Movie:
Neonatal cardiac
myocytes are plated on culture dish at high density. The cells grow and form syncytium
mimicking a piece of cardiac muscle tissue. These cells also have
spontaneous contraction
properties in culture dish as shown in Movie 1. The
cells are also responsible to drug stimulation. Movie
2 shows that the cells contract faster after stimulation of b adrenergic receptors with agonist isoproterenol. The change of
myocyte contraction rate can be used as a functional readout of the adrenergic receptor
signaling under an acute stimulation. It is a very sensitive assay. The contraction
properties are depended on temperature, gas, moisture, as well as mechanical pressure, so
we need to build a customized imaging system with top-notch environment control chamber
XL-3 from Zeiss to accommodate the requirement. The system serves as a very powerful
utility for us to dissect the cellular and molecular mechanisms in physiologically
relevant cardiac myocyte.
We also image
individual cellular signaling events in live cardiac myocytes. So far, we have three
probes to image cAMP and PKA (both are kindly provided by Dr. Jin Zhang of John Hopkins
and Dr. Roger Tsien of UCSD), and Ca2+ (either fura-2 dye or cameolon
indicator). We are in the process to develop quality movies on these subcellular signaling
events. These studies together with the contraction assay allow us to answer how
receptor-mediated intracellular signaling is related to the integrated functional
properties of cardiac cells. This system allows to elevate our understanding from
molecular level to integrated level of implication on signaling pathways in physiological
responses in cell based assay. Please check back for further updated progress.
Sympathetic ganglia
neurons innerve with cardiac muscle cells in animal heart. Neurotransmitters catecholamine
can be released from nerve terminus upon stimulation of neuron, which activates adrenergic
receptors to enhance contractile and heart rate. We try to regenerate the neuro-muscular
synapse in vitro by co-culturing symapthetic ganglia neurons and cardiac muscle cells.
Image below show two types of cells interact with each other by phase-contrast imaging.
To our surprise, we found that b1 and b2 adrenergic receptors have distinct distribution
relevant to the neuro-muscular synapse.in cardiac cells. B1AR is concentrated at the
post-synapse whereas b2AR are excluded from the region. The particular distribution of
bAR is correlated well with the long term unproved hypothesis that 1AR is neuronal
receptor where b2AR is hormonal receptor responding the stimulation by adrenaline released
from adrenal gland. We will pursuing the mechanism that how neuro-muscular synapse form
and regulate the receptor distribution in cardiac muscle cell, and how this distribution
affect the receptor function in cardiac muscle cell and animal heart.
Coming soon... abeta
peptide induced cAMP signaling in glia cells isolated from mouse.
