Trafficking of stem cells

Standardisation is the key to the sustained, rapid and healthy development of stem cell-based therapy

BACKGROUND

Stem cell-based therapy (SCT) is an important component of regenerative therapy that brings hope to many patients. After decades of development, SCT has made significant progress in the research of various diseases, and the market size has also expanded significantly. The transition of SCT from small-scale, customized experiments to routine clinical practice requires the assistance of standards. Many countries and international organizations around the world have developed corresponding SCT standards, which have effectively promoted the further development of the SCT industry.

METHODS

We conducted a comprehensive literature review to introduce the clinical application progress of SCT and focus on the development status of SCT standardization.

RESULTS

We first briefly introduced the types and characteristics of stem cells, and summarized the current clinical application and market development of SCT. Subsequently, we focused on the development status of SCT-related standards as of now from three levels: the International Organization for Standardization (ISO), important international organizations, and national organizations. Finally, we provided perspectives and conclusions on the significance and challenges of SCT standardization.

CONCLUSIONS

Standardization plays an important role in the sustained, rapid and healthy development of SCT.

Understanding the "SMART" features of hematopoietic stem cells and beyond

Since the huge success of bone marrow transplantation technology in clinical practice, hematopoietic stem cells (HSCs) have become the gold standard for defining the properties of adult stem cells (ASCs). Here, we describe the "self-renewal, multi-lineage differentiation, apoptosis, rest, and trafficking" or "SMART" model, which has been developed based on data derived from studies of HSCs as the most well-characterized stem cell type. Given the potential therapeutic applications of ASCs, we delineate the key characteristics of HSCs using this model and speculate on the physiological relevance of stem cells identified in other tissues. Great strides are being made in understanding the biology of ASCs, and efforts are now underway to develop safe and effective ASC-based therapies in this emerging area.

Postsynaptic damage and microglial activation in AD patients could be linked CXCR4/CXCL12 expression levels

Alzheimer's disease (AD) is one of the most common forms of dementia with still unknown pathogenesis. Several cytokines and chemokines are involved in the pathogenesis of AD. Among the chemokines, the CXCR4/CXCL12 complex has been shown to play an important role in the pathogenetic development of AD. We investigated the expression levels of CXCR4 / CXCL12 in fifteen brain regions of healthy non-demented subjects (NDHC) (2139 sample) and AD patients (1170 sample) stratified according to sex and age. Furthermore, we correlated their expressions with the Neurogranin (NRGN) and CHI3L1 levels, two inflamm-aging markers. We highlighted that CXCR4 gene expression levels were age-correlated in the brain of NDHC subjects and that AD nullified this correlation. A similar trend, but diametrically opposite was observed for CXCL12. Its expression was decreased during the aging in both sexes, and in the brains of AD patients, it underwent an inversion of the trend, only and exclusively in females. Brains of AD patients expressed high CXCR4 and CHI3L1, and low CXCL12 and Neurogranin levels compared to NDHC subjects. Both CXCR4 and CXCL12 correlated significantly with CHI3L1 and Neurogranin expression levels, regardless of disease. Furthermore, we showed a selective modulation of CXCL12 and CXCR4 only in specific brain regions. Taken together our results demonstrate that CXCL12 and CXCR4 are linked to Neurogranin and CHI3L1 expression levels and the relationship between postsynaptic damage and microglial activation in AD could be shown using all these genes. Further confirmations are needed to demonstrate the close link between these genes.

Current Understanding of the Pathways Involved in Adult Stem and Progenitor Cell Migration for Tissue Homeostasis and Repair

With the advancements in the field of adult stem and progenitor cells grows the recognition that the motility of primitive cells is a pivotal aspect of their functionality. There is accumulating evidence that the recruitment of tissue-resident and circulating cells is critical for organ homeostasis and effective injury responses, whereas the pathobiology of degenerative diseases, neoplasm and aging, might be rooted in the altered ability of immature cells to migrate. Furthermore, understanding the biological machinery determining the translocation patterns of tissue progenitors is of great relevance for the emerging methodologies for cell-based therapies and regenerative medicine. The present article provides an overview of studies addressing the physiological significance and diverse modes of stem and progenitor cell trafficking in adult mammalian organs, discusses the major microenvironmental cues regulating cell migration, and describes the implementation of live imaging approaches for the exploration of stem cell movement in tissues and the factors dictating the motility of endogenous and transplanted cells with regenerative potential.

