Analyze The Data

To better understand the potential of adult stem cells to differentiate into various cell types, the following studies were performed.

Bone marrow was harvested from adult male mice and then transplanted into isogeneic female recipient mice that had been treated with a level of irradiation sufficient to destroy their own hematopoetic stem cells (see the figure). Although the dose of irradiation given was lethal to mice that did not receive a transplant, the majority of the recipient mice receiving the transplant survived. After 4 weeks, peripheral blood from the recipient mice was analyzed. The composition of the blood was normal with respect to all blood cell types. Every blood cell examined was determined to be positive for the presence of the Y chromosome.

Male mouse

Male mouse o

Harvest marrow o o o o

Isogeneic female mouse

Isogeneic female mouse

Lethal irradiation

Lethal irradiation

Bone marrow transplant

"Labeled" mouse

"Labeled" mouse a. What was the purpose of using male mice as the bone marrow donors and female mice as the recipients? Would the converse experiment (female donors, male recipients) have worked?

b. What was the purpose of irradiating the recipient mice prior to transplantation? What outcome might you expect if bone marrow cells were transplanted to nonirradiated mice?

c. What method could have been used to purify hematopo-etic stem cells from bone marrow before transplanting these cells into the recipient mouse? How might a purification step have affected the outcome of the experiment?

After 8 weeks, some of the recipient mice were sacrificed and histochemical analysis was performed on tissue sections of various organs. Occasional Y chromosome-positive cells were found in the liver, skeletal muscle, and brain. Furthermore, the Y chromosome-positive cells were positive for markers of liver hepatocytes, skeletal muscle cells, and neurons (albumin, dystrophin, and NeuN, respectively).

d. What does the appearance of Y chromosome-positive cells in multiple organs and the expression of organ-specific markers indicate about the localization of cells derived from bone marrow? About their differentiation potential? About their function?

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