Stem Cell Transplantation in the Fetus

BACKGROUND

In utero transplantation (IUT) of hematopoietic stem cells has the potential to treat a large number of hematologic and metabolic diseases amenable to partial replacement of the hematopoietic system.

METHODS

A review of the literature was conducted that focused on the clinical and experimental experience with IUT and, in this context, the development of the hematopoietic and immune systems.

RESULTS

Successful application of IUT has been limited to the treatment of various types of immunodeficiencies that affect lymphocyte development and function. Other congenital defects such as the thalassemias have not resulted in clinically significant engraftment. Recent efforts at understanding and overcoming the barriers to engraftment in the fetus have focused on providing a selective advantage to donor stem cells and fostering immune tolerance toward the donor cells. The critical cellular components of the graft that promote engraftment and tolerance induction are being evaluated in animal models. Improvements in engraftment have resulted from the inclusion of T cells and/or dendritic cells in the graft, as well as a strategy of combined prenatal and postnatal transplantation.

CONCLUSIONS

The advantages, necessity, and benefits of early treatment will continue to encourage development of IUT as a means to treat hematopoietic and other types of birth defects.

The human chorion contains definitive hematopoietic stem cells from the fifteenth week of gestation

We examined the contribution of the fetal membranes, amnion and chorion, to human embryonic and fetal hematopoiesis. A population of cells displaying a hematopoietic progenitor phenotype (CD34⁺⁺ CD45^low) of fetal origin was present in the chorion at all gestational ages, associated with stromal cells or near blood vessels, but was absent in the amnion. Prior to 15 weeks of gestation, these cells lacked hematopoietic in vivo engraftment potential. Differences in the chemokine receptor and β1 integrin expression profiles of progenitors between the first and second trimesters suggest that these cells had gestationally regulated responses to homing signals and/or adhesion mechanisms that influenced their ability to colonize the stem cell niche. Definitive hematopoietic stem cells, capable of multilineage and long-term reconstitution when transplanted in immunodeficient mice, were present in the chorion from 15-24 weeks gestation, but were absent at term. The second trimester cells also engrafted secondary recipients in serial transplantation experiments. Thus, the human chorion contains functionally mature hematopoietic stem cells at mid-gestation.

Integrin α4-positive human trophoblast progenitors: functional characterization and transcriptional regulation

STUDY QUESTION

What are the functional characteristics and transcriptional regulators of human trophoblast progenitor cells (TBPCs)?

SUMMARY ANSWER

TBPC lines established from the human smooth chorion by cell sorting for integrin α4 expressed markers of stemness and trophoblast (TB) stage-specific antigens, invaded Matrigel substrates and contributed to the cytotrophoblasts (CTBs) layer of smooth chorion explants with high-mobility group protein HMGI-C (HMGA2) and transcription factor GATA-4 (GATA4) controlling their progenitor state and TB identity.

WHAT IS KNOWN ALREADY

Previously, we reported the derivation of TBPC lines by trypsinization of colonies that formed in cultures of chorionic mesenchyme cells that were treated with an activin nodal inhibitor. Microarray analyses showed that, among integrins, α4 was most highly expressed, and identified HMGA2 and GATA4 as potential transcriptional regulators.

STUDY DESIGN, SIZE, DURATION

The aim of this study was to streamline TBPC derivation across gestation. High-cell surface expression of integrin α4 enabled the use of a fluorescence-activated cell sorter (FACS) approach for TBPC isolation from the human smooth chorion (n = 6 lines). To confirm their TBPC identity, we profiled their expression of stemness and TB markers, and growth factor receptors. At a functional level, we assayed their invasive capacity (n = 3) and tropism for the CTB layer of the smooth chorion (n = 3). At a molecular level, we studied the roles of HMGA2 and GATA4.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Cells were enzymatically disassociated from the human smooth chorion across gestation. FACS was used to isolate the integrin α4-positive population. In total, we established six TBPC lines, two per trimester. Their identity was determined by immunolocalization of a suite of antigens. Function was assessed via Matrigel invasion and co-culture with explants of the human smooth chorion. An siRNA approach was used to down-regulate HMGA2 and GATA4 expression and the results were confirmed by immunoblotting and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses. The endpoints analyzed included proliferation, as determined by 5-bromo-2'-deoxyuridine (BrDU) incorporation, and the expression of stage-specific antigens and hormones, as determined by qRT-PCR and immunostaining approaches.

MAIN RESULTS AND THE ROLE OF CHANCE

As with the original cell lines, the progenitors expressed a combination of human embryonic stem cell and TB markers. Upon differentiation, they primarily formed CTBs, which were capable of Matrigel invasion. Co-culture of the cells with smooth chorion explants enabled their migration through the mesenchyme after which they intercalated within the chorionic CTB layer. Down-regulation of HMGA2 showed that this DNA-binding protein governed their self-renewal. Both HMGA2 and GATA4 had pleitropic effects on the cells' progenitor state and TB identity.

LIMITATIONS, REASONS FOR CAUTION

This study supported our hypothesis that TBPCs from the chorionic mesenchyme can contribute to the subpopulation of CTBs that reside in the smooth chorion. In the absence of in vivo data, which is difficult to obtain in humans, the results have the limitations common to all in vitro studies.

WIDER IMPLICATIONS OF THE FINDINGS

The accepted view is that progenitors reside among the villous CTB subpopulation. Here, we show that TBPCs also reside in the mesenchymal layer of the smooth chorion throughout gestation. We theorize that they can contribute to the CTB layer in this region. This phenomenon may be particularly important in pathological situations when CTBs of the smooth chorion might provide a functional reserve for CTBs of the placenta proper.

STUDY FUNDING/COMPETING INTERESTS

Research reported in this publication was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under award P50HD055764. O.G., N.L., K.O., A.P., T.G.-G., M.K., A.B., M.G. have nothing to disclose. S.J.F. received licensing fees and royalties from SeraCare Life Sciences for trisomic TBPC lines that were derived according to the methods described in this manuscript.

TRIAL REGISTRATION NUMBER

N/A.

Preeclampsia and Inflammatory Preterm Labor Alter the Human Placental Hematopoietic Niche

BACKGROUND

The human placenta is a source of hematopoietic stem and progenitor cells (HSPCs). The RUNX1 transcription factor is required for the formation of functional HSPCs. The impact of preeclampsia (PE) and preterm labor (PTL, spontaneous preterm labor [sPTL] and inflammatory preterm labor [iPTL]) on HSPC localization and RUNX1 expression in the human placenta is unknown.

METHODS

We compared the frequency and density of HSPC in control samples from sPTL (n = 6) versus PE (n = 6) and iPTL (n = 6). We examined RUNX1 protein and RNA expression in placentas from normal pregnancies (5-22 weeks, n = 8 total) and in placentas from the aforementioned pregnancy complications (n = 5/group).

RESULTS

Hematopoietic stem and progenitor cells were rare cell types, associated predominantly with the vasculature of placental villi. The HSPC density was greater in the chorionic plate (CP) compared to the villi (P < .001) and greater in PE and iPTL samples as compared to controls within the CP (not significant) and overall (P < .05). During the fetal period, RUNX1 was expressed in the mesenchyme of the CP and villi. Inflammatory PTL samples were more likely to exhibit intraluminal RUNX1(+) cell populations (P < .001) and RUNX1(+) cell clusters attached to arterial endothelial cells.

CONCLUSION

Placental HSPCs likely arise from hematopoietic niches comprised RUNX1(+) mesenchyme and vascular endothelium. Pregnancy complications that result in preterm birth differentially affect placental HSPC localization and RUNX1 expression. Our results support previous findings that inflammation positively regulates hematopoiesis. We present new evidence that hemogenic endothelium may be active at later stages of human fetal development in the context of inflammation.

