الفهرس 
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Abstract
Summary and conclusion
Stem cell therapy and transplantation has became the new era in treatment of many diseases, malignancies and vital to the development, growth, maintenance, and repair of brains, bones, muscles, nerves, blood, skin, and other organs.
Umbilical cord blood and bone marrow reported as an important sources of non embryonic stem cells as ethical, political, and biological issues limit the embryonic stem (ES) cell therapies.
CD34and CD45 expression became the hallmark for selection of human HSC, and CD34+ cells had subsequently been widely used both for human autologous and allogeneic transplantations, resulting in a rapid reconstitution of all blood lineages.
Stem cell banks gave attention to selection of high quality units to ensure higher rates of transplantation success.
Expression of CD34+ count is done by flowcytometry and it is very important in selecting stem cells units and to assess potency. CD34+ count is an indicator of success of transplantation; so many banks use it to characterize UCB units.
Cryopreservation is the process of storage of HSCs. After Cytoreduction, dimethyl sulfoxide (DMSO) is added to UCB unit and B.M unit to preserve cells. Temperature is gradually decreased at a rate of 1º C / minute using controlled rate freezer to prevent rapid decrease of temperature. The UCB unit is then transferred into liquid nitrogen tank at a temperature of -135º C .
Cryopreservation of UCB unit is expensive and public stem cell banks need a lot of financial support to maintain their service. Quality of stem cell units affects transplantation outcome. For these reasons, only high quality stem cell units should be preserved and for that a lot of strategies have been developed to improve donor selection,CD34+ve cells count play significant role in transplantation outcome.
This study was conducted on 20 UCB samples belonged to mothers undergoing caesarian section in Obstetrics and Gynecology Department, Sohag University Hospitals. Complete data about mother, delivery and fetus were collected. And 10 samples of Bone marrow aspirate from cases with non malignant non autoimmune diseases
Samples were processed in Stem Cell Unit Clinical Pathology Departments Sohag University . Mononuclear cells were separated using density gradient centrifugation and CD34+ ve cells and CD34\CD45 double positive cells were calculated for each sample before and after cryopreservation.
As regardCord blood samples:
• Concerning the effect of cryopreservation, there is significant depression on CD34 +ve cells percent and CD34+ve/CD45+ve cells percent after cryopreservation
• There is significant elevation in CD34+ve cells percent and CD34+ve/CD45+ve cells in male than female babies.
• There is no significant differences in CD34 +ve cells percent and CD34+ve/CD45+ve cells between preterm,term and post term babie,s samples
• There is significant elevation in CD34+ve cells percent and CD34+ve\CD45+ve cells percent with increase birth weight (gm).
• As regard maternal age, CD34 +ve cells percent and CD34+ve/CD45+ve cells percent is significantly higher in samples with maternal age more than 20 years old than samples with maternal age less than 20 years old.
• Bone marrow samples:
• Concerning the effect of cryopreservation of B.M samples, there is significant depression on CD34 +ve cells percent and CD34+ve/CD45+ve cells percent after cryopreservation.
• With comparison between cord blood and Bone marrow we found that CD34 +ve cells percent and CD34+ve/CD45+ve cells percent more in cord blood than bone marrow.
• As regard peripheral blood hematological indices in cases we took bone marrow samples from them, we noticed that there is increase in CD34 +ve cells percent and CD34+ve/CD45+ve cells percent with increase absolute lymphocytic count and increase Hb.