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Biomedical subjects

Martha C Sola

Publications and source records attributed to Martha C Sola.

14 recordsLinked to original sources
PubMed2005

Effects of hypoxia on megakaryocyte progenitors obtained from the umbilical cord blood of term and preterm neonates.

BACKGROUND: Placental insufficiency is associated with early-onset thrombocytopenia in preterm neonates. Prior studies demonstrated a reduction in circulating megakaryocyte (Mk) progenitors, suggesting decreased platelet production. We hypothesized that decreased Mk production is the result of a direct inhibitory effect of hypoxia on the proliferation of Mk progenitors, or a hypoxia-induced change in the fetal hematopoietic environment. OBJECTIVE: To test the effects of hypoxia on the clonogenic maturation of Mk progenitors obtained from term and preterm cord blood CD34(pos) cells, either cultured alone or in conjunction with CD34(neg) light density mononuclear cells (LDMCs). METHODS: CD34(pos) cells and CD34(neg) LDMCs were isolated from the cord blood of term and preterm deliveries, and mobilized peripheral blood CD34(pos) cells were obtained from healthy adults. CD34(pos) cells were then cultured alone or co-cultured with CD34(neg) LDMCs in a semisolid, serum-free media containing rTpo, IL-3, and IL-6. Cultures were exposed to 20%, 5%, or 1% oxygen for 10-12 days. Mk colonies were then quantified following immunohistochemical staining. RESULTS: Pure CD34(pos) cells from preterm (n = 5) and term (n = 5) neonates and from adults (n = 4) generated similar numbers of Mk colonies in all three oxygen concentrations. However, the number of Mk colonies in preterm co-cultures was progressively lower with decreasing O(2) concentrations. CONCLUSIONS: Hypoxia did not appear to directly inhibit colony formation of Mk progenitors from preterm and term cord blood CD34(pos) cells. However, co-culture studies showed a decrease in Mk colony formation with hypoxia, suggesting an indirect inhibitory effect of hypoxia on Mk clonogenic maturation mediated by non-progenitor cells in the hematopoietic microenvironment.

Antigens, CD34↗
PubMed2005

Developmental differences in megakaryocyte maturation are determined by the microenvironment.

Historically, physicians have attributed delayed platelet engraftment following umbilical cord blood transplant to decreased numbers of stem cells in cord blood compared with adult bone marrow. However, recent studies suggest that delayed platelet engraftment may be caused by an intrinsic inability of neonatal stem cells to produce mature, polyploid megakaryocytes. We tested this hypothesis by transplanting adult bone marrow and newborn liver hematopoietic stem and progenitor cells from transgenic mice expressing green fluorescent protein into myeloablated wild-type recipients and comparing the size and ploidy levels of megakaryocytes that developed in adult transplant recipients. Transplanted stem and progenitor cells, regardless of their source, gave rise to megakaryocytes that were larger than normal adult megakaryocytes as early as 7 days post-transplant. However, megakaryocytes that developed after transplant of neonatal stem and progenitor cells were significantly smaller than those derived from adult stem and progenitor cells. Furthermore, megakaryocytes derived from neonatal cells had lower ploidy values than megakaryocytes derived from adult cells at 18 days post-transplant, when ploidy could first be reliably measured in the bone marrow. These differences in size and ploidy disappeared by 1 month post-transplant. The largest megakaryocytes developed in the spleen. These results suggest that, in the mouse, the microenvironment is responsible for some of the maturational differences in size and ploidy between neonatal and adult megakaryocytes. Furthermore, neonatal and adult megakaryocyte progenitors also have cell-intrinsic differences in the way they engraft and respond to thrombocytopenic stress. These differences may contribute to the delay in platelet engraftment that frequently complicates cord blood transplants.

Age Factors↗
PubMed2004

Benign B-cell precursors (hematogones) are the predominant lymphoid population in the bone marrow of preterm infants.