Identification of small activating RNAs that enhance endogenous OCT4 expression in human mesenchymal stem cells

Ectopic overexpression of transcription factors has been used to reprogram cell fate. For example, virus-mediated overexpression of four transcription factors OCT4, SOX2, MYC, and KLF4, known as Yamanaka factors, can convert somatic cells to induced pluripotent stem (iPS) cells. However, gene-specific switch-on of endogenous gene production without the use of foreign DNA remains a challenge. The small RNA machinery that comprised small RNAs and Argonaute proteins is known to silence gene expression, but can be repurposed to activate gene expression when directed to gene promoters, a phenomenon known as RNA activation or RNAa. By screening of dsRNAs targeting OCT4 promoter, we identified a small activating RNA (saRNA) that activated OCT4 expression in several types of human mesenchymal stem cells (MSCs). We found that saRNA-induced OCT4 activation can be further enhanced by a histone deacetylase inhibitor, valproic acid. Furthermore, introducing OCT4 saRNA in combination with viruses encoding the remaining three Yamanaka factors (SOX2, MYC, and KLF4) into MSCs led to the derivation of partially reprogrammed iPS cells. Findings from this study suggest that, with further optimization, RNAa can be a powerful tool to reprogram cell fate by inducing the expression of endogenous genes.

The adult livers of immunodeficient mice support human hematopoiesis: evidence for a hepatic mast cell population that develops early in human ontogeny

The liver plays a vital role in hematopoiesis during mammalian prenatal development but its hematopoietic output declines during the perinatal period. Nonetheless, hepatic hematopoiesis is believed to persist into adulthood. We sought to model human adult-liver hematopoiesis by transplantation of fetal and neonatal hematopoietic stem cells (HSCs) into adult immunodeficient mice. Livers were found to be engrafted with human cells consisting primarily of monocytes and B-cells with lesser contributions by erythrocytes, T-cells, NK-cells and mast-cells. A resident population of CD117(++)CD203c(+) mast cells was also documented in human midgestation liver, indicating that these cells comprise part of the liver's resident immune cell repertoire throughout human ontogeny. The murine liver was shown to support human multilineage hematopoiesis up to 321 days after transplant. Evidence of murine hepatic hematopoiesis was also found in common mouse strains as old as 2 years. Human HSC engraftment of the murine liver was demonstrated by detection of high proliferative-potential colony-forming cells in clonal cultures, observation of CD38-CD34(++) and CD133(+)CD34(++) cells by flow cytometry, and hematopoietic reconstitution of secondary transplant recipients of chimeric liver cells. Additionally, chimeric mice with both hematopoietic and endothelial reconstitution were generated by intrasplenic injection of immunodeficient mice with liver specific expression of the urokinase-type plasminogen activator (uPA) transgene. In conclusion, the murine liver is shown to be a hematopoietic organ throughout adult life that can also support human hematopoiesis in severely immunodeficient strains. Further humanization of the murine liver can be achieved in mice harboring an uPA transgene, which support engraftment of non-hematopoietic cells types. Thus, offering a model system to study the interaction of diverse human liver cell types that regulate hematopoiesis and immune function in the liver.

Maternal decidual macrophages inhibit NK cell killing of invasive cytotrophoblasts during human pregnancy

Human pregnancy is an immunological paradox. Semiallogeneic (fetal) placental cells (extravillous cytotrophoblasts [CTBs]) invade the uterine lining (decidua), which contains a unique decidual natural killer (dNK) cell population, identified by the cell surface phenotype CD56(bright) CD16(-) CD3(-) and CD14(+) CD206(+) macrophages (dMac). Previous reports suggested that human dNK cells are not a threat to the fetoplacental unit because they are anergic. In contrast, here we showed that purified and exogenously stimulated dNK cells are capable killers of cellular targets, including semiallogeneic CTBs. However, dMacs in the decidual leukocyte (DL) population restrained dNK killing through a transforming growth factor beta1 (TGF-beta1)-dependent mechanism. Our findings support a new model whereby dNK cells, capable of killing CTBs, are prevented from doing so by neighboring macrophages, thus protecting the fetal cells from NK cell attack. We speculate that this mechanism would inhibit dNK cell-mediated killing, even under conditions where high levels of cytokines may stimulate dNK cells, which could pose a threat to the developing placenta.

Human placenta and chorion: potential additional sources of hematopoietic stem cells for transplantation

BACKGROUND

Hematopoietic stem cell (HSC) transplantation is an essential element of medical therapy, leading to cures of previously incurable hematological and nonhematological diseases. Many patients do not find matched donors in a timely manner, which has driven efforts to find alternative pools of transplantable HSCs. The use of umbilical cord blood (UCB) as a source of transplantable HSCs began more than two decades ago. However, the use of UCB as a reliable source of HSCs for transplantation still faces crucial challenges: the number of HSCs present in a unit of UCB is usually sufficient for younger children but not for adults, and the persistent delayed engraftment often seen can result in high rates of infection and mortality.

STUDY DESIGN AND METHODS

We propose a new approach to a solution of these problems: a potential increase of the limited number of UCB-HSCs available by harvesting HSCs contained in the placenta and the fetal chorionic membrane available at birth.

RESULTS

We investigated the presence of hematopoietic progenitors and HSCs in human placenta and chorion at different gestational ages. The characterization of these cells was performed by flow cytometry and immunolocalization, and their functional status was investigated by transplanting them into immunodeficient mice.

CONCLUSION

HSCs are present in extraembryonic tissues and could be banked in conjunction to the UCB-HSCs. This novel approach could have a large impact on the field of HSC banking and, more crucially, on the outcome of patients undergoing this treatment by greatly improving the use of life-saving hematopoietic transplants.

Coexpression of CD14 and CD326 discriminate hepatic precursors in the human fetal liver

The molecular and cellular profile of liver cells during early human development is incomplete, complicating the isolation and study of hepatocytes, cholangiocytes, and hepatic stem cells from the complex amalgam of hepatic and hematopoietic cells, that is, the fetal liver. Epithelial cell adhesion molecule, CD326, has emerged as a marker of hepatic stem cells, and lipopolysaccharide receptor CD14 is known to be expressed on adult hepatocytes. Using flow cytometry, we studied the breadth of CD326 and CD14 expression in midgestation liver. Both CD45(+) hematopoietic and CD45(-) nonhematopoietic cells expressed CD326. Moreover, diverse cell types expressing CD326 were revealed among CD45(-) cells by costaining for CD14. Fluorescence-activated cell sorting was used to isolate nonhematopoietic cells distinguished by expression of high levels of CD326 and low CD14 (CD326(++)CD14(lo)), which were characterized for gene expression associated with liver development. CD326(++)CD14(lo) cells expressed the genes albumin, α-fetoprotein, hepatic nuclear factor 3α, prospero-related homeobox 1, cytochrome P450 3A7, α(1)-antitrypsin, and transferrin. Proteins expressed included cell-surface CD24, CD26, CD29, CD34, CD49f, CD243, and CD324 and, in the cytoplasm, cytokeratins-7/8 (CAM 5.2 antigen) and some cytokeratin-19. Cultured CD326(++)CD14(lo) cells yielded albumin(+) hepatocytes, cytokeratin-19(+) cholangiocytes, and hepatoblasts expressing both markers. Using epifluorescence microscopy we observed CD326 and CD14 expression on fetal hepatocytes comprising the liver parenchyma, as well as on cells associated with ductal plates and surrounding large vessels. These findings indicate that expression of CD14 and CD326 can be used to identify functionally distinct subsets of fetal liver cells, including CD326(++)CD14(lo) cells, representing a mixture of parenchymal cells, cholangiocytes, and hepatoblasts.

Requirement of retinoids for the expression of CD38 on human hematopoietic progenitors in vitro

BACKGROUND

Cells expressing high levels of CD34 and little or no CD38 comprise a primitive compartment of progenitors, thought to include hematopoietic stem cells. In this study we sought to determine the feasibility of using CD34 and CD38 as markers of hematopoietic differentiation in vitro, using retinoids to induce the expression of CD38.

