Inhibition of Aldehyde Dehydrogenase-Activity Expands Multipotent Myeloid Progenitor Cells with Vascular Regenerative Function

GLP-1RA therapy increases circulating vascular regenerative cell content in people living with type 2 diabetes

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 (SGLT2) inhibitors are guideline-recommended therapies for the management of type 2 diabetes (T2D), atherosclerotic cardiovascular disease, heart failure, and chronic kidney disease. We previously observed in people living with T2D and coronary artery disease that circulating vascular regenerative (VR) progenitor cell content increased following 6-mo use of the SGLT2 inhibitor empagliflozin. In this post hoc subanalysis of the ORIGINS-RCE CardioLink-13 study (ClinicalTrials.gov Identifier NCT05253521), we analyzed the circulating VR progenitor cell content of 92 individuals living with T2D, among whom 20 were on a GLP-1RA, 42 were on an SGLT2 inhibitor but not a GLP-1RA, and 30 were on neither of these vascular protective therapies. In the GLP-1RA group, the mean absolute count of circulating VR progenitor cells defined by high aldehyde dehydrogenase (ALDH) activity (ALDHhiSSClow) and VR progenitor cells further characterized by surface expression of the proangiogenic marker CD133 (ALDHhiSSClowCD133+) was higher than the group receiving neither a GLP-1RA nor an SGLT2 inhibitor (P = 0.02) and comparable with that in the SGLT2 inhibitor group (P = 0.25). The absolute count of proinflammatory, granulocyte-restricted precursor cells (ALDHhiSSChi) was significantly lower in the GLP-1RA group compared with the group on neither therapy (P = 0.031). Augmented vessel repair initiated by VR cells with previously documented proangiogenic activity, alongside a reduction in systemic, granulocyte precursor-driven inflammation, may represent novel mechanisms responsible for the cardiovascular-metabolic benefits of GLP-1RA therapy. Prospective, randomized clinical trials are now warranted to establish the value of recovering circulating VR progenitor cell content with blood vessel regenerative functions.NEW & NOTEWORTHY In this post hoc subanalysis of 92 individuals living with T2D and at high cardiovascular risk, the authors summarize the differences in circulating vascular regenerative (VR) progenitor cell content between those on GLP-1RA therapy, on SGLT2 inhibitor without GLP-1RA therapy, and on neither therapy. Those on GLP-1RA therapy demonstrated greater circulating VR progenitor cell content and reduced proinflammatory granulocyte precursor content. These results offer novel mechanistic insights into the cardiometabolic benefits associated with GLP-1RA therapy.

Advances in ex vivo expansion of hematopoietic stem and progenitor cells for clinical applications

As caretakers of the hematopoietic system, hematopoietic stem cells assure a lifelong supply of differentiated populations that are responsible for critical bodily functions, including oxygen transport, immunological protection and coagulation. Due to the far-reaching influence of the hematopoietic system, hematological disorders typically have a significant impact on the lives of individuals, even becoming fatal. Hematopoietic cell transplantation was the first effective therapeutic avenue to treat such hematological diseases. Since then, key use and manipulation of hematopoietic stem cells for treatments has been aspired to fully take advantage of such an important cell population. Limited knowledge on hematopoietic stem cell behavior has motivated in-depth research into their biology. Efforts were able to uncover their native environment and characteristics during development and adult stages. Several signaling pathways at a cellular level have been mapped, providing insight into their machinery. Important dynamics of hematopoietic stem cell maintenance were begun to be understood with improved comprehension of their metabolism and progressive aging. These advances have provided a solid platform for the development of innovative strategies for the manipulation of hematopoietic stem cells. Specifically, expansion of the hematopoietic stem cell pool has triggered immense interest, gaining momentum. A wide range of approaches have sprouted, leading to a variety of expansion systems, from simpler small molecule-based strategies to complex biomimetic scaffolds. The recent approval of Omisirge, the first expanded hematopoietic stem and progenitor cell product, whose expansion platform is one of the earliest, is predictive of further successes that might arise soon. In order to guarantee the quality of these ex vivo manipulated cells, robust assays that measure cell function or potency need to be developed. Whether targeting hematopoietic engraftment, immunological differentiation potential or malignancy clearance, hematopoietic stem cells and their derivatives need efficient scaling of their therapeutic potency. In this review, we comprehensively view hematopoietic stem cells as therapeutic assets, going from fundamental to translational.

