Elizabeth Sánchez-Valle

Kinetics of Hematopoiesis in Dexter-Type Long-Term Cultures Established from Human Umbilical Cord Blood Cells

In the present study, we have established Dexter‐type long‐term cultures (D‐LTC) from human umbilical cord blood (UCB) and followed the kinetics of different hematopoietic progenitor cells (HPCs)—including multipotent (colony forming unit [CFU]‐ Mixture), erythroid (CFU‐erythroid, BFU‐E), and myeloid (CFU‐granulocyte, CFU‐macrophage, CFU‐granulocyte/macrophage) progenitors as well as of morphologically recognizable erythroid, myeloid and lymphoid cells—during a nine‐week culture period. D‐LTC were also established from adult bone marrow (BM) as controls. On day 0, both UCB and BM showed similar total numbers of HPCs (about 310/105 cells), however, UCB showed a higher proportion of primitive HPCs (i.e., CFU‐Mixture, CFU‐granulocyte/macrophage and BFU‐E). A poor adherent cell layer, consisting almost exclusively of macrophages, was developed in UCB D‐LTC and this correlated with a continuous decline in HPC numbers throughout the culture period. In contrast, adherent cell numbers in BM D‐LTC, including fibroblasts and macrophages, were two‐ to fourfold higher than in UCB cultures, and the numbers of HPCs were also significantly higher, reaching plateau levels between weeks 6 and 9. In both types of cultures, erythroid and multipotent progenitors declined relatively fast, reaching undetectable levels after five weeks of culture. Myeloid progenitors, on the other hand, were sustained longer (always at higher levels in BM cultures) and were still detected by week 9. Among myeloid progenitors, a shift towards the predominance of macrophage HPCs was observed, both in UCB and BM D‐LTC, and this correlated with an increase in the proportion of mature monocytes and macrophages. Taken together, our results indicate that myeloid progenitor cell growth is deficient in UCB D‐LTC and suggest that this is due to the impaired development of an adherent cell layer, unable to provide the factors and conditions required for their growth. Interestingly, throughout the culture period the total numbers of multipotent and erythroid progenitors were similar both in UCB and BM cultures regardless of the number and types of adherent cells present; this suggests that the stroma developed in D‐LTC is not sufficient for the proliferation of these progenitor cells.

Comparative analysis of the in vitro proliferation and expansion of hematopoietic progenitors from patients with aplastic anemia and myelodysplasia

Aplastic anemia (AA) and myelodysplasia (MDS) show great similarities in their biology. To date, however, it is still unclear to what extent hematopoietic progenitor cells (HPCs) from AA and MDS share biological properties and what the functional differences are between them. In trying to address this issue, in the present study we have analyzed, in a comparative manner, the proliferation and expansion capacities of bone marrow (BM) progenitor cells from AA and MDS in response to recombinant cytokines. BM samples from normal subjects (NBM) and patients with AA and MDS were enriched for HPC by immunomagnetic-based negative selection. Selected cells were cultured in the absence (control) or in the presence of early-acting cytokines (Mix I), or early-, intermediate- and late-acting cytokines (Mix II). Proliferation and expansion were assessed periodically. In NBM and MDS cultures apoptosis was also determined. In NBM cultures, Mix I induced a nine-fold increase in total cell numbers and a 3.6-fold increase in colony-forming cell (CFC) numbers. In Mix II-supplemented cultures, total cells were increased 643-fold, and CFC 12.4-fold. In AA cultures, no proliferation or expansion were observed in Mix I-supplemented cultures, whereas only a four-fold increase in total cell numbers was observed in the presence of Mix II. In MDS cultures, a 12-fold increase in total cells and a 2.9-fold increase in CFC were observed in the presence of Mix I; on the other hand, Mix II induced a 224-fold increase in total cells and a 5.9-fold increase in CFC. Apoptosis was reduced in cytokine-supplemented cultures from NBM. In contrast, Mix II induced a significant increase in the rate of apoptosis in MDS cultures. Our results demonstrate that, as compared to their normal counterparts, AA and MDS progenitors are deficient in their proliferation and expansion potentials. Such a deficiency is clearly more pronounced in AA cells, which seem to be unable to respond to several cytokines. MDS progenitors, on the other hand, are capable to proliferate and expand in response to cytokines; however, their rate of apoptosis is increased by intermediate- and late-acting cytokines, so that the overall proliferation and expansion are significantly lower than those of normal progenitor cells.