METHODS

The effects over time of culture, sera and retinoids on the expression of CD34 and CD38 were determined using a base-medium lacking serum. Two early progenitor populations, isolated by FACS from human fetal liver, were studied: CD38(-)CD34(++) and CD38(+)CD34(++) cells. Additionally, HL-60 cells were adapted to grow in serum-deprived medium to study factors that control CD38 expression. Colony forming cell (CFC) assays and short-term expansion cultures were used to measure the effects of all-trans-retinoic acid (ATRA) oil the growth of fetal progenitors.

RESULTS

Fetal progenitors and HL-60 cells grown under serum-deprived conditions exhibited almost no CD38 expression. However, CD34 expression was observed on fetal progenitors and declined slowly over time. Addition of FBS or human serum restored CD38 expression to cultured cells, but at levels below those found on progenitors in vivo. Addition of ATRA or 9-cis-retinoic acid (9CRA) to cultures of fetal progenitors or HL-60 cells, resulted in a time- and dose-dependent increase in CD38 expression, ATRA being the more potent of the two retinoids. However, ATRA inhibited colony formation, reduced the expansion of CFC and accelerated the loss of CD34 expression at doses required for the induction of CD38 expression.

DISCUSSION

ATRA-induced CD38 expression on cells to levels comparable to those found on progenitors in vivo. ATRA also inhibited the growth of early progenitors, which was partly due to ATRA accelerating the differentiation of the progenitors. These findings indicate that CD34 and CD38 expression may be followed as markers of hematopoietic differentiation in vitro, but at the cost of culture conditions that are less than optimal for maintaining early progenitors.

A new role for the human placenta as a hematopoietic site throughout gestation

We investigated whether the human placenta contributes to embryonic and fetal hematopoietic development. Two cell populations--CD34(++)CD45(low) and CD34( +)CD45(low)--were found in chorionic villi. CD34(++) CD45(low) cells display many markers that are characteristic of multipotent primitive hematopoietic progenitors and hematopoietic stem cells. Clonogenic in vitro assays showed that CD34(++)CD45( low) cells contained colony-forming units-culture with myeloid and erythroid potential and differentiated into CD56(+) natural killer cells and CD19(+) B cells in culture. CD34(+)CD45(low) cells were mostly enriched in erythroid- and myeloid-committed progenitors. While the number of CD34(++)CD45(low) cells increased throughout gestation in parallel with placental mass. However, their density (cells per gram of tissue) reached its peak at 5 to 8 weeks, decreasing more than 7-fold from the ninth week onward. In addition to multipotent progenitors, the placenta contained intermediate progenitors, indicative of active hematopoiesis. Together, these data suggest that the human placenta is potentially an important hematopoietic organ, opening the possibility of banking placental hematopoietic stem cells along with cord blood for transplantation.

The human placenta is a hematopoietic organ during the embryonic and fetal periods of development

We studied the potential role of the human placenta as a hematopoietic organ during embryonic and fetal development. Placental samples contained two cell populations-CD34(++)CD45(low) and CD34(+)CD45(low)-that were found in chorionic villi and in the chorioamniotic membrane. CD34(++)CD45(low) cells express many cell surface antigens found on multipotent primitive hematopoietic progenitors and hematopoietic stem cells. CD34(++)CD45(low) cells contained colony-forming units culture (CFU-C) with myeloid and erythroid potential in clonogenic in vitro assays, and they generated CD56(+) natural killer cells and CD19(+)CD20(+)sIgM(+) B cells in polyclonal liquid cultures. CD34(+)CD45(low) cells mostly comprised erythroid- and myeloid-committed progenitors, while CD34(-) cells lacked CFU-C. The placenta-derived precursors were fetal in origin, as demonstrated by FISH using repeat-sequence chromosome-specific probes for X and Y. The number of CD34(++)CD45(low) cells increased with gestational age, but their density (cells per gram of tissue) peaked at 5-8 wk, decreasing more than sevenfold at the onset of the fetal phase (9 wk of gestation). In addition to multipotent progenitors, the placenta contained myeloid- and erythroid-committed progenitors indicative of active in situ hematopoiesis. These data suggest that the human placenta is an important hematopoietic organ, raising the possibility of banking placental hematopoietic stem cells along with cord blood for transplantation.

Maintenance of proliferative capacity and retroviral transduction efficiency of human fetal CD38(-)/CD34(++) stem cells

Methods for the efficient transduction and expansion of fetal hematopoietic stem cells could lead to novel in utero therapies for blood cell disorders and enzymatic deficiencies. Here we describe a new assay to measure rapidly the effects of cytokines on the differentiation or expansion of primitive progenitors and stem cells found among CD38(-)CD34(++) lineage() cells isolated from human midgestation liver. Importantly, conditions that otherwise supported the expansion of clonogenic progenitors reduced their proliferative capacity. A combination of megakaryocyte growth and development factor and granulocyte-macrophage colony-stimulating factor maintained proliferative potential while also yielding an intermediate level of progenitor expansion. Retroviral transduction was achieved using Moloney murine leukemia virus-based vectors. Freshly isolated candidate stem cells could be transduced at almost 17% efficiency by a 1-h exposure to virus with centrifugation to aid transduction. This was increased to a mean 35.5% transduction efficiency after 1 day of culture. Additionally, the transduction efficiency of candidate stem cells isolated from fetal placental blood was 33.0%. These findings encourage further investigation into the feasibility of ex utero gene therapy whereby fetal cells are isolated from the circulation, transduced, and expanded ex utero before being returned to the fetus.

Megakaryocyte growth and development factor is a potent growth factor for primitive hematopoietic progenitors in the human fetus

Megakaryocyte growth and development factor (MGDF), or thrombopoietin, has received considerable attention as a therapeutic agent for treating thrombocytopenia or for its use in the ex vivo culture of hematopoietic stem cells. MGDF is known to support the growth of a broad spectrum of hematopoietic precursors obtained from adult or neonatal tissues, but its effects on the growth of fetal progenitors and stem cells has not been studied. Human CD38(+)CD34(2+) progenitors and CD38(-)CD34(2+) cells, a population that contains stem cells, were isolated from midgestation liver and grown under defined conditions with MGDF and various cytokines known to support the growth of primitive hematopoietic precursors. In clonal assays of colony-forming cells (CFCs), MGDF supported the growth of 15-25% of candidate stem cells when combined with granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor (GM-CSF), flk-2/flt3 ligand, or stem cell factor. MGDF was observed to strongly support the early stages of hematopoiesis and expansion of high proliferative potential CFCs. More mature progenitors were expanded nearly 78-fold in 1 wk of culture with MGDF+SCF+GM-CSF. MGDF alone was also found to support the short-term (2 d) survival of CD38(-)CD34(2+) high proliferative potential CFCs. The effects of MGDF were more modest on CD38(+)CD34(2+) progenitors with only additive increases in colony formation being observed. These findings suggest that MGDF administration in fetuses and neonates may strongly affect the growth and mobilization of primitive hematopoietic progenitors and that MGDF may find use in the ex vivo growth and expansion of fetal stem cells.

Ontogenic changes in CD95 expression on human leukocytes: prevalence of T-cells expressing activation markers and identification of CD95-CD45RO+ T-cells in the fetus

The ontogeny of the human immune system was studied by analyzing fetal and adult tissues for the presence of various lymphocyte populations and activation/maturation markers. CD95 (fas) was expressed in hematopoietic tissues during the final stages of development of monocytes, granulocytes, NK cells and T cells, but to a much lesser extent on B cells. In the periphery, CD95 expression declined on granulocytes and NK cells. CD95 was expressed at a higher level on CD45RA+ peripheral T-cells in the fetus than in the adult. Contrary to the belief that most fetal T-cells are naïve or resting, a notable number of CD45RO+ T-cells were observed as well as an unique CD95-CD45RO+ population. Activation markers CD25, CD122, CD69 and CD80 were also present on fetal T-cells. These findings indicate that in the initial weeks following thymic maturation, a high frequency of T-cells is activated in the periphery of the fetus.

