The i Blood Group Antigen as a Marker for Umbilical Cord Blood-Derived Mesenchymal Stem Cells

Abstract

Multipotent mesenchymal stem cells (MSCs) offer great promise for future regenerative and anti-inflammatory therapies. However, there is a lack of methods to quickly and efficiently isolate, characterize, and ex vivo expand desired cell populations for therapeutic purposes. Single markers to identify cell populations have not been characterized; instead, all characterizations rely on panels of functional and phenotypical properties. Glycan epitopes can be used for identifying and isolating specific cell types from heterogeneous populations, on the basis of their cell-type specific expression and prominent cell surface localization. We have now studied in detail the cell surface expression of the blood group i epitope (linear poly-N-acetyllactosamine chain) in umbilical cord blood (UCB)-derived MSCs. We used flow cytometry and mass spectrometric glycan analysis and discovered that linear poly-N-acetyllactosamine structures are expressed in UCB-derived MSCs, but not in cells differentiated from them. We further verified the findings by mass spectrometric glycan analysis. Gene expression analysis indicated that the stem-cell specific expression of the i antigen is determined by β3-N-acetylglucosaminyltransferase 5. The i antigen is a ligand for the galectin family of soluble lectins. We found concomitant cell surface expression of galectin-3, which has been reported to mediate the immunosuppressive effects exerted by MSCs. The i antigen may serve as an endogenous ligand for this immunosuppressive agent in the MSC microenvironment. Based on these findings, we suggest that linear poly-N-acetyllactosamine could be used as a novel UCB-MSC marker either alone or within an array of MSC markers.

Do ABO Blood Group Antigens Hamper the Therapeutic Efficacy of Mesenchymal Stromal Cells?

“…For both A and H determinants, branched or un-branched type 2 chains exist, with the unbranched type 2 chain (classical i antigen) being predominant in fetal/newborn cells, while the branched form (classical I antigen) is predominant in adult cells. A recent publication by Hirvonen et al [34] highlights that particularly umbilical cord blood derived MSCs show “immature” cell-specific expression of the blood group i epitope (linear poly- N -acetyllactosamine chain), which was not found in differentiated cells. Further in-depth studies on the “glycomics” of MSCs may therefore be of interest in “mesenchymal stem cell” phenotyping and to evaluate MSCs differentiation stages [35].…”

Production of a Recombinant Antibody Specific for i Blood Group Antigen, a Mesenchymal Stem Cell Marker

“…15 The capability of the five scFv hyperphages to recognize i antigen on the UCB-MSC surface was analyzed by flow cytometry. Three scFv hyperphages, B12.2, D10.1, and D10.2, bound to UCB-MSCs significantly better than the irrelevant hyperphage (Fig.…”

“…14 We have previously shown the linear poly-N-acetyllactosamine carbohydrate structure (i antigen) to be a marker for MSCs from umbilical cord blood (UCB). 15 …”

“…15 We used antibody phage display technology and constructed IgM single-chain variable fragment (scFv) phage display libraries from the lymphocytes of a donor with elevated anti-i antibody level. The selection of the libraries was performed utilizing RBC antigens.…”

Glycomic profiling of glycoproteins

“…In addition, optimal glycosylation is critical for both efficacy [9] and safety [10,11] of therapeutic monoclonal antibodies, calling for high-throughput methods to profile glycosylation of biotechnologically produced IgG [12]. Similar needs for glycan profiling apply in analyzing cells aimed at therapy, which quite often mediate their function by cell surface glycan structures [13].…”