Peripheral blood as a source of stem cells for regenerative medicine

Isolation and Culture of Non-adherent Cells for Cell Reprogramming

Coronary heart disease (CHD) is a leading cause of death globally, while its current management is limited to reducing the myocardial infarction area without actually replacing dead cardiomyocytes. Direct cell reprogramming is a method of cellular cardiomyoplasty which aims for myocardial tissue regeneration, and CD34⁺ cells are one of the potential sources due to their shared embryonic origin with cardiomyocytes. However, the isolation and culture of non-adherent CD34⁺ cells is crucial to obtain adequate cells for high-efficiency genetic modification. This study aimed to investigate the optimal method for isolation and culture of CD34⁺ peripheral blood cells using certain culture media. A peripheral blood sample was obtained from a healthy subject and underwent pre-enrichment, isolation, and expansion. The culture was subsequently observed for their viability, adherence, and confluence. Day 0 observation of the culture showed a healthy CD34⁺ cell with a round cell shape, without any adherent cells present yet. Day 4 of observation showed that CD34⁺ cells within the blood plasma medium became adherent, indicated by their transformations into spindle or oval morphologies. Meanwhile, CD34⁺ cells in vitronectin and fibronectin media showed no adherent cells and many of them died. Day 7 observation revealed more adherent CD34⁺ cells in blood plasma medium, and which had 75% of confluence. In conclusion, the CD34⁺ cells that were isolated using a combination of density and magnetic methods may be viable and adequately adhere in culture using blood plasma medium, but not in cultures using fibronectin and vitronectin.

Monitoring fibrogenic progression in the liver

The clinical course of chronic liver diseases is significantly dependent on the progression rate of fibrosis which is the unstructured replacement of injured parenchyma by extracellular matrix. Despite intensive studies, the clinical opportunities for patients with fibrosing liver diseases have not improved. This will be changed by increasing knowledge of new pathogenetic mechanisms, which complement the "canonical principle" of fibrogenesis. The latter is based on the activation of hepatic stellate cells and their transdifferentiation to myofibroblasts induced by hepatocellular injury and consecutive inflammatory mediators such as TGF-β. Stellate cells express a broad spectrum of matrix components. New mechanisms indicate that the heterogeneous pool of (myo-)fibroblasts can be supplemented by epithelial-mesenchymal transition (EMT) from cholangiocytes and potentially also from hepatocytes to fibroblasts, by influx of bone marrow-derived fibrocytes in the damaged liver tissue and by differentiation of a subgroup of monocytes to fibroblasts after homing in the damaged tissue. These processes are regulated by the cytokines TGF-β and BMP-7, chemokines, colony-stimulating factors, metalloproteinases and numerous trapping proteins. They offer innovative diagnostic and therapeutic options. As an example, modulation of TGF-β/BMP-7 ratio changes the rate of EMT, and so the simultaneous determination of these parameters and of the connective tissue growth factor (CTGF) in serum might provide information on fibrogenic activity. Also, proteomic and glycomic approaches of serum are under investigation to set up specific protein profiles in patients with liver fibrosis. The aim of this article is to present the current pathogenetic concepts of liver fibrosis and to discuss established and novel diagnostic approaches to reflect the process of hepatic fibrogenesis in the medical laboratory.

Comparative functional cell biological analysis of mesenchymal stem cells of the head and neck region: potential impact on wound healing, trauma, and infection

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent mesenchymal progenitor cells, originally identified in bone-marrow. Little is known about MSCs of the head and neck region. We investigated cell biological properties with a potential impact on wound healing of 2 different tissue-resident MSC populations.

METHODS

MSCs were isolated from human nasal mucosa (nmMSCs) and parotid gland (pgMSCs). Clonogenic potential, cell surface markers, cytokine secretion, chemokine receptor expression, mobility, and adhesion to extracellular matrix were examined in unstimulated and stimulated MSCs.

RESULTS

NmMSCs had the higher clonogenic potential. PgMSCs showed a broader panel of chemokine receptor expression and displayed higher mobility, especially after challenge with bacterial lipopolysaccharide (LPS). NmMSCs were less mobile and showed increased LPS-induced secretion of the inflammatory cytokine interleukin-8 (IL-8) compared with pgMSCs.

CONCLUSION

These data highlight functional differences between tissue-resident MSCs of the head and neck region, which may impact functional properties of these cells in response to trauma or infection.

