Bone marrow as a home of heterogenous populations of nonhematopoietic stem cells

Hydrogen generators-protected mesenchymal stem cells reverse articular redox imbalance-induced immune dysfunction for osteoarthritis treatment

Stem cell therapy has revolutionized the management of osteoarthritis (OA), but the articular dysregulated redox status diminishes cell engraftment efficiency and disrupts immune homeostasis, therefore compromising the overall therapeutic efficacy. Here, we present hydrogen (H2) generators-backpacked mesenchymal stem cells (MSCs) which preserve the biological functions and survival of transplanted cells and reverse articular immune dysfunction, mitigating OA. Specifically, post systemic transplantation, H2 generators-laden MSCs home to OA joints, and upon stimulation in acidic OA environment, H2 produced from the generators remodels articular redox balance, thereby relieving the loss of mitochondrial membrane potential, decreasing cell apoptosis rate, and maintaining pluripotent and paracrine functions of MSCs. Furthermore, the reactive oxygen species scavenging by H2 in combination with paracrine effects of the MSCs promote macrophage polarization towards the anti-inflammatory M2 phenotype, which contributes to reversing synovial immune disorder. In severe OA model, the backpacked MSCs reduce osteoarthritic degeneration, osteophyte formation and joint inflammation, and promote cartilage regeneration. In sum, our work demonstrates that arming with H2 generators effectively boosts the therapeutic efficacy of MSCs, which hold great potential for alleviating redox imbalance-related tissue lesions, including but not limited to OA.

Misconceptions Thrive in the Field of Cancer as Technological Advances Continue to Confuse Stem Cell Biology

Despite the huge thrust on targeted therapies, cancer survival rates have not improved and both cancer incidence and fatalities continue to rise globally. There is no consensus on how cancer initiates and two contrasting views were published in 2024 regarding cancer initiation. Based on the premise that no stem cells exist in tissues like liver, lungs, and pancreas but they are still affected by cancer; it was suggested that somatic cells dedifferentiate and undergo 'paligenosis' to initiate cancer. The second view discussed that tissue-resident, very small embryonic-like stem cells (VSELs) are vulnerable to extrinsic/intrinsic insults and their dysfunctions initiate cancer. The present article examines the underlying technical reasons that have led to these conflicting views. Scientists have struggled to detect quiescent cancer stem cells (CSCs) that survive chemotherapy, and radiotherapy and escape immunotherapy, cause recurrence and eventually therapeutic resistance leading to death. Lineage tracing studies fail to detect quiescent, acyclic stem cells and instead, the role of actively dividing LGR5+ cells was highlighted for tumor initiation, growth, and metastasis. Similarly, technologies like flow cytometry, and single-cell RNAseq, widely used to comprehend cancer biology, provide insights into cell populations present in abundance. Our article reviews why VSELs/CSCs in the pancreas have remained elusive despite employing advanced technologies, and the critique can be generalized to multiple other organs. This understanding is crucial as it will help to develop better therapeutic strategies for cancer, offer early detection when cancer is a weak disease, and pave the path for prevention over treatment.

Promoting epithelial regeneration in chemically induced acute lung injury through Sox9-positive alveolar type 2 epithelial cells

BACKGROUND

Chemical-induced acute lung injury is characterized by impaired epithelial regenerative capacity, leading to acute pulmonary edema. Numerous studies have investigated the therapeutic potential of endogenous stem cells with particular emphasis on alveolar type 2 epithelial (AEC2) cells owing to their involvement in lung cell renewal. Sox9, a transcription factor known for its role in maintaining stem cell properties and guiding cell differentiation, marks a subset of AEC2 cells believed to contribute to epithelial repair. However, the role of Sox9+AEC2 cells in the distal lung alveolar cells and the potential roles in chemically induced acute lung injury have never been explored.

METHODS

In this study, we generated Sox9flox/flox;SftpcCre-ERT2 mice and examined the effects of Sox9+AEC2 cells on the pathophysiology of epithelial damage during chemical-induced acute lung injury. Subsequently, Sox9-CreERT2 Ai9 mice were used for lineage tracing to elucidate the repair mechanisms.

RESULTS

Our findings revealed that Sox9+AEC2 cells endowed with stem cell properties induced cell proliferation during lung injury, predominantly in the damaged alveolar region. This process is accompanied by the regulation of inflammatory responses and orderly differentiation, thereby promoting epithelial regeneration.

CONCLUSION

These results provide compelling in vivo genetic evidence supporting the characterization of Sox9+AEC2 cells as bona fide lung epithelial stem cells, demonstrating their multipotency and self-renewal capabilities during lung repair and regeneration. The identification of Sox9+AEC2 cells as crucial contributors to the promotion of epithelial repair underscores their potential as therapeutic targets in chemical-induced acute lung injury.

Initiation of Cancer: The Journey From Mutations in Somatic Cells to Epigenetic Changes in Tissue-resident VSELs

Multiple theories exist to explain cancer initiation, although a consensus on this is crucial for developing effective therapies. 'Somatic mutation theory' suggests that mutations in somatic cells during DNA repair initiates cancer but this concept has several attached paradoxes. Research efforts to identify quiescent cancer stem cells (CSCs) that survive therapy and result in metastasis and recurrence have remained futile. In solid cancers, CSCs are suggested to appear during epithelial-mesenchymal transition by the dedifferentiation and reprogramming of epithelial cells. Pluripotent and quiescent very small embryonic-like stem cells (VSELs) exist in multiple tissues but remain elusive owing to their small size and scarce nature. VSELs are developmentally connected to primordial germ cells, undergo rare, asymmetrical cell divisions and are responsible for the regular turnover of cells to maintain tissue homeostasis throughout life. VSELs are directly vulnerable to extrinsic endocrine insults because they express gonadal and gonadotropin hormone receptors. VSELs undergo epigenetic changes due to endocrine insults and transform into CSCs. CSCs exhibit genomic instability and develop mutations due to errors during DNA replication while undergoing excessive proliferation and clonal expansion to form spheroids. Thus tissue-resident VSELs offer a connection between extrinsic insults and variations in cancer incidence reported in various body tissues. To conclude, cancer is indeed a stem cell disease with mutations occurring as a consequence. In addition to immunotherapy, targeting mutations, and Lgr5 + organoids for developing new therapeutics, targeting CSCs (epigenetically altered VSELs) by improving their niche and epigenetic status could serve as a promising strategy to treat cancer.

Non-haematopoietic Sca-1+ Cells in the Retina of Adult Mice Express Functional TLR2

The mammal retina does not have the capacity to regenerate throughout life, although some stem and progenitor cells persist in the adult retina and might retain multipotentiality, as previously described in many tissues. In this work we demonstrate the presence of a small lineage- Sca-1+ cell population in the adult mouse retina which expresses functional TLR2 receptors as in vitro challenge with the pure TLR2 agonist Pam3CSK4 increases cell number and upregulates TLR2. Therefore, this population could be of interest in neuroregeneration studies to elucidate its role in these processes.

Fibrosis and bone marrow: understanding causation and pathobiology

Bone marrow fibrosis represents an important structural change in the marrow that interferes with some of its normal functions. The aetiopathogenesis of fibrosis is not well established except in its primary form. The present review consolidates current understanding of marrow fibrosis. We searched PubMed without time restriction using key words: bone marrow and fibrosis as the main stem against the terms: growth factors, cytokines and chemokines, morphology, megakaryocytes and platelets, myeloproliferative disorders, myelodysplastic syndrome, collagen biosynthesis, mesenchymal stem cells, vitamins and minerals and hormones, and mechanism of tissue fibrosis. Tissue marrow fibrosis-related papers were short listed and analysed for the review. It emerged that bone marrow fibrosis is the outcome of complex interactions between growth factors, cytokines, chemokines and hormones together with their facilitators and inhibitors. Fibrogenesis is initiated by mobilisation of special immunophenotypic subsets of mesenchymal stem cells in the marrow that transform into fibroblasts. Fibrogenic stimuli may arise from neoplastic haemopoietic or non-hematopoietic cells, as well as immune cells involved in infections and inflammatory conditions. Autoimmunity is involved in a small subset of patients with marrow fibrosis. Megakaryocytes and platelets are either directly involved or are important intermediaries in stimulating mesenchymal stem cells. MMPs, TIMPs, TGF-β, PDGRF, and basic FGF and CRCXL4 chemokines are involved in these processes. Genetic and epigenetic changes underlie many of these conditions.

