CD34 antigen: molecular features and potential clinical applications

CD34 Protein: Its expression and function in inflammation

CD34 has spear-headed the field of basic research and clinical transplantation since the first reports of its expression on hematopoietic stem cells (HSCs). Expressed in mice, humans, rats and other species, CD34 has been used for more than 40 years as a hematopoietic stem and progenitor cell marker. It was later found that muscle satellite cells and epidermal precursors can also be identified with the aid of CD34. Despite the usefulness of CD34 as a marker of HSCs, its overall purpose in animal physiology has remained unclear. This review recaptures CD34 structure, evolutionary conservation, proposed functions, and role in lung inflammation, to describe current research findings and to provide guidance for future studies on CD34.

Development and clinical translation considerations for the next wave of gene modified hematopoietic stem and progenitor cells therapies

INTRODUCTION

Consistent and reliable manufacture of gene modified hematopoietic stem and progenitor cell (HPSC) therapies will be of the utmost importance as they become more mainstream and address larger populations. Robust development campaigns will be needed to ensure that these products will be delivered to patients with the highest quality standards.

AREAS COVERED

Through publicly available manuscripts, press releases, and news articles - this review touches on aspects related to HSPC therapy, development, and manufacturing.

EXPERT OPINION

Recent advances in genome modification technology coupled with the longstanding clinical success of HSPCs warrants great optimism for the next generation of engineered HSPC-based therapies. Treatments for some diseases that have thus far been intractable now appear within reach. Reproducible manufacturing will be of critical importance in delivering these therapies but will be challenging due to the need for bespoke materials and methods in combination with the lack of off-the-shelf solutions. Continued progress in the field will manifest in the form of industrialization which currently requires attention and resources directed toward the custom reagents, a focus on closed and automated processes, and safer and more precise genome modification technologies that will enable broader, faster, and safer access to these life-changing therapies.

Characterization of hematopoietic stem cells from the canine yolk sac

The characterization of hematopoietic stem cells (HSC) from the canine yolk sac (cYS) can contribute to future gene therapies because it is possible to obtain information about the beginning of the development of the circulatory system through the characterization. The cYS is a likely source of HSC, which is a source of blood cell development in mammals. Studies in this field have been conducted for decades; however, interest in cellular therapy is currently at its peak with greater visibility, and these cells are a promising therapeutic tool for the treatment of diseases related to animals and humans. The aim of this study was to isolate and characterize HSC from the cYS embryos at 30 to 45 days of gestational age. Our results showed that the cYS was macroscopically located in the ventral region with a central portion and extremities. The cells in culture presented a circular morphology and cell clusters. The average cell viability was 22.55% dead cells out of 6.5 × 10⁴ total cells. The cells were also able to form colonies on methylcellulose. Flow cytometry analysis revealed the expression of CD34, CD117, and CD45. Our results suggest that the cYS can be used as a source of hematopoietic cells, and this study is very important to understand the mechanism and development of the hematopoietic system in dogs.

Valid Presumption of Shiga Toxin-Mediated Damage of Developing Erythrocytes in EHEC-Associated Hemolytic Uremic Syndrome

The global emergence of clinical diseases caused by enterohemorrhagic Escherichia coli (EHEC) is an issue of great concern. EHEC release Shiga toxins (Stxs) as their key virulence factors, and investigations on the cell-damaging mechanisms toward target cells are inevitable for the development of novel mitigation strategies. Stx-mediated hemolytic uremic syndrome (HUS), characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal injury, is the most severe outcome of an EHEC infection. Hemolytic anemia during HUS is defined as the loss of erythrocytes by mechanical disruption when passing through narrowed microvessels. The formation of thrombi in the microvasculature is considered an indirect effect of Stx-mediated injury mainly of the renal microvascular endothelial cells, resulting in obstructions of vessels. In this review, we summarize and discuss recent data providing evidence that HUS-associated hemolytic anemia may arise not only from intravascular rupture of erythrocytes, but also from the extravascular impairment of erythropoiesis, the development of red blood cells in the bone marrow, via direct Stx-mediated damage of maturing erythrocytes, leading to “non-hemolytic” anemia.

Peripheral Blood Stem Cell Harvest HPC Count Is an Effective Surrogate Marker for CD34+ Cell Count in Allogeneic Stem Cell Transplant Setting

OBJECTIVE: We assessed the predictive potential of XN-HPC for CD34+ cell count as obtained through Sysmex automated hematology analyzers (XN-1000). METHODS: This study was conducted at the National Institute of Blood Diseases and Bone Marrow Transplantation in 84 donors between December 2012 and December 2017 in the first phase and later validated in 112 donors between December 2017 and December 2018. Sysmex XN-1000 and BD FACS Calibur estimated XN-HPC and CD34+ cells of peripheral blood apheresis product, respectively. Spearman's correlation was assessed between XN-HPC and CD34+ cell count followed by receiver operating characteristic curve calculation to determine the XN-HPC cutoff for a CD34+ count of ≥2 million cells/kg of recipient's body weight RESULTS: There is a moderately positive correlation (P value = .003) between XN-HPC and CD34+ count. Receiver operating characteristic curve analyses demonstrated that a cutoff value for XN-HPC of ≥1·845×10⁶cells/kg of recipient's body weight has a specificity and sensitivity of 100% and 78·2%, respectively, for predicting the CD34+ count of ≥2 million cells/kg of recipient's body weight. This cutoff value of XN-HPC was prospectively validated in 112 donors. The positive predictive value was found to be 100%, while negative predictive value was 17%. CONCLUSION: XN-HPC has a highly promising potential to serve as a cost-effective and time-saving surrogate for CD34+ cell count.