Isolation, growth and identification of colony-forming cells with erythroid, myeloid, dendritic cell and NK-cell potential from human fetal liver

The study of hematopoietic stem cells (HSCs) and the process by which they differentiate into committed progenitors has been hampered by the lack of in vitro clonal assays that can support erythroid, myeloid and lymphoid differentiation. We describe a method for the isolation from human fetal liver of highly purified candidate HSCs and progenitors based on the phenotypes CD38(-)CD34(++) and CD38(+)CD34(++), respectively. We also describe a method for the growth of colony-forming cells (CFCs) from these cell populations, under defined culture conditions, that supports the differentiation of erythroid, CD14/CD15(+) myeloid, CD1a(+) dendritic cell and CD56(+) NK cell lineages. Flow cytometric analyses of individual colonies demonstrate that CFCs with erythroid, myeloid and lymphoid potential are distributed among both the CD38(-) and CD38(+) populations of CD34(++) progenitors.

Broad distribution of colony-forming cells with erythroid, myeloid, dendritic cell, and NK cell potential among CD34(++) fetal liver cells

The generation of erythroid, myeloid, and lymphoid cells from human fetal liver progenitors was studied in colony-forming cell (CFC) assays. CD38(-) and CD38(+) progenitors that expressed high levels of CD34 were grown in serum-deprived medium supplemented with kit ligand, flk2/flt3 ligand, GM-CSF, c-mpl ligand, erythropoietin, and IL-15. The resulting colonies were individually analyzed by flow cytometry. CD56(+) NK cells were detected in 21.9 and 9.9% of colonies grown from CD38(-) and CD38(+) progenitors, respectively. NK cells were detected in mostly large CD14(+)/CD15(+) myeloid colonies that also, in some cases, contained red cells. NK cells were rarely detected in erythroid colonies, suggesting an early split between the erythroid and the NK cell lineages. CD1a(+) dendritic cells were also present in three-quarters of the colonies grown from CD38(-) and CD38(+) progenitors. Multilineage colonies containing erythrocytes, myeloid cells, and NK cells were present in 13.7 and 2.7% of colonies grown from CD38(-) and CD38(+) progenitors, respectively. High proliferative-potential CFCs that generated multilineage colonies were also detected among both populations of progenitors. The total number of high proliferative-potential CFCs with erythroid, myeloid, and NK cell potential was estimated to be 2-fold higher in the CD38(+) fraction compared with the CD38(-) fraction because of the higher frequency of CD38(+) cells among CD34(++) cells. The broad distribution of multipotent CFCs among CD38(-) and CD38(+) progenitors suggests that the segregation of the erythroid, myeloid, and lymphoid lineages may not always be an early event in hemopoiesis. Alternatively, some stem cells may be present among CD38(+) cells.

Further experience of nonagenarians with hip fractures

Our purpose was to investigate the factors after predictive outcome 3 months after the injury in terms of mortality and effective independent walking of nonagenarians with hip fracture. A prospective study was carried out for 2 yr in the orthopaedic wards on patients referred to geriatricians. The data were subjected to logistic regression forward stepwise analysis. Eighty-nine patients were included in the study; 55 (61.8%) had a trochanteric fracture and 86 required a surgical procedure. Before the fracture, 83 patients (93.3%) were able to walk by themselves or with minimal supervision. Forty-three patients (48.3%) had an American Society of Anaesthesiologists' of III-IV score. The mean number of postoperative complications was four. Mean hospital stay was 18.2 days. Within 3 months, 19 patients (21.3%) had died and 58 (69%) were living in their previous residence. Thirty-three (50% of living patients) were able to walk by themselves or with minimal help within 3 months of the fracture. Predictive variables for 3-month mortality were pre-fracture dependence on others for personal toilet and the presence of cognitive impairment. Predictive variables for independent efficient walking were bowel control and absence of cognitive impairment before the fracture, as well as no development of bed sores during hospitalization.These nonagenarian patients with hip fractures show low perioperative mortality, frequently return to their previous accommodation and present a limited recovery of walking ability.

High-efficiency retroviral transduction of fetal liver CD38-CD34++ cells: implications for in utero and ex utero gene therapy

OBJECTIVES

Defining methods for the efficient transduction of fetal stem cells could lead to novel fetal therapies for blood cell disorders and other birth defects. In this study, we analyzed the effects of various parameters on the retroviral transduction of primitive hematopoietic progenitors/stem cells isolated from fetal liver.

METHODS

Candidate stem cells were isolated by fluorescence-activated cell sorting from midtrimester human livers based on the phenotype CD38-CD34++lineage- (lineage = glycophorin A, CD3, CD14, CD19, CD20 and CD56). A murine retroviral vector with a truncated human low-affinity nerve growth factor receptor (Delta NGFR) gene was used to transduce the candidate stem cells. Marker gene expression was monitored by flow cytometry using an anti-NGFR mAb. Candidate stem cells were transduced immediately after isolation or after up to 4 days of culture in serum-deprived medium containing the growth factors kit ligand and granulocyte-macrophage colony-stimulating factor. The effects on transduction efficiency of the addition of 4 microg/ml protamine sulfate and/or centrifugation to concentrate the candidate stem cells and virus were tested. After transduction, the cells were expanded for 10-21 days before determining the frequency of NGFR+ cells among the different hematopoietic progeny.

RESULTS

Efficient transduction of candidate stem cells, at an average rate of 46%, was achieved after 3 days of culture with a single exposure to virus. Longer than 3 days of culture or repeated exposure to viral supernatant did not significantly improve the rate of transduction. The use of centrifugation at 1,200 g for 1 h and the addition of protamine sulfate during the transduction procedure were critical to achieving a high rate of transduction. Marker gene expression was observed on the progeny of the transduced cells in conjunction with CD34 (progenitors), glycophorin A (erythrocytes), CD14 (monocytes), CD15 (granulocytes) and CD41 (megakaryocytes).

CONCLUSIONS

This study demonstrates that the efficient transduction of fetal candidate stem cells can be achieved under defined culture conditions using a retroviral vector. These results encourage further examination of in utero and ex utero gene therapy as a means of treating birth defects.

Transplantation of a fetus with paternal Thy-1(+)CD34(+)cells for chronic granulomatous disease

A fetus diagnosed with X-linked chronic granulomatous disease was transplanted with Thy-1(+)CD34(+) cells of paternal origin. The transplant was performed at 14 weeks gestation by ultrasound guided injection into the peritoneal cavity. The fetus was delivered at 38 weeks gestation after an otherwise uneventful pregnancy. Umbilical cord blood was collected and used to determine the level of peripheral blood chimerism as well as levels of functional engrafted cells. Flow cytometry was used to detect donor leukocytes identified as HLA-A2(-)B7(+) cells, whereas recipient cells were identified as HLA-A2(+)B7(-) cells. No evidence of donor cell engraftment above a level of 0.01% was found. PCR was used to detect HLA-DRB1*15(+) donor cells among the recipient's HLA-DRB1*15(-) cells, but no engraftment was seen with a sensitivity of 1:1000. The presence of functional, donor-derived neutrophils was assessed by flow cytometry using two different fluorescent dyes that measure reactive oxygen species generated by the phagocyte NADPH oxidase. No evidence of paternal-derived functional neutrophils above a level of 0.15% was observed. Peripheral blood and bone marrow samples were collected at 6 months of age. Neither sample showed engraftment by HLA typing using both flow cytometry and PCR. Functional phagocytes were also not observed. Furthermore, no indication of immunological tolerance specific for the donor cells was indicated by a mixed lymphocyte reaction assay performed at 6 months of age. While there appears to be no engraftment of the donor stem cells, the transplant caused no harm to the fetus and the child was healthy at 6 months of age. Analyses of fetal tissues, obtained from elective abortions, revealed that CD3(+) T cells and CD56(+)CD3(-) NK cells are present in the liver at 8 weeks gestation and in the blood by 9 weeks gestation. The presence of these lymphocytes may contribute to the lack of donor cell engraftment in the human fetus.

