Stem Cell Treatment For Male Infertility

New research is looking at stem cells derived from bone marrow as a possible source for treating male factor infertility and the results are promising. The report, published in The American Journal of Pathology is called, "Fate of bone marrow stem cells transplanted into the testis: potential implication for men with testicular failure."

Modern researchers know that a man is just as often the source of an infertile couple's failure to conceive as is the woman. Male factor infertility may be due to germ cells that fail to proliferate and differentiate into sperm, or from a dysfunction of the cells that support sperm production. The focus of this current research is on stem cells as a possible means for the replacement of these non-functioning cells, no matter whether they are support cells or germ cells.

Fluorescing Cells

Harbor-UCLA Medical Center's Dr. Ronald S. Swerdloff has been directing this effort. Bone marrow stem cells were collected from mice whose cells express green fluorescent protein (GFP). The green cells were then injected into the testes of mice that had been rendered infertile, either by chemicals or through genetic engineering of the gene necessary for the production of sperm. These fluorescing cells are easy to track in their new hosts.

The GFP-expressing cells were well-tolerated by their new hosts and managed to survive in the testes of the recipient mice over the entire 12-week research project. These donor stem cells were found to have shapes characteristic of either supporting cells or germ cells. This suggests that the stem cells had become differentiated. The differentiated donor cells were found in the vicinity of cells of a similar type within the host. This told the scientists that the new cellular environment wielded some influence on the destiny of the donor cells.

Differentiated Cells

Researchers then followed these findings by attempting to confirm the differentiated status of the donor cells. To this end, the expression of certain cell surface proteins was examined. The scientists discovered that both supporting and germ cells expressed proteins that serve as markers only for differentiated cells and not for stem cells.

The data generated by this study is a clear demonstration that bone marrow stem cells can differentiate into the testicular cells necessary for sperm production, whether germ cells or supporting cells. But much more work remains to be done in order to make stem cell therapy a reasonable treatment for male infertility: the germ cells did not differentiate enough to become sperm. This suggests other factors or other cellular signals are at play in this process. 

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