Scientists usher in leukemia hope

A team from Shanghai has made great progress in the understanding of how hematopoietic stem cells (HSCs) “home” to hematopoietic tissue that could lead to more effective bone marrow transplants in the future.

The findings by a group of scientists at the Chinese Academy of Sciences' Shanghai Institute of Nutrition and Health were published yesterday on the website of the academic journal Nature.

The team spent six years working on HSCs, discovering “hotspots;” niches where hematopoietic stem cells accumulate. They also discovered a previously unknown “usher cell” that interacts with the HSCs and “direct” them into the hotspots, according to team leader Dr Pan Weijun.

Hematopoietic stem cells give rise to all blood lineages that support life. Just like seeds, they need a suitable environment to function. A process called “homing” allows HSCs to anchor in unique niches. The niche regulates this environment.

Previously, there was limited knowledge of the whole process of homing, which restricted clinical applications of HSCs.

Pan’s team developed a system that combines live imaging and cell labeling-tracing to analyze the entire process in zebrafish.

The researchers found that HSCs prefer hotspots associated with venous capillaries, minute vessels with extremely thin walls. Usher cells patrol areas close to the hotspots, check blood stem cells as they pass through, and guide HSCs into their niche.

Jing Naihe from Shanghai Institute of Biochemistry and Cell Biology said the team’s findings had increased understanding of HSC homing and the specific cells involved and could improve the success of transplant surgery.

“Currently, doctors have to transplant millions of cells into patients as we don’t know whether they will anchor in the niches or not, but in fact, only thousands are needed,” he said.

He said that the findings might also help prevent cancer metastasis and other pathological conditions.