Diabetic Kidney Disease Alters the Transcriptome and Function of Human Adipose-Derived Mesenchymal Stromal Cells but Maintains Immunomodulatory and Paracrine Activities Important for Renal Repair

Mitochondria-rich extracellular vesicles derived from the culture supernatant of human synovial Fluid-derived mesenchymal stem cells Inhibited senescence of Stressed/inflammatory Licensed chondrocytes and Delayed Osteoarthritis progression

BACKGROUND

Mitochondrial dysfunction induces chondrocyte senescence, thereby precipitating articular cartilage (AC) degeneration in the pathogenesis of osteoarthritis (OA). Although the transfer of mitochondria from mesenchymal stem cells (MSCs) to host cells and their potential protective role have been demonstrated, whether MSCs can alleviate chondrocyte mitochondrial dysfunction or reverse OA progression remains unclear.

METHODS

A mitochondrial tracer was used to investigate the transfer of mitochondria-rich extracellular vesicles (MEV) derived from the culture supernatant of human synovial fluid-derived mesenchymal stem cells (hSF-MSCs). Human articular chondrocytes (hACs) impaired by oxidative stress co-incubated with MEV were used for experimental research in vitro. Healthy hACs and stressed hACs were cultured separately acting as the control groups. The MEV was injected into the OA rats' knee joint serving as experimental group. Healthy and OA rats were served as the control groups. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot (WB), enzyme- linked immunosorbent assay (ELISA), flow cytometry (FC), immunofluorescence (IF), fluorescence spectrophotometer (FS), immunohistochemistry (IHC) and other methods are used to analyze the effect of MEV on hACs and OA progression.

RESULTS

MEV derived from hSF-MSCs could transfer into hACs. Compared to the negative control group, co-incubation with MEV resulted in a significant down-regulation of oxidative stress markers and senescence-associated proteins in hACs, while improved mitochondrial function of hACs. Moreover, the MEV could traverse the dense interstitial layer and migrate towards the deeper cartilage, while intra-articular injection of MEV could effectively attenuate AC degeneration.

CONCLUSION

The transfer of MEV derived from hSF-MSCs represents a promising strategy for safeguarding AC, thereby offering a potential avenue and mechanism for the treatment of OA.

Mesenchymal Stem Cell Therapy: Therapeutic Opportunities and Challenges for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD), which severely affects the quality of patients' lives. However, the current therapeutic approaches can only postpone its progression to ESRD. It is therefore imperative to develop a novel therapeutic strategy for renal injury in DKD, with the objective of restoring renal function and reversing the process of ESRD. In recent years, the potential of mesenchymal stem cell (MSC) therapy for DKD has garnered increasing attention within the scientific community. Preclinical research on MSC therapy has yielded promising results, and the safety of MSC treatment in vivo has been substantiated in clinical studies. An increasing body of evidence suggests that MSC therapy has significant potential for the treatment of DKD. This article reviews the existing research on MSCs and their derived exosomes in treating DKD and analyzes the underlying mechanism of MSC-based therapy for DKD. Additionally, we discuss the potential of combining MSC therapy with conventional pharmacological treatments, along with the constraints and prospects of MSC therapy for DKD. We hope this review can provide a precise and comprehensive understanding of MSCs for the treatment of DKD.

Optimizing Mesenchymal Stem Cells for Regenerative Medicine: Influence of Diabetes, Obesity, Autoimmune, and Inflammatory Conditions on Therapeutic Efficacy: A Review