[Geriatric management of the frail elderly with hip fracture may improve their clinical outcome]

BACKGROUND

The treatment of osteoporotic hip fracture requires the intervention of different medical specialties. The purpose of this study was to know the clinical profile of patients with an acute hip fracture referred for assessment and management to a geriatric assessment team (GAT) and the influence of this kind of geriatric care in their hospital outcome.

PATIENTS AND METHOD

All patients 65 year-old or older admitted in a teaching hospital for a hip fracture in a 12 month period were included. The clinical, functional, cognitive and social status were assessed at admission and at discharge in both groups: the patients managed by the GAT and the patients that were not. The patients' characteristics of both groups were compared, and a multivariant analysis was applied to search the variables independently associated wit a better clinical course.

RESULTS

On admission, the GAT patients (n = 202) were significantly (p < 0.05) older (84.4 vs 81.7 years), had more previous functional impairment (Barthel index 72 vs 79), more previous diseases (5.4 vs 3.3) and medications (3.2 vs 1.9), presented more frequency of cognitive impairment (52 vs 41%), of high surgical risk (54 vs 26%) and more need of social assistance at home (57 vs 38%) than non-referred patients (n = 200). At discharge, GAT patients had better functional status (Barthel index 38.5 vs 34), had been surgically treated (92 vs 84%), had received physiotherapy (83.7 vs 66.5%) and walked more (56.1% vs 33.8%) than others. In the multivariant analysis, the GAT intervention shows like an independent variable associated to higher frequency of surgical treatment (OR 4.21; CI, 2.80-6.34), to recovery of walking ability (OR, 8.26; CI, 5.23-13.04) and to receive more medical diagnosis (OR, 79.69; CI: 55.48-114.45). The GAT intervention was not associated to a longer hospital stay.

CONCLUSIONS

The patients with hip fracture in acute phase required for management by a GAT are more complex than those who were not consulted. In these patients GAT intervention improve their clinical outcome and the efficiency of hospital admission.

Differential effects of interleukin-3, interleukin-7, interleukin 15, and granulocyte-macrophage colony-stimulating factor in the generation of natural killer and B cells from primitive human fetal liver progenitors

The regulatory roles of a number of early-acting growth factors on the generation of natural killer (NK) cells and B cells from primitive progenitors were studied. Experiments focused on the contributions of granulocyte-macrophage colony-stimulates factor (GM-CSF) and interleukin-3 (IL-3) to the regulation of the early events of lymphopoiesis.Two progenitor populations isolated from human fetal liver were studied, CD38(-)CD34(++)lineage(-) (Lin(-)) cells (candidate hematopoietic stem cells [HSCs]) and the more mature CD38(+)CD34(++)Lin(-) cells. The effects of different cytokines on the generation of CD56(+)CD3(-) NK cells and CD19(+) B cells were studied in serum-deprived cultures in the absence of stroma.NK cells generated in vitro were able to kill NK-sensitive target cells, expressed NK-associated marker CD161 (NKR-P1A), but exhibited little or no expression of CD2, CD8, CD16, CD94/NKG2A, or killer cell inhibitory receptors (KIRs). Among the cytokine combinations tested, kit ligand (KL) and IL-15 provided the best conditions for generating CD56(+) NK cells from CD38(+)CD34(++)Lin(-) cells. However, either flk-2/flt3 ligand (FL), GM-CSF, IL-3, or IL-7 could partially substitute KL. All of these cytokines also supported the growth of NK-cell progenitors from candidate HSC, with the combination of IL-15, KL, GM-CSF, and FL generating the greatest number of CD56(+) cells. B cells were generated from both progenitor populations in response to the combined effects of KL, FL, and IL-7. Both B and NK cells were generated with the further addition of IL-15 to these cultures. The in vitro generated B cells were CD10(+), CD19(+), HLA-DR(+), HLA-DQ(+), and some were CD20(+), but no cytoplasmic or surface immunoglobulin M expression was observed. In contrast with NK lymphopoiesis, GM-CSF, IL-3, and IL-15 had no effect on the generation of B cells from CD38(-)CD34(++)Lin(-) cells, and GM-CSF inhibited B-cell generation from CD38(+)CD34(++)Lin(-) progenitors. These findings indicate a differential regulation of NK and B lymphopoiesis beginning in the early stages of hematopoiesis as exemplified by the distinctive roles of IL-7, IL-15, GM-CSF, and IL-3.

Fetal bone marrow as a source of stem cells for in utero or postnatal transplantation

We examined the potential of human fetal bone marrow (FBM) as a source of haematopoietic stem cells for transplantation. The median number of cells obtained between 20 and 24 weeks' gestation was 1.9 x 109 and a median 1.17 x 108 of these cells expressed CD34. Flow cytometry was also used to estimate the content of three different candidate stem cell populations in the tissues older than 20 weeks' gestation. A median 8.8 x 105 CD34++CD38- cells, 1.37 x 106 CD34++CD4+ cells and 2.20 x 106 CD34++CD90+ cells were detected. The content of colony-forming units culture (CFU-C) in the FBM ranged from 2.8 x 104 to 6.0 x 106 per fetus. The CFU-C content could be expanded 50-fold by culture for 1 week in serum-deprived medium and the growth factors kit ligand and granulocyte-macrophage colony-stimulating factor. Positive selection of FBM CD34+/++ cells was achieved using the Baxter Isolex 50 device. An average purity of 82% and yield of up to 19% of CD34+/++ cells was achieved. T cells were depleted by 99.84%. Analysis of candidate stem cell populations and primitive CFU-C suggested a preferential enrichment of these cells over the total population of CD34+/++ cells. All FBM samples were found to be free of microbial contamination at the time of harvest and after selection of CD34+/++ cells. Thus, FBM is a safe source of stem cells. The large number of progenitors and candidate stem cells that can be obtained from FBM makes it suitable for in utero and possibly postnatal transplantation.

Mid-trimester fetal livers are a rich source of CD34+/++ cells for transplantation

Human fetal livers (FL), between 16 and 24 weeks of gestation, were studied for their potential as a source of hematopoietic stem cells for prenatal and postnatal transplantation. In this report we give a quantitative evaluation of human FL as a source of candidate stem cells, and develop a protocol for the isolation of these cells free of microbial contaminants and almost free of mature T cells. Human FLs contained a median 1.9 x 10(9) viable cells and a mean of 1.3 x 10(8) CD34+/++ cells (range 1.1 x 10(7) to 4.7 x 10(8)). Regardless of gestational age, no significant differences were apparent in the numbers of total progenitors or in the numbers of candidate stem cells (CD34++ CD38- and CD34++CD4+), suggesting that the expansion in the liver of the early compartments of hematopoietic progenitors reaches a plateau after the sixteenth week of gestation. Colony-forming units culture (CFU-C) were found to range from 4.1 x 10(6) to 2.5 x 10(7) per FL. Positive selection of FL CD34++ cells was achieved using the Baxter Isolex 50 device. An average purity of 74% and yield of 29% of CD34+/++ cells was achieved. T cells were depleted by 99.95%, resulting in a mean of 6.5 x 10(3) T cells per processed liver. Analysis of candidate stem cell populations and primitive colony-forming cells (CFC) suggested a preferential enrichment of these cells over the total population of CD34+/++ cells. Processed CD34+/++cells were found to be sterile. In conclusion, purification of FL progenitors between 16 and 24 weeks of gestation results in a large number of early progenitors suitable for in utero and possibly post-natal transplantation.

Factors predictive of outcome on admission to an acute geriatric ward

AIM

To investigate which factors predict outcome of elderly patients on discharge and at 6 months.

METHODS

A prospective study in an acute geriatric ward. Within 48 h of admission, patients were assessed for social factors, geriatric problems, admission diagnoses, medication, function and mental ability. Outcome measures were mortality, length of stay, institutionalization, readmissions and attendance at accident and emergency within 6 months.