Bone marrow (BM) findings in 3rd-trimester stillborns and full-term living neonates have been previously described. However, there is no information regarding BM composition in living preterm infants. Specifically, it is unknown whether the BM lymphocytosis seen in full-term infants at 1-4 weeks of age also occurs in preterm infants. Furthermore, the lineage of these cells has never been investigated. We used a panel of immunohistochemical stains to characterize the BM composition in 11 neonates (8 living and 3 deceased). Unlike in the other age groups, immature B cells (hematogones) were the most common lymphoid population, accounting for 10-60% (mean 34%) of all cells. In two additional cases (both living patients), flow cytometry revealed a level of 3.8% of immature B cells in a <1-week-old neonate and 25.7% in a 19-week-old infant. Immature B cells were not identified in 6 peripheral blood samples from preterm neonates. These findings are pertinent for the interpretation of BM and peripheral blood samples in this age group as survival improves and diagnostic samples become more common.

Antigens, CD↗
PubMed2004

Platelet function in term and preterm neonates.

Platelet dysfunction likely contributes to the pathophysiology of catastrophic hemorrhages in preterm neonates. In vitro studies have demonstrated that platelets of both term and preterm neonates are hyporesponsive to a variety of agonists. In contrast,template bleeding times of term neonates are shorter than those from adults. Very little is known about this and other tests of primary hemostasis in premature and sick neonates in the neonatal intensive care unit (NICU). This article covers the current knowledge of platelet function in preterm and term neonates and review show new agents (such as recombinant thrombopoietin and recombinant factor VIIa) may enhance neonatal platelet function.

Blood Platelets↗
PubMed2004

Evaluation and treatment of severe and prolonged thrombocytopenia in neonates.

Thrombocytopenia is one of the most common hematologic problems in the neonatal intensive care unit (NICU). Despite its prevalence,several basic pathophysiologic questions remain unanswered. For instance, there is a lack of evidence-based guidelines for treatment,and the kinetic mechanisms (decreased platelet production,increased platelet consumption, or sequestration) responsible for most varieties of neonatal thrombocytopenia are not well defined.Moreover, a clear correlation between degree of thrombocytopenia and the resulting bleeding risk has not been demonstrated, and no transfusion-trigger studies have been conducted in neonates. As a consequence of these deficiencies in knowledge, there is great variability in platelet transfusion practices among NICUs. This article presents an overview of the evaluation of a neonate with severe thrombocytopenia and a review of current and projected therapeutic options.

Chronic Disease↗
PubMed2004

The concentration of circulating megakaryocyte progenitors in preterm neonates is a function of post-conceptional age.

Circulating megakaryocyte (Mk) progenitors have been used as a measure of megakaryocytopoiesis in neonates. Prior studies have shown a gestational age-dependent decrease in their concentration, but it is unclear how this process continues after birth in preterm neonates. To answer this question, we quantified the Mk progenitors in the blood of 42 neonates of varying post-conceptional ages (gestational age+days of life). We found an inverse relationship between concentration of circulating Mk progenitors and post-conceptional age (r=-0.54, p=0.0002).

Blood Cell Count↗
PubMed2004

A neonate with severe thrombocytopenia and radio-ulnar synostosis.

Bone marrow failure syndromes can be associated with abnormalities of the forearms. We observed a neonate with congenital thrombocytopenia who had bilateral radio-ulnar synostosis and fifth finger clinodactly. We performed an evaluation of the mechanism causing the thrombocytopenia using a combination of direct and indirect measures of thrombopoiesis. These tests indicated decreased platelet production. This entity of congenital hyporegenerative thrombocytopenia with bilateral radio-ulnar synostosis and fifth-finger clinodactly is an uncommon but easily recognizable form of congenital amegakaryocytic thrombocytopenia (CAMT). This entity can be distinguished from the TAR syndrome (thrombocytopenia and absent radii) by the distinctive orthopedic issues, different underlying genetic mutations, and a more worrisome prognosis for CAMT than for TAR.

Diagnosis, Differential↗
PubMed2004

Pseudothrombocytopenia in a preterm neonate.