Characterization of putative haematopoietic cells from bovine yolk sac

The yolk sac is an extra-embryonic membrane that plays an important role in early embryonic survival. It is the production site for blood cells during embryonic mammalian development and is a likely source of stem cells. The aim of this study was to identify and characterize the putative haematopoietic cells from the yolk sac of bovine embryos at different stages of gestation. The yolk sac regresses according to gestational age and embryos are characterized into groups (I-V) according to the crown-rump measurement. Groups I-III survived in culture longer and exhibited the formation of cell clusters, whereas groups IV and V could not be maintained in culture for an extended period of time. Flow-cytometry analysis revealed that groups I-III had similar characteristics, including high expression levels of the haematopoietic markers CD34, CD90 and CD117. In groups IV and V, decreases were observed in the expression levels of CD117 and CD34. Cells were found to be capable of survival post-cryopreservation and exhibited varying abilities to form colonies in a methylcellulose matrix, depending on gestational age. Cytological analysis revealed the presence of blood cells (lymphocytes and monocytes). Quantitative PCR analysis demonstrated the presence of the haematopoietic progenitor genes GATA3 and LMO2, but not RUNX1. Thus, we have successfully isolated and characterized haematopoietic cells from the bovine embryo yolk sac at varying gestational ages. This study is crucial for the understanding of the development of the haematopoietic system and the embryonic function of this organ. Copyright © 2015 John Wiley & Sons, Ltd.

Identify multiple myeloma stem cells: Utopia?

Multiple myeloma (MM) is a hematologic malignancy of monoclonal plasma cells which remains incurable despite recent advances in therapies. The presence of cancer stem cells (CSCs) has been demonstrated in many solid and hematologic tumors, so the idea of CSCs has been proposed for MM, even if MM CSCs have not been define yet. The existence of myeloma CSCs with clonotypic B and clonotypic non B cells was postulated by many groups. This review aims to focus on these distinct clonotypic subpopulations and on their ability to develop and sustain MM. The bone marrow microenvironment provides to MM CSCs self-renewal, survival and drug resistance thanks to the presence of normal and cancer stem cell niches. The niches and CSCs interact each other through adhesion molecules and the interplay between ligands and receptors activates stemness signaling (Hedgehog, Wnt and Notch pathways). MM CSCs are also supposed to be responsible for drug resistance that happens in three steps from the initial cancer cell homing microenvironment-mediated to development of microenvironment-independent drug resistance. In this review, we will underline all these aspects of MM CSCs.

Sonic Hedgehog signaling regulates vascular differentiation and function in human CD34 positive cells: vasculogenic CD34(+) cells with Sonic Hedgehog

Identification of pivotal factors potentially present in the in situ environment and capable of influencing the function of CD34(+) cells, which can be used for autologous cell therapy, is of paramount interest. SHh is one of the morphogens essential for embryonic vascular development as well as postnatal neovascularization, and the activation of SHh signaling with angiogenic and vascular differentiation responses in CD34(+) cells by SHh treatment differed depending on the G-CSF treatment or the background disease. SHh enhanced the migration, proliferation, adhesion, and EPC colony forming capacities of G-CSF mobilized CD34(+) cells, increasing the vasculogenic/angiogenic potential for neovascularization. An increase in the differentiation potential of CD34(+) cells toward vascular lineages was demonstrated with SHh treatment involving TGFβ signaling pathway. The SHh-activated G-CSF mobilized CD34(+) cells directly contributed to vascular regeneration while non-activated CD34(+) cells showed a lower regenerative capacity in a mouse ischemic hindlimb model. SHh signaling regulates human CD34(+) cell fate and function, and may potentiate the therapeutic effect of G-CSF mobilized CD34(+) cells on ischemic diseases.

Optimizing autologous stem cell mobilization strategies to improve patient outcomes: consensus guidelines and recommendations

Autologous hematopoietic stem cell transplantation (aHSCT) is a well-established treatment for malignancies such as multiple myeloma (MM) and lymphomas. Various changes in the field over the past decade, including the frequent use of tandem aHSCT in MM, the advent of novel therapies for the treatment of MM and lymphoma, and the addition of new stem cell mobilization techniques, have led to the need to reassess current stem cell mobilization strategies. Mobilization failures with traditional strategies are common and result in delays in treatment and increased cost and resource utilization. Recently, plerixafor-containing strategies have been shown to significantly reduce mobilization failure rates, but the ideal method to maximize stem cell yields and minimize costs associated with collection has not yet been determined. A panel of experts convened to discuss the currently available data on autologous hematopoietic stem cell mobilization and transplantation and to devise guidelines to optimize mobilization strategies. Herein is a summary of their discussion and consensus.

A novel approach to collecting satellite cells from adult skeletal muscles on the basis of their stress tolerance

Stem cells are generally collected using flow cytometry, but this method is not applicable when the cell surface marker is not well determined. Satellite cells, which are skeletal muscle stem cells, have the ability to regenerate damaged muscles and are expected to be applicable for treatment of muscle degeneration. Although the transcription factor Pax7 is a known specific marker of satellite cells, it is not located on the cell surface and therefore flow cytometry is not directly applicable. In the present study, we turned our attention to the stress tolerance of adult stem cells, and we propose long-term trypsin incubation (LTT) as a novel approach to collecting satellite cells from mouse and human skeletal muscles. LTT led to a remarkable increase in the ratio of Pax7(+) cells that retain normal myogenic stem cell function. In particular, human Pax7(+) cells made up approximately 30% of primary cultured cells, whereas after LTT, the ratio of Pax7(+) cells increased up to ∼80%, and the ratio of Pax7(+) and/or MyoD(+) myogenic cells increased to ∼95%. Once transplanted, LTT-treated cells contributed to subsequent muscle regeneration following repetitive muscle damage without additional cell transplantation. The stress tolerance of Pax7(+) cells is related to heat shock protein 27 and αB-crystallin, members of the small heat shock protein family. This approach, based on the stress resistance of adult stem cells, is a safe and inexpensive method of efficiently collecting human satellite cells and may also be used for collecting other tissue stem cells whose surface marker is unknown.

