ABSTRACT
Mesenchymal stem cells (MSCs) are the most promising seed cells for cell therapy and can be isolated from various sources of human adult tissues such as bone marrow (BM-MSC) and adipose tissue. However, cells from these tissues must be obtained through invasive procedures. We, therefore, characterized MSCs isolated from fresh placenta (Pl-MSC) and fetal membrane (Mb-MSC) through morphological and fluorescent-activated cell sorting (FACS). MSC frequency is higher in membrane than placenta (2.14% ± 0.65 versus 15.67% ± 0.29%). Pl/Mb-MSCs in vitro expansion potential was significantly higher than BM-MSCs. We demonstrated that one of the MSC-specific marker is sufficient for MSC isolation and that culture in specific media is the optimal way for selecting very homogenous MSC population. These MSCs could be differentiated into mesodermal cells expressing cell markers and cytologic staining consistent with mature osteoblasts and adipocytes. Transcriptomic analysis and cytokine arrays demonstrated broad similarity between placenta- and membrane-derived MSCs and only discrete differences with BM-MSCs with enrichment of networks involved in bone differentiation. Pl/Mb-MSCs displayed higher osteogenic differentiation potential than BM-MSC when their response to osteoactivin was evaluated. Fetal-tissue-derived mesenchymal cells may, therefore, be considered as a major source of MSCs to reach clinical scale banking in particular for bone regeneration.
ABSTRACT
BACKGROUND: A relation between telomere attrition in early carcinogenesis and activation of DNA damage response (DDR) has been proposed. We explored telomere length and its link with DDR in colorectal multistep carcinogenesis. PATIENTS AND METHODS: We studied normal mucosa, low-grade dysplasia (LGD) and high-grade dysplasia (HGD) and invasive carcinoma (IC) in matched human colon specimens by evaluating p-ataxia telangiectasia mutated (ATM), p-checkpoint kinase 2 (Chk2), c-H2AX, TRF1 and TRF2 expressions by immunohistochemistry. FISH was used to assess telomere length. RESULTS: Telomeres shortened significantly from normal (N) to LGD and HGD (P < 0.0001; P = 0.012), then increased in length in IC (P = 0.006). TRF1 and TRF2 expressions were diminished from N to LGD and HGD (P = 0.004, P < 0.0001, ns) and were reexpressed at the invasive stage (P = 0.053 and P = 0.046). Phosphorylated ATM, Chk2 and H2AX appeared already in LGD (respectively, P = 0.001, P = 0.002 and P = 0.02). Their expression decreased from HGD to IC (respectively, P = 0.03, P = 0.02 and P = 0.37). These activating phosphorylations were inversely correlated with telomere length and TRF1/2 expression. CONCLUSION: In a model of colon multistep carcinogenesis, our data indicate that telomeric length and protein expression levels are inversely correlated with the activation of the DDR pathway.