Establishing a cord blood banking and transplantation program in Mexico: a single institution experience

BACKGROUND: Over the past decade, umbilical cord blood (UCB) banking and transplantation have increased significantly worldwide. The experience in developing countries, however, is still limited. In January 2005 the Mexican Institute of Social Security (IMSS) initiated its UCB banking and transplantation program. This study reports on the experience generated at this institution during the first 2 years of activities.

Incidence of Aplastic Anemia in a Defined Subpopulation from Mexico City

Abstract Aplastic anemia (AA) is a hematological disease characterized by the deficient production of blood cells. The incidence of AA worldwide is low (1-5 new cases per 106 individuals per year). In contrast to other countries, no current reports exist on the incidence of this disorder in Mexico. In the present study, we have determined the incidence of AA in a defined subpopulation from Mexico City during the period 1996-2000. For the purpose of this study, we focused on the experience from a single medical institution: the Mexican Institute of Social Security (IMSS), which covers around 50% of Mexicos population. The incidence of AA was determined based on the actual number of patients diagnosed with this disease at the IMSS in Mexico City in a given year and the total number of individuals registered at the IMSS in Mexico City in the same year. Considering the IMSS population as a whole, the annual incidence of AA was 3.9 new cases per 106 individuals per year. In the pediatric population, the annual incidence was 4.2 new cases per 106 individuals per year, whereas in people 15-years-old and older the incidence was 3.8 new cases per 106 individuals per year. These incidences were higher than those reported in most studies from the USA, Europe and Israel. Compared to the incidence in Thailand, the incidence we observed in children was considerably higher, whereas the one in adults was similar to the one in that country. The results of the present study suggest that the incidence of AA in Mexico City is one of the highest worldwide, particularly in terms of the pediatric population; however, these results must be taken with caution since this study comprises only a subpopulation from Mexico City and not the entire population. Thus, further studies including a broader population, both in Mexico City and other urban and rural areas of this country, will be necessary in order to obtain better and more complete estimates of the actual incidence of AA in Mexico.

High Doses of Dexamethasone in Adult Patients with Idiopathic Thrombocytopenic Purpura

BACKGROUND High-dose dexamethasone (DXM) has been used in treatment of patients with idiopathic thrombocytopenic purpura (ITP) who are refractory to other treatments such as prednisone and splenectomy; nevertheless, different studies show variable success rates, this postulated as possibly being due to racial differences. The objective of this study was to determine DXM effectiveness at high doses in Mexican mestizo adult patients diagnosed with ITP with and without splenectomy. METHODS Nonhospitalized adult patients with ITP were included, eight patients previously splenectomized (group 1) and 11 who had not undergone splenectomy (group 2). Patients received DXM 40 mg/day intravenously (i.v.) during 4 consecutive days every 4 weeks until six cycles were completed. RESULTS There were no differences between the two groups regarding age (mean 39 vs. 33 years of age) and initial platelet count (M 17 vs. 24 x 10(9)/L). Median evolution time was 84 months for group 1 and 7 months for group 2 (p = 0.002). Of 19 patients, nine achieved a favorable response (FR), six belonged to group 1, and three to group 2 (Fisher p = 0.07). Nevertheless, after 6 months only two group 1 patients and two group 2 patients maintained FR (Fisher exact test p = 1). Patients achieving FR to initiation of second cycle maintained FR at the end of six cycles. CONCLUSIONS Thus, the previously mentioned high-dose DXM therapy appears to be useful for both patients with ITP with and without splenectomy and high-dose DXM appears to be a good alternative therapy for postsplenectomy and relapse patients. However, duration of FR to treatment was brief; therefore, other treatment plans might be required to achieve longer remission duration. Response was similar to that observed in other studies carried out in different populations; thus, apparently no genetic or racial variations exist. In addition, whether patients not responding after second cycle should continue until completing the 6-month plan or should try a different therapeutic approach must be considered in the treatment plan.