Dysembryoplastic neuroepithelial tumors share with pleomorphic xanthoastrocytomas and gangliogliomas BRAF(V600E) mutation and expression

Pediatric cortical glioneuronal benign tumors mainly include gangliogliomas (GG) [differential diagnoses pilocytic astrocytomas (PA) and pleomorphic xanthoastrocytomas (PXA)] and dysembryoplastic neuroepithelial tumor (DNT). DNT include the specific form and the controversial non-specific form that lack the specific glioneuronal element. Our aims were to search for BRAF(V600E) mutation and CD34 expression in DNT, PXA, GG and PA to correlate BRAF(V600E) mutation with BRAF(V600E) expression and to evaluate their diagnostic and prognostic values. Ninety-six children were included. BRAF(V600E) mutation was studied by sequencing and immunohistochemistry; CD34 expression was analyzed by immunohistochemistry. BRAF(V600E) mutation was detected in PXA (60%), GG (38.7%), DNT (30%, including 3/11 specific and 3/9 non-specific forms) and PA (12.5%). BRAF(V600E) expression was recorded in PXA (60%), GG (45.2%) and DNT (30%). CD34 expression was recorded in PXA (60%), GG (58.1%), DNT (25%) and PA (12.5%). Neither CD34 expression nor BRAF(V600E) status was predictive of prognosis, except for PA tumors where CD34 expression was associated with a shorter overall survival. In conclusion, DNT shared with PXA and GG, BRAF(V600E) mutation and/or CD34 expression, which represent molecular markers for these tumors, and we recommend searching for CD34 expression and BRAF(V600E) mutation in all DNT, especially the non-specific forms.

Characteristics of myeloid differentiation and maturation pathway derived from human hematopoietic stem cells exposed to different linear energy transfer radiation types

Exposure of hematopoietic stem/progenitor cells (HSPCs) to ionizing radiation causes a marked suppression of mature functional blood cell production in a linear energy transfer (LET)- and/or dose-dependent manner. However, little information about LET effects on the proliferation and differentiation of HSPCs has been reported. With the aim of characterizing the effects of different types of LET radiations on human myeloid hematopoiesis, in vitro hematopoiesis in Human CD34⁺ cells exposed to carbon-ion beams or X-rays was compared. Highly purified CD34⁺ cells exposed to each form of radiation were plated onto semi-solid culture for a myeloid progenitor assay. The surviving fractions of total myeloid progenitors, colony-forming cells (CFC), exposed to carbon-ion beams were significantly lower than of those exposed to X-rays, indicating that CFCs are more sensitive to carbon-ion beams (D₀ = 0.65) than to X-rays (D₀ = 1.07). Similar sensitivities were observed in granulocyte-macrophage and erythroid progenitors, respectively. However, the sensitivities of mixed-type progenitors to both radiation types were similar.

In liquid culture for 14 days, no significant difference in total numbers of mononuclear cells was observed between non-irradiated control culture and cells exposed to 0.5 Gy X-rays, whereas 0.5 Gy carbon-ion beams suppressed cell proliferation to 4.9% of the control, a level similar to that for cells exposed to 1.5 Gy X-rays. Cell surface antigens associated with terminal maturation, such as CD13, CD14, and CD15, on harvest from the culture of X-ray-exposed cells were almost the same as those from the non-irradiated control culture. X-rays increased the CD235a⁺ erythroid-related fraction, whereas carbon-ion beams increased the CD34⁺CD38⁻ primitive cell fraction and the CD13⁺CD14^+/−CD15⁻ fraction. These results suggest that carbon-ion beams inflict severe damage on the clonal growth of myeloid HSPCs, although the intensity of cell surface antigen expression by mature myeloid cells derived from HSPCs exposed to each type of radiation was similar to that by controls.

Diffuse form of dysembryoplastic neuroepithelial tumour: the histological and immunohistochemical features of a distinct entity showing transition to dysembryoplastic neuroepithelial tumour and ganglioglioma

AIMS

A diffuse variant of dysembryoplastic neuroepithelial tumour (dDNT) has previously been described, which although composed of oligodendroglia-like cells (OLC), astrocytes and mature neurones, lacks the multinodularity and 'specific component' of typical DNT. The dDNT poses a significant challenge to the neuropathologist. This study was undertaken to further characterize the histological and immunohistochemical features of dDNT.

MATERIALS AND METHODS

Review of our archived material from epilepsy surgery identified 16 cases, in which features of dDNT predominated. Their histological and immunohistochemical features, including CD34 and nestin immunohistochemistry, were analysed.

RESULTS

Seven cases had the characteristics of pure dDNT. A further two cases of dDNT showed extension into the white matter with occasional dysplastic neurones. Two additional cases had similar features but with the presence of either single, or multiple small nodular clusters of OLC, in keeping with transition to classical DNT. Five cases showed ganglioglioma-like areas, of which three cases had micronodule formation but with predominant dDNT pattern. In all the cases the dDNT areas showed strong CD34 and less intense nestin immunoreactivity and microglial activation highlighting the full extent of the lesions. There was variable overlap between CD34 and nestin positivity within the micronodular and/or ganglioglioma-like areas.

CONCLUSIONS

Immunoreactivity for CD34 and nestin characterizes the dDNT and helps to distinguish it from other lesions associated with epilepsy. Histological evidence indicative of transition of dDNT to other forms of DNT and ganglioglioma suggests that dDNT might be an early histogenetic form of these glioneuronal tumours.

Novel measurements of mammary stem cells in human umbilical cord blood as prospective predictors of breast cancer susceptibility in later life

BACKGROUND

The size of the breast stem-cell pool could underlie the intrauterine roots of breast cancer. We studied whether breast stem cells exist in umbilical cord blood and if they correlate with hematopoietic stem-cell measurements that have been positively associated with perinatal risk factors for breast cancer.

SUBJECTS AND METHODS

We isolated mononuclear cells from umbilical cord blood of 170 singleton full-term pregnancies and determined, by reverse transcription polymerase chain reaction, the presence of genes of putative breast epithelial stem-cell/progenitor markers [including epithelial cell adhesion molecule (EpCAM), CD49f (α6-integrin), CD117 (c-kit receptor), CD24, and CD29 (β1-integrin)]. By immunocytochemistry, we colocalized protein expressions of EpCAM+CD49f+, CD49f+CD24+, and CD24+CD29+. We correlated concentrations of putative breast stem-cell/progenitor subpopulations, quantified by flow cytometry, with concentrations of hematopoietic stem cells.