Can yoga therapy stimulate stem cell trafficking from bone marrow?

It has been established that mesenchymal stromal cells (MSCs) from bone marrow enter the peripheral circulation intermittently for possible tissue regeneration, repair and to take care of daily wear and tear. This is evident from the detection of MSCs from peripheral blood. The factors governing this migration remain elusive. These MSCs carry out the work of policing and are supposed to repair the injured tissues. Thus, these cells help in maintaining the tissue and organ homeostasis. Yoga and pranayama originated in India and is now being practiced all over the world for positive health. So far, the chemical stimulation of bone marrow has been widely used employing injection of colony stimulating factor. However, the role of physical factors such as mechanical stimulation and stretching has not been substantiated. It is claimed that practicing yoga delays senescence, improves the physiological functions of heart and lung and yoga postures make the body elastic. It remains to be seen whether the yoga therapy promotes trafficking of the stem cells from bone marrow for possible repair and regeneration of worn out and degenerating tissues. We cover in this short review, mainly the role of physical factors especially the yoga therapy on stem cells trafficking from bone marrow.

Adolescent Klinefelter syndrome: is there an advantage to testis tissue harvesting or not?

It is currently unclear whether an adolescent with 47,XXY Klinefelter syndrome will be better off having testicular sperm extraction (TESE) performed in an effort to ‘preserve fertility’ for the future or, alternatively, should be advised to simply wait until adulthood when he and his partner are ready to begin a family. This report will provide data suggesting that there is no obvious ‘preservation’ benefit and that recommending TESE to the 47,XXY boy and his parents may not be as helpful as it might appear and may be overly aggressive.

Sympathetic nervous system regulation of the tumour microenvironment

The peripheral autonomic nervous system (ANS) is known to regulate gene expression in primary tumours and their surrounding microenvironment. Activation of the sympathetic division of the ANS in particular modulates gene expression programmes that promote metastasis of solid tumours by stimulating macrophage infiltration, inflammation, angiogenesis, epithelial-mesenchymal transition and tumour invasion, and by inhibiting cellular immune responses and programmed cell death. Haematological cancers are modulated by sympathetic nervous system (SNS) regulation of stem cell biology and haematopoietic differentiation programmes. In addition to identifying a molecular basis for physiologic stress effects on cancer, these findings have also identified new pharmacological strategies to inhibit cancer progression in vivo.

Stem Cells and Regenerative Medicine: Myth or Reality of the 21th Century

Since the 1960s and the therapeutic use of hematopoietic stem cells of bone marrow origin, there has been an increasing interest in the study of undifferentiated progenitors that have the ability to proliferate and differentiate into various tissues. Stem cells (SC) with different potency can be isolated and characterised. Despite the promise of embryonic stem cells, in many cases, adult or even fetal stem cells provide a more interesting approach for clinical applications. It is undeniable that mesenchymal stem cells (MSC) from bone marrow, adipose tissue, or Wharton's Jelly are of potential interest for clinical applications in regenerative medicine because they are easily available without ethical problems for their uses. During the last 10 years, these multipotent cells have generated considerable interest and have particularly been shown to escape to allogeneic immune response and be capable of immunomodulatory activity. These properties may be of a great interest for regenerative medicine. Different clinical applications are under study (cardiac insufficiency, atherosclerosis, stroke, bone and cartilage deterioration, diabetes, urology, liver, ophthalmology, and organ's reconstruction). This review focuses mainly on tissue and organ regeneration using SC and in particular MSC.

