TLR expression profile of human alveolar bone proper-derived stem/progenitor cells and osteoblasts

Alveolar bone proper-derived mesenchymal stem/progenitor cells (AB-MSCs) and alveolar osteoblasts (OBs) are pivotal cells with positive attributes in regenerative medicine. During regenerative approaches, AB-MSCs may interact with their surrounding environment via their expressed toll-like-receptors (TLRs). This study aimed to depict for the first time the TLRs expression profile of AB-MSCs and OBs. Cells were isolated from human alveolar bone proper, and STRO-1-immunomagnetically sorted to segregate AB-MSCs and OBs. Cell populations were separately seeded out to obtain single colony forming units (CFUs), and were characterized for CD14, CD34, CD45, CD73, CD90, CD105, and CD146 expression as well as for their multilineage differentiation potential. Following incubation of AB-MSCs and OBs in basic medium, their TLRs expression profiles were characterized at mRNA and protein levels. In contrast to OBs, AB-MSCs showed all predefined mesenchymal stem/progenitor cell characteristics. At a protein level, AB-MSCs showed a distinctive expression profile of TLRs 1, 2, 3, 4, 5, 6, 7, 8, and 10 in different quantities, without TLR9 expression. According to their median expression values, TLR2 was the highest expressed, followed by TLRs 4, 5, 7, 1, 10, 8, 3, and finally 6. In contrast, OBs did not express TLR3 and TLR9. According to their median expression values they further showed a different sequence of TLRs expression, with TLR2 highest expressed, followed by TLRs 10, 4, 7, 5, 1, 8, and 6. This study describes for the first time the characteristic TLRs expression profile of AB-MSCs as well as OBs, which could impact their specific sensitivity to pathogenic as well as body tissue compounds, and their therapeutic potential in-vivo.