RESULTS

Mammary stem-cell phenotypes were identified in umbilical cord blood. The measured EpCAM+ subpopulation was positively correlated with concentrations of CD34+ and CD34+CD38- hematopoietic stem cells (both P=0.006). Additionally, EpCAM+CD49f+ and CD49f+CD24+ subpopulations were positively correlated to the CD34+ cells (P=0.03 and 0.008, respectively).

CONCLUSION

The positive association between measurable breast and hematopoietic stem cells in human umbilical cord blood suggests plausible mechanisms for a prenatal influence on breast cancer risk.

PTP1B deficiency exacerbates inflammation and accelerates leukocyte trafficking in vivo

It is reported that PTP1B limits cytokine signaling in vitro. However, PTP1B's function during inflammation in vivo is not known. In this report, we determined whether PTP1B deficiency affects allergic inflammation in vivo. Briefly, lungs of OVA-challenged PTP1B(-/-) mice had elevated numbers of eosinophils and eosinophil progenitors at 6 h after one OVA challenge and at 24 h after a third OVA challenge as compared with OVA-challenged wild-type mice. There was also an increase in numbers of CD11b(+)SiglecF(+)CD34(+)IL-5Rα(+) eosinophil progenitors in the bone marrow, peripheral blood, and spleens of OVA-challenged PTP1B(-/-) mice. Intravital microscopy revealed that, in OVA-challenged PTP1B(-/-) mice, blood leukocytes rapidly bound to endothelium (5-30 min), whereas, in wild-type mice, blood leukocytes bound to endothelium at the expected 6-18 h. Consistent with early recruitment of leukocytes, lung eotaxin and Th2 cytokine levels were elevated early in the PTP1B(-/-) mice. Interestingly, spleen leukocytes from PTP1B(-/-) mice exhibited an increased chemotaxis, chemokinesis, and transendothelial migration in vitro. In summary, PTP1B functions as a critical negative regulator to limit allergic responses.

Focal epilepsy associated with glioneuronal tumors

Glioneuronal tumors are an increasingly recognized cause of partial seizures that occur primarily in children and young adults. Focal epilepsy associated with glioneuronal tumors is often resistant to pharmacological treatment. The cellular mechanisms underlying the epileptogenicity of glioneuronal tumors remain largely unknown. The involved mechanisms are certain to be multifactorial and depend on specific tumor histology, integrity of the blood-brain barrier, characteristics of the peritumoral environment, circuit abnormalities, or cellular and molecular defects. Glioneuronal tumors presenting with epilepsy were observed to have relatively benign biological behavior. The completeness of the tumor resection is of paramount importance in avoiding tumor progression and malignant transformation, which are rare in cases of epileptogenic glioneuronal tumors. An evolving understanding of the various mechanisms of tumor-related epileptogenicity may also lead to a more defined surgical objective and effective therapeutic strategies, including antiepileptogenic treatments, to prevent epilepsy in at-risk patients.

Role of NFKB2 on the early myeloid differentiation of CD34+ hematopoietic stem/progenitor cells

To better understand the early events regulating lineage-specific hematopoietic differentiation, we analyzed the transcriptional profiles of CD34+ human hematopoietic stem and progenitor cells (HSPCs) subjected to differentiation stimulus. CD34+ cells were cultured for 12 and 40h in liquid cultures with supplemented media favoring myeloid or erythroid commitment. Serial analysis of gene expression (SAGE) was employed to generate four independent libraries. By analyzing the differentially expressed regulated transcripts between the un-stimulated and the stimulated CD34+ cells, we observed a set of genes that was initially up-regulated at 12h but were then down-regulated at 40h, exclusively after myeloid stimulus. Among those we found transcripts for NFKB2, RELB, IL1B, LTB, LTBR, TNFRSF4, TGFB1, and IKBKA. Also, the inhibitor NFKBIA (IKBA) was more expressed at 12h. All those transcripts code for signaling proteins of the nuclear factor kappa B pathway. NFKB2 is a subunit of the NF-κB transcription factor that with RELB mediates the non-canonical NF-κB pathway. Interference RNA (RNAi) against NFKB1, NFKB2 and control RNAi were transfected into bone marrow CD34+HSPC. The percentage and the size of the myeloid colonies derived from the CD34+ cells decreased after inhibition of NFKB2. Altogether, our results indicate that NFKB2 gene has a role in the early commitment of CD34+HSPC towards the myeloid lineage.

Haploidentical bone marrow transplantation in primary immune deficiency: stem cell selection and manipulation

Since the early 1980s T-cell depletion has allowed haploidentical bone marrow transplantation to be performed in patients with primary immunodeficiency for whom a matched sibling donor was not available, without causing severe graft versus host disease (GVHD). This review article presents the available data in the literature on survival, GVHD, and immune reconstitution in different categories of patients, with special emphasis on the impact of different T-cell depletion methods.

Haemopoietic processes in allergic disease: eosinophil/basophil development

Haemopoietic myeloid progenitors contribute to the ongoing recruitment of pro-inflammatory cells, such as eosinophils and basophils (Eo/B), to target tissue sites in allergic diseases. It is apparent that the development of allergic inflammation is critically dependent on the ability of the bone marrow to support the proliferation, differentiation and mobilization of haemopoietic progenitors. The haemopoietic inductive microenvironment in the bone marrow is crucial for providing signals necessary for maintenance of progenitor populations at varying stages of lineage commitment and permitting these cells to circulate in the bloodstream. Progenitors demonstrate responsiveness to specific cytokines, which varies with stage of differentiation. Pro-inflammatory signals, Th2 cytokines in particular, generated following allergen challenge, can impact on haemopoietic progenitor differentiation and mobilization, leading to accelerated Eo/B production. Allergen inhalation by allergic asthmatics induces a time-dependent change in cytokine levels within the bone marrow compartment, influencing differentiation of Eo/B progenitors, as evidenced by the relationship between increased bone marrow IL-5 levels and Eo/B production. It is proposed that inhaled allergen induces trafficking of IL-5-producing T lymphocytes to the bone marrow, further promoting eosinophilopoiesis through IL-5R signalling. In this manner, Th2 lymphocyte trafficking from the airway may regulate events occurring in the bone marrow. Negative regulators of Eo/B differentiation, including Th1 cytokines, may prove to be important for restoring homeostasis. Eo/B progenitors are also altered in cord blood of infants at risk of atopy and asthma, offering a potential biomarker for, and raising the possibility that Eo/B progenitors are directly involved in the development of allergic disease. For example, changes in the expression of haemopoietic cytokine receptors on cord blood progenitor cells are associated with maternal allergic sensitization, atopic risk and its development, suggesting that haemopoietic processes underlying the allergic phenotype may begin to evolve in the perinatal period.