Mesenchymal stem cells (MSCs) are a promising tool that may be used in regenerative medicine. Thanks to their ability to differentiate and paracrine signaling, they can be used in the treatment of many diseases. Undifferentiated MSCs can support the regeneration of surrounding tissues through secreted substances and exosomes. This is possible thanks to the production of growth factors. These factors stimulate the growth of neighboring cells, have an anti-apoptotic effect, and support angiogenesis, and MSCs also have an immunomodulatory effect. The level of secreted factors may vary depending on many factors. Apart from the donor's health condition, it is also influenced by the source of MSCs, methods of harvesting, and even the banking of cells. This work is a review of research on how the patient's health condition affects the properties of obtained MSCs. The review discusses the impact of the patient's diabetes, obesity, autoimmune diseases, and inflammation, as well as the impact of the source of MSCs and methods of harvesting and banking cells on the phenotype, differentiation capacity, anti-inflammatory, angiogenic effects, and proliferation potential of MSCs. Knowledge about specific clinical factors allows for better use of the potential of stem cells and more appropriate targeting of procedures for collecting, multiplying, and banking these cells, as well as for their subsequent use. This article aims to review the characteristics, harvesting, banking, and paracrine signaling of MSCs and their role in diabetes, obesity, autoimmune and inflammatory diseases, and potential role in regenerative medicine.

Addition of Polyphenols to Drugs: The Potential of Controlling "Inflammaging" and Fibrosis in Human Senescent Lung Fibroblasts In Vitro

The combination of a polyphenol, quercetin, with dasatinib initiated clinical trials to evaluate the safety and efficacy of senolytics in idiopathic pulmonary fibrosis, a lung disease associated with the presence of senescent cells. Another approach to senotherapeutics consists of controlling inflammation related to cellular senescence or "inflammaging", which participates, among other processes, in establishing pulmonary fibrosis. We evaluate whether polyphenols such as caffeic acid, chlorogenic acid, epicatechin, gallic acid, quercetin, or resveratrol combined with different senotherapeutics such as metformin or rapamycin, and antifibrotic drugs such as nintedanib or pirfenidone, could present beneficial actions in an in vitro model of senescent MRC-5 lung fibroblasts. A senescent-associated secretory phenotype (SASP) was evaluated by the measurement of interleukin (IL)-6, IL-8, and IL-1β. The senescent-associated β-galactosidase (SA-β-gal) activity and cellular proliferation were assessed. Fibrosis was evaluated using a Picrosirius red assay and the gene expression of fibrosis-related genes. Epithelial-mesenchymal transition (EMT) was assayed in the A549 cell line exposed to Transforming Growth Factor (TGF)-β in vitro. The combination that demonstrated the best results was metformin and caffeic acid, by inhibiting IL-6 and IL-8 in senescent MRC-5 cells. Metformin and caffeic acid also restore cellular proliferation and reduce SA-β-gal activity during senescence induction. The collagen production by senescent MRC-5 cells was inhibited by epicatechin alone or combined with drugs. Epicatechin and nintedanib were able to control EMT in A549 cells. In conclusion, caffeic acid and epicatechin can potentially increase the effectiveness of senotherapeutic drugs in controlling lung diseases whose pathophysiological component is the presence of senescent cells and fibrosis.

The impact of hypoxia preconditioning on mesenchymal stem cells performance in hypertensive kidney disease

BACKGROUND

Autologous mesenchymal stem cells (MSCs) have emerged as a therapeutic option for many diseases. Hypertensive kidney disease (HKD) might impair MSCs' reparative ability by altering the biomolecular properties, but the characteristics of this impairment are unclear. In our previous pre-clinical studies, we found hypoxic preconditioning (HPC) enhanced angiogenesis and suppressed senescence gene expression. Thus, we hypothesize that HPC would improve human MSCs by enhancing their functionality and angiogenesis, creating an anti-inflammatory and anti-senescence environment.

METHODS

MSC samples (n = 12 each) were collected from the abdominal fat of healthy kidney donors (HC), hypertensive patients (HTN), and patients with hypertensive kidney disease (HKD). MSCs were harvested and cultured in Normoxic (20% O2) or Hypoxic (1% O2) conditions. MSC functionality was measured by proliferation assays and cytokine released in conditioned media. Senescence was evaluated by senescence-associated beta-galactosidase (SA-beta-gal) activity. Additionally, transcriptome analysis using RNA-sequencing and quantitative PCR (qPCR) were performed.