Exploring the Effects of Human Bone Marrow-Derived Mononuclear Cells on Angiogenesis In Vitro

Cell therapies involving the administration of bone marrow-derived mononuclear cells (BM-MNCs) for patients with chronic limb-threatening ischemia (CLTI) have shown promise; however, their overall effectiveness lacks evidence, and the exact mechanism of action remains unclear. In this study, we examined the angiogenic effects of well-controlled human bone marrow cell isolates on endothelial cells. The responses of endothelial cell proliferation, migration, tube formation, and aortic ring sprouting were analyzed in vitro, considering both the direct and paracrine effects of BM cell isolates. Furthermore, we conducted these investigations under both normoxic and hypoxic conditions to simulate the ischemic environment. Interestingly, no significant effect on the angiogenic response of human umbilical vein endothelial cells (HUVECs) following treatment with BM-MNCs was observed. This study fails to provide significant evidence for angiogenic effects from human bone marrow cell isolates on human endothelial cells. These in vitro experiments suggest that the potential benefits of BM-MNC therapy for CLTI patients may not involve endothelial cell angiogenesis.

Human umbilical cord blood mesenchymal stem cells as a potential therapy for schistosomal hepatic fibrosis: an experimental study

The objective of our study was to assess the effect of human umbilical cord blood (HUCB) mesenchymal stem cells (MSCs) transplantation on schistosomal hepatic fibrosis in mice. The study animals were divided into three groups. Group I is a control group, where the mice were infected with Schistosoma mansoni cercariae and remained untreated. The mice of the other two groups were infected and treated with either praziquantel (Group II) or HUCB-MSCs (Group III). Liver function tests, as well as histopathological evaluation of liver fibrosis using hematoxylin and eosin and Masson's trichrome stains, were performed. Additionally, an immunohistochemical study was carried out using anti-glial fibrillary acidic protein (GFAP) in hepatic stellate cells. Compared to the control group, the treated (praziquantel and MSCs) groups showed a substantial improvement, with a significant difference regarding the histopathological evaluation of liver fibrosis in the MSCs-treated group. In conclusion, MSCs could be a promising and efficient cell therapy for liver fibrosis.

Effects of Coupled-/soluble-Copper, Generating from Copper-doped Titanium Dioxide Nanotubes on Cell Response

BACKGROUND

Endothelialization in vitro is a very common method for surface modification of cardiovascular materials. However, mature endothelial cells are not suitable because of the difficulty in obtaining and immunogenicity.

METHODS

In this patent work, we determined the appropriate amount of copper by constructing a copper- loaded titanium dioxide nanotube array that can catalyze the release of nitric oxide, compared the effects of coupled-/soluble-copper on stem cells, and then induced stem cells to differentiate into endothelial cells.

RESULTS

The results showed that it had a strong promotion effect on the differentiation of stem cells into endothelial cells, which might be used for endothelialization in vitro.

CONCLUSION

SEM and EDS results prove that a high content of copper ions are indeed doped onto the surface of nanotubes with small amounts of Cu release. The release of NO confirms that the release of several samples within a period of time is within the physiological concentration.

Strategies for modelling endometrial diseases

Each month during a woman's reproductive years, the endometrium undergoes vast changes to prepare for a potential pregnancy. Diseases of the endometrium arise for numerous reasons, many of which remain unknown. These endometrial diseases, including endometriosis, adenomyosis, endometrial cancer and Asherman syndrome, affect many women, with an overall lack of efficient or permanent treatment solutions. The challenge lies in understanding the complexity of the endometrium and the extensive changes, orchestrated by ovarian hormones, that occur in multiple cell types over the period of the menstrual cycle. Appropriate model systems that closely mimic the architecture and function of the endometrium and its diseases are needed. The emergence of organoid technology using human cells is enabling a revolution in modelling the endometrium in vitro. The goal of this Review is to provide a focused reference for new models to study the diseases of the endometrium. We provide perspectives on the power of new and emerging models, from organoids to microfluidics, which have opened up a new frontier for studying endometrial diseases.

Evidence of Stem Cells Mobilization in the Blood of Patients with Pancreatitis: A Potential Link with Disease Severity

A growing number of studies indicate the potential involvement of various populations of bone marrow-derived stem cells (BMSCs) in tissue repair. However, the mobilization of BMSCs to the peripheral blood (PB) in acute and chronic pancreatitis (AP and CP) has not been investigated. A total of 78 patients were assigned into AP, CP, and healthy control groups in this study. Using flow cytometry, we found that VSELs, EPCs, and CD133+SCs were mobilized to the PB of patients with both AP and CP. Interestingly, AP and CP patients exhibited lower absolute number of circulating MSCs in the PB compared to healthy individuals. SC mobilization to the PB was more evident in patients with AP than CP and in patients with moderate/severe AP than mild AP. Using ELISA, we found a significantly increased HGF concentration in the PB of patients with AP and SDF1α in the PB of patients with CP. We noted a significant positive correlation between SDF1α concentration and the mobilized population of CD133+SCs in AP and between C5a and the mobilized population of VSELs moderate/severe AP. Thus, bone marrow-derived SCs may play a role in the regeneration of pancreatic tissue in both AP and CP, and mobilization of VSELs to the PB depends on the severity of AP.

Gastrin producing syngeneic mesenchymal stem cells protect non-obese diabetic mice from type 1 diabetes

Progressive destruction of pancreatic islet β-cells by immune cells is a primary feature of type 1 diabetes (T1D) and therapies that can restore the functional β-cell mass are needed to alleviate disease progression. Here, we report the use of mesenchymal stromal/stem cells (MSCs) for the production and delivery of Gastrin, a peptide hormone that is produced by intestinal cells and foetal islets and can increase β-Cell mass, to promote protection from T1D. A single injection of syngeneic MSCs that were engineered to express Gastrin (Gastrin-MSCs) caused a significant delay in hyperglycaemia in non-obese diabetic (NOD) mice compared to engineered control-MSCs. Similar treatment of early-hyperglycaemic mice caused the restoration of euglycemia for a considerable duration, and these therapeutic effects were associated with the protection of, and/or higher frequencies of, insulin-producing islets and less severe insulitis. While the overall immune cell phenotype was not affected profoundly upon treatment using Gastrin-MSCs or upon in vitro culture, pancreatic lymph node cells from Gastrin-MSC treated mice, upon ex vivo challenge with self-antigen, showed a Th2 and Th17 bias, and diminished the diabetogenic property in NOD-Rag1 deficient mice suggesting a disease protective immune modulation under Gastrin-MSC treatment associated protection from hyperglycaemia. Overall, this study shows the potential of production and delivery of Gastrin in vivo, by MSCs, in protecting insulin-producing β-cells and ameliorating the disease progression in T1D.

Bone marrow-derived mononuclear stem cells in the treatment of retinal degenerations

Retinal degenerative diseases affecting the outer retina in its many forms (inherited, acquired or induced) are characterized by photoreceptor loss, and represent currently a leading cause of irreversible vision loss in the world. At present, there are very few treatments capable of preventing, recovering or reversing photoreceptor degeneration or the secondary retinal remodeling, which follows photoreceptor loss and can also cause the death of other retinal cells. Thus, these diseases are nowadays one of the greatest challenges in the field of ophthalmological research. Bone marrow derived-mononuclear stem cell transplantation has shown promising results for the treatment of photoreceptor degenerations. These cells may have the potential to slow down photoreceptor loss, and therefore should be applied in the early stages of photoreceptor degenerations. Furthermore, because of their possible paracrine effects, they may have a wide range of clinical applications, since they can potentially impact on several retinal cell types at once and photoreceptor degenerations can involve different cells and/or begin in one cell type and then affect adjacent cells. The intraocular injection of bone marrow derived-mononuclear stem cells also enhances the outcomes of other treatments aimed to protect photoreceptors. Therefore, it is likely that future investigations may combine bone marrow derived-mononuclear stem cell therapy with other systemic or intraocular treatments to obtain greater therapeutic effects in degenerative retinal diseases.