P-Selectin–Coated Microtube for Enrichment of CD34+ Hematopoietic Stem and Progenitor Cells from Human Bone Marrow

Background: Enrichment and purification of hematopoietic stem and progenitor cells (HSPCs) is important in transplantation therapies for hematologic disorders and in basic stem cell research. Primitive CD34+ HSPCs have demonstrated stronger rolling adhesion on selectins than mature CD34− mononuclear cells (MNCs). We have exploited this differential rolling behavior to capture and purify HSPCs from bone marrow by perfusing MNCs through selectin-coated microtubes.

Methods: Bone marrow MNCs were perfused through the cell-capture microtubes coated with adhesion molecules. We washed the device lumen and visualized and estimated captured cells by video microscopy. Adherent cells were eluted by high shear, calcium-free buffer, and air embolism. We used immunofluorescence staining followed by flow cytometry to analyze CD34+ HSPCs.

Results: CD34+ HSPC purity of cells captured in adhesion molecule–coated devices was significantly higher than the fraction of CD34+ cells found in bone marrow MNCs [mean (SE) 2.5% (0.8%)]. P-selectin–coated surfaces yielded 16% to 20% CD34+ cell purity, whereas antibody-coated surfaces yielded 12% to 18%. Although CD34+ cell purity was comparable between selectin and antibody surfaces, the total number of CD34+ HSPCs captured was significantly higher in P-selectin devices (approximately 5.7 × 104 to 7.1 × 104) than antibody devices (approximately 1.74 × 104 to 2.61 × 104).

Conclusions: P-selectin can be used in a compact flow device to capture HSPCs. Selectin-mediated capture of CD34+ HSPCs resulted in enrichment approximately 8-fold higher than the CD34+ cell population from bone marrow MNCs. This study supports the hypothesis that flow-based, adhesion molecule–mediated capture may be a viable alternative approach to the capture and purification of HSPCs.

Expression of CD34 as a novel marker for glioneuronal lesions associated with chronic intractable epilepsy

The spectrum of glioneuronal lesions underlying intractable epilepsies includes malformative pathologies like focal cortical dysplasia (FCD); and neoplastic lesions like gangliogliomas (GG) and dysembryoplastic neuroepithelial tumours (DNT). These may occur either singly or as dual lesions, having simultaneous presence of both elements. Currently, the relationship between the malformative and neoplastic glioneuronal lesions is poorly understood. Recently, CD34, a stem cell marker transiently expressed during early neurulation, has been identified in these tumours. This study was undertaken to (i) evaluate the role of CD34 as a diagnostic marker for glioneuronal lesions of epilepsy, namely, GG, DNT and FCD, and (ii) attempt to define the relationship among these lesions, using CD34 as a marker. Tissues resected from 47 patients with intractable epilepsy due to glioneuronal lesions (GG, FCD, DNT) were studied. These were evaluated for CD34 expression, using immunohistochemistry. Dysplastic or atypically differentiated neural precursors which could not be identified on routine haematoxylin and eosin (H&E) staining were highlighted by CD34 immunostaining. The pattern of immunostaining was diffuse in GGs, unlike FCDs, wherein cells were present singly or in small clusters. However, cases of DNT and control tissue were largely CD34-immunonegative. Based on these findings, we propose a possible common origin of GG and FCD, from a bipotent precursor that undergoes abnormal glioneuronal development, while DNTs possibly have a different origin. The CD34-immunoreactive cells represent dysplastic or undifferentiated neural precursors, which may signify a valuable marker for the diagnostic evaluation of neoplastic and/or malformative pathologies in patients with intractable epilepsy.

Beyond mere markers: functions for CD34 family of sialomucins in hematopoiesis

CD34, podocalyxin, and endoglycan are members of a family of single-pass transmembrane proteins that show distinct expression on early hematopoietic precursors and vascular-associated tissue. In spite of the fact that the expression of CD34 on these early progenitors has been known for over 20 yr and used clinically in hematopoietic stem cell transplantation for more than 15 yr, little is known about its exact role or function. More recently, CD34 expression has been shown to distinguish activated early progenitors from quiescent cells. With the subsequent identification of podocalyxin and endoglycan as related family members also expressed on early progenitor cells, attention is slowly shifting toward understanding how these molecules might contribute to progenitor function and behavior. In this review we examine the existing evidence and propose testable models to reveal the importance of these molecules for stem and progenitor cell function.

Beyond mere markers: functions for CD34 family of sialomucins in hematopoiesis

CD34, podocalyxin, and endoglycan are members of a family of single-pass transmembrane proteins that show distinct expression on early hematopoietic precursors and vascular-associated tissue. In spite of the fact that the expression of CD34 on these early progenitors has been known for over 20 yr and used clinically in hematopoietic stem cell transplantation for more than 15 yr, little is known about its exact role or function. More recently, CD34 expression has been shown to distinguish activated early progenitors from quiescent cells. With the subsequent identification of podocalyxin and endoglycan as related family members also expressed on early progenitor cells, attention is slowly shifting toward understanding how these molecules might contribute to progenitor function and behavior. In this review we examine the existing evidence and propose testable models to reveal the importance of these molecules for stem and progenitor cell function.