Roles and relation between C/EBPα and PARs in the activation of hepatic stellate cells

Protease activated receptors (PARs) are main components of the fibrotic cascade mediated by the trypsin and thrombin that amplifies liver inflammation and fibrosis. Gene transcription initiation induced by PARs plays an important role in the activation of hepatic stellate cells (HSCs). HSC activation can be inhibited by the expression of transcription factor CCAAT enhancer binding proteins α (C/EBPα). Further research of the relation between C/EBPα and PARs will contribute to the understanding of the pathogenesis of liver fibrosis and provide a theoretical basis for further exploration of anti-fibrotic strategies.

Interferon-gamma and tumor necrosis factor-alpha differentially affect cytokine expression and migration properties of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity to differentiate into different tissue cell types such as chondrocytes, osteocytes, and adipocytes. In addition, they can home to damaged, in-flamed, and malignant tissues and display immunomodulatory properties. Since tissue-derived factors might modulate these properties, we decided to explore the impact of prototypic tissue-derived inflammatory cytokines such as TNF-alpha and IFN-gamma on immunomodulatory MSCs functions. To this end, we used primary bone marrow and cord blood-derived MSCs as well as an immortalized MSC line (V54/2) as model systems. We demonstrate that under unstimulated conditions, V54/2 cells constitutively express low levels of indoleamine 2,3-dioxygenase (IDO), exert an immunosuppressive effect on activated T-lymphocyte proliferation, secrete a distinct set of cytokines, and express a wide range of chemokine receptors. Upon stimulation, the proinflammatory cytokines IFN-gamma and TNF-alpha did not inhibit suppression of T-cell proliferation, although IDO expression was up-regulated by IFN-gamma. In contrast, TNF-alpha but not IFN-gamma amplified the cytokine production of V54/2 and primary MSCs. Interestingly, IFN-gamma was superior to TNF-alpha in up-regulating expression of chemokine receptors and migration of the V54/2 cell line, while TNF-alpha was the predominant regulator of migration in primary MSCs. Altogether, our data show that properties of MSCs depend on local environmental factors. In particular, we have shown that IFN-gamma and TNF-alpha differentially regulate cytokine expression and migration of MSCs.

Endothelial progenitor cells bind and inhibit platelet function and thrombus formation

BACKGROUND

Interactions of endothelial progenitor cells (EPCs) with vascular and blood cells contribute to vascular homeostasis. Although platelets promote the homing of EPCs to sites of vascular injury and their differentiation into endothelial cells, the functional consequences of such interactions on platelets remain unknown. Herein, we addressed the interactions between EPCs and platelets and their impact on platelet function and thrombus formation.

METHODS AND RESULTS

Cultured on fibronectin in conditioned media, human peripheral blood mononuclear cells differentiated, within 10 days of culture, into EPCs, which uptake acetylated low-density lipoprotein, bind ulex-lectin, lack monocyte/leukocyte markers (CD14, P-selectin glycoprotein ligand-1, L-selectin), express progenitor/endothelial markers (CD34, vascular endothelial growth factor receptor-2, von Willebrand factor, and vascular endothelial cadherin), and proliferate in culture. These EPCs bound activated platelets via CD62P and inhibited its translocation, glycoprotein IIb/IIIa activation, aggregation, and adhesion to collagen, mainly via prostacyclin secretion. Indeed, this was associated with upregulation of cyclooxygenase-2 and inducible nitric oxide synthase. However, the effects on platelets in vitro were reversed by cyclooxygenase and cyclooxygenase-2 inhibition but not by nitric oxide or inducible nitric oxide synthase inhibition. Moreover, in a ferric chloride-induced murine arterial thrombosis model, injection of EPCs led to their incorporation into sites of injury and impaired thrombus formation, leading to an incomplete occlusion with 50% residual flow.

CONCLUSIONS

Peripheral blood mononuclear cell-derived EPCs bind platelets via CD62P and inhibit platelet activation, aggregation, adhesion to collagen, and thrombus formation, predominantly via upregulation of cyclooxygenase-2 and secretion of prostacyclin. These findings add new insights into the biology of EPCs and define their potential roles in regulating platelet function and thrombosis.

Changing the pathogenetic roadmap of liver fibrosis? Where did it start; where will it go?

