Computational modeling of lumbar disc degeneration before and after spinal fusion.

BACKGROUND: Advancing age and degeneration frequently lead to low back pain, which is the most prevalent musculoskeletal disorder worldwide. Degenerative changes in intervertebral discs and musculo-ligamentous incapacity to compensate sagittal imbalance are typically amongst the sources of instability, with spinal fusion techniques being the main treatment options to relieve pain. The aims of this work were to: (i) assess the link between ligament degeneration and spinal instability by determining the role of each ligament per movement, (ii) evaluate the impact of disc height reduction in degenerative changes, and (iii) unveil the most advantageous type of posterior fixation in Oblique Lumbar Interbody Fusion to prevent adjacent disc degeneration. METHODS: Two L3-L5 finite element models were developed, being the first in healthy condition and the second having reduced L4-L5 height. Different degrees of degeneration were tested, combined with different fixation configurations for Oblique Lumbar Interbody Fusion. FINDINGS: Facet capsular ligament and anterior longitudinal ligament were the most influential ligaments for spinal stability, particularly with increasing degeneration and disc height reduction. Pre-existent degeneration had lower influence than the fusion procedure for the risk of adjacent disc degeneration, being the highest stability and minimal degeneration achieved with bilateral fixation. Right unilateral fixation was more suited to reduce disc stress than left unilateral fixation. INTERPRETATION: Bilateral fixation is the best option to stabilize the spinal segment, but unilateral right fixation may suffice. This has direct implications for clinical practice, and the extension to a population-based study will allow for more efficient fusion surgeries.

Analysis of surface markers on CD34+ cells, isolated from cord blood and G-CSF primed peripheral blood.

We report a comparative study of the expression of multilineage and adhesion molecules on CD34+ cells isolated from human umbilical cord blood (CB) and G-CSF-mobilized peripheral blood progenitor cells (PBPC) from healthy volunteers. The major difference found between the two sources of CD34+ populations was the expression of CD54 molecule, which was higher in CB in comparison to PBPC.

Umbilical cord blood processing: volume reduction and recovery of CD34+ cells.

One of the main problems for the establishment of umbilical cord blood (UCB) banks is the storage space needed for the frozen samples. The aim of this study was to find a method of reducing the volume of UCB units without major losses of the haematopoietic progenitor-CD34+ cells. The UCB was collected into a triple blood bag system, in which the anti-coagulant had been previously adjusted. The blood bag was first centrifuged for red cell depletion followed by a second centrifugation for plasma reduction. At this point, the main bag containing the white blood cell (WBC) rich fraction "buffy coat' (BC) and the "waste bag' were sealed and detached. Haematologic cell counts and CD34+ cell quantification were done in whole blood and in the isolated fractions. The average volume of the 19 UCB samples processed was 103 ml. Separation by centrifugation led to a mean volume reduction of 56% with red cell depletion of 59%. The white blood cell recovery was of 72% with a significant CD34+ cell recovery of 87%. This seems a promising method for cord blood volume reduction and enrichment of CD34+ cells.

Umbilical cord blood processing with the Optipress II blood extractor.

BACKGROUND: We have previously shown that UC blood (UCB) units can be volume-reduced manually, in a closed system, without major losses of nucleated and CD34(+) cells and without the addition of exogenous material. Our aim was to use an automated method for the separation of the UCB components using the Optipress II, extractor, with the 'buffy-coat' collection in a standardized volume. METHODS: After centrifugation, the 51 UCB units were separated into the three blood components, plasma, buffy coat (BC) and red cells, using the Optipress II. The final volume of the BC fraction, rich in nucleated and progenitor CD34(+) cells, was set at 30 mL. The nucleated and CD34(+) cell content of the UCB collections and the resulting BC were evaluated. RESULTS: The UCB units were grouped according to the volume collected: Group I < 80 mL and Group II > or = 80 mL. Standardization of the BC at 30 mL resulted in significant volume reduction for both groups, with median values of 51% in Group I and 70% in Group II. The nucleated and CD34(+) cell recoveries in the BC from Group I were 88% and 99% respectively; for Group II they were 80% and 97%. DISCUSSION: This semi-automated method of volume reduction efficiently reduces low, as well as high volume UCB units, with good nucleated- and progenitor-cell yields. Being a closed system and free of external material, the risk of contamination is minimized. The resulting fractions are then available for validation studies of the unit, effectively fulfilling the main requisites for UCB banking.

Single- versus dual-platform assays for human CD34+ cell enumeration.

We comparatively assessed CD34+ cell quantification by two of the recently available single platform assays, the IMAGN 2000 STELLer (Immucor, Lisbon, Portugal) microvolume fluorimetry and the ProCOUNT (BD-ENZIfarma, Lisbon, Portugal) flow cytometry, with our "in-house" dual-platform flow cytometric assay. The performance of the methods was evaluated by linearity and reproducibility tests. The linearity study, over a range of 0-1,200 CD34+ cell/microl, gave a good linear relationship for the three methods, with R(2) > 0.99. Precision tested at three different concentrations gave coefficients of variation ranging from 3.6-26.4% for the STELLertrade mark, 2.4-13.8% for the ProCOUNT, and 3.2-6.4% for flow cytometry. CD34+ cells were quantified in umbilical cord blood (UCB), UCB enriched-leukocyte buffy-coat (BC), mobilized peripheral blood (PB) and mobilized peripheral blood progenitor cells (PBPC) collected by leucapheresis, from a total of 72 samples. Flow cytometric results showed good linear correlation to the absolute counts obtained by the STELLer and ProCOUNT for all samples (R > 0.90 for all methods), with no differences when compared by paired tests (P > 0.05). Linear correlations between methods were also found when individually looking at the different cell sources: UCB or PB, BC, and PBPC, with low, intermediate and high CD34+ cell concentrations, respectively. Furthermore, with the exception of a significant difference between the ProCOUNT and STELLer results for UCB (P < 0.05), no other difference between methods was found for each of the individual populations (P > 0.05). To our knowledge, this is the first report in which the results are presented and analyzed according to each source of CD34+ cells. Our results show that the STELLer and the ProCOUNT are equally efficient for the dual-platform flow cytometric assay in CD34+ cell quantification.

Immunophenotyping by flow cytometry of fine needle aspirates in the diagnosis of lymphoproliferative disorders: A retrospective study.

In order to determine the value of flow cytometric (FCM) immunophenotyping of fine-needle aspirates (FNA) in the diagnosis and classification of lymphoproliferative diseases, 61 tissue samples were studied and compared with the cytologic/histological results. In vivo and ex vivo FNA biopsy yielded the material for FCM, which comprised an extensive number of lymphoid cell markers. In all but three cases sufficient cells were collected. Overall, malignancy was diagnosed in 33 cases from a total of 47 (70.2%), and in the remaining cases malignancy was not detected. Eleven cases were correctly diagnosed as reactive processes (11/11). There were no false positive cases of malignancy, as diagnosed by FCM-FNA. The best accuracy was achieved in the low-grade B-cell lymphomas and lymphoblastic lymphoma/leukemia. We conclude that in a significant number of cases, FCM-FNA permits the separation between lymphoid malignancies and reactive processes without false positive results. It was found to be particularly useful in the differential diagnosis of mantle-cell and small-lymphocytic lymphoma and in the identification of lymphoblastic lymphoma/leukemia.