Deficient proliferation and expansion in vitro of two bone marrow cell populations from patients with acute myeloid leukemia in response to hematopoietic cytokines.

One has previously characterized two different hematopoietic cell populations (obtained by negative-selection) from normal bone marrow. Population I was enriched for CD34+ Lin− cells, whereas Population II was enriched for CD34+ CD38− Lin− cells. Both populations showed elevated proliferation and expansion potentials in serum-free liquid cultures, supplemented with a combination of eight different cytokines, with the latter displaying more immature features than the former. One has also characterized the chronic myeloid leukemia (CML) counterparts of these two populations and demonstrated functional deficiencies in terms of their growth in culture. In keeping with this line of research, the goal of the present study was to obtain the same two populations (Populations I and II) from acute myeloid leukemia (AML) bone marrow and to characterize their biological behavior under the same culture conditions. The results demonstrated that AML-derived Populations I and II were unable to proliferate in culture conditions that allowed significant proliferation of Populations I and II from normal marrow. Population I from AML also showed a deficient expansion capacity; in contrast, Population II cells were able to expand to a similar extent to the one observed for Population II from normal marrow. Both normal and AML populations were highly sensitive to the inhibitory effects of TNF-α; interestingly, whereas in normal fractions TNF-α showed a more pronounced inhibitory effect on more mature cells (Population I), this cytokine inhibited proliferation and expansion of AML Populations I and II in a similar degree. It is noteworthy that the functional deficiencies observed in AML cells were even more pronounced than those previously reported for cultures of CML cells. The results reported here may be of relevance considering the interest by several groups in developing methods for the in vitro purging of leukemic cells, as part of protocols for autologous transplantation of hematopoietic cells in leukemic patients.

Effect of rhGM-CSF on the kinetics of hematopoiesis in long-term marrow cultures from patients with acute myelogenous leukemia.

In the present study, we have assessed the effects of recombinant human Granulocyte-Macrophage Colony-Stimulating Factor (rhGM-CSF) in Dexter-type long-term marrow cultures (LTMC) from patients with acute myelogenous leukemia (AML). Addition of rhGM-CSF to AML LTMC resulted in a significant increase in the number of total nucleated cells (1.3-4.3-fold, as compared to untreated cultures). However, a simultaneous decrease in the numbers of myeloid progenitor cells (CFU) was observed. Interestingly, there was a selective stimulation of the growth of leukemic progenitors (AML-CFU). Indeed, whereas on day 0 these cells were detected in only 2 patients, between weeks 1 and 5 they were detected in 10 of the 14 patients included in the study. It is noteworthy that around 50% of the cells detected in the non-adherent fraction of rhGM-CSF-treated AML LTMC were blasts, whereas in untreated cultures, blasts corresponded to only 23% of the non-adherent cells, and the majority corresponded to cells of the monocyte-macrophage lineage. These results indicate that rhGM-CSF is a cytokine with a significant stimulatory activity for the in vitro growth of AML progenitor and blast cells, and, together with previous reports in the literature, suggest that the use of rhGM-CSF in clinical settings must be taken with caution since this cytokine, although beneficial in reducing the risk of infections after chemotherapy, may induce the reappearance of the disease after treatment. Further studies should be encouraged to understand in greater detail the effects of rhGM-CSF, and other cytokines, on the hematopoietic system of AML patients.