Intestinal stromal tumors in a simian immunodeficiency virus-infected, simian retrovirus-2 negative rhesus macaque (Macaca mulatta)

Multifocal submucosal stromal tumors were diagnosed in a 5.5-year-old rhesus macaque (Macaca mulatta) experimentally infected with simian immunodeficiency virus, strain SIVsmE660, and CD4+ T cell depleted. The animal was negative for simian retroviruses, SRV-1, -2, and -5. Polymerase chain reaction analysis of DNA from tumor and spleen tissue revealed abundant, preferential presence of retroperitoneal fibromatosis herpesvirus, the macaque homologue of the Kaposi sarcoma-associated herpesvirus (human herpesvirus-8), in the tumors. This was corroborated by demonstration of viral latent nuclear antigen-1 in the nuclei of a majority of the spindeloid tumor cells. Low levels of an additional macaque herpesvirus, rhesus rhadinovirus, were also detected in the spleen and tumor tissues. The spindeloid cells labeled positively for vimentin and CD117 but were negative for CD31, CD68, desmin, and smooth muscle cell actin. Collectively, these findings suggest a relation to but not absolute identity with simian mesenchymoproliferative disorders (MPD) or typical gastrointestinal stromal tumors (GISTs).

Eosinophil function in allergic inflammation: from bone marrow to tissue response

The role of the eosinophil in the pathophysiology of allergy and asthma has been the focus of intense interest during the past two decades. Although the presence of eosinophils in humans with allergy and asthma is well established, the precise role of this cell in human and animal tissue response is still unclear. However, recent developments in research on many organ systems have provided novel insights into the possible underlying role of the eosinophil in both allergic and nonallergic inflammation. In this review, we examine the pathways associated with eosinophil recruitment and activation, and discuss these findings with reference to clinically defined categories.

CD34-immunoreactive balloon cells in cortical malformations

Balloon cells are histopathological hallmarks of various cortical malformations, i.e., focal cortical dysplasia (Taylor's type, FCD IIb), hemimegalencephaly (HME) or cortical tubers (tuberous sclerosis, TSC). Whether this intriguing cell type results from similar pathogenetic pathways remains to be shown. Here, we analyzed the immunohistochemical distribution pattern of the CD34 epitope in surgical specimens from 34 patients with FCD IIb, compared to that of 6 patients with TSC and 3 patients with HME. In normal brain, CD34 occurs only transiently during neurulation, but cannot be detected in mature neuroectodermal cell progenies. In contrast, 58% of our patients showed CD34 immunoreactivity within a subpopulation of balloon cells. Interestingly, CD34-positive balloon cells were confined to the white matter, but never observed in neocortical layers. Furthermore, balloon cells expressing neurofilament protein were also restricted to white matter, whereas GFAP-positive balloon cells were observed either in white or gray matter location. Clinical characteristics did not significantly differ between patients with CD34-positive versus CD34-negative lesions. No significant correlation was found between CD34 expression and genetic alterations of the TSC1 gene, which is affected in many FCD and TSC patients and which plays a role in the regulation of cell size. Further studies are warranted to clarify the restricted expression of CD34 in balloon cells of the white matter.

Human embryonic stem cell-derived CD34+ cells: efficient production in the coculture with OP9 stromal cells and analysis of lymphohematopoietic potential

Embryonic stem (ES) cells have the potential to serve as an alternative source of hematopoietic precursors for transplantation and for the study of hematopoietic cell development. Using coculture of human ES (hES) cells with OP9 bone marrow stromal cells, we were able to obtain up to 20% of CD34+ cells and isolate up to 10(7) CD34+ cells with more than 95% purity from a similar number of initially plated hES cells after 8 to 9 days of culture. The hES cell-derived CD34+ cells were highly enriched in colony-forming cells, cells expressing hematopoiesis-associated genes GATA-1, GATA-2, SCL/TAL1, and Flk-1, and retained clonogenic potential after in vitro expansion. CD34+ cells displayed the phenotype of primitive hematopoietic progenitors as defined by co-expression of CD90, CD117, and CD164, along with a lack of CD38 expression and contained aldehyde dehydrogenase-positive cells as well as cells with verapamil-sensitive ability to efflux rhodamine 123. When cultured on MS-5 stromal cells in the presence of stem cell factor, Flt3-L, interleukin 7 (IL-7), and IL-3, isolated CD34+ cells differentiated into lymphoid (B and natural killer cells) as well as myeloid (macrophages and granulocytes) lineages. These data indicate that CD34+ cells generated through hES/OP9 coculture display several features of definitive hematopoietic stem cells.

Intracerebral transplantation of marrow stromal cells cultured with neurotrophic factors promotes functional recovery in adult rats subjected to traumatic brain injury

This study was designed to examine the effects of bone marrow stromal cells (MSCs) cultured in vitro with or without neurotrophic factors transplanted into adult male Wistar rats after traumatic brain injury (TBI). MSCs harvested from donor Wistar rats were cultured with either the culture medium containing brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) or the same culture media without these factors. Control and experimental animals were then traumatized by a controlled cortical impact. One day after the impact, either the placebo or the washed MSCs (1 x 10(6)) cultured with or without NGF and BDNF were transplanted adjacent to the site of injury. In addition, a nontreated group of rats was employed. Motor function of the animals was evaluated by the Rotarod test both before and after the injury. All animals were sacrificed 8 days after TBI, and the brain sections were stained by H&E as well as for immunohistochemistry. MSCs survived and migrated toward the injury site. The group treated with MSCs cultured with BDNF and NGF had a significantly higher number of engrafted cells than the group treated with MSCs cultured without BDNF and NGF (6.3 x 10(4) +/- 4250 compared to 4.1 x 10(4) +/- 3684; p < 0.05). In both groups, some transplanted MSCs showed positive staining for astrocytic (GFAP) and neuronal markers (Neu N and MAP-2). The groups treated with MSCs had better motor function than the groups receiving no treatment or receiving the placebo (PBS; p < 0.05); however, the improvement reached statistical significance only in the group treated with MSCs cultured with neurotrophic factors. These data suggest that more robust motor function described in rats subjected to TBI and treated with intracerebral transplantation of MSCs was achieved by the use of MSCs cultured with neurotrophic factors.