Restoration of blood vessel regeneration in the era of combination SGLT2i and GLP-1RA therapy for diabetes and obesity

Ischaemic cardiovascular diseases, including peripheral and coronary artery disease, myocardial infarction, and stroke, remain major comorbidities for individuals with type 2 diabetes (T2D) and obesity. During cardiometabolic chronic disease (CMCD), hyperglycaemia and excess adiposity elevate oxidative stress and promote endothelial damage, alongside an imbalance in circulating pro-vascular progenitor cells that mediate vascular repair. Individuals with CMCD demonstrate pro-vascular 'regenerative cell exhaustion' (RCE) characterized by excess pro-inflammatory granulocyte precursor mobilization into the circulation, monocyte polarization towards pro-inflammatory vs. anti-inflammatory phenotype, and decreased pro-vascular progenitor cell content, impairing the capacity for vessel repair. Remarkably, targeted treatment with the sodium-glucose cotransporter-2 inhibitor (SGLT2i) empagliflozin in subjects with T2D and coronary artery disease, and gastric bypass surgery in subjects with severe obesity, has been shown to partially reverse these RCE phenotypes. SGLT2is and glucagon-like peptide-1 receptor agonists (GLP-1RAs) have reshaped the management of individuals with T2D and comorbid obesity. In addition to glucose-lowering action, both drug classes have been shown to induce weight loss and reduce mortality and adverse cardiovascular outcomes in landmark clinical trials. Furthermore, both drug families also act to reduce systemic oxidative stress through altered activity of overlapping oxidase and antioxidant pathways, providing a putative mechanism to augment circulating pro-vascular progenitor cell content. As SGLT2i and GLP-1RA combination therapies are emerging as a novel therapeutic opportunity for individuals with poorly controlled hyperglycaemia, potential additive effects in the reduction of oxidative stress may also enhance vascular repair and further reduce the ischaemic cardiovascular comorbidities associated with T2D and obesity.

Cell therapy in end-stage liver disease: replace and remodel

Liver disease is prevalent worldwide. When it reaches the end stage, mortality rises to 50% or more. Although liver transplantation has emerged as the most efficient treatment for end-stage liver disease, its application has been limited by the scarcity of donor livers. The lack of acceptable donor organs implies that patients are at high risk while waiting for suitable livers. In this scenario, cell therapy has emerged as a promising treatment approach. Most of the time, transplanted cells can replace host hepatocytes and remodel the hepatic microenvironment. For instance, hepatocytes derived from donor livers or stem cells colonize and proliferate in the liver, can replace host hepatocytes, and restore liver function. Other cellular therapy candidates, such as macrophages and mesenchymal stem cells, can remodel the hepatic microenvironment, thereby repairing the damaged liver. In recent years, cell therapy has transitioned from animal research to early human studies. In this review, we will discuss cell therapy in end-stage liver disease treatment, especially focusing on various cell types utilized for cell transplantation, and elucidate the processes involved. Furthermore, we will also summarize the practical obstacles of cell therapy and offer potential solutions.

Decellularized adipose tissue scaffolds guide hematopoietic differentiation and stimulate vascular regeneration in a hindlimb ischemia model

Cellular therapies to stimulate therapeutic angiogenesis in individuals with critical limb ischemia (CLI) remain under intense investigation. In this context, the efficacy of cell therapy is dependent on the survival, biodistribution, and pro-angiogenic paracrine signaling of the cells transplanted. Hematopoietic progenitor cells (HPC) purified from human umbilical cord blood using high aldehyde dehydrogenase-activity (ALDH^hi cells) and expanded ex vivo, represent a heterogeneous mixture of progenitor cells previously shown to support limb revascularization in mouse models of CLI. The objectives of this study were to investigate the utility of bioscaffolds derived from human decellularized adipose tissue (DAT) to guide the differentiation of seeded HPC in vitro and harness the pro-angiogenic capacity of HPC at the site of ischemia after implantation in vivo. Probing whether the DAT scaffolds altered HPC differentiation, label-free quantitative mass spectrometry and flow cytometric phenotype analyses indicated that culturing the HPC on the DAT scaffolds supported their differentiation towards the pro-angiogenic monocyte/macrophage lineage at the expense of megakaryopoiesis. Moreover, implantation of HPC in DAT scaffolds within a unilateral hindlimb ischemia model in NOD/SCID mice increased cell retention at the site of ischemia relative to intramuscular injection, and accelerated the recovery of limb perfusion, improved functional limb use and augmented CD31⁺ capillary density when compared to DAT implantation alone or saline-injected controls. Collectively, these data indicate that cell-instructive DAT scaffolds can direct therapeutic HPC differentiation towards the monocyte/macrophage lineage and represent a promising delivery platform for improving the efficacy of cell therapies for CLI.