Cell-based treatment of cerebral palsy: still a long way ahead

BACKGROUND

Cerebral palsy (CP) is a permanent neurodevelopmental disorder with considerable global disability. Various rehabilitation strategies are currently available. However, none represents a convincing curative result. Cellular therapy recently holds much promise as an alternative strategy to repair neurologic defects.

METHOD

In this narrative review, a comprehensive search of the MEDLINE and ClinicalTrials.gov was made, using the terms: "cell therapy" and "cerebral palsy", including published and registered clinical studies, respectively.

RESULTS

The early effects of these studies demonstrated that using cell therapy in CP patients is safe and improves the deficits for a variable duration. Despite such hopeful early bird results, the long-term outcomes are not conclusive.

CONCLUSIONS

Due to the heterogeneous nature of CP, personal factors seem essential to consider. Cell dosage, routes of administration, and repeated dosing are pivotal to establish optimal personalized treatments. Future clinical trials should consider employing other cell types, specific cell modifications before administration, and cell-free platforms.

Are We Ready for Cell Therapy to Treat Stroke?

Clinical trials of cell therapies that target stroke started at the beginning of this century and they have experienced a significant boost in recent years as a result of promising data from basic research studies. The increase in the information available has paved the way to carry out more innovative and varied human studies. Efforts have focused on the search for a safe and effective treatment to stimulate neuro-regeneration in the brain and to reduce the sequelae of stroke in patients. Therefore, this review aims to evaluate the clinical trials using cell therapy to treat stroke published to date and assess their limitations. From 2000 to date, most of the published clinical trials have focused on phases I or II, and the vast majority of them demonstrate that stem cells are essentially safe to use when administered by different routes, with transient and mild adverse events that do not generally have severe consequences for health. In general, there is considerable variation in the trials in terms of statistical design, sample size, the cells used, the routes of administration, and the functional assessments (both at baseline and follow-up), making it difficult to compare the studies. From this general description, possibly the experimental protocol is the main element to improve in future studies. Establishing an adequate experimental and statistical design will be essential to obtain favorable and reliable results when conducting phase III clinical trials. Thus, it is necessary to standardize the criteria used in these clinical trials in order to aid comparison. Shortly, cell therapy will be a key approach in the treatment of stroke if adequate and comprehensive levels of recovery are to be achieved.

Stem Cells and the Endometrium: From the Discovery of Adult Stem Cells to Pre-Clinical Models

Adult stem cells (ASCs) were long suspected to exist in the endometrium. Indeed, several types of endometrial ASCs were identified in rodents and humans through diverse isolation and characterization techniques. Putative stromal and epithelial stem cell niches were identified in murine models using label-retention techniques. In humans, functional methods (clonogenicity, long-term culture, and multi-lineage differentiation assays) and stem cell markers (CD146, SUSD2/W5C5, LGR5, NTPDase2, SSEA-1, or N-cadherin) facilitated the identification of three main types of endogenous endometrial ASCs: stromal, epithelial progenitor, and endothelial stem cells. Further, exogenous populations of stem cells derived from bone marrow may act as key effectors of the endometrial ASC niche. These findings are promoting the development of stem cell therapies for endometrial pathologies, with an evolution towards paracrine approaches. At the same time, promising therapeutic alternatives based on bioengineering have been proposed.

Improved survival in amyotrophic lateral sclerosis patients following autologous bone marrow mononuclear cell therapy: a long term 10-year retrospective study

Background:

Promising results from previous studies using cell therapy have paved the way for an innovative treatment option for amyotrophic lateral sclerosis (ALS). There is considerable evidence of immune and inflammatory abnormalities in ALS. Bone marrow mononuclear cells (BMMNCs) possess immunomodulatory properties and could contribute to slowing of disease progression.

Objective:

Aim of our study was to evaluate the long-term effect of autologous BMMNCs combined with standard treatment on survival duration in a large population and to evaluate effect of type of onset and hormonal status on survival duration in the intervention group.

Methods:

This controlled, retrospective study spanned over 10 years, 5 months; included 216 patients with probable or definite ALS, 150 in intervention group receiving autologous BMMNCs and standard treatment, and 66 in control group receiving only standard treatment. The estimated survival duration of control group and intervention group was computed and compared using Kaplan Meier analysis. Survival duration of patients with different types of onset and hormonal status was compared within the intervention group.

Results:

None of the patients reported any major adverse events related to cell administration or the procedure. Kaplan Meier analysis estimated survival duration in the intervention group to be 91.7 months while 49.7 months in the control group (p = 0.008). Within the intervention group, estimated survival was significantly higher (p = 0.013) in patients with limb onset (102.3 months) vs. bulbar onset (49.9 months); premenopausal women (93.1 months) vs. postmenopausal women (57.6 months) (p = 0.002); and preandropausal men (153.7 months) vs. postandropausal males (56.5 months) (p = 0.006).

Conclusion:

Cell therapy using autologous BMMNCs along with standard treatment offers a promising and safe option for ALS with the potential of long term beneficial effect and increased survival. Limb onset patients, premenopausal women and men ≤ 40 years of age demonstrated better treatment efficacy.

Cell-Based Therapies for Chronic Wounds Tested in Clinical Studies: Review

INTRODUCTION

Transplantation of the keratinocytes, fibroblasts, bone marrow, and adipose tissue-derived mesenchymal stem cells may improve chronic wound healing by delivery of different cytokines, chemokines, and growth factors, which play an essential role in wound healing. The purposes of this review were to check which cell lines are potentially beneficial in enhancement of wound healing and to describe the safety and efficacy of cell therapies in the clinical treatment of chronic wounds, as well as to summarize the pertinent literature and research progress in this field.

METHODS

PubMed search engine and ClinicalTrials.gov were used to analyze the available data on cell therapies applied in treatment of chronic wound. The analysis included 51 articles, assessing the use of keratinocytes (10), fibroblasts (7), keratinocytes and fibroblasts (10), bone marrow-derived cells (20), and adipose tissue cells (4). Studies on the cell-based products that are currently available on the market (Dermagraft, EpiDex, Apligraf, and HP802-247) were also included, with majority of reports found on fibroblasts and keratinocytes studies.

RESULTS

Cell-based therapies have a great potential to improve wound healing without major surgical procedures and donor-site morbidity. There is, however, a lack of guidelines on how the age of the patients, the general health conditions, and the coexistence of different diseases may affect the success of these therapies. Further studies are needed to determine the fate of transplanted cells and the number of cells required to obtain optimal effects and outcomes.

CONCLUSIONS

Despite many promising clinical trials on application of various stem cell-based therapies for treatment of chronic wounds, there is still a need for multicenter comparative studies assessing the dose response and the cell source response on the efficacy of chronic wound healing.

Characterization and Isolation of Very Small Embryonic-like (VSEL) Stem Cells Obtained from Various Human Hematopoietic Cell Sources

Stem cell transplantation is one of the available treatments for leukemia, lymphoma, hereditary blood diseases and bone marrow failure. Bone marrow (BM), peripheral blood progenitor cells (PBPC), and cord blood (CB) are the predominant sources of stem cells. Recently a new type of stem cell with a pluripotent potential has been identified. These cells were named "very small embryonic like stem cells (VSELs)". It is claimed that VSEL stem cells can be found in adult BM, peripheral blood (PB), CB and other body tissues. This study is designed to characterize and isolate VSEL stem cells from different human hematopoietic sources; CB, PB and apheresis material (PBPC). VSEL stem cells were isolated from MNC and erythrocyte layers for all materials by using centrifugation and ficoll gradient method. We determined embryonic markers by flow cytometry, immunofluorescence and western blotting methods. Results from western blotting and immunofluorescence show high level of NANOG and OCT4 protein expression in PB, apheresis material and CB. Immunofluorescence images showed cytoplasmic and nuclear presence of these proteins. Flow cytometry results exhibited a higher expression of VSELs markers on debris area than CD45- population and higher expression on CB than PB. As a result, these findings have shown that it is necessary to investigate the function of pluripotent stem cell markers in differentiated adult cells. We further conclude that erythrocyte lysis method had the highest cell recovery amount among erythrocyte lysis and ficoll gradient methods. Consequently, this study gives us new information and viewpoints about expression of pluripotent stem cell (PSC) markers in adult tissues.

