Mesenchymal stem cells (MSCs) can be isolated from various tissues and represent an attractive cell
population for tissue-engineering purposes. MSCsfrom bonemarrow(bonemarrowstromal cells [BMSCs])
are negative for immunologically relevant surface markers and inhibit proliferation of allogenic T cells
in vitro. Therefore, BMSCs are said to be available for allogenic cell therapy. Although the immunological
characteristics of BMSCs have been the subject of various investigations, those of stem cells
isolated from adipose tissue (ASCs) have not been adequately described. In addition, the influence of
osteogenic differentiation in vitro on the immunological characteristics of BMSCs and ASCs is the subject
of this article.
Before and after osteogenic induction, the influence of BMSCs and ASCs on the proliferative behavior of
resting and activated allogenic peripheral blood mononuclear cells (PBMCs) was studied as a measure of
the immune response (mixed lymphocyte culture). At the same points, the expression of immunologically
relevant surface markers (e.g., major histocompatibility complex (MHC)-I, MHC-II, CD40, CD40L) was
measured, and correlations between the different sets of results were sought.
The pattern of surface antigen expression of BMSCs is the same as that of ASCs. Analogous to BMSCs,
undifferentiated cells isolated from adipose tissue lack expression ofMHC-II; this is not lost in the course of
the osteogenic differentiation process. In co-culture with allogenic PBMCs, both cell types fail to lead to any
significant stimulation, and they both retain these characteristics during the differentiation process. BMSCs
and ASCs suppress proliferation on activated PBMCs before and after osteogenic differentiation.
Our results confirm that MSCs are immune modulating cells. These properties are retained even after
osteogenic induction in vitro and seem to be similar in BMSCs and ASCs. Our results suggest that allogenic
transplantation of BMSCs and ASCs would be possible, for example, in the context of tissue engineering.
