Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells

Robert A Boomsma,David L Geenen

doi:10.1155/2014/653734

Robert A Boomsma, David L Geenen

Open Access

https://doi.org/10.1155/2014/653734

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Abstract

This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1 : 4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction.

Highlights

We have previously shown that injection of mouse bone marrow mesenchymal stem cells (MSC) prevents the loss of function that occurs in mouse hearts after coronary artery occlusion [1]
In order to study the formation of gap junctions between MSC and HL-1 cells, confluent cultures of HL-1 cells were double labeled with the cytoplasmic gap junction impermeant dye CMFDA and the gap junction permeant dye calcein red-orange AM (Figure 1)
Unlabeled MSC were layered on top of the confluent labeled HL-1 cells in a 1 : 4 ratio to mimic the lower number of transplanted MSC compared to endogenous myocytes when used in vivo

Summary

Introduction

We have previously shown that injection of mouse bone marrow mesenchymal stem cells (MSC) prevents the loss of function that occurs in mouse hearts after coronary artery occlusion [1]. The mechanism for this protective effect is unclear since there was no reduction in ventricular scarring or evidence of cardiomyocyte differentiation in integrated. MSC express connexins and are able to form gap junctions with cardiac ventricular myocytes [7] and HL-1 cardiac cells [8]. Gap junctions may provide a conduit for the cardioprotective effects of MSC in the heart [8, 9]

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