The pathophysiology of liver injury has attracted the interest of experimentalists and clinicians over many centuries. With the discovery of liver-specific pericytes - formerly called fat-storing cells, Ito-cells, lipocytes, and currently designated as hepatic stellate cells (HSC) - the insight into the cellular and molecular pathobiology of liver fibrosis has evolved and the pivotal role of HSC as a precursor cell-type for extracellular matrix-producing myofibroblasts has been established. Although activation and transdifferentiation of HSC to myofibroblasts is still regarded as the pathogenetic key mechanism of fibrogenesis, recent studies point to a prominent heterogeneity of the origin of myofibroblasts. Currently, the generation of matrix-synthesizing fibroblasts by epithelial-mesenchymal transition, by influx of bone marrow-derived fibrocytes into damaged liver tissue, and by differentiation of circulating monocytes to fibroblasts after homing in the injured liver are discussed as important complementary mechanisms to enlarge the pool of (myo-)fibroblasts in the fibrosing liver. Among the molecular mediators, transforming growth factor-beta (TGF-beta) plays a central role, which is controlled by the bone-morphogenetic protein (BMP)-7, an important antagonist of TGF-beta action. The newly discovered pathways supplement the linear concept of HSC activation to myofibroblasts, point to fibrosis as a systemic response involving extrahepatic organs and reactions, add further evidence to a more or less uniform concept of organ fibrosis in general (e.g. liver, lung, kidney), and offer innovative approaches for the development of non-invasive biomarkers and antifibrotic trials.

Essential but differential role for CXCR4 and CXCR7 in the therapeutic homing of human renal progenitor cells

Recently, we have identified a population of renal progenitor cells in human kidneys showing regenerative potential for injured renal tissue of SCID mice. We demonstrate here that among all known chemokine receptors, human renal progenitor cells exhibit high expression of both stromal-derived factor-1 (SDF-1) receptors, CXCR4 and CXCR7. In SCID mice with acute renal failure (ARF), SDF-1 was strongly up-regulated in resident cells surrounding necrotic areas. In the same mice, intravenously injected renal stem/progenitor cells engrafted into injured renal tissue decreased the severity of ARF and prevented renal fibrosis. These beneficial effects were abolished by blocking either CXCR4 or CXCR7, which dramatically reduced the number of engrafting renal progenitor cells. However, although SDF-1–induced migration of renal progenitor cells was only abolished by an anti-CXCR4 antibody, transendothelial migration required the activity of both CXCR4 and CXCR7, with CXCR7 being essential for renal progenitor cell adhesion to endothelial cells. Moreover, CXCR7 but not CXCR4 was responsible for the SDF-1–induced renal progenitor cell survival. Collectively, these findings suggest that CXCR4 and CXCR7 play an essential, but differential, role in the therapeutic homing of human renal progenitor cells in ARF, with important implications for the development of stem cell–based therapies.

Biomarkers of hepatic fibrosis, fibrogenesis and genetic pre-disposition pending between fiction and reality

Fibrosis is a frequent, life-threatening complication of most chronic liver diseases. Despite major achievements in the understanding of its pathogenesis, the translation of this knowledge into clinical practice is still limited. In particular, non-invasive and reliable (serum-) biomarkers indicating the activity of fibrogenesis are scarce. Class I biomarkers are defined as serum components having a direct relation to the mechanism of fibrogenesis, either as secreted matrix-related components of activated hepatic stellate cells and fibroblasts or as mediators of extracellular matrix (ECM) synthesis or turnover. They reflect primarily the activity of the fibrogenic process. Many of them, however, proved to be disappointing with regard to sensitivity and speci-ficity. Up to now hyaluronan turned out to be the relative best type I serum marker. Class II biomarkers comprise in general rather simple standard laboratory tests, which are grouped into panels. They fulfil most criteria for detection and staging of fibrosis and to a lesser extent grading of fibrogenic activity. More than 20 scores are currently available, among which Fibrotest™ is the most popular one. However, the diagnostic use of many of these scores is still limited and standardization of the assays is only partially realized. Combining of panel markers in sequential algorithms might increase their diagnostic validity. The translation of genetic pre-disposition biomarkers into clinical practice has not yet started, but some polymorphisms indicate a link to progression and outcome of fibrogenesis. Parallel to serum markers non-invasive physical techniques, for example, transient elastography, are developed, which can be combined with serum tests and profiling of serum proteins and glycans.