RESULTS

At baseline, normoxic HTN-MSCs had higher proliferation capacity compared to HC. However, HPC augmented proliferation in HC. HPC did not affect the release of pro-angiogenic protein VEGF, but increased EGF in HC-MSC, and decreased HGF in HC and HKD MSCs. Under HPC, SA-β-gal activity tended to decrease, particularly in HC group. HPC upregulated mostly the pro-angiogenic and inflammatory genes in HC and HKD and a few senescence genes in HKD.

CONCLUSIONS

HPC has a more favorable functional effect on HC- than on HKD-MSC, reflected in increased proliferation and EGF release, and modest decrease in senescence, whereas it has little effect on HTN or HKD MSCs.

Therapeutic potential: The role of mesenchymal stem cells from diverse sources and their derived exosomes in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most common microvascular complications in diabetic patients, with its incidence continuously increasing in recent years. DN causes renal tissue damage and functional decline, expedites the aging process of the kidneys, and may ultimately progress leading to end-stage renal disease, severely impacting the patient's quality of life and prognosis. Mesenchymal stem cells (MSCs) are highly valued for their multipotent differentiation, paracrine functions, immunomodulatory effects, and capacity for tissue repair. Particularly, exosomes (Exo) derived from MSCs (MSCs-Exo) are rich in bioactive molecules and facilitate intercellular communication, participating in various physiological and pathological processes. MSCs and MSCs-Exo, in particular, have been demonstrated to have therapeutic effects in DN treatment research by encouraging tissue repair, fibrosis inhibition, and inflammation reduction. Research has shown that MSCs and MSCs-Exo have therapeutic effects in DN treatment by promoting tissue repair, inhibiting fibrosis, and reducing inflammation. Recent studies underscore the potential of MSCs and MSCs-Exo, highlighting their broad applicability in DN treatment. This review aims to provide a comprehensive summary of the scientific developments in treating DN using MSCs and MSCs-Exo from diverse sources, while also exploring their future therapeutic possibilities in detail.

GKT137831 in combination with adipose-derived stem cells alleviates high glucose-induced inflammaging and improves diabetic wound healing

Adipose-derived stem cells (ADSCs) have been proven to promote healing in diabetic wounds, which are one of the most serious chronic refractory wounds. However, reactive oxygen species (ROS) induced by high glucose (HG) lead to oxidative stress and aging in ADSCs, which limits the therapeutic effect of ADSCs. In this study, we investigated the role of GKT137831, a NOX1/4 inhibitor that can reduce ROS production, in protecting ADSCs from hyperglycemia and in diabetic wound healing. In vitro, ROS levels and NOX4 expression were increased after HG treatment of ADSCs, while the oxidative stress marker malondialdehyde was increased; mitochondrial membrane potential was decreased; inflammatory aging-related indicators such as p16, p21, matrix metalloproteinase-1 (MMP1), MMP3, interleukin-6, and β-galactosidase were increased; and migration was weakened. In vivo, we constructed a diabetic mouse wound model and found that the combination of ADSCs and GKT137831 synergistically promoted the 21-day wound healing rate, increased the expression of collagen and hydroxyproline, increased the number of blood vessels and the expression of CD31, and reduced the expression of interleukin-6, MMP1, MMP3, and p21. These results suggest that GKT137831 could protect ADSCs from oxidative stress and aging induced by HG and enhance the therapeutic effect of ADSCs on diabetic wounds.