RESULTS

353 patients were studied, with a mean age of 81.8 years. Logistic regression analyses showed that variables predicting hospital mortality were Barthel index on admission, pre-morbid disability and polypharmacy. The only variable independently predictive of prolonged stay in hospital was a Barthel score of <45 on admission. Functional disability on admission was predictive of institutionalization on discharge. Variables predicting mortality within 6 months of discharge were Barthel index on admission <65, presence of pressure sores, malnutrition and polypharmacy. Variables independently predictive of institutionalization were mental state and a low pension. Those who took more than five drugs on admission were more likely to attend accident and emergency and be readmitted.

CONCLUSION

Limited activities of daily living and geriatric problems on admission are the strongest predictive factors of outcome, independent of diagnoses.

Role of CD95/Fas and its ligand in the regulation of the growth of human CD34(++)CD38(-) fetal liver cells

The functional significance of CD95/Fas expressed by candidate hematopoietic stem cells (HSCs) from human fetal liver was studied by testing the effect of agonistic anti-CD95 monoclonal antibody (mAb) CH-11 and soluble CD95 ligand (sCD95L) on the growth of CD34(++)CD38(-)lineage cells in vitro. Candidate fetal HSCs exhibited a dose-dependent proliferative response to CH-11 as well as to sCD95L when combined with kit ligand (KL) + interleukin 3 (IL-3) under serum-deprived culture conditions. CH-11 mAb increased, in a synergistic fashion, the number of myeloid colony-forming unit culture (CFU-C) generated by candidate HSCs in liquid cultures with the cytokine combinations KL + IL-3, KL + granulocytemacrophage colony-stimulating factor, and KL + IL-6. CH-11 mAb and sCD95L also enhanced erythropoiesis supported by KL + IL-3 + erythropoietin (Epo). Furthermore, sCD95L was able to increase the number of megakaryocytes, granulocytes, and CD34- cells generated in the presence of KL + IL-3 + Epo + thrombopoietin. An analysis performed using Western blotting revealed that the membrane-bound CD95L (mCD95L) was expressed by both immature (total CD34+/++) and mature (CD34-) hematopoietic lin(-) FL cells. Among the CD34(++)lin(-)cells, both the freshly isolated CD38+ and CD38 subsets as well as CD95+ and CD95- cells constitutively expressed mCD95L, demonstrating that the CD95/CD95L system represents a paracrine and potentially autocrine regulator of early hematopoiesis. To study the role of the endogenously produced CD95L, we determined the effects of a neutralizing anti-CD95L NOK-1 on the growth of candidate HSCs. By blocking the endogenous CD95L with NOK-1 mAb, we observed an increase in CFU-C generated by candidate HSCs. We conclude that the endogenous CD95L has an inhibitory effect on fetal candidate HSCs, which can be blocked by sCD95L and CH-11 mAb.

Idiopathic normal pressure hydrocephalus: analysis of factors related to cerebrospinal fluid dynamics determining functional prognosis

This investigation has been undertaken to analyze the findings with both the cerebrospinal fluid (CSF) pressure (Pcsf) and CSF pulse pressure (PP) in order to predict the outcome of patients with the syndrome of idiopathic normal pressure hydrocephalus (NPH). Accordingly, a prospective clinical study was planned in which two groups of patients with NPH, having analogous prevalence of several matched clinical and radiological parameters, were separated on the basis of their positive or negative response to shunting. Both the resting Pcsf and CSF PP profiles were compared in these two groups, and between them and normal controls. CSF PP amplitude and CSF PP latency correlated directly in conditions associated with either normal or high compliance (controls and patients with Alzheimer-like disorders), whereas this correlation was inverse in states of low compliance (NPH). On the other hand, shunt-responders showed a resting Pcsf significantly higher than both non-responders and controls. The following conclusions were obtained: 1) CSF PP is a high-amplitude and relative low-latency wave in NPH when compared with controls: 2) CSF PP amplitude and latency correlate directly in normal subjects and in those with primary cerebral atrophy; 3) a non-reversible stage of NPH could be conceived in contradistinction to the reversible one, in both of which an inverse correlation between the amplitude and the latency takes place, the main difference between them being the resting Pcsf, which is significantly lower in the former than in the latter, depending on the degree of atrophic changes developed.

Expression of Fas/CD95 and Bcl-2 by primitive hematopoietic progenitors freshly isolated from human fetal liver

The cell-surface expression and the functional status of the CD95/Fas antigen on primitive hematopoietic progenitors (PHPs) freshly isolated from human fetal liver (FL) were studied. PHPs were phenotypically defined as CD34++ CD38 -/+ cells. The most immature subfractions of PHPs, CD34++CD38- and CD34+2CD38+ FL cells, expressed CD95, whereas the more mature CD34++CD38++ and CD34+CD38++2 FL cells displayed low CD95 expression. Combinations of cytokines, such as kit ligand (KL) + interleukin-3 or KL + granulocyte-macrophage colony-stimulating factor (GM-CSF) upregulated the expression of CD95 on PHPs upon in vitro culture. Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) further increased the CD95 expression induced by KL+GM-CSF. The hematopoietic potential of sorted CD34++lineage (lin)- CD95+ versus CD34++ lin-CD95-FL cells was compared by colony-forming unit-culture (CFU-C) assays performed in serum-deprived medium. Lin+ cells were composed of erythrocytes, monocytes, T cells, B cells, and natural killer cells. Our results indicated that both CD95- and CD95+ subsets contained pluripotent progenitors, generating myeloid and erythroid progenitors. The functional status of CD95 and the effects of TNF-alpha and IFN-gamma, cytokines known to induce CD95-mediated apoptosis, were analyzed by incubation of PHPs in the presence of anti-CD95 monoclonal antibodies (MoAbs). The effect of anti-CD95 MoAbs was measured by viable cell counting, flow cytometry, and CFU-C assays. A decrease of CFU-C numbers was observed in the presence of anti-CD95 MoAbs and TNF-alpha and/or IFN-gamma. However, whereas growth factor deprivation induced apoptosis of PHPs, cross-linking of CD95 did not lead to apoptosis of PHPs measured by flow cytometry and viable cell counting. The correlation of increased intracytoplasmic levels of bcl-2 with high levels of cell-surface CD34 and the presence of CD95 on fresh FL cells suggests that bcl-2 may be involved in protecting against CD95-mediated apoptosis of FL PHPs.

Tracing the expression of CD7 and other antigens during T- and myeloid-cell differentiation in the human fetal liver and thymus

During the last decade, the function/s of the cell membrane CD7 antigen have been investigated in human mature T and NK cells, showing the direct involvement of this molecule in multiple effector functions related with activation, proliferation, production of cytokines and modification of adhesion properties. The CD7 glycoprotein is not only expressed by mature lymphoid cells, but also by early hematopoietic progenitors and several types of leukemias, suggesting a role of CD7 during hematopoiesis. However, the function of CD7 in the early stages of hematopoietic development has not yet been elucidated. CD7 has been classically considered the earliest T-cell specific marker. This assumption was based on data indicating the presence of CD45+CD7+CD3-CD4-CD8- cells in the human embryonic/fetal liver at the gestational age at which the thymic rudiment is colonized by T-cell progenitors. In the present article, we review recent results obtained by several groups concerning the expression of CD7 and various other cell surface antigens by T-, B- and myeloid-cell progenitors generated in the adult bone marrow and fetal liver. In addition, we present an hypothetical model of hematopoiesis in the fetal liver and thymus.

[Decrease in isoflurane requirements and of postoperative pain with preanesthetic intrathecal morphine]

OBJECTIVES

1) To determine whether preanesthetic intrathecal administration of 0.5 mg morphine reduces isoflurane requirements for anesthetic maintenance. 2) To assess the duration of postoperative analgesia and the type and frequency of complications attributable to the procedure.