Bilateral epiretinal membrane formation following intravitreal injections of autologous mesenchymal stem cells

PURPOSE

The authors describe a case of new bilateral epiretinal membranes and vitreous cells following intravitreal and subTenon's injections of bone marrow-derived stem cells.

METHODS

Case report of a 43-year-old man with OPA-1 autosomal dominant optic atrophy who self-enrolled in a stem cell therapy clinical trial and received simultaneous bilateral intravitreal and subTenon's injections of bone marrow-derived stem cells.

RESULTS

Within one month of receiving the injections, the patient developed epiretinal membranes and vitreous cells in both eyes, seen with optical coherence tomography.

CONCLUSION

Stem cell therapy has been gaining popularity as a potential intervention for progressive retinal and optic nerve diseases; however, the mechanism of action of bone marrow-derived stem cells is still not well understood and may result in unintended cell differentiation.

Why do anti-inflammatory signals of bone marrow-derived stromal cells improve neurodegenerative conditions where anti-inflammatory drugs fail?

Neurodegenerative disorders share the final degenerative pathway, the inflammation-induced apoptosis and/or necrosis, irrespective of their etiology, be it of acute and chronic traumatic, vascular and idiopathic origin. Although disease-modifying strategies are an unmet need in these disorders, lately, (pre)clinical studies suggested favorable effects after an intervention with bone marrow-derived stromal cells (bm-SC). Recent interventions with intrathecal transplantation of these cells in preclinical rodent models improved the functional outcome and reduced the inflammation, but not anti-inflammatory drugs. The benefit of bm-SCs was demonstrated in rats with an acute (traumatic spinal cord injury, tSCI) and in mice with a chronic [amyotrophic lateral sclerosis (ALS)-like FUS 1-358 or SOD1-G93-A mutation] neurodegenerative process. Bm-SCs, were found to modify underlying disease processes, to reduce final clinical SCI-related outcome, and to slow down ALS-like clinical progression. After double-blind interventions with bm-SC transplantations, Vehicle (placebo), and (non)steroidal anti-inflammatory drugs (Methylprednisolone, Riluzole, Celecoxib), clinical, histological and histochemical findings, serum/spinal cytokines, markers for spinal microglial activation inclusive, evidenced the cell-to-cell action of bm-SCs in both otherwise healthy and immune-deficient tSCI-rats, as well as wild-type and FUS/SOD1-transgenic ALS-like mice. The multi-pathway hypothesis of the cell-to-cell action of bmSCs, presumably using extracellular vesicles (EVs) as carriers of messages in the form of RNAs, DNA, proteins, and lipids rather than influencing a single inflammatory pathway, could be justified by the reported differences of cytokines and other chemokines in the serum and spinal tissue. The mode of action of bm-SCs is hypothesized to be associated with its dedicated adjustment of the pro-apoptotic glycogen synthase kinase-3β level towards an anti-apoptotic level whereas their multi-pathway hypothesis seems to be confirmed by the decreased levels of the pro-inflammatory interleukin (IL)-1β and tumor necrosis factor (TNF) as well as the level of the marker of activated microglia, ionized calcium binding adapter (Iba)-1 level.

When Bio Meets Technology: Biohybrid Neural Interfaces

The development of electronics capable of interfacing with the nervous system is a rapidly advancing field with applications in basic science and clinical translation. Devices containing arrays of electrodes can be used in the study of cells grown in culture or can be implanted into damaged or dysfunctional tissue to restore normal function. While devices are typically designed and used exclusively for one of these two purposes, there have been increasing efforts in developing implantable electrode arrays capable of housing cultured cells, referred to as biohybrid implants. Once implanted, the cells within these implants integrate into the tissue, serving as a mediator of the electrode-tissue interface. This biological component offers unique advantages to these implant designs, providing better tissue integration and potentially long-term stability. Herein, an overview of current research into biohybrid devices, as well as the historical background that led to their development are provided, based on the host anatomical location for which they are designed (CNS, PNS, or special senses). Finally, a summary of the key challenges of this technology and potential future research directions are presented.

Interference of bone marrow CD56+ mesenchymal stromal cells in minimal residual disease investigation of neuroblastoma and other CD45- /CD56+ pediatric malignancies using flow cytometry

BACKGROUND

Bone marrow (BM) samples obtained from minimal residual disease (MRD)-negative children with B-cell acute lymphoblastic leukemia (B-ALL) were used in our laboratory as negative biological controls for the development of a neuroblastoma (NBL) flow-cytometric (FC) protocol. The accidental, but systematic, identification of rare cell populations (RCP) mimicking NBL cells (CD45^- /CD56⁺ ) in these samples indicated the need for their thorough immunophenotypic identification, in order to elucidate their possible interference in NBL-MRD assessment.

PROCEDURE

RCP observed in BM samples from 14 children recovering from BM aplasia due to intensive chemotherapy for B-ALL were investigated with the following markers: CD81, CD200, CD24, GD2, CD73, CD13, CD90, CD146, CD9, CD117, CD10, CD99, and NG2. BM samples from six newly diagnosed patients with NBL and an NBL cell line were simultaneously investigated as positive controls.

RESULTS

The frequency of RCP in B-ALL BM samples was < 1/1 × 10⁴ cells (bulky lysis), and their immunophenotypic profile was indicative of CD56⁺ mesenchymal stromal cells (MSCs) (CD45^- , CD90⁺ , CD146⁺ , CD73⁺ ). Also, RCP expressed CD81 and CD200, simulating NBL cells. The most useful discriminative markers for CD56⁺ MSCs were CD13 and CD73. An appropriate protocol consisting of two tubes with seven color combinations was further proposed: SYTO-16, GD2 (first tube) or CD73 (second tube)-PE, CD24-ECD, CD13-PC5.5, CD45-PC7, CD81-APC, and CD56-APC700.

CONCLUSIONS

RCP that were immunophenotypically similar to NBL were identified as CD56⁺ MSCs. As these cells might pose an obstacle to accurate NBL disease assessment by FC, especially MRD, an enhanced NBL-FC protocol is proposed for prospective evaluation.

The Pluripotent Microvascular Pericytes Are the Adult Stem Cells Even in the Testis

The pericytes of the testis are part of the omnipresent population of pericytes in the vertebrate body and are the only true pluripotent adult stem cells able to produce structures typical for the tree primitive germ layers: ectoderm, mesoderm, and endoderm. They originate very early in the embryogenesis from the pluripotent epiblast. The pericytes become disseminated through the whole vertebrate organism by the growing and differentiating blood vessels where they remain in specialized periendothelial vascular niches as resting pluripotent adult stem cells for tissue generation, maintenance, repair, and regeneration. The pericytes are also the ancestors of the perivascular multipotent stromal cells (MSCs). The variable appearance of the pericytes and their progeny reflects the plasticity under the influence of their own epigenetic and the local environmental factors of the host organ. In the testis the pericytes are the ancestors of the neuroendocrine Leydig cells. After activation the pericytes start to proliferate, migrate, and build transit-amplifying cells that transdifferentiate into multipotent stromal cells. These represent progenitors for a number of different cell types in an organ. Finally, it becomes evident that the pericytes are a brilliant achievement of the biological nature aiming to supply every organ with an omnipresent population of pluripotent adult stem cells. Their fascinating features are prerequisites for future therapy concepts supporting cell systems of organs.