Oxidative Stress: A Culprit in the Progression of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the principal culprit behind chronic kidney disease (CKD), ultimately developing end-stage renal disease (ESRD) and necessitating costly dialysis or kidney transplantation. The limited therapeutic efficiency among individuals with DKD is a result of our finite understanding of its pathogenesis. DKD is the result of complex interactions between various factors. Oxidative stress is a fundamental factor that can establish a link between hyperglycemia and the vascular complications frequently encountered in diabetes, particularly DKD. It is crucial to recognize the essential and integral role of oxidative stress in the development of diabetic vascular complications, particularly DKD. Hyperglycemia is the primary culprit that can trigger an upsurge in the production of reactive oxygen species (ROS), ultimately sparking oxidative stress. The main endogenous sources of ROS include mitochondrial ROS production, NADPH oxidases (Nox), uncoupled endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), cytochrome P450 (CYP450), and lipoxygenase. Under persistent high glucose levels, immune cells, the complement system, advanced glycation end products (AGEs), protein kinase C (PKC), polyol pathway, and the hexosamine pathway are activated. Consequently, the oxidant-antioxidant balance within the body is disrupted, which triggers a series of reactions in various downstream pathways, including phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), transforming growth factor beta/p38-mitogen-activated protein kinase (TGF-β/p38-MAPK), nuclear factor kappa B (NF-κB), adenosine monophosphate-activated protein kinase (AMPK), and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. The disease might persist even if strict glucose control is achieved, which can be attributed to epigenetic modifications. The treatment of DKD remains an unresolved issue. Therefore, reducing ROS is an intriguing therapeutic target. The clinical trials have shown that bardoxolone methyl, a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, blood glucose-lowering drugs, such as sodium-glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists can effectively slow down the progression of DKD by reducing oxidative stress. Other antioxidants, including vitamins, lipoic acid, Nox inhibitors, epigenetic regulators, and complement inhibitors, present a promising therapeutic option for the treatment of DKD. In this review, we conduct a thorough assessment of both preclinical studies and current findings from clinical studies that focus on targeted interventions aimed at manipulating these pathways. We aim to provide a comprehensive overview of the current state of research in this area and identify key areas for future exploration.

Therapeutic Potential of Mesenchymal Stem Cell‐Derived Conditioned Medium for Diabetes Mellitus and Related Complications

Diabetes mellitus (DM) is one of the most life‐threatening metabolic disorders, with 9% of the global prevalence, and it is estimated to be rising to 12.2% in 2045. Currently, there is no definitive treatment for DM. Although life‐saving, insulin administration to control blood sugar is not a cure for DM and is insufficient to prevent DM‐related complications such as nephropathy, neuropathy, or retinopathy. For this reason, studies are continuing to develop treatments that will provide β‐cell regeneration while suppressing autoimmunity. Mesenchymal stem cells (MSCs) are multipotent stem cells with a high proliferation capacity, immunosuppression, and immunomodulation ability. MSCs have gained therapeutic importance with these properties besides their differentiation ability. The immunosuppressive and immunomodulatory properties of the cells arise from the soluble and insoluble factors they secrete into the extracellular environment. Therefore, the culture medium where these cells grow has therapeutic value and is named conditioned medium (CM). In this context, CM obtained from MSCs can provide a similar therapeutic effect with fewer safety concerns. Furthermore, preconditioning of MSCs can improve the effectiveness of these cells and associated cellular products. So, this review summarizes the recent advances in MSC‐derived CMs and their therapeutic potential for DM and related complications.

Diabetic kidney disease induces transcriptome alterations associated with angiogenesis activity in human mesenchymal stromal cells

BACKGROUND

Therapeutic interventions that optimize angiogenic activities may reduce rates of end-stage kidney disease, critical limb ischemia, and lower extremity amputations in individuals with diabetic kidney disease (DKD). Infusion of autologous mesenchymal stromal cells (MSC) is a promising novel therapy to rejuvenate vascular integrity. However, DKD-related factors, including hyperglycemia and uremia, might alter MSC angiogenic repair capacity in an autologous treatment approach.

METHODS

To explore the angiogenic activity of MSC in DKD, the transcriptome of adipose tissue-derived MSC obtained from DKD subjects was compared to age-matched controls without diabetes or kidney impairment. Next-generation RNA sequencing (RNA-seq) was performed on MSC (DKD n = 29; Controls n = 9) to identify differentially expressed (DE; adjusted p < 0.05, |log2fold change|> 1) messenger RNA (mRNA) and microRNA (miRNA) involved in angiogenesis (GeneCards). Paracrine-mediated angiogenic repair capacity of MSC conditioned medium (MSCcm) was assessed in vitro using human umbilical vein endothelial cells incubated in high glucose and indoxyl sulfate for a hyperglycemic, uremic state.

