontinuation from long-term peritoneal dialysis. However, the precise mechanisms underlying such injury remain unclear. Suitable animal models of peritoneal injury may be useful to analyze pathogenic mechanisms and facilitate the development of therapeutic approaches. We describe herein two rat models of peritoneal injury that we have recently proposed.

Are They Really Stem Cells? Scrutinizing the Identity of Cells and the Quality of Reporting in the Use of Adipose Tissue-Derived Stem Cells

There is an increasing concern that the term adipose tissue-derived stem cell (ASC) is inappropriately used to refer to the adipose stromal vascular fraction (SVF). To evaluate the accuracy and quality of reporting, 116 manuscripts on the application of ASC in humans and animals were examined based on the 2013 published International Federation for Adipose Therapeutics and Science (IFATS)/ International Society for Cellular Therapy (ISCT) joint statement and in reference to current guidelines for clinical trials and preclinical studies. It is disconcerting that 4 among the 47 papers or 8.51% (CI 2.37-20.38) surveyed after publication of IFATS/ISCT statement reported using ASCs but in fact they used unexpanded cells. 28/47 or 59.57% (CI 44.27-73.63) explicitly reported that adherent cells were used, 35/47 or 74.47% (CI 59.65-86.06) identified expression of surface markers, and 25/47 or 53.19% (CI 14.72-30.65) verified the multilineage potential of the cells. While there are a number of papers examined in this survey that were not able to provide adequate information on the characteristics of ASCs used with some erroneously referring to the SVF as stem cells, there are more room for improvement in the quality of reporting in the application of ASCs in humans and animals.

Therapeutic Potential of Stem Cells from Human Exfoliated Deciduous Teeth in Models of Acute Kidney Injury

Background

Acute kidney injury (AKI) is a critical condition associated with high mortality. However, the available treatments for AKI are limited. Stem cells from human exfoliated deciduous teeth (SHED) have recently gained attention as a novel source of stem cells. The purpose of this study was to clarify whether SHED have a therapeutic effect on AKI induced by ischemia-reperfusion injury.

Methods

The left renal artery and vein of the mice were clamped for 20 min to induce ischemia. SHED, bone marrow derived mesenchymal stem cells (BMMSC) or phosphate-buffered saline (control) were administered into the subrenal capsule. To confirm the potency of SHED in vitro, H₂O₂ stimulation assays and scratch assays were performed.

Results

The serum creatinine and blood urea nitrogen levels of the SHED group were significantly lower than those of the control group, while BMMSC showed no therapeutic effect. Infiltration of macrophages and neutrophils in the kidney was significantly attenuated in mice treated with SHED. Cytokine levels (MIP-2, IL-1β, and MCP-1) in mice kidneys were significantly reduced in the SHED group. In in vitro experiments, SHED significantly decreased MCP-1 secretion in tubular epithelial cells (TEC) stimulated with H₂O₂. In addition, SHED promoted wound healing in the scratch assays, which was blunted by anti-HGF antibodies.

Discussion

SHED attenuated the levels of inflammatory cytokines and improved kidney function in AKI induced by IRI. SHED secreted factors reduced MCP-1 and increased HGF expression, which promoted wound healing. These results suggest that SHED might provide a novel stem cell resource, which can be applied for the treatment of ischemic kidney injury.