الفهرس 
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Abstract
Regenerative medicine is an evolving field of medical researchesthis field holds the promise of regenerating damaged tissues and organs in the body by replacing damaged tissue and 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 become afield 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 adultmesenchymal stem cells is bone marrow but this source involve invasive procedure to have the cells but now cord blood offered an alternative source for mesenchymal stem cells this source have the advantage of availability due to high birth rate and being easy accessible and havinghighdifferentiation potential and higher telomere length than other adult stem cells.
The aim of our work was to study osteogenicdifferentiation potential of mesenchymal stem cells isolated from human BM and UCB towards osteogenic lineage in order to help choose a better cell source fortreatment and osteogenicrepair.
This study was conducted in tissue culture unit, medical biochemistry department, oncology diagnostic unitand (the umbilical cord blood and bone marrow samples) were collected from obestetric and orthopedic surgical department of Faculty of Medicine,Suez Canal University.
Both types of samples were subjected to mesenchymal stem cell isolation and culture in CO2 incubator (37ºC, humidified atmosphere containing 5% CO2) and media change till reaching 50% confluence and then induction of osteogensiswas done by addition ofdexamethazone and ascorbate-2 phosphate to the media.
RNA were extracted frominducedMSCs after 24 hours for BM and after (24 –72) hours for UCB cells and from untreated control samples from both groups, then RNA was reverse transcribed to cDNA.ThenRunx-2,Osterix ALP,ColI and GAPDH as a housekeeping gene expressionweredeterminedby real-time PCR ABI 7000 using hot start SYBR Green master mix.
In our study, we found that both types of cells exhibited typical MSCscharacteristics, which are adherenceto the plastic surface of the flask,and alsoexhibited fibroblastoid morphology with no morphologic differences between cells from both sources.
Our results showed that Runx-2 gene was significantly expressed in BM derived cellswhich was treated for 24 hours compared to control about 7 folds.Also there was significantexpression about 3 to 4 folds in UCB treated samples for (24-72) hours compared to control sample,but there was no significant changes in expression in UCBtreated samplesfor 72 hours in comparedto treated samples for 24 hours and runx-2 expression in 24 hours BM-MSCs treated samples was significantly higher than it is expression in 72 hours UCB-MSCs treated samples.
Our results also showed that Osterix gene was significantly expressed in BMderived cells treated for 24 hours about 3 fold compared to control. Osterixgene expression was detected in UCB samples and it was significantly expressed for (24- 72) hours in UCBtreated samples compared to control and this expression was significantly higher in treatedcord blood samples for 72 hours thantreated BM samples for 24 hours.
Regarding alkaline phosphatase gene expression, it was detected in BMmesenchymal cell control and 24 hours treated samples but was not detected in cord blood mesenchymal stem cell samples and also there was significant expression of ALP in treated BM samples for 24 hours in compared to control sample.
While collagen type 1gene expression was not detected either in bone marrow control ortreated samples for 24 hours or in cord blood control or treated samples for (24 - 72) hours.
In conclusion, our study results showed that there were significant changes in genes expression of Runx-2 and Osterix(up-stream)in treated samples compared to control and this expression in BM was higher than cord bloodwhichmay indicate that bone marrow mesenchymal stem cells have a higher osteogenic potential than the cord blood.
Our results may be explained bythe cellsniche, as BM-MSCs are already present in niches surrounded by bony environment and growth factors thatmay make these cells more committed to differentiate to osteogenic linages more than UCB-MSCs.
Umbilical cord blood has proven to be an alternative source for mesenchymal stem cells and these cells are characterized by their ability to proliferate in culture with attached spindle-shaped morphology and their successful differentiation into osteoblasts by the presence of consistent set of osteogenic genes as markers.
hMSCs from umbilical cord blood can be regarded as osteogenicprogenitor/precursor cellpopulation .It has proven that, hMSCs from the umbilical cord blood have the skills to proliferate extensively and maintain its osteogenic differentiation in vitro.