PATIENTS AND METHODS

A series of 45 adults were distributed into 3 groups of 15 patients each based on site of surgery and site of preanesthetic (30 min) injection of 0.5 mg pure morphine. Control group (C0) patients underwent lumbar surgery and received subcutaneous morphine. Group C0.5 patients also underwent lumbar surgery but received intrathecal morphine. Group A0.5 patients underwent long-duration high abdominal surgery and received intrathecal morphine. Anesthesia was maintained with nitrous oxide (60%) in oxygen (40%) and a variable concentration of isoflurane. Isoflurane needs were assessed by averaging six consecutive measurements of end-tidal isoflurane pressure (M30FETiso) taken at intervals of 5 min. Postoperative analgesia was evaluated by means of a visual analog scale that was converted to numerical units (VASn).

RESULTS

M30FETiso in group C0 (0.8%) was always higher (p < 0.01) than in the other two groups. M30FETiso in group A0.5 was higher (p < 0.01) than in group C0.5 during the first 150 min of surgery. After 180 min, there were no differences in M30FETiso (0.10-0.16%) between the two groups receiving intrathecal morphine. VASn results (mean +/- SD) in the first 4 hours were higher in group C0 (7.33 +/- 0.6) than in group C0.5 (1.13 +/- 0.35) and group A0.5 (1.07 +/- 0.26). The time of morphine-dependent analgesia was shorter (p < 0.01) in group C0 (0.62 +/- 0.38 hours) than in groups C0.5 (30.4 +/- 5.11 hours) and A0.5 (28 +/- 4.34 hours). There were no significant differences between the two groups receiving intrathecal morphine.

CONCLUSIONS

Preanesthetic subarachnoid lumbar injection of 0.5 mg of pure morphine reduced early requirements for isoflurane in lumbar surgery (0.14% after 60 min). This reduction was initially less in patients undergoing abdominal surgery (0.44% at 60 min) but was the same after 150 min. Postoperative analgesia was long-term and independent of type or duration of surgery. There was no respiratory depression after surgery and the incidence of postoperative complications was similar in the two groups that received subarachnoid morphine.

Progress in the ex vivo expansion of hematopoietic progenitors

In this review we describe how studies on the cytokine-stimulated growth of murine bone marrow (BM) progenitors have lead to the observations that large increases in progenitor numbers can be achieved in short-term cytokine-stimulated liquid cultures. Transplantation of these ex vivo expanded murine BM cells was shown to decrease the number of BM cells required to confer radioprotection and to increase the recovery rate of both myeloid and erythroid peripheral blood cells. The ex vivo expansion of murine BM cells does not however, markedly diminish stem cells capable of long-term hematopoietic reconstitution. Investigations on the expansion of human BM, peripheral blood, umbilical cord blood and fetal hematopoietic progenitors have demonstrated that clinically useful increases in progenitor numbers from these tissues are possible. Thus, ex vivo progenitor expansion may soon be of use in transplantation protocols to accelerate hematopoietic reconstitution and in gene therapy protocols if hematopoietic stem cells can be maintained during ex vivo culture.

Lymphoid and myeloid differentiation of fetal liver CD34+lineage- cells in human thymic organ culture

In this article, we report that the human fetal thymus contains CD34bright cells (< 0.01% of total thymocytes) with a phenotype that resembles that of multipotent hematopoietic progenitors in the fetal bone marrow. CD34bright thymocytes were CD33-/dull and were negative for CD38, CD2, and CD5 as well as for the lineage markers CD3, CD4, and CD8 (T cells), CD19 and CD20 (B cells), CD56 (NK cells), glycophorin (erythrocytes), and CD14 (monocytes). In addition, total CD34+ lineage negative (lin-) thymocytes contained a low number of primitive myeloid progenitor cells, thus suggesting that the different hematopoietic lineages present in the thymus may be derived from primitive hematopoietic progenitor cells seeding the thymus. To investigate whether the thymus is permissive for the development of non-T cells, human fetal organ culture (FTOC) assays were performed by microinjecting sorted CD34+lin- fetal liver cells into fragments of HLA-mismatched fetal thymus. Sequential phenotypic analysis of the FTOC-derived progeny of CD34+lin- cells indicated that the differentiation into T cells was preceded by a wave of myeloid differentiation into CD14+CD11b+CD4dull cells. Donor-derived B cells (CD19+CD20+) were also generated, which produced immunoglobulins (IgG and IgM) when cultured under appropriate conditions, as well as functional CD56+CD3- NK cells, which efficiently killed K562 target cells in cytotoxicity assays. These results demonstrate that the microinjection of fetal liver hematopoietic progenitors into fetal thymic organ fragments results in multilineage differentiation in vitro.

In vivo cytokine expression in the thymus. CD3high human thymocytes are activated and already functionally differentiated in helper and cytotoxic cells

CD4 and CD8 are expressed on mutually exclusive T cell populations that can recognize peptides bound to class II and class I MHC Ags, respectively. These populations have different functions and are different in their capacity to produce cytokines. In this paper we demonstrate that this functional differentiation occurs at the CD3low- CD3high transitional stage: single positive mature CD4+ thymocytes express IL-2 mRNA in vivo, whereas CD8+ thymocytes primarily express perforin. IL-2, perforin, and IFN-gamma mRNAs were almost absent in CD4+CD8+ CD3low but were clearly detectable in CD4+CD8+ CD3high cells, indicating that these genes are induced at the CD3low- CD3high transitional stage. In contrast, IL-4 mRNA levels were highest in the precursor cells but dropped sharply at the CD3low-CD3high transitional stage. These data are consistent with and link two earlier observations, i.e., that activation occurs at the CD3low-CD3high transition and that functional differentiation in helper and cytotoxic cells is already accomplished in the single positive thymocytes. This activation may reflect positive selection and concomitant functional differentiation into helper and cytotoxic T cells.

In vivo cytokine expression in the thymus. CD3high human thymocytes are activated and already functionally differentiated in helper and cytotoxic cells

CD4 and CD8 are expressed on mutually exclusive T cell populations that can recognize peptides bound to class II and class I MHC Ags, respectively. These populations have different functions and are different in their capacity to produce cytokines. In this paper we demonstrate that this functional differentiation occurs at the CD3low- CD3high transitional stage: single positive mature CD4+ thymocytes express IL-2 mRNA in vivo, whereas CD8+ thymocytes primarily express perforin. IL-2, perforin, and IFN-gamma mRNAs were almost absent in CD4+CD8+ CD3low but were clearly detectable in CD4+CD8+ CD3high cells, indicating that these genes are induced at the CD3low- CD3high transitional stage. In contrast, IL-4 mRNA levels were highest in the precursor cells but dropped sharply at the CD3low-CD3high transitional stage. These data are consistent with and link two earlier observations, i.e., that activation occurs at the CD3low-CD3high transition and that functional differentiation in helper and cytotoxic cells is already accomplished in the single positive thymocytes. This activation may reflect positive selection and concomitant functional differentiation into helper and cytotoxic T cells.

Phenotypic and functional analysis of T-cell precursors in the human fetal liver and thymus: CD7 expression in the early stages of T- and myeloid-cell development

It has been proposed that the CD7 molecule is the first antigen expressed on the membrane of cells committed to the T-cell lineage during human fetal T-cell ontogeny. To further identify the pre-T cell subpopulation that migrates to the thymus early in ontogeny, we analyzed the phenotypic and functional characteristics of the fetal liver populations separated on the basis of CD7 expression. Three populations expressing different levels of CD7 were observed: CD7bright, CD7dull, and CD7-. A CD7bright population depleted of mature T, B, and myeloid cells (lineage negative, lin-) and mostly composed of CD56+ CD34- natural killer cells did not mature into T cells in a fetal thymic organ culture (FTOC) assay and was devoid of myeloid progenitors in a clonal colony-forming cell assay. In contrast, the CD7-/dull CD34+ lin- populations were capable of differentiating into phenotypically mature T cells after injection into FTOC and contained early myeloid progenitors. Here we phenotypically compared the fetal liver CD7 populations with the most immature fetal thymic subset that differentiated in the FTOC assay, namely the triple negative (TN, CD3-CD4-CD8-) thymocytes. Fetal TN lin- expressed high levels of CD34 marker and were further subdivided by their expression of CD1 antigen, because CD1- TN thymocytes express higher levels of CD34 antigen compared with CD1+ TN cells. CD1- lin -TN thymocytes are characterized by expressing high levels of CD2, CD7, and CD34 markers and dull levels of CD5, CD10, and CD28 molecules. We could not find fetal liver pre-T cells with a phenotype equivalent to that of TN thymocytes. Our data show that CD7 does not necessarily identify T-cell precursors during fetal T-cell development and strongly support the hypothesis that the acquisition of early T-cell markers as CD2, CD28, and CD5 molecules on the cell surface of T-cell progenitors takes place intrathymically.

