Kanchan Jeswani, Product Manager – Hematology, Transasia Bio-Medicals elaborates how hematopoietic progenitor cells (HPC) is emerging as a novel parameter in hematology analyzers
Peripheral blood stem cells (PBSC) are increasingly used to restore hematopoiesis as an alternative to bone marrow transplantation. It is important to determine the precise time for HSCs (hematopoietic stem cells) to be collected for a reliable, rapid and successful haematological recovery.
HPC and HSC express high levels of the cell surface glycoprotein, adhesion receptor CD34. The levels of CD34 expression decreases with cell maturation and differentiation. Expression of CD34+ is thus a defining hallmark for hematopoietic stem cells (HSCs) and progenitor cells (HPCs) in bone marrow (BM), peripheral blood (PB) and cord blood. An accurate quantification of circulating CD34+ stem cells is important to decide the optimal time for collection.
Flow cytometric enumeration of CD34+is the standard method of counting. The International Society of Hematotherapy and Graft Engineering (ISHAGE) gating strategy isused for CD34+ cell detection. An alternate method for quantification of circulating HSC minimises the number of CD34 determination, thus saving important resources. Since the introduction of the HPC software in 1997 in the high end Sysmex analyers, many studies of HPC determination versus CD34+ cell enumeration have been performed. The HPC parameter serves as an inexpensive and fast alternative for quantification of the circulating HSC Cells.
Sysmex Corporation, Japan offers the latest and best technology in hematology analyzers. Marketed in India, exclusively by Transasia Bio-Medicals, Sysmex offers a whole range of systems ranging from 3 to 6 Part Differential Analyzers. Infact the newly launched Sysmex XN series is equipped with a White Precursor Cell (WPC) channel to differentiate abnormal lymphocytes and blasts by using the optical detection system and Fluoroscence flow cytometry.
A study (published in December, 2013, in the International Journal of Laboratory Hematology) conducted by the scientists at the National Cancer Center Hospital (Tokyo, Japan) concluded that the HPC count obtained on a Sysmex XN analyzer correlates accurately with the enumerated CD34 cells. Cells expressing the CD34+ and hematopoietic progenitor cells (HPCs) were compared in 76 granulocyte colony-stimulating factor (G-CSF) mobilised blood or apheresis samples taken from 18 healthy donors and 6 patients undergoing autologous PBSCT. CD34+ cells were isolated using MACS magnetic cell separation kits (MiltenyiBiotec – BergischGladbach, Germany).
The investigators found a strong correlation between the numbers of HPCs and CD34+ cells. The expected total number of HPCs in the final product was estimated from HPCs in pre apheresis peripheral blood (PB) or mid apheresis product. This count was found to correlate well with the total number of CD34+ cells in the final products. Moreover, the change in HPCs in PB closely resembled that of CD34+ cells during mobilization. Further, studies using immunomagnetic beads suggested that majority of CD34+ cells existed in HPCs, and vice versa.
Conclusion
The Sysmex XN analyzer can carry out an HPC enumeration without the use of monoclonal antibodies
Sensitivity of flagging of blasts is enhanced in the WPC channel of the instrument. It gives a clear demarcation between the blasts and the abnormal lymphocytes.
The total number of HPCs in the final products, as well as from pre apheresis PB and intermediate products during apheresis, can be used to predict the final amount of collected CD34+ cells.
The detection and number of HPC in the peripheral blood could possibly provide a standard and rapid alternative for predicting the yield of stem cells collected by apheresis.
HPCs may also be a good indicator to know the optimal timing for collection of the peripheral blood stem cells.
The HPC count can thus be a useful potential parameter in optimising timing for CD34+ enumeration prior to leukapheresis.
References:
1. Bali Medical Journal (Bali Med. J.) 2014, Volume 3, Number 3: 112-115\P-ISSN.2089-1180, E-ISSN.2302-2914 www.balimedicaljournal.org or www.ojs. unud.ac.id 112
HEMATOPOIETIC PROGENITOR CELLS AS A PREDICTIVE OF CD34+ENUMERATION PRIOR TO PERIPHERAL BLOOD STEM CELLS HARVESTING1Zefarina Zulkafli, 2Rapiaah Mustaffa, and 2Shafini Mohammed Yusoff
2. Hemopoietic Progenitor Cell (HPC) Enumeration: A Comparitive Study betweenFlow Cytometry and Sysmex XE-2100Hematology Analyzer-Salem H. Khalil, Barbara GengJournal of Appplied Hematology 2010
3. http://www.bloodjournal.org/content/122/21/2032November 15, 2013; Blood: 122 (21)
4. December 27, 2013, in the International Journal of Laboratory Hematology