Osteoblast dysfunctions in bone diseases: from cellular and molecular mechanisms to therapeutic strategies

Several metabolic, genetic and oncogenic bone diseases are characterized by defective or excessive bone formation. These abnormalities are caused by dysfunctions in the commitment, differentiation or survival of cells of the osteoblast lineage. During the recent years, significant advances have been made in our understanding of the cellular and molecular mechanisms underlying the osteoblast dysfunctions in osteoporosis, skeletal dysplasias and primary bone tumors. This led to suggest novel therapeutic approaches to correct these abnormalities such as the modulation of WNT signaling, the pharmacological modulation of proteasome-mediated protein degradation, the induction of osteoprogenitor cell differentiation, the repression of cancer cell proliferation and the manipulation of epigenetic mechanisms. This article reviews our current understanding of the major cellular and molecular mechanisms inducing osteoblastic cell abnormalities in age-related bone loss, genetic skeletal dysplasias and primary bone tumors, and discusses emerging therapeutic strategies to counteract the osteoblast abnormalities in these disorders of bone formation.

Impaired glucose tolerance alters functional ability of peripheral blood-derived mononuclear cells in Asian Indian men

AIM

To compare the adhesion, migration and endothelial differentiation potential of peripheral blood-derived mononuclear cells (PBMCs) obtained from drug-naive normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) Asian Indian men.

METHODS

Based on the 75-g oral glucose tolerance test, 30 NGT and 31 IGT subjects were recruited into the study. PBMCs were isolated from fasting blood using histopaque density gradient centrifugation. Isolated PBMCs were analysed for their ability to adhere to extracellular matrices, incorporation into tubular structures formed by matured endothelial cells and differentiation into endothelial cells upon 7-day culture in endothelial-specific growth medium.

RESULTS

PBMCs obtained from IGT subjects exhibit poor adherence to fibronectin and reduced incorporation into tubular structures. Migration towards stromal cell-derived factor-1α (SDF-1α) in a trans-well filter assembly was also reduced for these cells. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis revealed decreased expression of CXCR4 and β2 integrin and increased expression of arginase II in IGT subjects. No differences were observed with regard to endothelial differentiation; however, cultured PBMCs of IGT subjects had decreased intracellular nitric oxide (NO) production.

CONCLUSION

In pre-diabetic, Asian Indian men, PBMCs exhibit defective migration and homing potential.

Native adipose stromal cells egress from adipose tissue in vivo: evidence during lymph node activation

Adipose tissue (AT) has become accepted as a source of multipotent progenitor cells, the adipose stromal cells (ASCs). In this regard, considerable work has been performed to harvest and characterize this cell population as well as to investigate the mechanisms by which transplanted ASCs mediate tissue regeneration. In contrast the endogenous release of native ASCs by AT has been poorly investigated. In this work, we show that native ASCs egress from murine AT. Indeed, we demonstrated that the release of native ASCs from AT can be evidenced both using an ex vivo perfusion model that we set up and in vivo. Such a mobilization process is controlled by CXCR4 chemokine receptor. In addition, once mobilized from AT, circulating ASCs were found to navigate through lymph fluid and to home into lymph nodes (LN). Therefore, we demonstrated that, during the LN activation, the fat depot encapsulating the activated LN releases native ASCs, which in turn invade the activated LN. Moreover, the ASCs invading the LN were visualized in close physical interaction with podoplanin and ER-TR7 positive structures corresponding to the stromal network composing the LN. This dynamic was impaired with CXCR4 neutralizing antibody. Taken together, these data provide robust evidences that native ASCs can traffic in vivo and that AT might provide stromal cells to activated LNs.