Severe and prolonged thrombocytopenia is not uncommon among ill preterm infants. Pseudothrombocytopenia, which has the appearance of severe and prolonged thrombocytopenia, has not been described in this population. We observed a preterm neonate who had EDTA-independent pseudothrombocytopenia and conclude that this condition should be considered when severe and prolonged thrombocytopenia occurs in a neonate in the absence of clinical signs of platelet-type hemorrhage.

Diagnostic Errors↗
PubMed2004

Reticulated platelet percentages in term and preterm neonates.

OBJECTIVES: The authors aimed to determine whether their reticulated platelet percentage (RP%) analysis technique was suitable for use in term and preterm neonates and to characterize RP% values among nonthrombocytopenic neonates. METHODS: The authors modified a whole blood method that uses dual-color CD41 staining for platelet gating and thiazole orange for RNA content, combined with RNase treatment of half the sample to subtract non-RNA fluorescence. The RP% was measured in samples from 10 healthy adults and then a longitudinal study was performed in 15 nonthrombocytopenic preterm neonates on days of life 0 to 1, 2 to 5, 6 to 10, and then weekly until day 28. The authors also performed a cross-sectional study of RP% in 22 nonthrombocytopenic neonates of different gestational age (GA) and postconceptional age (PCA). RESULTS: Overall, neonates had a higher RP% (2.7 +/- 1.6%) than adults (1.1 +/- 0.5%; P < 0.01). In preterm neonates, an increase in the RP% occurred between days 0 and 1 (3.3 +/- 1.3%) and days 2 and 5 (5.1 +/- 1.8%; P = 0.003). By days 6 to 10, the RP% decreased to 3.2 +/- 1.1% and remained unchanged throughout the rest of the study period. In neonates less than 7 days old, an inverse relationship was observed between RP% and GA (n = 20, r = -0.70; P = 0.0005). A correlation between RP% and PCA was not seen in neonates 7 days of age or older. CONCLUSIONS: This method for determining RP% is suitable for use in term and preterm neonates. In preterm infants, the RP% significantly increases over the first 2 to 5 days of life and then decreases to a stable level over the first 28 days. RP% is generally higher in neonates than in adults. Among preterm infants in the first week of life, the RP% is inversely related to GA.

Adult↗
PubMed2003

Hepatic erythropoietin gene regulation by GATA-4.

Erythropoietin production switches from fetal liver to adult kidney during development. GATA transcription factors 2 and 3 could be involved in modulating this switch, because they were shown to negatively regulate erythropoietin gene transcription through a promoter proximal GATA site. Herein, we analyzed the role of several GATA factors in the regulation of the erythropoietin gene in human liver and in hepatoma cells. Although GATA-3 expression in hepatocytes increases during human development, erythropoietin mRNA accumulation is unaltered in mutant mice lacking GATA-3. We found that GATA-2, -3, -4, and -6 are all expressed in human hepatocytes and that GATA-4 exhibits the most prominent Epo promoter binding activity in vitro and in vivo. Inhibition of GATA-4 expression by RNA interference leads to a dramatic reduction in Epo gene transcription in Hep3B cells. Moreover, GATA-4 expression is high and limited to hepatocytes in the fetal liver, whereas GATA-4 expression in the adult liver is low and restricted to epithelial cells surrounding the biliary ducts. Thus, GATA-4 is critical for transcription of the Epo gene in hepatocytes and may contribute to the switch in the site of Epo gene expression from the fetal liver to the adult kidney.

Animals↗
PubMed2003

Effects of anoxia on megakaryocyte progenitors derived from cord blood CD34pos cells.

