Methods of Study of Neuron Structural Heterogeneity: Flow Cytometry vs. Laser Interferometry

Neuronal cells are probably the less studied cells regarding their heterogeneity on a single cell or population levels. One of the main problems of studying of individual neurons is the presence of long processes (axons) on differentiated adult neurons that hamper their isolation without significant damage to the cells. Therefore, the most common method to study neuronal cells is immunofluorescent microscopy of sections of the brain, which remains poorly quantitative and allows analyzing a small number of fixed cells. Also, immunofluorescent microscopy has a number of staining artifacts since histology section has high level of autofluorescence and non-specific binding of fluorescent probes. Alternative methods that could overcome disadvantages of immunofluorescent histology include flow cytometry, scanning cytometry, and laser interferometry. Flow cytometry and, to some extent of degree, scanning cytometry allow performing analysis of multiple markers with a low level of non-specific background and very robust statistics. Laser interferometry allows studies intact, alive neurons without staining. Limitations and advantages of these methods are discussed in this chapter.

A European reference protocol for quality assessment and clinical validation of autologous haematopoietic blood progenitor and stem cell grafts

Recently, the regulatory authorities have begun to show interest in haematopoietic stem cell products. On a professional rather than a regulatory basis, the International Society for Hematotherapy and Graft Engineering (ISHAGE) has established the Foundation for the Accreditation of Haematopoietic Cell Therapy (FACHT), which has drawn up guidelines for standards and accreditation of such activity. In Europe, the regulatory environment with regard to haematopoietic stem cell grafts, processing and storage are currently less stringent. However, in 1998 the European Joint Accreditation Committee Euro-ISHAGE/EBMT (JACIE) prepared a regulatory document 'Standards for Blood and Marrow Progenitor Cell Collection, Processing and Transplantation' which was approved by the EBMT General Assembly. The major objectives were to promote quality of medical and laboratory practice in haematopoietic progenitor cell transplantation. The standards extend and detail the pre-existing activity of EBMT centres including all phases of collection, processing and administration of these cells. This is the platform for the proposed reference protocol for CD34(+) cell enumeration and clinical validation of quality assessment to ensure that appropriate standards of work and product quality are established and will be maintained.

Technical aspects and clinical impact of hematopoietic progenitor subset quantification

As high-dose therapy for malignancies is now being applied to newly diagnosed patients as adjuvant therapy, it has become a requirement that quality and safety assessment of hematopoietic stem cell grafts be evidence-based. This process has developed a new institution in medicine, the stem cell laboratory. In most cases this speciality has evolved from or within hematological research laboratories. However, the increased routine technologies applied in quality evaluation, ex vivo manipulation and safety assessment in stem cell handling naturally places this activity in transfusion medicine. Multiparametric flow cytometry can identify progenitor subsets in normal human bone marrow and peripheral blood, and such subset quantification has been used retrospectively to predict three-lineage engraftment following high-dose therapy for malignancies. Published single center data have suggested an impact on clinical outcome, and a standardized technique for subset enumeration needs to be established before prospective multicenter trials can be initiated to document the prognostic value of such quality assessment in autografting. Based on experiences of CD34 enumeration, which we consider to be the first step in quality assessment of hematopoietic stem cell grafts, this review discusses flow cytometry subset identification by lineage-specific differentiation markers, stromal-dependent adherence molecules, and regulatory growth factor receptors from a technical point of view. The aim of this review is:To recommend a simple method based on the experiences of the Nordic workshop III on subset identification; To present new molecular genetic-based methods for future use in quality assessment; and To propose new endpoints necessary for validation of the likely clinical impact of subsets in prospective trials. As sample differences between blood and marrow result in technical difficulties, this review only focuses on the methodology of identifying subsets in blood and leukapheresis products. Methods for subset analysis in diagnostic bone marrow samples will be covered in a forthcoming review.

Use of fluorescence threshold triggering and high-speed flow cytometry for rare event detection

A simple rare event detection method utilizing dual-parameter flow cytometry is described, which allows quantitation of specific cellular events at the level of two cells in 10(7) total cells. Using a standard unmodified single laser flow cytometer sampling at a rate of 25,000 events/sec and a fluorescence discriminator, 10(7) total cells are processed in 7 min. The assay involves precise characterization of instrument flow rates to calculate total events processed by the cytometer rather than accumulate total events in computer memory. This method of detecting rare events is demonstrated by using a model system of breast cancer cells labeled with a metabolically activated dye and serially diluted into normal peripheral blood. Potential applications include validation of methods to detect minimum residual disease following myeloablative therapy, detection of any remaining tumor cells following purging methods, and validation of methods to detect circulating fetal cells in maternal blood.