The role of SDF-1α-ECM crosstalk in determining neural stem cell fate

The consequences of central nervous system injury are far-reaching and debilitating and, while an endogenous repair response to neural injury has been observed in recent years, the mechanisms behind this response remain unclear. Neural progenitor/stem cell (NPSC) migration to the site of injury from the neural stem cell niches (e.g. subventricular zone and hippocampus) has been observed to be vasophilic in nature. While the chemotactic stimuli directing NPSC homing to injury is not well established, it is thought to be due in part to an increasing gradient of chemotactic cytokines, such as stromal cell-derived factor 1α (SDF-1α). Based on these recent findings, we hypothesize that critical crosstalk between SDF-1α and the extracellular matrix (ECM) drives injury-induced NPSC behavior. In this study, we investigated the effect of SDF-1α and ECM substrates (Matrigel, laminin, and vitronectin) on the migration, differentiation, and proliferation of NPSCs in vitro using standard assays. The results demonstrated that SDF-1α and laminin-based ECM (Matrigel and laminin) significantly and synergistically enhanced NPSC migration and acute neuronal differentiation. These effects were significantly attenuated with the addition of AMD3100 (an antagonist against the SDF-1α receptor, CXCR4). SDF-1α alone significantly increased NPSC proliferation regardless of ECM substrate, however no synergy was observed between SDF-1α and the ECM. These results serve to elucidate the relationship between adhesive and soluble signaling factors of interest and their effect on NPSC behavior following neural injury. Furthermore, these results better inform the next generation of biomaterials aimed at stimulating endogenous neural regeneration for neural injury and neurodegenerative diseases.

Ex vivo microperfusion system of the adipose organ: a new approach to studying the mobilization of adipose cell populations

BACKGROUND/OBJECTIVES

Adipose tissue (AT) is a dynamic organ that expands and contracts rapidly. It is composed of adipocytes and of cell populations among which immune cells and mesenchymal progenitors known as adipose stromal cells (ASCs). The AT cell turnover has been extensively studied. Surprisingly it has only been viewed as the result of both cell proliferation/death and cell infiltration. Nevertheless, both immune cells and ASCs exhibit migration abilities; therefore their egress from AT in response to physiological/pathophysiological stimuli has to be considered. To do so, the aim of the present work was to develop a model allowing the study of cell release from the adipose organ.

SUBJECTS/METHODS

Mesenteric (Mes) ATs were isolated from 9-week-old C57BL/6 male mice and were catheterized via the superior mesenteric artery and were perfused with a saline solution. After an equilibration period, the mesenteric fat pad was perfused with CXCL12 (stromal-derived factor-1, SDF-1) or sphingosine 1-phosphate (S1P) to trigger cell mobilization and perfusates were collected every 30 min for subsequent flow cytometry analyses.

RESULTS

We report here that CXCL12 induces the specific release of ASCs from MesAT thus demonstrating that ASCs are specifically mobilized from fat depots by a CXCL12-dependent pathway. Moreover, we showed that leukocyte mobilization can be triggered via a S1P-dependent pathway.

CONCLUSIONS

We have developed a microperfusion model of an intact fat depot allowing the study of AT cell release in response to various molecules. The perfusion system described here demonstrates that ASCs and leukocytes can be pharmacologically mobilized from AT. Therefore, AT microperfusion might constitute an appropriate and reliable approach for evaluating the mobilization of different cell populations from AT in various physiological and pathophysiological contexts. Such a model might help in identifying factors and drugs controlling AT cell release, impacting the medical fields of regenerative medicine and of obesity or its associated comorbidities.

Immunosuppressants affect human neural stem cells in vitro but not in an in vivo model of spinal cord injury

Clinical immunosuppression protocols use calcineurin inhibitors, such as cyclosporine A (CsA) or tacrolimus (FK506), or mammalian target of rapamycin (mTOR) inhibitors, such as sirolimus (rapamycin). These compounds alter immunophilin ligand signaling pathways, which are known to interact downstream with mediators for human neural stem cell (hNSC) differentiation and proliferation, suggesting that immunosuppressants may directly alter hNSC properties. We investigated whether immunosuppressants can exert direct effects on the differentiation, proliferation, survival, and migration of human central nervous system-derived stem cells propagated as neurospheres (hCNS-SCns) in vitro and in an in vivo model of spinal cord injury. We identified unique, immunosuppressant-dependent effects on hCNS-SCns differentiation and proliferation in vitro. All immunosuppressants tested increased neuronal differentiation, and CsA and rapamycin inhibited proliferation in vitro. No immunosuppressant-mediated effects on hCNS-SCns survival or migration in vitro were detected. These data suggested that immunosuppressant administration could alter hCNS-SCns properties in vivo. We tested this hypothesis by administering immunosuppressants to constitutively immunodeficient spinal cord injured mice and assessed survival, proliferation, differentiation, and migration of hCNS-SCns after 14 weeks. In parallel, we administered immunosuppressants to immunocompetent spinal cord injury (SCI) mice and also evaluated hCNS-SCns engraftment and fate. We identified no effect of immunosuppressants on the overall hCNS-SCns fate profile in either xenotransplantation model. Despite a lower level of human cell engraftment in immunocompetent SCI mice, functional locomotor recovery was observed in animals receiving hCNS-SCns transplantation with no evidence of allodynia. These data suggest that local cues in the microenvironment could exert a stronger influence on hCNS-SCns than circulating levels of immunosuppressants; however, differences between human and rodent metabolism/pharmokinetics and xenograft versus allograft paradigms could be determining factors.