BACKGROUND: Severe hypoxic insults to the fetus and neonate are associated with the development of thrombocytopenia. The thrombocytopenia in some cases is the result of disseminated intravascular coagulation, but that mechanism fails to account for all, perhaps the majority, of cases. OBJECTIVE: We hypothesized that human fetal megakaryocyte (Mk) progenitors are directly adversely affected by transient anoxia. DESIGN AND METHODS: To test this, we isolated CD34pos cells from the umbilical cord blood of 10 healthy term neonates, and exposed these to 0% or 20% O2 for 24 h, with or without recombinant thrombopoietin (rTpo, 50 ng/mL). After 24 h, a portion of the CD34pos cells were harvested for flow cytometric evaluation of apoptosis. The remaining cells were cultured for an additional 10-12 days, under normoxic conditions, in a collagen-based serum-free system containing rTpo, IL-3, and IL-6. In this way, we sought to determine the effect of transient anoxia on clonogenic capacity of Mk progenitors. RESULTS: Contrary to our hypothesis, anoxia did not increase either apoptosis or cell death of the CD34pos cells. The addition of rTpo was protective, with a significant decrease in apoptosis and cell death (P < 0.0001), and an increase in the number of Mk colonies cultured (P = 0.04). There was no difference between the normoxic and anoxic groups in proliferative potential of the Mk progenitor cells. CONCLUSIONS: The thrombocytopenia observed in neonates following an acute hypoxic event is not likely due to a direct deleterious effect of hypoxia on Mk progenitors.

Antigens, CD34↗
PubMed2002

Developmental changes in the expression of transcription factors GATA-1, -2 and -3 during the onset of human medullary haematopoiesis.

Regulation of gene expression during the ontogeny of haematopoiesis in the human fetal bone marrow is poorly understood. Studies in mice demonstrated that GATA-1, -2 and -3 play pivotal roles in haematopoiesis. In this study, we identified GATA-1-, GATA-2- and GATA-3-expressing cells in bone marrow sections and analysed the expression of GATA-transcription factors during the development of human fetal bone marrow haematopoiesis using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). We showed that GATA-1, -2 and -3 were expressed only in haematopoietic cells in the bone marrow. RT-PCR analysis demonstrated that (1) GATA-1 expression significantly increased during gestation; (2) GATA-2 expression peaked at the onset of medullary haematopoiesis, declined thereafter, and remained at a constant level after 30 weeks post conception; and (3) GATA-3 expression revealed no changes during development. The results indicated that the onset of medullary haematopoiesis in humans is accompanied by high expression of GATA-2, reflecting high proliferation rates of early haematopoietic progenitor cells, whereas expression of GATA-1 mirrors haematopoietic activity.

Bone Marrow↗
PubMed2002

Multicenter analysis of platelet transfusion usage among neonates on extracorporeal membrane oxygenation.

OBJECTIVE: Multiple platelet transfusions are invariably given to neonates on extracorporeal membrane oxygenation (ECMO), and no alternative to repeated transfusions exists. Before any alternatives, such as administration of thrombopoietic stimulators, could be contemplated, data regarding the number of platelet transfusions received by neonatal ECMO patients is needed, and the mechanisms that cause the thrombocytopenia of these patients must be better defined. As a step toward determining this, we analyzed the use of platelet transfusions in this group of neonates. We conducted a historic cohort study of neonates who were treated with ECMO to determine the number of platelet units received as a function of 1) days on ECMO, 2) medical diagnosis for which ECMO was instituted, and 3) type of ECMO used (venovenous [VV] vs venoarterial [VA]). METHODS: We reviewed the hospital records of all neonates who were admitted to the neonatal intensive care units at Shands Children's Hospital, Arnold Palmer Hospital for Children and Women, and Tampa General Hospital and treated with ECMO between January 1, 1995, and June 30, 2000. Data were expressed as the number of platelet transfusions versus number of days on ECMO, diagnosis for which ECMO was instituted, and type of ECMO used. RESULTS: Of the 234 ECMO patients, 81 were placed on VV, 138 were placed on VA, and 15 were converted from VV to VA. The average number of platelet transfusions received per day was 1.3 and varied by diagnosis and by type of ECMO. Neonates with meconium aspiration and sepsis required more platelet transfusions per day than neonates with other conditions. Infants who were converted from VV to VA required more transfusions per day (mean: 1.57) than did patients on VA (1.47) or VV (1.06). CONCLUSIONS: Platelet transfusions among neonates on ECMO are dependent of their medical diagnosis; they average 1.3 transfusions per day and are higher on VA than VV ECMO.

Birth Weight↗