Glucagon-like peptide-1 analogue liraglutide ameliorates atherogenesis via inhibiting advanced glycation end product-induced receptor for advanced glycosylation end product expression in apolipoprotein-E deficient mice

Glucagon-like peptide-1 (GLP-1) can protect arteriosclerotic lesions in apolipoprotein-E deficient (ApoE-/-) mice. Advanced glycation end products (AGEs)/receptor for advanced glycation end products (RAGE) interaction serves a key role in the development of diabetic vascular complications. The present study examined whether the GLP-1 analogue liraglutide can ameliorate atherogenesis via inhibiting AGEs-induced RAGE expression. Male ApoE-/- mice (age, 10 weeks) were divided into control, GLP-1, AGEs and AGEs+GLP-1 group. All mice were fed a high-fat diet. The AGEs and AGEs+GLP-1 groups were treated with intraperitoneal injection of AGEs (30 mg/kg/day). The GLP-1 and AGEs+GLP-1 groups were treated with subcutaneous injections of liraglutide (0.4 mg/kg/day). After 9 weeks, blood was drawn and the aortas were rapidly procured. The serum levels of AGEs, soluble RAGE (sRAGE), stromal cell-derived factor-1α (SDF-1α), total cholesterol and triacylglycerol were measured. Atherosclerotic plaque area was determined by Sudan IV staining. The mRNA and protein expression levels of RAGE were determined using reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The results demonstrated that AGEs treatment increased serum AGEs levels, increased the expression of RAGE in the aorta, and aggravated atherosclerotic lesions compared with the control. Liraglutide treatment reduced serum AGEs levels, reduced the expression of RAGE in aorta, and relieved atherosclerotic lesions compared with the control. In conclusion, these data suggested that liraglutide serves an anti-atherosclerotic effect via inhibiting AGEs-induced RAGE expression in ApoE-/- mice. These findings provide novel evidence for the use of GLP-1-type agents for the treatment of diabetic vascular complications.

A Novel View of the Adult Stem Cell Compartment From the Perspective of a Quiescent Population of Very Small Embryonic-Like Stem Cells

Evidence has accumulated that adult hematopoietic tissues and other organs contain a population of dormant stem cells (SCs) that are more primitive than other, already restricted, monopotent tissue-committed SCs (TCSCs). These observations raise several questions, such as the developmental origin of these cells, their true pluripotent or multipotent nature, which surface markers they express, how they can be efficiently isolated from adult tissues, and what role they play in the adult organism. The phenotype of these cells and expression of some genes characteristic of embryonic SCs, epiblast SCs, and primordial germ cells suggests their early-embryonic deposition in developing tissues as precursors of adult SCs. In this review, we will critically discuss all these questions and the concept that small dormant SCs related to migratory primordial germ cells, described as very small embryonic-like SCs, are deposited during embryogenesis in bone marrow and other organs as a backup population for adult tissue-committed SCs and are involved in several processes related to tissue or organ rejuvenation, aging, and cancerogenesis. The most recent results on successful ex vivo expansion of human very small embryonic-like SC in chemically defined media free from feeder-layer cells open up new and exciting possibilities for their application in regenerative medicine.

Biohybrid cochlear implants in human neurosensory restoration

BACKGROUND

The success of cochlear implantation may be further improved by minimizing implantation trauma. The physical trauma of implantation and subsequent immunological sequelae can affect residual hearing and the viability of the spiral ganglion. An ideal electrode should therefore decrease post-implantation trauma and provide support to the residual spiral ganglion population. Combining a flexible electrode with cells producing and releasing protective factors could present a potential means to achieve this. Mononuclear cells obtained from bone marrow (BM-MNC) consist of mesenchymal and hematopoietic progenitor cells. They possess the innate capacity to induce repair of traumatized tissue and to modulate immunological reactions.

METHODS

Human bone marrow was obtained from the patients that received treatment with biohybrid electrodes. Autologous mononuclear cells were isolated from bone marrow (BM-MNC) by centrifugation using the Regenlab™ THT-centrifugation tubes. Isolated BM-MNC were characterised using flow cytometry. In addition, the release of cytokines was analysed and their biological effect tested on spiral ganglion neurons isolated from neonatal rats. Fibrin adhesive (Tisseal™) was used for the coating of silicone-based cochlear implant electrode arrays for human use in order to generate biohybrid electrodes. Toxicity of the fibrin adhesive and influence on insertion, as well on the cell coating, was investigated. Furthermore, biohybrid electrodes were implanted in three patients.

RESULTS

Human BM-MNC release cytokines, chemokines, and growth factors that exert anti-inflammatory and neuroprotective effects. Using fibrin adhesive as a carrier for BM-MNC, a simple and effective cell coating procedure for cochlear implant electrodes was developed that can be utilised on-site in the operating room for the generation of biohybrid electrodes for intracochlear cell-based drug delivery. A safety study demonstrated the feasibility of autologous progenitor cell transplantation in humans as an adjuvant to cochlear implantation for neurosensory restoration.

CONCLUSION

This is the first report of the use of autologous cell transplantation to the human inner ear. Due to the simplicity of this procedure, we hope to initiate its widespread utilization in various fields.

Identification of New Rat Bone Marrow-Derived Population of Very Small Stem Cell with Oct-4A and Nanog Expression by Flow Cytometric Platforms

Very small embryonic-like stem cells (VSELs) represent a unique rare population of adult stem cells (SCs) sharing several structural, genetic, biochemical, and functional properties with embryonic SCs and have been identified in several adult murine and human tissues. However, rat bone marrow- (BM-) derived SCs closely resembling murine or human VSELs have not been described. Thus, we employed multi-instrumental flow cytometric approach including classical and imaging cytometry and we established that newly identified population of nonhematopoietic cells expressing CD106 (VCAM-I) antigen contains SCs with very small size, expressing markers of pluripotency (Oct-4A and Nanog) on both mRNA and protein levels that indicate VSEL population. Based on our experience in both murine and human VSEL isolation procedures by fluorescence-activated cell sorting (FACS), we also optimized sorting protocol for separation of CD45⁻/Lin⁻/CD106⁺ rat BM-derived VSELs from wild type and eGFP-expressing rats, which are often used as donor animals for cell transplantations in regenerative studies in vivo. Thus, this is a first study identifying multiantigenic phenotype and providing sorting protocols for isolation VSELs from rat BM tissue for further examining of their functional properties in vitro as well as regenerative capacity in distinct in vivo rat models of tissue injury.

Identification and Characterization of Lineage(-)CD45(-)Sca-1(+) VSEL Phenotypic Cells Residing in Adult Mouse Bone Tissue

Murine bone marrow (BM)-derived very small embryonic-like stem cells (BM VSELs), defined by a lineage-negative (Lin(-)), CD45-negative (CD45(-)), Sca-1-positive (Sca-1(+)) immunophenotype, were previously reported as postnatal pluripotent stem cells (SCs). We developed a highly efficient method for isolating Lin(-)CD45(-)Sca-1(+) small cells using enzymatic treatment of murine bone. We designated these cells as bone-derived VSELs (BD VSELs). The incidences of BM VSELs in the BM-derived nucleated cells and that of BD VSELs in bone-derived nucleated cells were 0.002% and 0.15%, respectively. These BD VSELs expressed a variety of hematopoietic stem cell (HSC), mesenchymal stem cell (MSC), and endothelial cell markers. The gene expression profile of the BD VSELs was clearly distinct from those of HSCs, MSCs, and ES cells. In the steady state, the BD VSELs proliferated slowly, however, the number of BD VSELs significantly increased in the bone after acute liver injury. Moreover, green fluorescent protein-mouse derived BD VSELs transplanted via tail vein injection after acute liver injury were detected in the liver parenchyma of recipient mice. Immunohistological analyses suggested that these BD VSELs might transdifferentiate into hepatocytes. This study demonstrated that the majority of the Lin(-)CD45(-)Sca-1(+) VSEL phenotypic cells reside in the bone rather than the BM. However, the immunophenotype and the gene expression profile of BD VSELs were clearly different from those of other types of SCs, including BM VSELs, MSCs, HSCs, and ES cells. Further studies will therefore be required to elucidate their cellular and/or SC characteristics and the potential relationship between BD VSELs and BM VSELs.