Ultrafiltration and Injection of Islet Regenerative Stimuli Secreted by Pancreatic Mesenchymal Stromal Cells

The secretome of mesenchymal stromal cells (MSCs) is enriched for biotherapeutic effectors contained within and independent of extracellular vesicles (EVs) that may support tissue regeneration as an injectable agent. We have demonstrated that the intrapancreatic injection of concentrated conditioned media (CM) produced by bone marrow MSC supports islet regeneration and restored glycemic control in hyperglycemic mice, ultimately providing a platform to elucidate components of the MSC secretome. Herein, we extend these findings using human pancreas-derived MSC (Panc-MSC) as "biofactories" to enrich for tissue regenerative stimuli housed within distinct compartments of the secretome. Specifically, we utilized 100 kDa ultrafiltration as a simple method to debulk protein mass and to enrich for EVs while concentrating the MSC secretome into an injectable volume for preclinical assessments in murine models of blood vessel and islet regeneration. EV enrichment (EV+) was validated using nanoscale flow cytometry and atomic force microscopy, in addition to the detection of classical EV markers CD9, CD81, and CD63 using label-free mass spectrometry. EV+ CM was predominately enriched with mediators of wound healing and epithelial-to-mesenchymal transition that supported functional regeneration in mesenchymal and nonmesenchymal tissues. For example, EV+ CM supported human microvascular endothelial cell tubule formation in vitro and enhanced the recovery of blood perfusion following intramuscular injection in nonobese diabetic/severe combined immunodeficiency mice with unilateral hind limb ischemia. Furthermore, EV+ CM increased islet number and β cell mass, elevated circulating insulin, and improved glycemic control following intrapancreatic injection in streptozotocin-treated mice. Collectively, this study provides foundational evidence that Panc-MSC, readily propagated from the subculture of human islets, may be utilized for regenerative medicine applications.

Isolation and characterization of circulating pro-vascular progenitor cell subsets from human whole blood samples

The examination of circulating pro-vascular progenitor cell frequency and function is integral in understanding aberrant blood vessel homeostasis in individuals with cardiometabolic disease. Here, we outline the characterization of progenitor cell subsets from peripheral blood using high aldehyde dehydrogenase (ALDH) activity, an intracellular detoxification enzyme previously associated with pro-vascular progenitor cell status. Using this protocol, cells can be examined by flow cytometry for ALDH activity and lineage restricted cell surface markers simultaneously.

For complete details on the use and execution of this protocol, please refer to Terenzi et al. (2019) and Hess et al. (2019, 2020).

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Aldehyde dehydrogenase is superior in the isolation of progenitor cells

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Flow cytometry is an effective method to characterize pro-vascular cells

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Aggressive gating strategies allows for in-depth progenitor cell characterization

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The use of fresh blood samples will yield most accurate cell prevalence

Alda-1, an Aldehyde Dehydrogenase 2 Agonist, Improves Cutaneous Wound Healing by Activating Epidermal Keratinocytes via Akt/GSK-3β/β-Catenin Pathway

BACKGROUND

The cutaneous wound healing process mainly comprises re-epithelialization, fibrosis, and neovascularization. Impaired wound healing is common but tricky in plastic surgery. Aldehyde dehydrogenase 2 (ALDH2), the most effective subset of the ALDH enzyme family, is known to exert a major role in detoxification of aldehydes. Activation of ALDH2 by Alda-1 (a specific agonist) has been found to protect against cardiovascular diseases. However, no research has paid attention to the potential of ALDH2 activation in regulating wound healing. The previous studies suggested a high expression of ALDH2 in normal skin tissue. The aim of this study was to investigate if Alda-1 may ameliorate wound healing.

