Biomedical Engineering Reference
In-Depth Information
promotes better muscle formation. The Bioheart MyoCell
™
process ensures that
the active ingredient consists of a cell population with the propensity to engraft,
proliferate, adapt to the cardiac microenvironment, and support cardiac workload.
The myoblasts have been delivered via percutaneous catheter system as well as part
of a coronary artery bypass graft surgery.
In 2001, the first percutaneous nonsurgical transplantation was performed by
injecting cultured autologous myoblasts from a biopsy of the patient's thigh muscle
(Bioheart Inc's MyoCell) to a damaged area of a patient's heart following myocar-
dial infarction. The procedure was performed by a team of interventional cardiolo-
gists at the Thorax Center of the University of Rotterdam in the Netherlands. Ten
injections totaling 25 million cells were made into the damaged portion of the
patient's heart using an endoventricular catheter introduced into the patient's groin.
The patient was discharged within 24 h and was doing well at home 3 days later.
This study was part of a safety evaluation of the Bioheart's MyoCell product that
has now progressed to phase III clinical trials in Europe. This may be one of the
most significant developments in the history of treating heart disease patients.
Cardiac Stem Cells
The average heart contains approximately 600 million myocytes. They are lost at a
rate of approximately 100 million myocytes per year. However, the heart of an
80-year-old person still has approximately 400 million myocytes. It is assumed that
there is a mechanism for regeneration, despite the old belief about the heart being
a postmitotic organ with lack of regeneration of myocytes. Mitosis was identified
in myocytes more than 50 years ago. Cardiac side population cells are a distinct
cardiac progenitor cell population, capable of cardiomyogenic differentiation into
mature cardiomyocytes through a process mediated by cellular coupling with adult
cardiomyocytes. According to the new paradigm, parenchymal and nonparenchy-
mal cells are continuously replaced by newly formed younger populations of myo-
cytes as well as by vascular smooth muscle and endothelial cells (Anversa et al.
2006
). Heart homeostasis is regulated by a stem cell compartment characterized by
multipotent cardiac stem cells that possess the ability to acquire the distinct cell
lineages of the myocardium.
The number of stem cells and progenitor cells identified in normal myocardium
increases in transplanted hearts. When the heart is transplanted it suffers some damage
but the recipient's stem cells pitch in to help heal the new organ by migrating to it.
The Y chromosome can be used to detect migrated undifferentiated cells expressing
stem-cell antigens and to discriminate between primitive cells derived from the
recipient and those derived from the donor.
In 2006, three different teams announced discovery of so-called master heart
cells that hold the promise of treating patients with serious cardiovascular disease.
Each team identified cardiovascular “precursor” cells from cultures of mouse
ESCs. It is very likely that these versatile cells will also be found in the embryonic
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