Bioengineering laboratory

Lab head: Munira Xaymardan
Location: Bioengineering laboratory, Dental School. Westmead Hospital, Westmead, NSW 2145

Congenital malformation, injury, infection and tumour removal surgeries can inflict defects on the facial region that result in diminished oral health and life quality of the patients. For example, tongue squamous cell carcinoma is one of the most prevalent malignant tumours of the head and neck region with surgical management remaining as the principle treatment. After lesions excision, many patients are left with functional impairment of gustation, mastication and phonetic articulations that cannot be fully restored by current reconstructive treatments. Stem and progenitor cells can provide novel strategies for repair of the damaged tissue. However, harnessing the full potential of the stem cells will require understanding of the regulatory mechanisms that control tongue and facial tissue during morphogenesis.

In our laboratory, we found that contrary to thecurrent concept that the tongue muscle originate from paraxial mesoderm similar to those of the limb and trunk muscles originate from a pool of cardiac progenitors bearing the cardiac TF Nkx2-5, which was accompanied by further expressions of the cardiac markers Tbx1, Isl-1, MEF2C and to a lesser extent, GATA4. Additionally, we have found that these cardiac markers co-localise with the skeletal myocyte markers MYF5, MYOGENIN and MYOD starting from the embryonic day 12.5 in mouse. Supporting a hypothesis that the tongue muscle progenitors originate from the heart field muscle stem cell pool, ingress through pharyngeal arches to found the orofacial muscle primordia. These primary muscle cells carrying cardiac genes would later adopt number of skeletal TFs to develop into a hybrid muscle phenotype, perhaps an adaption necessary for functional integrity of the regional tissues.

To further our understanding of the molecular mechanism of the tongue myogenesis, we propose to use a human pluripotent stem cell (hPSC) line to generate the tongue muscle cells with cardiac-skeletal hybrid muscle characteristics in vitro. By careful literature analysis and in reference to our own preliminary experiments, we have identified that the mechanisms responsible for this “hybrid” characteristic in the orofacial muscles may be due to the dual modulation of Wnt and notch pathways. The cell differentiation assays are currently being performed and the honours project will involve in the assistance with cell culture, PCR and immunohistochmical characterisation of myogenic markers.

Funding: University Internal Funding, ADRF
Research approach equipment: Embryonic stem cell culture; Cell differentiation; PCR, Immunohistochemistry

Investigation of Telocyte-like Cardiac Insterstitial Cells Using 3D BlockFace Microscopy

Primary supervisor: Munira Xaymardan

A new type of interstitial cells, the telocytes, has emerged as a newly recognised entity of the cardiac interstitium. Telocytes were first reported in the intestine as Cajal interstitial cells that regulate the slow wave potential leading to contraction of the smooth muscles of the gastrointestinal tract. Cells bearing similar morphological properties such as elongated cellular processes and telopodes have recently been detected in many tissues including the heart. The definition of telocytes is largely confined to regional electron microscopic studies while no reliable molecular markers have been described. Little is known of the extent of telocyte distribution, identity and roles in development, health and disease of the heart. Factors including lack of appropriate markers for the cardiac interstitial cells, methodological limitations of resolving delicate processes by light microscopy; and further time-consuming nature of visualising global cellular patterns with the transmission electron microscope may have contributed to hampering the progress of cardiac interstitial cell identification.     A 3D blockface electron microscopic images will be used to map the cardiac interstitial cellular network. This will shed light onto the spatial relationships and communication system between telocyte-like CICs and cardiomyocytes, vascular structures, fibroblasts and the conductive system in healthy hearts.  Using the newly available 3D BlockFace scanning electron microscope to establish the network structures of the cardiac tissue. The automated block-face imaging is combined with serial sectioning inside the chamber of a scanning electron microscope. Backscattering contrast is used to visualize heavy metal staining of tissue prepared using techniques that are routine for transmission electron microscopy, providing an excellent method to reconstruct over hundreds of micrometers and obtaining high-resolution structures that are sufficient to follow the finest of cellular processes, and to identify small organelles such as synaptic vesicles. This opens the possibility of automatically obtaining at the electron-microscope-level, 3D datasets needed to completely reconstruct the connectivity of interstitial-vascular circuits. This work will reveal the heart’s architectural configurations at a scale and resolution that has not been previously achieved.A new type of interstitial cells, the telocytes, has emerged as a newly recognised entity of the cardiac interstitium. Telocytes were first reported in the intestine as Cajal interstitial cells that regulate the slow wave potential leading to contraction of the smooth muscles of the gastrointestinal tract. Cells bearing similar morphological properties such as elongated cellular processes and telopodes have recently been detected in many tissues including the heart. The definition of telocytes is largely confined to regional electron microscopic studies while no reliable molecular markers have been described. Little is known of the extent of telocyte distribution, identity and roles in development, health and disease of the heart. Factors including lack of appropriate markers for the cardiac interstitial cells, methodological limitations of resolving delicate processes by light microscopy; and further time-consuming nature of visualising global cellular patterns with the transmission electron microscope may have contributed to hampering the progress of cardiac interstitial cell identification.   Using the newly available 3D BlockFace scanning electron microscope to establish the network structures of the cardiac tissue. The automated block-face imaging is combined with serial sectioning inside the chamber of a scanning electron microscope. Backscattering contrast is used to visualize heavy metal staining of tissue prepared using techniques that are routine for transmission electron microscopy, providing an excellent method to reconstruct over hundreds of micrometers and obtaining high-resolution structures that are sufficient to follow the finest of cellular processes, and to identify small organelles such as synaptic vesicles. This opens the possibility of automatically obtaining at the electron-microscope-level, 3D datasets needed to completely reconstruct the connectivity of interstitial-vascular circuits. This work will reveal the heart’s architectural configurations at a scale and resolution that has not been previously achieved.


Discipline: Applied Medical Sciences, Westmead
Co-supervisors: James Cornwell, Sean Lal
Keywords: Cardiomyocyte, Stem cell biology, Cardiac interstitial cells
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