Evolving concepts of liver fibrogenesis provide new diagnostic and therapeutic options

Despite intensive studies, the clinical opportunities for patients with fibrosing liver diseases have not improved. This will be changed by increasing knowledge of new pathogenetic mechanisms, which complement the "canonical principle" of fibrogenesis. The latter is based on the activation of hepatic stellate cells and their transdifferentiation to myofibroblasts induced by hepatocellular injury and consecutive inflammatory mediators such as TGF-beta. Stellate cells express a broad spectrum of matrix components. New mechanisms indicate that the heterogeneous pool of (myo-)fibroblasts can be supplemented by epithelial-mesenchymal transition (EMT) from cholangiocytes and potentially also from hepatocytes to fibroblasts, by influx of bone marrow-derived fibrocytes in the damaged liver tissue and by differentiation of a subgroup of monocytes to fibroblasts after homing in the damaged tissue. These processes are regulated by the cytokines TGF-beta and BMP-7, chemokines, colony-stimulating factors, metalloproteinases and numerous trapping proteins. They offer innovative diagnostic and therapeutic options. As an example, modulation of TGF-beta/BMP-7 ratio changes the rate of EMT, and so the simultaneous determination of these parameters and of connective tissue growth factor (CTGF) in serum might provide information on fibrogenic activity. The extension of pathogenetic concepts of fibrosis will provide new therapeutic possibilities of interference with the fibrogenic mechanism in liver and other organs.

99mTc-HMPAO labelling inhibits cell motility and cell proliferation and induces apoptosis of NC-NC cells

(99m)Tc-hexamethyl-propylenamine-oxime ((99m)Tc-HMPAO)-labelled leukocytes have been used in standard diagnostic procedures for the detection of infection and inflammation. Although some investigators have already pointed out that labelling of leukocytes with (99m)Tc-HMPAO has detrimental effects on the cells, still very little is known regarding the effects of ionizing radiation on lymphocyte function. The effects of (99m)Tc-HMPAO-labelling on lymphocyte adhesion, proliferation, mitotic index, migration and apoptosis were evaluated. The lymphoblastoid cell line NC-NC was used as the lymphocyte population. (99m)Tc-HMPAO-labelling decreased cell adhesion, proliferation, mitotic index and motility, whereas it induced apoptosis and cell-cycle arrest. The rate of decrease in cell proliferation was up to 70% (P<0.001) by day 4 after labelling. (99m)Tc-HMPAO-labelling led a 35% decrease (P<0.001) in adhesion ability of the cells on fibronectin at 16h. Using the Boyden chamber motility assay, it was shown that both spontaneous and monocyte chemotactic protein (MCP-1)-induced lymphocyte motility were strongly reduced by (99m)Tc-HMPAO-labelling. The decrease in motility was approximately five-fold (P<0.05). In addition, a 12-fold increase (P<0.05) was observed in apoptosis of the (99m)Tc-HMPAO-treated cells compared with control cells. Besides, it was shown that cell-cycle arrest was induced starting from the 3rd day after treatment with (99m)Tc-HMPAO. Our observations indicate that (99m)Tc-HMPAO-labelling has damaging effects on lymphocyte function including cell adhesion, proliferation, mitotic index, motility and cell cycle under in vitro conditions.

Isolation and characterization of multipotent progenitor cells from the Bowman's capsule of adult human kidneys

Regenerative medicine represents a critical clinical goal for patients with ESRD, but the identification of renal adult multipotent progenitor cells has remained elusive. It is demonstrated that in human adult kidneys, a subset of parietal epithelial cells (PEC) in the Bowman's capsule exhibit coexpression of the stem cell markers CD24 and CD133 and of the stem cell-specific transcription factors Oct-4 and BmI-1, in the absence of lineage-specific markers. This CD24+CD133+ PEC population, which could be purified from cultured capsulated glomeruli, revealed self-renewal potential and a high cloning efficiency. Under appropriate culture conditions, individual clones of CD24+CD133+ PEC could be induced to generate mature, functional, tubular cells with phenotypic features of proximal and/or distal tubules, osteogenic cells, adipocytes, and cells that exhibited phenotypic and functional features of neuronal cells. The injection of CD24+CD133+ PEC but not of CD24-CD133- renal cells into SCID mice that had acute renal failure resulted in the regeneration of tubular structures of different portions of the nephron. More important, treatment of acute renal failure with CD24+CD133+ PEC significantly ameliorated the morphologic and functional kidney damage. This study demonstrates the existence and provides the characterization of a population of resident multipotent progenitor cells in adult human glomeruli, potentially opening new avenues for the development of regenerative medicine in patients who have renal diseases.