Rapid assay of stem cell functionality and potency using electric cell-substrate impedance sensing

Regenerative medicine studies using autologous bone marrow mononuclear cells (BM-MNCs) have shown improved clinical outcomes that correlate to in vitro BM-MNC invasive capacity. The current Boyden-chamber assay for testing invasive capacity is labor-intensive, provides only a single time point, and takes 36 hours to collect data and results, which is not practical from a clinical cell delivery perspective. To develop a rapid, sensitive and reproducible invasion assay, we employed Electric Cell-substrate Impedance Sensing (ECIS) technology. Chemokine-directed BM-MNC cell invasion across a Matrigel-coated Transwell filter was measurable within minutes using the ECIS system we developed. This ECIS-Transwell chamber system provides a rapid and sensitive test of stem and progenitor cell invasive capacity for evaluation of stem cell functionality to provide timely clinical data for selection of patients likely to realize clinical benefit in regenerative medicine treatments. This device could also supply robust unambiguous, reproducible and cost effective data as a potency assay for cell product release and regulatory strategies.

Stem cells for respiratory failure

PURPOSE OF REVIEW

The prognosis of patients with respiratory failure in the ICU remains poor, while current therapeutic approaches are aimed at minimizing ventilator-induced lung injury. Stem cell-based therapies have the potential to transform respiratory failure treatment by achieving lung repair. The purpose of this article is to critically review the large body of clinical and experimental work performed with respect to the use of stem/progenitor cells in respiratory failure, and to discuss current challenges and future directions.

RECENT FINDINGS

Since the initial report of cell therapy for lung injury in 2005, numerous preclinical and clinical studies have been performed that support the ability of various stem cell populations to improve physiologic lung function and reduce inflammation in both infective and sterile acute respiratory distress syndrome. Nevertheless, many important issues (e.g., mechanism of action, long-term engraftment, optimal cell type, dose, route of administration) remain to be resolved.

SUMMARY

Cell-based therapeutics hold promise, particularly for acute respiratory distress syndrome, and early preclinical testing has been encouraging. To advance clinical testing of cell therapies in respiratory failure, and to help ensure that this approach will facilitate bench-to-bedside and bedside-to-bench discoveries, parallel paths of basic and clinical research are needed, including measures of cell therapy effectiveness in vivo and in vitro.

Bone Marrow Homing Enriches Stem Cells Responsible for Neogenesis of Insulin-Producing Cells, While Radiation Decreases Homing Efficiency

Small-sized adult bone marrow cells isolated by counterflow centrifugal elutriation and depleted of lineage markers (Fr25lin(-)) have the capacity to differentiate into insulin-producing cells and stabilize glycemic control. This study assessed competitive migration of syngeneic stem cells to the bone marrow and islets in a murine model of chemical diabetes. VLA-4 is expressed in ∼ 25% of these cells, whereas CXCR4 is not detected, however, it is transcriptionally upregulated (6-fold). The possibility to enrich stem cells by a bone marrow homing (BM-H) functional assay was assessed in sequential transplants. Fr25lin(-) cells labeled with PKH26 were grafted into primary myeloablated recipients, and mitotically quiescent Fr25lin(-)PKH(bright) cells were sorted from the bone marrow after 2 days. The contribution of bone marrow-homed stem cells was remarkably higher in secondary recipients compared to freshly elutriated cells. The therapeutic efficacy was further increased by omission of irradiation in the secondary recipients, showing a 25-fold enrichment of islet-reconstituting cells by the bone marrow homing assay. Donor cells identified by the green fluorescent protein (GFP) and a genomic marker in sex-mismatched transplants upregulated PDX-1 and produced proinsulin, affirming the capacity of BM-H cells to convert in the injured islets. There was no evidence of transcriptional priming of freshly elutriated subsets to express PDX-1, insulin, and other markers of endocrine progenitors, indicating that the bone marrow harbors stem cells with versatile differentiation capacity. Affinity to the bone marrow can be used to enrich stem cells for pancreatic regeneration, and reciprocally, conditioning reduces the competitive incorporation in the injured islets.

Hepatic regenerative potential of mouse bone marrow very small embryonic-like stem cells

Very small embryonic-like stem cells (VSELs) are a Sca-1 (+)  Lin(-) CD45(-) cell population that has been isolated from the bone marrow of mice. The similarities and differences between the mRNA profiles of VSELs and embryonic stem (ES) cells have not yet been defined. Here, we report the whole genome gene expression profile of VSELs and ES cells. We analyzed the global gene expression of VSELs and compared it with ES cells by microarray analysis. We observed that 9,521 genes are expressed in both VSELs and ES cells, 1,159 genes are expressed uniquely in VSELs, and 420 genes are expressed uniquely in ES cells. We found that although VSELs are similar to ES cells in their expression of genes associated with stem cell behavior and pluripotency, there are also differences in their mRNA expression. We further analyzed the expression of stem cell-associated genes in VSELs and ES cells, and found that there were differences in these genes. For instance, the Pkd2 and Yap1 gene were reduced in their expression in VSELs when compared with ES cells. But we also found Zfp54 gene expression was higher in VSELs compared with ES cells. More interestingly, we demonstrated that VSELs express c-kit, the stem cell factor (SCF) receptor. In vitro, SCF promoted VSEL differentiation into hepatic colonies in the presence of hepatocyte growth factor. In vivo, transplantation of VSELs directly into CCl4-induced injured livers significantly reduced serum ALT and AST levels. Therefore, these data suggest that VSELs play a role in the repair of injured livers.

Multipotent Adult Progenitor Cells from Bone Marrow Differentiate into Chondrocyte-Like Cells

Cartilage tissue engineering has great potential for treating chondral and osteochondral injuries. Efficient seed cells are the key to cartilage tissue engineering. Multipotent adult progenitor cells (MAPCs) have greater differentiation ability than other bone-marrow stem cells, and thus may be candidate seed cells. We attempted to differentiate MAPCs into chondrocyte-like cells to evaluate their suitability as seed cells for cartilage tissue engineering. Toluidine blue and Alcian blue staining suggested that glycosaminoglycan was expressed in differentiated cells. Immunofluorostaining indicated that differentiated human MAPCs (hMAPCs) expressed collagen II. Based on these results, we concluded that bone-marrow-derived hMAPCs could differentiate into chondrocyte-like cells in vitro.

In-vitro culture system for mesenchymal progenitor cells derived from waste human ovarian follicular fluid

To characterize different cell populations in the human ovary, morphological and functional characteristics of cell populations collected during routine IVF procedures were studied. Cells obtained from follicular fluid grew in vitro under minimal medium conditions, without growth factor, including leukaemia-inhibiting factor. Morphological analysis revealed a heterogeneous cell population, with cells displaying a fibroblast-like, epithelial-like and also neuron-like features. Morpho-functional characteristics of fibroblast-like cells were similar to mesenchymal stem cells, and, in particular, were positive for mesenchymal stemness markers, including CD90, CD44, CD105, CD73, but negative for epithelial proteins, such as cytokeratins, CD34 and CD45 antigens. Cell proliferation activity at different times and colony-forming unit capability were evaluated, and multipotency of a subset of granulosa cells was established by in-vitro differentiation studies (e.g. osteogenic, chondrogenic and adipogenic differentiation). This study suggests that cells provided by mesenchymal plasticity can be easily isolated by waste follicular fluid, avoiding scraping of human ovaries, and cultivated in minimal conditions. Successful growth of such progenitor cells on three-dimensional cryogel scaffold provides the basis for future developments in tissue engineering. This culture system may be regarded as an experimental model in which biological behaviour is not influenced by specific growth factors.