Precursors of CD3+CD4+CD8+ cells in the human thymus are defined by expression of CD34. Delineation of early events in human thymic development

Studies of the most immature T cell progenitors in the human thymus have been hampered by the lack of markers and assays that define these cells. In this report we used a novel human fetal thymic organ culture system to determine the potential of T cell precursors isolated from human postnatal thymus, to differentiate into CD3+ thymocytes, and to investigate early stages of human T cell development. It was found that thymocytes that lack the markers CD3, CD4, and CD8 (triple negative [TN]) can differentiate in an allogeneic organotypic thymic culture. The capacity of TN thymocytes to differentiate was exclusively confined to the CD34+ population. CD34- TN thymocytes failed to differentiate in this system. In contrast, cloned lines of CD3- thymocytes could only be established from CD34- TN thymocytes. Five subsets of CD3- thymocytes were found with the following phenotype: CD1-TN, CD1+TN, CD1+CD4+CD8-, CD1+CD4+CD8 alpha+ beta-, and CD1+CD4+CD8 alpha beta+. These subpopulations expressed decreasing levels of CD34. The CD1-CD3- population expressed the highest levels of CD34 supporting the notion that this population is the most immature T cell precursor in the thymus, whereas the CD1+CD4+CD8 alpha+ beta+ which did not express CD34 seems to be the most mature of these CD3- populations. This notion is supported by the observations that CD34+ cells isolated from fetal liver, which differentiated into T cells in a FTOC, developed into CD3+ cells via CD1- and CD4+CD8- intermediates. Based on these data, we present a model of early stages in human intrathymic development.

Involvement of the interleukin 4 pathway in the generation of functional gamma delta T cells from human pro-T cells

We have used the technique of in situ hybridization to investigate the transcription of genes encoding the CD3 complex and the lymphokine interleukin 4 (IL-4) by human pro-T cells--i.e., cells that phenotypically resemble those T-cell precursors that colonize the thymus during early intrathymic development. CD1-2-3-4-7+8-45+ pro-T cells isolated from postnatal thymi via immunoselection with a panel of specific monoclonal antibodies are already committed to the T-cell lineage because most of them transcribe the genes encoding the delta and epsilon chains of the CD3 complex. About half of such pro-T cells synthesize IL-4 mRNA in the absence of any exogenous stimulation. Upon culture with IL-4, pro-T cells extensively proliferate and differentiate into functionally competent, mature gamma delta T cells expressing a T-cell receptor repertoire similar to that of gamma delta T cells that can be found in postnatal thymus. The IL-4 response of pro-T cells is not mediated by induction of the interleukin 2 (IL-2)-IL-2 receptor pathway and, unlike IL-2-driven T-cell differentiation, does not require the presence of stromal cells. Taken altogether, these findings suggest that an autocrine IL-4-mediated pathway might be implicated in early thymocyte differentiation--namely, in the generation of T cells bearing the gamma delta T-cell receptor.

Interplay between IL-2 and IL-4 in human thymocyte differentiation: antagonism or agonism

The effect of recombinant interleukin 2 (IL-2) and IL-4, as well as a combination of both lymphokines on human post-natal thymocytes at different maturation stages, was analyzed by culturing highly purified pro-T cells, pre-T cells, double-negative and double-positive thymocyte subsets in the presence of IL-2 and/or IL-4. Both IL-2 and IL-4 responsiveness are developmentally regulated in human thymocytes, since IL-2 and IL-4 responses decline with increasing thymocyte differentiation, double-positive T cells displaying far less proliferation than immature thymocytes. IL-2 and IL-4 may influence pro-T cell growth in both an antagonistic and additive fashion. At low doses, IL-4 inhibits IL-2-supported growth of pro-T cells, whereas, at higher concentrations, this inhibitory effect is masked by the ability of IL-4 to stimulate pro-T cell proliferation. In contrast to peripheral lymphocytes, IL-4 does not down-regulate the expression of the IL-2 receptor light chain on thymocytes. In pro-T cell cultures, IL-2 and IL-4 favour the differentiation of distinct cell populations, namely lymphocytes displaying preferentially a TCR alpha/beta+ and CD4+CD8- phenotype versus predominantly TCR gamma/delta+ and CD4-CD8+ cells, respectively. The effect of IL-2 dominates over that of IL-4, since the composition of cultures set up in the presence of IL-2 plus IL-4 resembles that of cells cultured with IL-2 alone. In synthesis, IL-2 and IL-4 exhibit reciprocal inter-relations in human thymocyte cultures, thus supporting the notion that these lymphokines are implicated in the complex regulation of a local cytokine network.

A role for interleukin 4 in the differentiation of mature T cell receptor gamma/delta + cells from human intrathymic T cell precursors

We have analyzed the effect of human recombinant interleukin 4 (rIL-4) on the growth and differentiation of human intrathymic pre-T cells (CD7+2+1-3-4-8-). We describe that this population of T cell precursors proliferates in response to rIL-4 (in the absence of mitogens or other stimulatory signals) in a dose-dependent way. The IL-4-induced proliferation is independent of the IL-2 pathway, as it cannot be inhibited with an anti-IL-2 receptor alpha chain antibody. In our culture conditions, rIL-4 also promotes the differentiation of pre-T cells into phenotypically mature T cells. Although both CD3/T cell receptor (TCR)-alpha/beta + and CD3-gamma/delta + T cells were obtained, the preferential differentiation into TCR-gamma/delta + cells was a consistent finding. These results suggest that, in addition to IL-2, IL-4 plays a critical role in promoting growth and differentiation of intrathymic T cell precursors at early stages of T cell development.

Involvement of the interleukin 2 pathway in the rearrangement and expression of both alpha/beta and gamma/delta T cell receptor genes in human T cell precursors

In this report, we have undertaken the phenotypic, functional and molecular characterization of a minor (less than 5%) subpopulation of adult thymocytes regarded as the earliest intrathymic T-cell precursors. Pro-T cells were immunoselected and shown to express different hematopoietic cell markers (CD45, CD38, CD7, CD5) and some activation-related molecules (4F2, Tr, HLA class II), but lack conventional T cell antigens (CD2-1-3-4-8-). TCR-gamma RNA messages are already expressed at this early ontogenic stage, while alpha and beta chain TCR genes remain in germline configuration. In vitro analyses of the growth requirements of pro-T cells demonstrated the involvement of the IL-2 pathway in promoting their proliferation and differentiation into CD3+ CD4+ or CD8+ mature thymocytes. Moreover, during the IL-2-mediated maturation process rearrangements and expression of both alpha and beta chain TCR genes occurred, and resulted in the acquisition of alpha/beta as well as gamma/delta (either disulphide-linked or non-disulphide-linked) heterodimeric TCR among the pro-T cell progeny.

Intraventricular hemorrhage in severe head injury

A series of 30 patients suffering posttraumatic intraventricular hemorrhage (IVH) after closed head injury is reviewed. Clotted blood and a mixture of blood and cerebrospinal fluid could be distinguished by computerized tomography (CT). Posttraumatic IVH was associated with diffuse brain lesions in most cases; intracerebral lesions with contusion, and subdural hematomas coexisted with posttraumatic IVH in eight and four instances, respectively. In two more cases, no CT abnormality other than IVH was noted. All patients in this series were in deep coma at the time of CT examination, and only seven survived. The early clinical findings, the site of ventricular hematoma, and the final outcome are analyzed.