The consequences of Sickle Cell Disease (SCD), including ongoing hematopoietic stress and hemolysis, vascular damage and chronic therapies , such as blood transfusions and Hydroxyurea on hematopoietic stem and progenitor cell (HSPC) have not been characterized. We have quantified the frequencies of nine HSPC populations by flow cytometry in the peripheral blood of pediatric and adult patients stratified by treatment and controls. We observed broad differences between SCD patients and healthy controls. SCD is associated with 10 to 20-fold increase in CD34dim cells, and two to five-fold more CD34bright cells, a depletion in Megakaryocyte-Erythroid Progenitors and an increase in hematopoietic stem cells, when compared to controls. SCD is also associated with abnormal expression of CD235a and by very high levels of expression of the CD49f antigen. These findings were present to varying degrees in all patients, whether or not they were naïve or on chronic therapy. HU treatment tended to normalizes many of these parameters. Chronic stress erythropoiesis, inflammation caused by SCD and hydroxyurea therapy have long been suspected of causing premature aging of the hematopoietic system, and potentially increasing the risk of hematological malignancies. An important finding of this study was that the observed concentration of CD34bright cells and of all the HSPCs decreased logarithmically with time of treatment with HU. This correlation was independent of age and specific to HU treatment. Although the number of circulating HSPCs is influenced by many parameters, our findings suggest that HU treatment may decrease premature aging and hematologic malignancy risk compared to the other therapeutic modalities in SCD.

The cytostatic agent hydroxyurea (HU) has proven to be beneficial for a variety of conditions in the disciplines of oncology, hematology, infectious disease and dermatology. It disrupts the S-phase of the cell cycle by inhibiting the ribonucleotide reductase enzyme, thus blocking the transformation of ribonucleotides into deoxyribonucleotides, a rate limiting step in DNA synthesis. HU is listed as an essential medicine by the World Health Organization. Several studies have indicated that HU is well tolerated and safe in pregnant women and very young pediatric patients. To our knowledge, only a few controlled studies about the adverse effects of HU therapy have been done in humans. Despite this, the prevalence of central nervous system abnormalities, including ischemic lesions and stenosis have been reported. This review will summarize and present the effects of HU-exposure on the prenatal and perinatal development of the rat cerebellar cortex and deep cerebellar nuclei neurons. Our results call for the necessity to better understand HU effects and define the administration of this drug to gestating women and young pediatric patients.

Extramedullary hematopoiesis is a compensatory response in chronic hemolytic anemia, such as thalassemia, and can lead to spinal cord compression. This case report describes a 36-year-old woman with β-thalassemia who presented with lower extremity motor deficiency, pelvic paresthesia, and bladder dysfunction. The patient had a history of low back pain, bilateral lower limb weakness, and poor compliance with iron chelation therapy. MRI revealed compression of the spinal cord due to extramedullary hematopoiesis. Surgical intervention was not feasible, and the patient underwent hypertransfusion and iron chelation therapy. Neurological symptoms improved, but urinary retention persisted. The patient continues to receive iron chelation treatment and undergoes transfusions. Extramedullary hematopoiesis is a common complication in thalassemia and requires an individualized treatment approach.

Sickle cell disorder (SCD) is a multisystem disease with heterogeneous phenotypes. Although all patients have the mutated haemoglobin (Hb) in the SS phenotype, the severity and frequency of complications are variable. When exposed to low oxygen tension, the Hb molecule becomes dense and, forms tactoids which, lead to the peculiar sickled shapes of the affected red blood cells, giving the disorder its name. This sickle cell morphology is responsible for the profound and widespread pathologies associated with this disorder, such as vaso-occlusive crisis, (VOC). How much of the clinical manifestation is due to sickled erythrocytes and what is due to the relative contributions of other elements in the blood, especially in the microcapillary circulation, is usually not visualized and quantified for each patient during clinical management. Here, we used a microfluidic microcirculation mimetic (MMM) which has 187 capillary-like constrictions to impose deformations on erythrocytes of SCD patients, visualizing and characterizing the morpho-rheological properties of the cells in normoxic, hypoxic (using of sodium meta-bisulfite) and in treatment conditions (using hydroxyurea). The MMM enabled a patient-specific quantification of shape descriptors (circularity and roundness) and transit time through the capillary constrictions, which are readouts for morphorheological properties implicated in VOC. Our results demonstrate the feasibility of microfluidics-based monitoring of individual patients for personalized care in the context of SCD complications such as VOC, even in re-source-challenged settings.

Unlike plants which have special gravity-sensing cells, such special cells in animals are yet to be discovered. However, microgravity, the condition of apparent weightlessness, causes bone, muscular and immune system dysfunctions in astronauts following spaceflights. Decades of investigations show correlations between these organ and system-level dysfunctions with changes induced at the cellular level both by simulated microgravity as well as microgravity conditions in outer space. Changes in single bone, muscle and immune cells include morphological abnormalities, altered gene expression, protein expression, metabolic pathways and signaling pathways. These suggest that human cells mount some response to microgravity. However, the implications of such adjustments on many cellular functions and responses are not clear. Here, we addressed the question whether microgravity induces alterations to drug response in cancer cells. We used both adherent cancer cells (T98G) and cancer cells in suspension (K562) to confirm known effects of microgravity and then treated the K562 cells with common cancer drugs (hydroxyurea and paclitaxel) following 48 hours of exposure to microgravity via a NASA-developed rotary cell culture system. Fluorescence-guided morphometry revealed microgravity-induced loss of the significant reduction (p < 0.0l) to the nuclear to cytoplasm ratio of cancer cells treated with hydroxyurea. Our results call for more studies on impact of microgravity on cellular drug-response, in view of the growing need for space medicine, as space exploration grows.

Patients with polycythemia vera (PV) are at increased risk of thrombosis and hemorrhages. Although hydroxyurea (HU) has been the frontline therapy for patients at high-risk of vascular complications, about 25% of patients develop resistance/intolerance to this therapy. The aim of this non-interventional, multicenter cohort study was to understand the clinical characteristics and HU treatment response of Portuguese PV patients. HU resistance/intolerance was defined according to adjusted European LeukemiaNet (ELN) criteria. 134 PV patients with a mean disease duration of 4.8±5.0 years were included and followed up for 2 years. At baseline, most patients were ≥60 years old (83.2%), at high risk for thrombotic events (87.2%), and receiving HU therapy (79.1%). A total of 10 thrombotic events and 8 hemorrhagic events were reported, resulting in a 5-year probability of thrombo-hemorrhagic events of 17.2%. Hematocrit (p=0.007), hemoglobin (p=0.012) and MPN10 symptom score (12.0±11.6 vs 10.3±9.1; p=0.041) decreased significantly at the 24-month visit compared to baseline. Overall, 75.9% of patients met at least one of the adjusted ELN criteria for HU resistance. 14.4% of patients remained on HU throughout the study. The results from this real-world study may help identify the subset of patients at higher risk of disease sequelae who may benefit from earlier second-line treatment.