These human
pacemaker cells were tested in rat hearts and were shown to function as a biological pacemaker, by activating the electrical impulses that trigger the contraction of the heart.
The heartbeat originates in the sinoatrial node of the heart's right upper chamber, where
pacemaker cells are clustered.
Although we and others have created primitive biological pacemakers before, this study is the first to show that a single gene can direct the conversion of heart muscle cells to genuine
pacemaker cells.
In cardiac muscle, however, the increased cellular Ca concentration does not greatly exceed the on-off trigger level of 1 uM, and it always remains around this level despite the all-or-none nature of electrical signals given by
pacemaker cells, although the reason behind this is unclear.
Specialized atypical smooth muscle cells in the upper urinary system, which are in close association with each other and with smooth muscle cells, have been thought to be the
pacemaker cells.
The work, reported in the journal Nature Biotechology on Sunday, uses a virus to deliver a human gene called Tbx18, whose normal role is to coax immature cells into becoming
pacemaker cells.
This process may be related to the hyperactivity of the
pacemaker cells due to microstasis from local obstruction or irritation and/or inflammation induced by the stone.
Some clusters started to beat, indicating the presence of heart-muscle cells and
pacemaker cells.
Researchers showed human embryonic stemcells can be encouraged to become
pacemaker cells that regulate heartbeat.
The impulses travel from the
pacemaker cells down certain electrical paths in the muscle walls, producing a contraction.
Such
pacemaker cells could be important in activating colon and bladder muscles for defecation and urination.
To create biological pacemakers, one approach is to coax stem cells to become specialized cardiac
pacemaker cells that are normally found within the sinoatrial node of the heart.