Anti-inflammatory effects of angiotensin-(1-7) in ischemic stroke

Previously we demonstrated that central administration of angiotensin-(1-7) [Ang-(1-7)] into rats elicits significant cerebroprotection against ischemic stroke elicited by endothelin-1 induced middle cerebral artery occlusion. Ang-(1-7), acting via its receptor Mas, reduced cerebral infarct size, and rats exhibited improved performance on neurological exams. These beneficial actions of Ang-(1-7) were not due to inhibition of the effects of endothelin-1 on cerebral vasoconstriction or effects on cerebral blood flow, and so we considered other potential mechanisms. Here we investigated the possibility that the Ang-(1-7)-induced cerebroprotection involves an anti-inflammatory effect, since stroke-induced cerebral damage includes an excessive intracerebral inflammatory response. Our quantitative RT-PCR analyses revealed that central Ang-(1-7) treatment attenuates the increased expression of mRNAs for inducible nitric oxide synthase (iNOS), several pro-inflammatory cytokines and cluster of differentiation molecule 11b (microglial marker) within the cerebral cortex following endothelin-1 induced stroke. Western blotting confirmed similar changes in iNOS protein expression in the cerebral cortex. In support of these observations, immunostaining revealed the presence of immunoreactive Mas on activated microglia within the cerebral cortical infarct zone, and in vitro experiments demonstrated that lipopolysaccharide-induced increases in nitric oxide production in glial cultures are attenuated by Ang-(1-7) acting via Mas. Collectively these findings demonstrate an anti-inflammatory action of Ang-(1-7) in the brain, and suggest that the cerebroprotective action of this peptide in ischemic stroke may involve effects on nitric oxide generation by microglia.

Tspan8, CD44v6 and alpha6beta4 are biomarkers of migrating pancreatic cancer-initiating cells

Pancreatic adenocarcinoma (PaCa) being the deadliest cancer is partly due to early metastatic spread. Thus, we searched for PaCa-initiating cell (PaCIC) markers with emphasis on markers contributing to metastatic progression. PaCIC were enriched from long-term and freshly established lines by repeated selection for spheroid or holoclone growth in advance of evaluating PaCIC markers. Sphere and holoclone formation steeply increased by recloning and remained stable thereafter. Cells not forming spheres or holoclones died on recloning. PaCIC enrichment in spheres and holoclones was accompanied by increased motility, anchorage independence and upregulated CXCR4 expression. After subcutaneous injection in NOD/SCID mice tumorigenicity and, impressively, recovery of metastasizing tumor cells in peripheral blood, spleen, bone marrow, lung and pancreas was strongly increased in spheres and holoclones. PaCIC enrichment in spheres and holoclones was accompanied, besides CXCR4, by upregulated CD44v6, alpha6beta4, weakly CD133 and tetraspanin Tspan8 expression. Notably, CD44v6, alpha6beta4, CXCR4 and Tspan8 expressing PaCa cells had a growth advantage in vivo and became dominating in migrating and in distant organs settled tumor cells. This is the first report showing that CD44v6, alpha6beta4, Tspan8 and CXCR4 are biomarkers in PaCIC allowing for long-term survival, expansion and migration in immunocompromised mice. The stability of the percentage of PaCIC in long-term and freshly established lines after a roughly 8-fold enrichment by cloning indicates PaCIC, though required for long-term survival, concomitantly depending on support by non-CIC.