CD34 is a specific marker of mature murine mast cells

OBJECTIVE

CD34 is a 90- to 120-kDa cell surface sialomucin that is widely used for the enrichment of human hematopoietic stem cells (HSCs) because of its selective expression on progenitor cells and absence on mature hematopoietic cells. Recently we found that CD34 is the prototypic member of a family of three proteins with similar structure and gene organization. In light of this observation, we further examined the distribution of CD34 family members in the mouse.

MATERIALS AND METHODS

Hematopoietic cell lines and primary tissues were evaluated for CD34 mRNA expression by Northern blot and protein expression by cell surface immunofluorescence. To confirm specific reactivity of the CD34 antibody, cells from CD34-deficient mice were used as controls.

RESULTS

Although CD34 mRNA was undetectable in all murine progenitor cell lines tested, high level expression was detected for bone marrow-derived mast cells (BMMCs). Likewise, cell surface immunofluorescence confirmed that CD34 is expressed by BMMCs and by in vivo peritoneal mast cells. No protein expression was observed for CD34-deficient mast cells. In addition, our data show that mast cells highly express the stem cell antigen Sca-1 and the well-known stem cell and mast cell antigen c-kit.

CONCLUSIONS

Our results demonstrate that, contrary to current dogma, CD34 is expressed by one mature hematopoietic lineage: mast cells. Our data also demonstrate that antigenically, murine mast cells and their precursors closely resemble HSCs and suggest caution should be used in the phenotypic characterization of HSCs to prevent mast cell contamination of stem cell preparations.

Mechanisms of eosinophil recruitment and activation

The role of the eosinophil in the pathophysiology of allergy and asthma has been the focus of intense interest during the last two decades. While the presence of eosinophils in humans with allergy and asthma is well established, the precise role of this cell in humans and in animal models is less clear. However, recent developments in research on many organ systems have provided novel insights into the possible underlying role of the eosinophil in both allergic and nonallergic inflammation. This review examines the pathways associated with eosinophil recruitment and activation and discusses these findings, with reference to clinically defined categories.

Quantitative expression of adhesion molecules on granulocyte colony-stimulating factor-mobilized peripheral blood, bone marrow, and cord blood CD34+ cells

The purpose of this study is to investigate the function of the main adhesion receptors on CD34(+) cells during hematopoietic stem cell transplantation. Expression was quantified by flow cytometry using calibration beads. CD34(+) cells were isolated from either bone marrow (BM), cord blood (CB), or peripheral blood (PB) from study patients and a control group after granulocyte colony-stimulating factor (G-CSF) administration. The study of the CD34(+) cell differentiation showed that CD34(+) cells are mainly CD38(+) and HLA-DR(+), whatever the type of harvest. However, quantitative analysis elicited a weaker expression of CD38 on PB and CB CD34(+) cells in comparison to BM CD34(+) cells. The proportions of CD34(+)/CD49d(+) and CD34(+)/CD49e(+) were smaller on PB cells, without quantitative expression variation. This phenotypic variation promotes CD34(+) cells to exit from BM into circulation, inducing the mobilization. The homing of the CD34(+) cells to the BM involves the CD62L receptor. The expression of this receptor was found to be more frequent and stronger on PB cells than on BM or CB cells. The CD11b, CD18, and CD54 receptors are implicated in CD34(+) cell adhesion to BM microenvironment. No significant variation in CD34(+)/CD11b(+) and CD34(+)/CD18(+) cell frequency was noted. Moreover, the CD54 receptor was more frequently expressed on CB and PB cells. Quantitative analysis revealed that CD18 was more strongly expressed on BM than on PB cells to promote progenitors adhesion by interacting with stromal cells. Finally, the quantitative expression of the main receptors on CD34(+) cells explained cellular functions during the different steps of hematopoietic stem cells transplantation.

[Quantitative expression of the adhesion receptors VLA-4, VLA-5, L-selectin, MAC-1, and ICAM-1 on the surface of CD34+ cells]

The aim of this work was to quantify by flow cytometry the main adhesion receptors on CD34+ cells. These cells were isolated from bone marrow (BM) or mobilized peripheral blood (PB). The proportions of CD34+/CD49d+ and CD34+/CD49e+ are weaker on PB cells, without quantitative expression variation. This phenotypic variation may induce CD34+ cells exist from BM into circulation, promoting the mobilization. The homing to the BM implicate the CD62L receptor, which expression was found more frequently and stronger on PB cells than on BM. The CD11b, CD18 and CD54 receptors are implicated in CD34+ cells adhesion to BM micro-environment. No significant variation in CD34+/CD11b+ and CD34+/CD18+ cells frequency was noted. Moreover, CD54 receptor was more frequently expressed on PB cells. Quantitative analysis revealed that CD18 was more strongly expressed on BM than on PB cells. This quantitative variation could promote progenitor adhesion by interacting with stromal cells. Finally, quantitative expression of the main receptors on CD34+ cells provides an original option for studying CD34+ cells during the mobilization, the homing or the adhesion to BM micro-environment.

Human reserve pluripotent mesenchymal stem cells are present in the connective tissues of skeletal muscle and dermis derived from fetal, adult, and geriatric donors

This study details the profile of 13 cell surface cluster differentiation markers on human reserve stem cells derived from connective tissues. Stem cells were isolated from the connective tissues of dermis and skeletal muscle derived from fetal, mature, and geriatric humans. An insulin/dexamethasone phenotypic bioassay was used to determine the identity of the stem cells from each population. All populations contained lineage-committed myogenic, adipogenic, chondrogenic, and osteogenic progenitor stem cells as well as lineage-uncommitted pluripotent stem cells capable of forming muscle, adipocytes, cartilage, bone, fibroblasts, and endothelial cells. Flow cytometric analysis of adult stem cell populations revealed positive staining for CD34 and CD90 and negative staining for CD3, CD4, CD8, CD11c, CD33, CD36, CD38, CD45, CD117, Glycophorin-A, and HLA DR-II.

