Matrix metalloproteinases (MMPs) have been known to affect to cell migration, proliferation, morphogenesis and apoptosis by degrading the extracellular matrix. In the previous studies, undifferentiated mouse embryonic stem cells (ESCs) were successfully proliferated inside the extracellular matrix (ECM) analog-conjugated three-dimensional (3D) poly ethylene glycol (PEG)-based hydrogel. However, there is no report about MMP secretion in ESCs, which makes it difficult to understand and explain how ESCs enlarge space and proliferate inside 3D PEG-based hydrogel constructed by crosslinkers containing MMP-specific cleavage peptide sequence. Therefore, we investigated what types of MMPs are released from undifferentiated ESCs and how extracellular signals derived from various niche conditions affect MMP expression of ESCs at the transcriptional level. Results showed that undifferentiated ESCs expressed specifically MMP2 and MMP3 mRNAs. Transcriptional up-regulation of MMP2 was caused by the 3D scaffold, and activation of integrin inside the 3D scaffold upregulated MMP2 mRNAs synergistically. Moreover, mouse embryonic fibroblasts (MEFs) on 2D matrix and 3D scaffold induced upregulation of MMP3 mRNAs, and activation of integrins through conjugation of extracellular matrix (ECM) analogs with 3D scaffold upregulated MMP3 mRNAs synergistically. These results suggest that successful proliferation of ESCs inside the 3D PEG-based hydrogel may be caused by increase of MMP2 and MMP3 expression resulting from 3D scaffold itself as well as activation of integrins inside the 3D PEG-based scaffold.

ABSTRACT   
INTRODUCTION  
 MATERIALS AND METHODS    
ESC Culture    
Encapsulation of ESCs into PEG-based Hydrogel and Culture    
Extraction of mRNA and Synthesis of cDNA    
Real-Time PCR    
Statistical Analysis   
RESULTS    
Identification of MMP Genes Expressed in UndifferentiatedMouse ESCs    
The Effects of Extracellular Signaling Derived from DifferentNiche on the Transcriptional Regulation of MMP2 and MMP3 Expressed in Undifferentiated Mouse ESCs   
DISCUSSION   
REFERENCES

• Jung Im Yun(Department of Agricultural Biotechnology, Seoul National University)
• Min Seong Kim(Department of Animal Biotechnology, Kangwon National University)
• Seung Tae Lee(Department of Animal Biotechnology, Kangwon National University) Corresponding author