Deficient proliferation of myeloid, erythroid, and multipotent progenitor cells in long-term marrow cultures from patients with aplastic anemia treated with immunosuppressive therapy

By using Dexter‐type long‐term marrow cultures (D‐LTMC), it has been shown previously that hematopoietic progenitor cells (HPC) from patients with aplastic anemia (AA) have a deficient proliferation in vitro. The studies reported to date, however, have focused exclusively on granulomonocytic progenitors and no information exists on erythroid or multipotent progenitor cells. On the other hand, in such studies, the input progenitor cell numbers were significantly below normal levels, thus suggesting that the rapid disappearance of myeloid progenitor cells from AA D‐LTMC could also be due, at least in part, to their reduced number at culture onset. In the present study, we have followed the kinetics of myeloid, erythroid, and multipotent progenitors, from 24 AA patients subjected to immunosuppressive therapy (including patients that achieved complete, partial, or no remission at all), throughout a seven‐week culture period. For analysis, we grouped all the patients based on their initial content of all three types of progenitors. Thus, we were able to evaluate separately the kinetics of these cells in D‐LTMC from patients with normal and subnormal levels of progenitor cells. At the time of marrow sampling, most patients showed decreased levels of HPC; in fact, only 21%, 8%, and 16% of them showed normal levels of myeloid, erythroid, and multipotent progenitors, respectively. When cultured in D‐LTMC, HPC from all AA patients analyzed showed a relatively fast disappearance from the cultures. Indeed, myeloid progenitors could be detected for only six weeks, whereas erythroid and multipotent progenitors disappeared from the cultures after two and one weeks of culture, respectively. In contrast, in normal marrow D‐LTMC, myeloid, erythroid, and multipotent progenitors were detected for at least seven, five, and three weeks, respectively. Such a deficient proliferation was observed even in cultures of AA patients that contained normal levels of HPC at culture onset. Interestingly, no correlation was found between HPC proliferation in D‐LTMC and response to treatment. Thus, the results of this study indicate the presence of a functional in vitro deficiency in the hematopoietic system of patients with AA, including those that achieved partial or complete remission after immunosuppressive treatment. Furthermore, this work suggests that such a proliferation deficiency is more pronounced in erythroid and multipotent progenitors than in their myeloid counterparts. Am. J. Hematol. 59:149–155, 1998.

Kinetics of hematopoiesis in bone marrow cultures from patients with chronic myeloid leukemia: effect of recombinant cytokines in dexter-type long-term cultures.