Evidence for developmental precursor lesions in epilepsy-associated glioneuronal tumors

The etiology and pathogenesis of epilepsy-associated local lesions remain largely unknown. Histopathologically, the most frequent lesions comprise gangliogliomas and glioneuronal malformations, i.e., hamartias or hamartomas, with a preferred location in the temporal lobe of young patients. A characteristic histopathological admixture of glial and neuronal elements, the focal appearance and the benign clinical behaviour suggest a malformative nature. So far, no molecular genetic alterations specifically involved in the pathogenesis of these glioneuronal lesions have been identified. However, immunohistochemical analysis revealed distinct distribution patterns of oncofetal antigens. The embryonic form of the neural cell adhesion molecule is present within glioneuronal hamartias, indicating an early migrational disorder. Recently, we have observed immunoreactivity for the stem cell marker CD34 in the majority of gangliogliomas and glioneuronal hamartomas. Based on these findings, we propose a common origin of gangliogliomas and glioneuronal hamartomas from a bipotent precursor that undergoes abnormal glioneuronal development.

Different vascular patterns of medulloblastoma and supratentorial primitive neuroectodermal tumors

Astrocytoma vasculature patterns differ according to histological grade of malignancy with glioblastoma multiforme (WHO grade IV) showing most extensive endothelial proliferation. Here, we determined whether the vascular patterns of medulloblastoma and supratentorial primitive neuroectodermal tumors (PNETs), which can be hardly distinguished histopathologically, differ. We evaluated the spatial organization of vessels in medulloblastomas and PNETs using antibodies to von Willebrand factor (vWF) and CD34. Medulloblastoma capillaries showed slight endothelial cell hyperplasia. Microvessels sprouted from the capillaries and formed glomeruloid clusters. There were areas with chains of unopposed endothelial cells (3-10 cells). Supratentorial PNETs had highly branched capillaries with extensive endothelial cell hyperplasia. Glomeruloid arrays of microvessels extended from the capillaries. Small fragments of endothelial tubes were scattered throughout the tumor. Therefore, medulloblastomas and supratentorial PNETs showed different spatial organization of tumor vessels which can be used for differentiation of each tumor entity. These vascular patterns may reflect different tumor derived angiogenic stimuli.

Cell analysis for hematopoietic stem/progenitor cell transplantation

Cytometric analysis has become an important aspect in the quality control of cells in all phases of hematopoietic cell transplantation. In the stage of donor conditioning the counting of stem and progenitor cells is important and several reliable single platform tests for CD34+ cells have become available recently. It has been shown, that the count of certain subsets of CD34 may predict best time for harvesting stem cells better than just CD34. In many cases manipulation of the cell sample after collection from the donor is necessary before the cells are adequate for transplantation. Characterization of the resulting cell preparations requires reliable quantitative analysis of a variety of cell types like the enumeration of T-cells at the level of one in ten thousand for some allogeneic transplantations. It is discussed how these clinical requirements will need a refinement of cytometric procedures to achieve adequate clinical decisions.

How should CD34+ cells be analysed? A study of three classes of antibody and five leucocyte preparation procedures

For patients undergoing stem cell transplantation after intensive marrow ablative therapy it is important to enumerate the CD34+ stem cells in peripheral blood so that the harvest can be timed in order to maximize the number of cells collected by leucophoresis for subsequent haematopoietic reconstitution. The use of rapid flow cytometric techniques for the determination CD34+ leucocyte numbers has been advocated, although there is no consensus as to the best method. In this study, we have examined the effects of preparation procedures for flow cytometry on the binding of four CD34 antibodies (Immu-133, QBEND-10, HPCA2 and BIRMA-K3) to the three classes of epitopes on leucocytes. Whole blood, bone marrow and leucophoresis samples were analysed either directly after labelling with a vital nuclear dye (LDS-751) and fluorochrome-conjugated antibodies or after additional erythrocyte lysis and leucocyte fixation using four commercially available reagents (Q-Prep, OptiLyse B, OptiLyse C and FACS Lysing Solution). By comparison with the results obtained from viable leucocytes in unmanipulated samples, it was found that the binding of all four antibodies could be affected by lysis and fixation procedures and that the binding of the class I antibody Immu-133 was most markedly decreased. We conclude that CD34+ cells are best analysed using a whole blood procedure in which nucleated cells are identified by their side light scatter and the fluorescence associated with a vital nuclear dye (in this instance LDS-751) and the CD34+ cells are detected with fluorescein isothiocyanate- or phycoerythrin-conjugated antibodies.

Marrow stromal cells as stem cells for nonhematopoietic tissues

Marrow stromal cells can be isolated from other cells in marrow by their tendency to adhere to tissue culture plastic. The cells have many of the characteristics of stem cells for tissues that can roughly be defined as mesenchymal, because they can be differentiated in culture into osteoblasts, chondrocytes, adipocytes, and even myoblasts. Therefore, marrow stromal cells present an intriguing model for examining the differentiation of stem cells. Also, they have several characteristics that make them potentially useful for cell and gene therapy.

Immunomagnetic selection of CD34+ cells from fresh peripheral blood mononuclear cell preparations using two different separation techniques

Immunomagnetic separation using anti-CD34 monoclonal antibodies and paramagnetic microspheres has been used to enrich hematopoietic stem cells from human bone marrow, whole cord blood, or mobilized peripheral blood mononuclear cell collections. The aim of the present study was to compare the efficacy of two different CD34+ cell selection techniques in enriching CD34+ cells from mobilized fresh peripheral blood mononuclear cells. Using the magnetic cell sorter (MACS), the final product purity was 74.1% CD34+ cells (starting population 2.3% +/- 3.3%) with a 60.3% CD34+ cell yield. Using Dynabeads and subsequent chymopapain incubation for releasing the target cells from the beads (Isolex system), the released cells contained 83.3% CD34+ cells (starting population 1.2% +/- 0.7%) with a 43.4% yield. These results indicate that CD34+ cells can be isolated with high purity from fresh leukapheresis products using both immunomagnetic techniques.