The natural history of endocrine function and spermatogenesis in Klinefelter syndrome: what the data show

Once thought to be a chromosomal aberration associated with absolute sterility, Klinefelter syndrome may now be potentially treatable by testicular sperm retrieval coupled with intracytoplasmic sperm injection. With these therapeutic advances, azoospermic 47,XXY men now may have an opportunity for biological paternity. However, our knowledge of the basic mechanisms underlying germ cell loss and Leydig cell compromise is lagging, and is just now beginning to evolve and provide answers to some of the field's most vexing questions: how to maximize and preserve fertility in Klinefelter males many years or even decades before they wish to actively pursue fatherhood. This article reviews the development of the androgenic and spermatogenic compartments of the Klinefelter testis through puberty, and recommends that it is only with a clear understanding of the basic facts that a rational, considered approach to fertility optimization and preservation can be determined.

Differential effects of mixed lymphocyte reaction supernatant on human mesenchymal stromal cells

The concept that mesenchymal stromal cells (MSCs), a component of the hematopoietic microenvironment, can be a target for alloreactive effector cells in the context of graft-vs-host disease has not been investigated in detail. Mixed lymphocyte reaction (MLR) supernatant was used to mimic the inflammatory milieu induced by an allogeneic immune response in vitro. In addition to phenotype and proliferation, we monitored MSC differentiation, gene expression, and support of CD34(+) hematopoietic stem and progenitor cells after priming with MLR supernatant. Priming of MSCs with MLR supernatant led to an 11-fold decrease in cobblestone area-forming cells in the 4-week coculture (p < 0.05) and a threefold decrease of colony-forming unit macrophage in the colony-forming cell assay (p < 0.05). MSC proliferation over 8 days was increased 2.5-fold (p < 0.05). Osteogenic differentiation was enhanced, while adipogenesis was concurrently suppressed. In addition, the surface expression of HLA-DR and intercellular adhesion molecule-1 was increased 20-fold (p = 0.06) and 45-fold (p < 0.05), respectively. This was associated with increased adhesion of hematopoietic stem and progenitor cells to MLR-treated MSCs. In summary, our data shed light on the dysfunction of the stromal environment during graft-vs-host disease, possibly aggravating cytopenia and leading to an enhanced immunogenicity of MSCs.

Cellular host responses to gliomas

Background

Glioblastoma multiforme (GBM) is the most aggressive type of malignant primary brain tumors in adults. Molecular and genetic analysis has advanced our understanding of glioma biology, however mapping the cellular composition of the tumor microenvironment is crucial for understanding the pathology of this dreaded brain cancer. In this study we identified major cell populations attracted by glioma using orthotopic rodent models of human glioma xenografts. Marker-specific, anatomical and morphological analyses revealed a robust influx of host cells into the main tumor bed and tumor satellites.

Methodology/Principal Findings

Human glioma cell lines and glioma spheroid orthotopic implants were used in rodents. In both models, the xenografts recruited large numbers of host nestin-expressing cells, which formed a ‘network’ with glioma. The host nestin-expressing cells appeared to originate in the subventricular zone ipsilateral to the tumor, and were clearly distinguishable from pericytes that expressed smooth muscle actin. These distinct cell populations established close physical contact in a ‘pair-wise’ manner and migrated together to the deeper layers of tumor satellites and gave rise to tumor vasculature. The GBM biopsy xenografts displayed two different phenotypes: (a) low-generation tumors (first in vivo passage in rats) were highly invasive and non-angiogenic, and host nestin-positive cells that infiltrated into these tumors displayed astrocytic or elongated bipolar morphology; (b) high-generation xenografts (fifth passage) had pronounced cellularity, were angiogenic with ‘glomerulus-like’ microvascular proliferations that contained host nestin-positive cells. Stromal cell-derived factor-1 and its receptor CXCR4 were highly expressed in and around glioma xenografts, suggesting their role in glioma progression and invasion.

Conclusions/Significance

Our data demonstrate a robust migration of nestin-expressing host cells to glioma, which together with pericytes give rise to tumor vasculature. Mapping the cellular composition of glioma microenvironment and deciphering the complex ‘crosstalk’ between tumor and host may ultimately aid the development of novel anti-glioma therapies.