Hematopoietic and mesenchymal stem cells for the treatment of chronic respiratory diseases: role of plasticity and heterogeneity

Chronic lung diseases, such as cystic fibrosis (CF), asthma, and chronic obstructive pulmonary disease (COPD) are incurable and represent a very high social burden. Stem cell-based treatment may represent a hope for the cure of these diseases. In this paper, we revise the overall knowledge about the plasticity and engraftment of exogenous marrow-derived stem cells into the lung, as well as their usefulness in lung repair and therapy of chronic lung diseases. The lung is easily accessible and the pathophysiology of these diseases is characterized by injury, inflammation, and eventually by remodeling of the airways. Bone marrow-derived stem cells, including hematopoietic stem/progenitor cells (HSPCs) and mesenchymal stromal (stem) cells (MSCs), encompass a wide array of cell subsets with different capacities of engraftment and injured tissue regenerating potential. Proof-of-principle that marrow cells administered locally may engraft and give rise to specialized epithelial cells has been given, but the efficiency of this conversion is too limited to give a therapeutic effect. Besides the identification of plasticity mechanisms, the characterization/isolation of the stem cell subpopulations represents a major challenge to improving the efficacy of transplantation protocols used in regenerative medicine for lung diseases.

Very small embryonic-like cells: biology and function of these potential endogenous pluripotent stem cells in adult tissues

Very small embryonic-like cells (VSELs), found in murine bone marrow and other adult tissues, are small, non-hematopoietic cells expressing markers of pluripotent embryonic and primordial germ cells. A similar cell type in humans has begun to be characterized, though with a slightly different phenotype and surface markers. Consistent with expression of pluripotency genes, murine VSELs differentiate into cell types from three germ-layer lineages in vitro, though pluripotency has yet to be shown at the single-cell level or in vivo. VSELs appear to be quiescent under steady state conditions, apparently due to partially erased imprinting and overexpression of cell cycle inhibitory genes. In vivo, VSELs can enter the cell cycle under stress conditions, but which factors regulate quiescence versus proliferation and self-renewal versus differentiation are as yet unknown, and in vitro conditions that induce proliferation and self-renewal have yet to be defined. Future experiments are needed to address whether a VSEL niche actively regulates quiescence in vivo or quiescence is cell autonomous under steady state conditions. Insights into these mechanisms may help to address whether or not VSELs could play a role in regenerative medicine in the future.

Cell therapy demonstrates promise for acute respiratory distress syndrome - but which cell is best?

Acute respiratory distress syndrome (ARDS) constitutes a spectrum of increasingly severe acute respiratory failure and is the leading cause of death and disability in the critically ill. There are no therapies for ARDS, and management remains supportive. Cell therapy, particularly with allogeneic mesenchymal stem/stromal cells (MSCs), has emerged as a promising therapeutic strategy for ARDS, favorably modulating the immune response to reduce lung injury, while facilitating lung regeneration and repair. In this issue of the journal, Rojas and colleagues provide us with a rationale to consider autologous bone marrow-mononuclear cells as an alternative to MSCs for this devastating disease.

Rehmannia glutinosa extract activates endothelial progenitor cells in a rat model of myocardial infarction through a SDF-1 α/CXCR4 cascade

Objectives

Endothelial progenitor cells (EPCs) can be used to repair tissues after myocardial infarction (MI) but EPC activators have adverse reactions. Rehmannia glutinosa is a herb used in traditional Chinese medicine, which can promote bone-marrow proliferation and protect the ischemic myocardium. We investigated the effects of Rehmannia glutinosa extract (RGE) on EPCs in a rat model of MI.

Methods

A total of 120 male Wistar rats were randomized to 2 groups (n = 60 each) for treatment: high-dose RGE (1.5 g·kg⁻¹·day⁻¹ orally) for 8 weeks, then left anterior descending coronary artery ligation, mock surgery or no treatment, then RGE orally for 4 weeks; or normal saline (NS) as the above protocol. The infarct region of the left ventricle was assessed by serial sectioning and morphology. EPCs were evaluated by number and function. Protein and mRNA levels of CD133, vascular endothelial growth factor receptor 2 (VEGFR2), chemokine C-X-C motif receptor 4 (CXCR4), stromal cell–derived factor-1α (SDF-1α) were measured by immunohistochemistry, Western blot and quantitative PCR analysis.

Results

RGE significantly improved left ventricular function, decreased the ischemic area and the apoptotic index in the infarct myocardium, also decreased the concentration of serum cardiac troponin T and brain natriuretic peptide at the chronic stage after MI (from week 2 to week 4). RGE increased EPC number, proliferation, migration and tube-formation capacity. It was able to up-regulate the expression of angiogenesis-associated ligand/receptor, including CD133, VEGFR2 and SDF-1α/CXCR4. In vitro, the effect of RGE on SDF-1α/CXCR4 cascade was reversed by the CXCR4 specific antagonist AMD3100.

Conclusion

RGE may enhance the mobilization, migration and therapeutic angiogenesis of EPCs after MI by activating the SDF-1α/CXCR4 cascade.

Global remodeling of the vascular stem cell niche in bone marrow of diabetic patients: implication of the microRNA-155/FOXO3a signaling pathway

RATIONALE

The impact of diabetes mellitus on bone marrow (BM) structure is incompletely understood.

OBJECTIVE

Investigate the effect of type-2 diabetes mellitus (T2DM) on BM microvascular and hematopoietic cell composition in patients without vascular complications.

METHODS AND RESULTS

Bone samples were obtained from T2DM patients and nondiabetic controls (C) during hip replacement surgery and from T2DM patients undergoing amputation for critical limb ischemia. BM composition was assessed by histomorphometry, immunostaining, and flow cytometry. Expressional studies were performed on CD34(pos) immunosorted BM progenitor cells (PCs). Diabetes mellitus causes a reduction of hematopoietic tissue, fat deposition, and microvascular rarefaction, especially when associated with critical limb ischemia. Immunohistochemistry documented increased apoptosis and reduced abundance of CD34(pos)-PCs in diabetic groups. Likewise, flow cytometry showed scarcity of BM PCs in T2DM and T2DM+critical limb ischemia compared with C, but similar levels of mature hematopoietic cells. Activation of apoptosis in CD34(pos)-PCs was associated with upregulation and nuclear localization of the proapoptotic factor FOXO3a and induction of FOXO3a targets, p21 and p27(kip1). Moreover, microRNA-155, which regulates cell survival through inhibition of FOXO3a, was downregulated in diabetic CD34(pos)-PCs and inversely correlated with FOXO3a levels. The effect of diabetes mellitus on anatomic and molecular end points was confirmed when considering background covariates. Furthermore, exposure of healthy CD34(pos)-PCs to high glucose reproduced the transcriptional changes induced by diabetes mellitus, with this effect being reversed by forced expression of microRNA-155.

CONCLUSIONS

We provide new anatomic and molecular evidence for the damaging effect of diabetes mellitus on human BM, comprising microvascular rarefaction and shortage of PCs attributable to activation of proapoptotic pathway.

Angiogenesis following cell injection is induced by an excess inflammatory response coordinated by bone marrow cells

The aim of this study was to identify novel angiogenic mechanisms underlying the regenerative process. To that end, interactions between adipose tissue-derived stromal cells (ASCs) and bone marrow cells (BMCs) were initially investigated using real-time fluorescence optical imaging. To monitor cell behavior in mice, we injected green fluorescent protein-positive (GFP(+)) BMCs into the tail vein and injected PKH26-labeled ASCs behind the ears. Angiogenesis and inflammation were observed at these sites via an optical imaging probe. Injected GFP(+) BMCs migrated from the blood vessels into the tissues surrounding the ASC injection sites. Many of the migrating GFP(+) BMCs discovered at the ASC injection sites were inflammatory cells, including Gr-1(+), CD11b(+), and F4/80(+) cells. ASCs cocultured with inflammatory cells secreted increased levels of chemokines such as macrophage inflammatory protein (MIP)-1α, MIP-1β, keratinocyte-derived chemokines, and monocyte chemotactic protein 1. Similarly, these ASCs secreted increased levels of angiogenic growth factors such as hepatocyte growth factor and vascular endothelial growth factor. However, when anti-CXC chemokine receptor type 4 antibody was injected at regular intervals, the migration of GFP(+) BMCs (especially Gr-1(+) and CD11b(+) cells) to ASC injection sites was inhibited, as was angiogenesis. The collective influence of the injected ASCs and BMC-derived inflammatory cells promoted acute inflammation and angiogenesis. Together, the results suggest that the outcome of cell-based angiogenic therapy is influenced not only by the injected cells but also by the effect of intrinsic inflammatory cells.