RESULTS

RNA-seq analyses revealed 133 DE mRNAs (77 upregulated and 56 down-regulated) and 208 DE miRNAs (119 up- and 89 down-regulated) in DKD-MSC versus Control-MSC. Interestingly, miRNA let-7a-5p, which regulates angiogenesis and participates in DKD pathogenesis, interacted with 5 angiogenesis-associated mRNAs (transgelin/TAGLN, thrombospondin 1/THBS1, lysyl oxidase-like 4/LOXL4, collagen 4A1/COL4A1 and collagen 8A1/COL8A1). DKD-MSCcm incubation with injured endothelial cells improved tube formation capacity, enhanced migration, reduced adhesion molecules E-selectin, vascular cell adhesion molecule 1 and intercellular adhesion molecule 1 mRNA expression in endothelial cells. Moreover, angiogenic repair effects did not differ between treatment groups (DKD-MSCcm vs. Control-MSCcm).

CONCLUSIONS

MSC from individuals with DKD show angiogenic transcriptome alterations compared to age-matched controls. However, angiogenic repair potential may be preserved, supporting autologous MSC interventions to treat conditions requiring enhanced angiogenic activities such as DKD, diabetic foot ulcers, and critical limb ischemia.

Mesenchymal Stem Cells Promote Intestinal Mucosal Repair by Positively Regulating the Nrf2/Keap1/ARE Signaling Pathway in Acute Experimental Colitis

BACKGROUND/AIMS

Mesenchymal stem cells (MSCs) are a type of adult pluripotent stem cell that has anti-inflammatory and immunomodulatory effects, and whose conditioned medium (CM) has also been found to be effective. We used MSC and CM enemas to investigate their ameliorative effects in a mouse model of colitis.

METHODS

We employed MSCs, CM, and MSCs + ML385 (an inhibitor of Nrf2) in dextran sodium sulfate (DSS)-induced colitis. Mice were sacrificed on day 8, and the effects of MSC or CM treatment on the levels of inflammation and oxidative stress in colonic epithelial cells were evaluated by histological analyses.

RESULTS

MSCs inhibited inflammatory cell infiltration and proinflammatory cytokine expression in the colon. In addition, MSCs reduced extracellular matrix deposition and maintained the mechanical barrier and permeability of colonic epithelial cells. Mechanistically, MSCs activated Nrf2, which then increased HO-1 and NQO-1 levels and downregulated the expression of Keap1 to suppress reactive oxygen species production and MDA generation, accompanied by increases in components of the enzymatic antioxidant system, including SOD, CAT, GSH-Px, and T-AOC. However, after administering an Nrf2 inhibitor (ML385) to block the Nrf2/Keap1/ARE pathway, we failed to observe protective effects of MSCs in mice with colitis. CM alone also produced some of the therapeutic benefits of MSCs but was not as effective as MSCs.

CONCLUSIONS

Our data confirmed that MSCs and CM can effectively improve intestinal mucosal repair in experimental colitis and that MSCs can improve this condition by activating the Nrf2/Keap1/ARE pathway.

Cellular senescence: the good, the bad and the unknown

Cellular senescence is a ubiquitous process with roles in tissue remodelling, including wound repair and embryogenesis. However, prolonged senescence can be maladaptive, leading to cancer development and age-related diseases. Cellular senescence involves cell-cycle arrest and the release of inflammatory cytokines with autocrine, paracrine and endocrine activities. Senescent cells also exhibit morphological alterations, including flattened cell bodies, vacuolization and granularity in the cytoplasm and abnormal organelles. Several biomarkers of cellular senescence have been identified, including SA-βgal, p16 and p21; however, few markers have high sensitivity and specificity. In addition to driving ageing, senescence of immune and parenchymal cells contributes to the development of a variety of diseases and metabolic disorders. In the kidney, senescence might have beneficial roles during development and recovery from injury, but can also contribute to the progression of acute kidney injury and chronic kidney disease. Therapies that target senescence, including senolytic and senomorphic drugs, stem cell therapies and other interventions, have been shown to extend lifespan and reduce tissue injury in various animal models. Early clinical trials confirm that senotherapeutic approaches could be beneficial in human disease. However, larger clinical trials are needed to translate these approaches to patient care.