METHODS

A full-thickness excisional wound model was established in vivo. Adult male C57BL/6 mice were randomly divided into DMSO and Alda-1 groups. Mice received an intraperitoneal injection of DMSO or 10 mg/mL Alda-1 (10 mg/kg body weight, dissolved in DMSO) for 7 days. The wound healing rate was measured at 0, 3, 5, and 7 days. Distribution of ALDH2 in wound tissue was showed. ALDH2 enzymatic activity was examined at 3, 5, and 7 days. The elongation of epithelial tongue was detected by hematoxylin-eosin staining, and collagen deposition was analyzed by Masson's trichrome staining at 7 days. Expressions of alpha-smooth muscle actin (alpha-SMA), transforming growth factor beta (TGF-beta), CD31, collagen 1, collagen 3, and elastin were stained by immunohistochemistry at 5 and 7 days. The HaCaT cell line was applied in vitro. Proliferation and migration were tested using CCK8 and wound healing assay separately. The level of TGF-β was examined by ELISA. Protein levels of the Akt/glycogen synthase kinase-3 beta (GSK-3 beta)/beta-catenin pathway were determined by western blotting.

RESULTS

Alda-1 accelerated wound healing rates. ALDH2 activity in wound sites was restored. Alda-1 promoted the length of the epithelial tongue, collagen deposition, as well as expressions of alpha-SMA, TGF-beta, collagen 1/3, elastin, but did not affect CD31. Proliferation, migration, and TGF-β secretion were promoted by Alda-1 and deregulated by CVT-10216 (an ALDH2 inhibitor). Protein variations of the Akt/GSK-3β/β-catenin pathway were found to accord with ALDH2 changes.

CONCLUSIONS

Alda-1, an ALDH2 agonist, improves cutaneous wound healing in a full-thickness excisional wound model. Alda-1 activates proliferation, migration, and TGF-β secretion of HaCaT (epidermal keratinocytes) by regulating the Akt/GSK-3β/β-catenin pathway.

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SGLT-2 Inhibitors and Regenerative Cell Exhaustion

In response to the Letter by Fadini, Hess et al. discuss the interpretation of their data and the details of the multiparametric analyses employed to measure the changes in circulating provascular cell content in patients with type 2 diabetes receiving empagliflozin compared to placebo treatment.

Characterization of a Vimentinhigh /Nestinhigh proteome and tissue regenerative secretome generated by human pancreas-derived mesenchymal stromal cells

Multipotent/mesenchymal stromal cells (MSCs) exist within a variety of postnatal tissues; however, global proteomic analyses comparing tissue-specific MSC are limited. Using human bone marrow (BM)-derived MSCs as a gold standard, we used label-free mass spectrometry and functional assays to characterize the proteome, secretome, and corresponding function of human pancreas-derived MSCs (Panc-MSCs) with a classical phenotype (CD90+/CD73+/CD105+/CD45-/CD31-). Both MSC subtypes expressed mesenchymal markers vimentin, α-SMA, and STRO-1; however, expression of nestin was increased in Panc-MSCs. Accordingly, these Vimentin^high /Nestin^high cells were isolated from fresh human pancreatic islet and non-islet tissues. Next, we identified expression of >60 CD markers shared between Panc-MSCs and BM-MSCs, including validated expression of CD14. An additional 19 CD markers were differentially expressed, including reduced pericyte-marker CD146 expression on Panc-MSCs. Panc-MSCs also showed reduced expression of proteins involved in lipid and retinoid metabolism. Accordingly, Panc-MSCs showed restricted responses to adipogenic stimuli in vitro, although both MSC types demonstrated trilineage differentiation. In contrast, Panc-MSCs demonstrated accelerated growth kinetics and competency to pro-neurogenic stimuli in vitro. The secretome of Panc-MSCs was highly enriched for proteins associated with vascular development, wound healing and chemotaxis. Similar to BM-MSCs, Panc-MSCs conditioned media augmented endothelial cell survival, proliferation, and tubule formation in vitro. Importantly, the secretome of both MSC types was capable of stimulating chemotactic infiltration of murine endothelial cells in vivo and reduced hyperglycemia in STZ-treated mice following intrapancreatic injection. Overall, this study provides foundational knowledge to develop Panc-MSCs as a unique MSC subtype with functional properties beneficial in regenerative medicine for diabetes and vascular disease.