Bone marrow progenitor cells do not contribute to liver fibrogenic cells

AIM

To investigate the contribution of bone marrow (BM) cells to hepatic fibrosis.

METHODS

To establish a model of chimerism, C57Bl/6 female mice were subjected to full-body irradiation (7 Gy) resulting in BM myeloablation. BM mononuclear cells obtained from male transgenic mice expressing enhanced green fluorescent protein (GFP) were used for reconstitution. Engraftment was confirmed by flow cytometry. To induce liver injury, chimeric animals received carbon tetrachloride (CCl(4)) 0.5 mL/kg intraperitoneally twice a week for 30 d (CCl(4) 30 d) and age-matched controls received saline (Saline 30 d). At the end of this period, animals were sacrificed for post mortem analysis. Liver samples were stained with hematoxylin and eosin to observe liver architectural changes and with Sirius red for collagen quantification by morphometric analysis. α-smooth muscle actin (α-SMA) was analyzed by confocal microscopy to identify GFP+ cells with myofibroblast (MF) characteristics. Liver tissue, BM and peripheral blood were collected and prepared for flow cytometric analysis using specific markers for detection of hepatic stellate cells (HSCs) and precursors from the BM.

RESULTS

Injury to the liver induced changes in the hepatic parenchymal architecture, as reflected by the presence of inflammatory infiltrate and an increase in collagen deposition (Saline 30 d = 11.10% ± 1.12% vs CCl(4) 30 d = 12.60% ± 0.73%, P = 0.0329). Confocal microscopy revealed increased reactivity against α-SMA in CCl(4) 30 d compared to Saline 30 d, but there was no co-localization with GFP+ cells, suggesting that cells from BM do not differentiate to MFs. Liver flow cytometric analysis showed a significant increase of CD45+/GFP+ cells in liver tissue (Saline 30 d = 3.2% ± 2.2% vs CCl(4) 30 d = 5.8% ± 1.3%, P = 0.0458), suggesting that this increase was due to inflammatory cell infiltration (neutrophils and monocytes). There was also a significant increase of common myeloid progenitor cells (CD117+/CD45+) in the livers of CCl(4)-treated animals (Saline 30 d = 2.16% ± 1.80% vs CCl(4) 30 d = 5.60% ± 1.30%, P = 0.0142). In addition the GFP-/CD38+/CD45- subpopulation was significantly increased in the CCl(4) 30 d group compared to the Saline 30 d group (17.5% ± 3.9% vs 9.3% ± 2.4%, P = 0.004), indicating that the increase in the activated HSC subpopulation was not of BM origin.

CONCLUSION

BM progenitor cells do not contribute to fibrosis, but there is a high recruitment of inflammatory cells that stimulates HSCs and MFs of liver origin.

Mesenchymal stem cells combined with an artificial dermal substitute improve repair in full-thickness skin wounds

Autografts represent the gold standard for the treatment of full thickness burns. Factors such as lack of suitable donor sites and poor skin quality, however, have led to the development of artificial dermal substitutes. The investigation of mechanisms leading to enhanced functionality of these skin substitutes has been attracting great attention. This study aimed to investigate the effect of autologous stem cells on the integration and vascularization of a dermal substitute in full-thickness skin wounds, in a murine model. Two cell populations were compared, whole bone marrow cells and cultivated mesenchymal stem cells, isolated from mice transgenic for the enhanced green fluorescent protein, which allowed tracking of the transplanted cells. The number of cells colonizing the dermal substitute, as well as vascular density, were higher in mice receiving total bone marrow and particularly mesenchymal stem cells, than in control animals. The effect was more pronounced in animals treated with mesenchymal stem cells, which located primarily in the wound bed, suggesting a paracrine therapeutic mechanism. These results indicate that combining mesenchymal stem cells with artificial dermal substitutes may represent an important potential modality for treating full thickness burns, even in allogeneic combinations due to the immunoregulatory property of these cells.

70th Birthday symposium of Prof. Dr. Riederer: autologous adult stem cells in ischemic and traumatic CNS disorders

Ischemic and traumatic insults of the central nervous system both result in definite chronic disability, only to some extent responsive to rehabilitation. Recently, the application of autologous stem cells (fresh bone marrow-derived mononuclear cells including mesenchymal and hematopoietic stem cells) was suggested to provide a strategy to further improve neurological recovery in these disorders. During the acute phase, stem cells act mainly by neuroprotection with prevention of apoptosis, whereas during the chronic situation they provide neurorestoration by transdifferentiation and/or the secretion of neurotrophic factors. To reach these goals, in the acute phase, stem cells (10 million mononuclear cells per kg body weight) might be best applied intravenously, as during the first 7 days after the lesion, the blood-brain barrier permits passage of cells from the blood into the brain or the spinal cord. In the more chronic situation, though, those cells might be applied best intrathecally by lumbar puncture. Based on the reported results so far, it seems justified to develop well-designed clinical double-blind trials in chronic spinal cord injury and ischemic stroke patients, as efficacy and safety concerns might not be answered by preclinical studies.

Concise review: bone marrow mononuclear cells for the treatment of ischemic syndromes: medicinal product or cell transplantation?

In November of 2011, the Committee for Advanced Therapies (CAT) of the European Medicines Agency (EMA) published two scientific recommendations regarding the classification of autologous bone marrow-derived mononuclear cells (BM-MNCs) and autologous bone marrow-derived CD133+ cells as advanced therapy medicinal products (ATMPs), specifically tissue-engineered products, when intended for regeneration in ischemic heart tissue on the basis that they are not used for the same essential function (hematological restoration) that they fulfill in the donor. In vitro and in vivo evidence demonstrates that bone marrow cells are physiologically involved in adult neovascularization and tissue repair, making their therapeutic use for these purposes a simple exploitation of their own essential functions. Therefore, from a scientific/legal point of view, nonsubstantially manipulated BM-MNCs and CD133+ cells are not an ATMP, because they have a physiological role in the processes of postnatal neovascularization and, when used therapeutically for vascular restoration in ischemic tissues, they are carrying out one of their essential physiological functions (the legal definition recognizes that cells can have several essential functions). The consequences of classifying BM-MNCs and CD133+ cells as medicinal products instead of cellular transplantation, like bone marrow transplantation, in terms of costs and time for these products to be introduced into clinical practice, make this an issue of crucial importance. Therefore, the recommendations of EMA/CAT could be reviewed in collaboration with scientific societies, in light of organizational and economic consequences as well as scientific knowledge recently acquired about the mechanisms of postnatal neovascularization and the function of bone marrow in the regeneration of remote tissues.

A comparison of stem cells for therapeutic use

A critical comparison of the attributes of several types of stem cells is presented, with particular emphasis on properties that are critical for the application of these cells for therapeutic purposes. The importance of an autologous source of pluripotent stem cells is stressed. It is apparent that two sources currently exist for non-embryonic pluripotent stem cells--very small embryonic-like stem cells (VSELs) and induced pluripotent stem cells (iPS). The impact of the emerging iPS research on therapy is considered.

Regenerative Cells for Transplantation in Hepatic Failure

Human embryonic stem (ES) cells and induced pluripotent stem (iPS) cells have an enormous potential; however, their potential clinical application is being arrested due to various limitations such as teratoma formation followed by tumorigenesis, emergent usage, and the quality control of cells, as well as safety issues regarding long-term culture are also delaying their clinical application. In addition, human ES cells have two crucial issues: immunogenicity and ethical issues associated with their clinical application. The efficient generation of human iPS cells requires gene transfer, yet the mechanism underlying pluripotent stem cell induction has not yet been fully elucidated. Otherwise, although human adult regenerative cells including mesenchymal stem cells have a limited capacity for differentiation, they are nevertheless promising candidates for tissue regeneration in a clinical setting. This review highlights the use of regenerative cells for transplantation in hepatic failure.