hucMSC-sEVs-Derived 14-3-3ζ Serves as a Bridge between YAP and Autophagy in Diabetic Kidney Disease

As nanoscale membranous vesicles, human umbilical cord mesenchymal stem cell-derived small extracellular vesicles (hucMSC-sEVs) have attracted extensive attention in the field of tissue regeneration. Under the premise that the mechanisms of hucMSC-sEVs on the treatment of diabetic kidney disease (DKD) have not been revealed clearly, we constructed DKD rat model with success. After tail vein injection, hucMSC-sEVs effectively reduced blood glucose, maintained body weight and improved renal function in DKD rats. Notably, we found that hucMSC-sEVs suppressed YAP expression in renal cortical regions. Further in vitro experiments, we confirmed that the expression of YAP in the nucleus of renal podocytes was increased, and the level of autophagy was inhibited in the high-glucose environment, which could be reversed by intervention with hucMSC-sEVs. We screened out the key protein 14-3-3ζ, which could not only promote YAP cytoplasmic retention instead of entering the nucleus, but also enhance the level of autophagy in the cytoplasm. Ultimately, excessive YAP protein was removed by autophagy, a classic way of protein degradation. In conclusion, our study provides new strategies for the prevention of DKD and proposes the possibility of hucMSC-sEVs becoming a new treatment for DKD in the future.

Equilibrium among Inflammatory Factors Determines Human MSC-Mediated Immunosuppressive Effect

Mesenchymal stem cells (MSCs) are thought to be a promising therapeutic agent due to their multiple paracrine and immunomodulatory properties, providing protection from chronic inflammation and promoting tissue repair. MSCs can regulate the balance of pro-inflammatory and anti-inflammatory factors in inflamed tissues, creating a microenvironment necessary for successful healing; however, their interactions with immune cells are still poorly studied. We examined the temporal and spatial changes in gene regulation and the paracrine milieu accompanying the MSC-mediated immunosuppression effect in mixed cultures with activated peripheral blood mononuclear cells (PBMCs). Our data reveal that the peak of suppression of PBMC proliferation was achieved within 48 h following co-culture with MSCs and subsequently did not undergo a significant change. This effect was accompanied by an increase in COX-2 expression and an induction of IDO synthesis in MSCs. At this point, the expression of IL-1, IL-6, IL-8, IFN-γ, MCP-1, and G-CSF was upregulated in co-cultured cells. On the contrary, we observed a decrease in the concentrations of IL-10, IL-13, IL-5, and MIP-1b in co-culture supernatants compared to intact cultures of activated PBMCs. The regulation of IDO, IL-1, IL-6, and G-CSF production was accomplished with the involvement of direct cell-cell contact between MSCs and PBMCs. These findings provide new insights into the use of potential precondition inducers or their combinations to obtain functionally qualified MSCs for more effective treatment of inflammatory diseases.

Dapagliflozin Reduces Urinary Albumin Excretion by Downregulating the Expression of cAMP, MAPK, and cGMP-PKG Signaling Pathways Associated Genes