Inhibition of Retinoic Acid Production Expands a Megakaryocyte-Enriched Subpopulation with Islet Regenerative Function

Islet regeneration is stimulated after transplantation of human umbilical cord blood (UCB) hematopoietic progenitor cells with high aldehyde dehydrogenase (ALDH)-activity into NOD/SCID mice with streptozotocin (STZ)-induced β cell ablation. ALDH^hi progenitor cells represent a rare subset within UCB that will require expansion without the loss of islet regenerative functions for use in cell therapies. ALDH^hi cells efficiently expand (>70-fold) under serum-free conditions; however, high ALDH-activity is rapidly diminished during culture coinciding with emergence of a committed megakaryocyte phenotype CD41+/CD42+/CD38+. ALDH-activity is also the rate-limiting step in retinoic acid (RA) production, a potent driver of hematopoietic differentiation. We have previously shown that inhibition of RA production during 9-day cultures, using diethylaminobenzaldehyde (DEAB) treatment, enhanced the expansion of ALDH^hi cells (>20-fold) with vascular regenerative paracrine functions. Herein, we sought to determine if DEAB-treatment also expanded ALDH^hi cells that retain islet regenerative function following intrapancreatic transplantation into hyperglycemic mice. After DEAB-treatment, expanded ALDH^hi cell subset was enriched for CD34+/CD38- expression and demonstrated enhanced myeloid multipotency in vitro compared to the ALDH^lo cell subset. Unfortunately, DEAB-treated ALDH^hi cells did not support islet regeneration after transplantation. Conversely, expanded ALDH^lo cells from DEAB-treated conditions reduced hyperglycemia, and increased islet number and cell proliferation in STZ-induced hyperglycemic NOD/SCID mice. DEAB-treated ALDH^lo cells were largely committed to a CD41+/CD42+ megakaryocyte phenotype. Collectively, this study provides preliminary evidence that committed cells of the megakaryocyte-lineage support endogenous islet regeneration and/or function, and the retention of high ALDH-activity did not coincide with islet regenerative function after expansion under serum-free culture conditions.

BMS 493 Modulates Retinoic Acid-Induced Differentiation During Expansion of Human Hematopoietic Progenitor Cells for Islet Regeneration

Cellular therapies are emerging as a novel treatment strategy for diabetes. Thus, the induction of endogenous islet regeneration in situ represents a feasible goal for diabetes therapy. Umbilical cord blood-derived hematopoietic progenitor cells (HPCs), isolated by high aldehyde dehydrogenase activity (ALDH^hi), have previously been shown to reduce hyperglycemia after intrapancreatic (iPan) transplantation into streptozotocin (STZ)-treated nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) mice. However, these cells are rare and require ex vivo expansion to reach clinically applicable numbers for human therapy. Therefore, we investigated whether BMS 493, an inverse retinoic acid receptor agonist, could prevent retinoic acid-induced differentiation and preserve islet regenerative functions during expansion. After 6-day expansion, BMS 493-treated cells showed a twofold increase in the number of ALDH^hi cells available for transplantation compared with untreated controls. Newly expanded ALDH^hi cells showed increased numbers of CD34 and CD133-positive cells, as well as a reduction in CD38 expression, a marker of hematopoietic cell differentiation. BMS 493-treated cells showed similar hematopoietic colony-forming capacity compared with untreated cells, with ALDH^hi subpopulations producing more colonies than low aldehyde dehydrogenase activity subpopulations for expanded cells. To determine if the secreted proteins of these cells could augment the survival and/or proliferation of β-cells in vitro, conditioned media (CM) from cells expanded with or without BMS 493 was added to human islet cultures. The total number of proliferating β-cells was increased after 3- or 7-day culture with CM generated from BMS 493-treated cells. In contrast to freshly isolated ALDH^hi cells, 6-day expansion with or without BMS 493 generated progeny that were unable to reduce hyperglycemia after iPan transplantation into STZ-treated NOD/SCID mice. Further strategies to reduce retinoic acid differentiation during HPC expansion is required to expand ALDH^hi cells without the loss of islet regenerative functions.