Abstract Chronic myeloid leukemia (CML) is a hematological neoplasia that results from the transformation of a hematopoietic stem cell. It is characterized by the expansion of the myeloid lineage, which results in the accumulation of mature and immature granulocytes in peripheral blood and bone marrow. However, when CML marrow cells are cultured in Dexter-type long-term cultures (LTMC) hematopoiesis is defective and can be sustained for only a few weeks. One possible explanation for the deficient growth of hematopoietic cells in CML LTMC is that some factors that act as key regulators of hematopoiesis are absent in this experimental system. Thus, we tested this hypothesis by adding recombinant cytokines to these cultures. As a first approach, we added recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF), rhGranulocyte-CSF (rhG-CSF) and rhErythropoietin (rhEPO); each factor was added individually once a week. Addition of rhGM-CSF and rhG-CSF resulted in a significant increase in the levels of nucleated cells and myeloid progenitors; the highest effects were seen in the presence of rhGM-CSF. Interestingly, such a cytokine also induced a significant decrease in the levels of erythroid progenitors. Recombinant hEPO had no significant effects on nucleated cells or myeloid progenitors, however, it induced a significant, although transient, increase in the levels of erythroid cells. The above results indicate that the hematopoietic regulators used here (rhGM-CSF, rhG-CSF and rhEPO) are capable of stimulating the growth of hematopoietic cells in LTMC from CML patients. Thus, this study demonstrates that it is, indeed, possible to manipulate CML LTMC by the addition of recombinant cytokines; this observation may be of particular relevance, since this in vitro experimental system has already been used as a method for purging of leukemic cells in autologous transplant settings. By using specific recombinant hematopoietic modulators it might be possible to make LTMC a more efficient system for such a clinical purpose.Chronic myeloid leukemia (CML) is a hematological neoplasia that results from the transformation of a hematopoietic stem cell. It is characterized by the expansion of the myeloid lineage, which results in the accumulation of mature and immature granulocytes in peripheral blood and bone marrow. However, when CML marrow cells are cultured in Dexter-type long-term cultures (LTMC) hematopoiesis is defective and can be sustained for only a few weeks. One possible explanation for the deficient growth of hematopoietic cells in CML LTMC is that some factors that act as key regulators of hematopoiesis are absent in this experimental system. Thus, we tested this hypothesis by adding recombinant cytokines to these cultures. As a first approach, we added recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF), rhGranulocyte-CSF (rhG-CSF) and rhErythropoietin (rhEPO); each factor was added individually once a week. Addition of rhGM-CSF and rhG-CSF resulted in a significant increase in the levels of nucleated cells and myeloid progenitors; the highest effects were seen in the presence of rhGM-CSF. Interestingly, such a cytokine also induced a significant decrease in the levels of erythroid progenitors. Recombinant hEPO had no significant effects on nucleated cells or myeloid progenitors, however, it induced a significant, although transient, increase in the levels of erythroid cells. The above results indicate that the hematopoietic regulators used here (rhGM-CSF, rhG-CSF and rhEPO) are capable of stimulating the growth of hematopoietic cells in LTMC from CML patients. Thus, this study demonstrates that it is, indeed, possible to manipulate CML LTMC by the addition of recombinant cytokines; this observation may be of particular relevance, since this in vitro experimental system has already been used as a method for purging of leukemic cells in autologous transplant settings. By using specific recombinant hematopoietic modulators it might be possible to make LTMC a more efficient system for such a clinical purpose.

Severe hematopoietic alterations in vitro, in bone marrow transplant recipients who develop graft-versus-host disease.

Graft-versus-host disease (GVHD) is currently one of the major obstacles for successful allogeneic bone marrow transplantation (BMT). GVHD results from a complex set of interactions between donor T cells and a variety of target tissues from the host. To gain a better understanding of the biology of the human hematopoietic system in GVHD patients, in the present study we have determined the progenitor cell content in bone marrow (BM) samples from BMT recipients, with and without GVHD, and followed their growth kinetics in Dexter-type long-term marrow cultures (LTMC). We have also assessed some aspects regarding the composition of the hematopoietic microenvironment developed in vitro. As compared to normal subjects, BMT recipients showed decreased numbers of myeloid, erythroid, and multipotent progenitor cells. Interestingly, progenitor levels were significantly lower in GVHD patients (7% of the levels in normal marrow) than in those without GVHD (44% of the levels in normal marrow). When marrow cells from BMT recipients were cultured in LTMC, hematopoiesis was sustained at lower levels and for shorter periods of time, as compared to cultures from normal subjects. The hematopoietic deficiencies observed in this in vitro system were also more pronounced in GVHD patients. In terms of the microenvironment elements, reduced numbers of fibroblastic progenitors and adherent stromal cells were observed in BMT recipients, as compared to normal subjects, who showed 7 colony-forming unit fibroblast (CFU-F)/10(5) marrow cells and 320,000 adherent cells in LTMC. Again, GVHD patients showed more severe deficiencies (0.16 CFU-F/10(5) marrow cells and 34,000 adherent cells in LTMC) than patients without GVHD (2 CFU-F/10(5) marrow cells and 122,000 adherent cells in LTMC). Our results demonstrate that the hematopoietic system of BMT recipients is impaired, both in terms of its in vitro composition and function, and that these deficiencies are clearly more pronounced in patients with GVHD than in those without GVHD. Finally, although the evidence is still preliminary, our results also indicate that the severity of the hematopoietic alterations may be greater in acute GVHD than in chronic GVHD.