Objective: Diabetic nephropathy (DN), the most severe complication of diabetes mellitus, is characterized by albuminuria and progressive loss of kidney function. Dapagliflozin (DAP), a sodium-glucose cotransporter inhibitor, is an oral medication that improves blood glucose control in diabetic patients. However, the effects and mechanisms of DAP on DN remain unclear. Materials and Methods: The effect of DAP was based on a retrospective cohort study of patients who underwent 2-year surveillance, and the concentration of urine albumin-to-creatinine ratio, glomerular filtration rate, and serum creatinine were collected after treatment with DAP. To investigate the underlying mechanisms through which DAP reduces urinary albumin excretion, we used RNA-sequencing (RNA-seq) to analyze gene expression in human kidney 2 (HK-2) cells treated with DAP. Results: The retrospective cohort analysis indicated that DAP could reduce the excretion rate of urinary albumin in patients with type 2 diabetes and renal impairment. The results of the RNA-seq experiments showed 349 differentially expressed genes between DAP-treated HK-2 cells and control cells. Gene ontology annotation enrichment analysis showed that DAP mainly affected the expression of integral component of membrane- and cell junction-related genes, while the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that DAP primarily downregulated the expression of gene clusters associated with cyclic adenosine monophosphate, mitogen-activated protein kinase, and cyclic guanosine monophosphate-protein kinase G signaling pathways, which play critical roles in the progression of DN. Conclusion: Our results shed light on the mechanism by which DAP controls DN progression and provide a theoretical basis for the clinical treatment of DN.

Strategies for Targeting Senescent Cells in Human Disease

Cellular senescence represents a distinct cell fate characterized by replicative arrest in response to a host of extrinsic and intrinsic stresses. Senescence provides programming during development and wound healing, while limiting tumorigenesis. However, pathologic accumulation of senescent cells is implicated in a range of diseases and age-associated morbidities across organ systems. Senescent cells produce distinct paracrine and endocrine signals, causing local tissue dysfunction and exerting deleterious systemic effects. Senescent cell removal by apoptosis-inducing "senolytic" agents or therapies that inhibit the senescence-associated secretory phenotype, SASP inhibitors, have demonstrated benefit in both pre-clinical and clinical models of geriatric decline and chronic diseases, suggesting senescent cells represent a pharmacologic target for alleviating effects of fundamental aging processes. However, senescent cell populations are heterogeneous in form, function, tissue distribution, and even differ among species, possibly explaining issues of bench-to-bedside translation in current clinical trials. Here, we review features of senescent cells and strategies for targeting them, including immunologic approaches, as well as key intracellular signaling pathways. Additionally, we survey current senolytic therapies in human trials. Collectively, there is demand for research to develop targeted senotherapeutics that address the needs of the aging and chronically-ill.

A systematic review and meta-analysis of cell-based interventions in experimental diabetic kidney disease

Regenerative, cell‐based therapy is a promising treatment option for diabetic kidney disease (DKD), which has no cure. To prepare for clinical translation, this systematic review and meta‐analysis summarized the effect of cell‐based interventions in DKD animal models and treatment‐related factors modifying outcomes. Electronic databases were searched for original investigations applying cell‐based therapy in diabetic animals with kidney endpoints (January 1998‐May 2019). Weighted or standardized mean differences were estimated for kidney outcomes and pooled using random‐effects models. Subgroup analyses tested treatment‐related factor effects for outcomes (creatinine, urea, urine protein, fibrosis, and inflammation). In 40 studies (992 diabetic rodents), therapy included mesenchymal stem/stromal cells (MSC; 61%), umbilical cord/amniotic fluid cells (UC/AF; 15%), non‐MSC (15%), and cell‐derived products (13%). Tissue sources included bone marrow (BM; 65%), UC/AF (15%), adipose (9%), and others (11%). Cell‐based therapy significantly improved kidney function while reducing injury markers (proteinuria, histology, fibrosis, inflammation, apoptosis, epithelial‐mesenchymal‐transition, oxidative stress). Preconditioning, xenotransplantation, and disease‐source approaches were effective. MSC and UC/AF cells had greater effect on kidney function while cell products improved fibrosis. BM and UC/AF tissue sources more effectively improved kidney function and proteinuria vs adipose or other tissues. Cell dose, frequency, and administration route also imparted different benefits. In conclusion, cell‐based interventions in diabetic animals improved kidney function and reduced injury with treatment‐related factors modifying these effects. These findings may aid in development of optimal repair strategies through selective use of cells/products, tissue sources, and dose administrations to allow for successful adaptation of this novel therapeutic in human DKD.