الفهرس 
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Abstract
Regenerative medicine is an evolving field of medical researchers. This field holds the promise of regenerating damaged tissues and organs in the body by replacing damaged tissue and or by stimulating the body’s own repair mechanisms to heal previously irreparable tissues or organs.
Human body have a system for repair through stem cell which has become a field of researches because of it is promising result as these cell can renew themselves and can differentiate to other cell types according to their potency which differ according to source of cells whether embryonic or adult stem cells.
One of the most important sources of adult mesenchymal stem cells is bone marrow, but this source involve invasive procedure to have the cells now placenta offer an alternative source for mesenchymal stem cells, this source have the advantage of availability due to high birth rate and being easily accessible and has high differenation potential than other adult stem cells. These unique properties of PL-MSCs give them several advantages for clinical use, making them an interesting and attractive alternative to MSCs for regenerative medicine. (Erices et al., 2000).
The aim of our study was to detect the differentiation potential of mesenchymal stem cells isolated from human bone marrow and placenta towards osteogenic lineage, in order to help choose a better cell source for treatment of osteogenic trauma.
This study was conducted in tissue culture unit and in Medical Biochemistry Department (oncology diagnostic unit) .Faculty of Medicine, Suez Canal University.
The present study included both bone marrow mesenchymal stem cell samples obtained from patient undergoing total hip replacement in orthopedic surgery department and placental samples from full term babies of healthy mothers at the obstetric emergency room of Suez Canal University Hospital.
Both types of samples was subjected to mesenchymal stem cell isolation and culture in CO2 incubator (37ºC, humidified atmosphere containing 5% CO2) and media exchange till reaching 50% confluence and then induction of osteogensis by dexamethazone and ascorbate 2 phosphate , then RNA extraction of induced samples after 24 hours for bone and 24 and 72 hours for placental cells and for control of both groups , then reverse transcription of RNA to cDNA and the final step was detection of gene expression by comparative Ct methods by real-time PCR ABI 7000 using hot start SYBR Green master mix and genes primers.
In our study we found that both types of cells exhibited typical MSCs characteristics which are adherence to plastic surface of the flask, fibroblastoid morphology with no morphologic differences between cells from both sources.
We found that Runx-2 gene was significantly expressed in24hours bone treated samples in comparison to control about 7 fold in compared to control.
Regarding expression in placenta 24 hours treated samples in comparison to control, there was significant expression about 3 to 4 fold but there was no significant change in expression in 72 hours treated samples in comparison to 24 hours treated samples ,which mean more time was needed to detect significant change in expression.
Regarding alkaline phosphatase was expressed in BM-MSCs and was significantly higher than control BM-MSCs samples, but was not detected in PL-MSCs in 24 or 72 hours treated samples. Collagen type 1 was not detected either in bone marrow control or 24 hours treated samples, or in placenta control or treated samples after 24and 72 hours.
In conclusion in this study we found that there was significant change in Runx-2 and Osterix genes expression in treated samples in comparison to control and that expression in bone marrow stem cells was higher than placenta, thus may indicate that bone marrow mesenchymal stem cells have a higher osteogenic differentiation potential than placenta, and that BM mesenchymal stem cells would present a better source of stem cells for regenerative medicine and treatment of bone defects.
This is may be explained by the cell niche as BM-MSCs are already present in niches surrounded by a bony environment this may made these cells more committed to differentiate to osteogenic lineages than placental-MSCs .
Also it may be due to short term culture condition in our study for placenta, may be if we induce it for a longer time it will show expression level similar or higher than bone especially because these cell occupy intermediate age stage between embryonic and adult stem cell which lead to higher proliferating potential than other somatic stem cells, or if we add a growth factors for induction of osteogensis as there are a lot of growth factors involved in osteogensis that could result in better result for placenta.
We found also that ALP was only expressed in BM samples after 24 hours, and Col-1 expression was not detected in both cell types.
These observations implicate the postpartum human placenta as an important and novel source of multipotent stem cells that could potentially be used for investigating osteogenic mesenchymal stem cells differentiation.