Michele de Luca
Regenerative Medicine by Somatic Stem Cells: The Paradigm of Epithelial Stem Cells
Monday July 22, 17.00
Adult stem cells are cells with a high capacity for self-renewal that can produce terminally differentiated progeny. Stem cells generate an intermediate population of committed progenitors, often referred to as transit amplifying (TA) cells, that terminally differentiate after a limited number of cell divisions. Human keratinocyte stem cells are clonogenic and are known as holoclones. Human corneal stem cells are segregated in the limbus while limbal-derived TA cells form the corneal epithelium. Self-renewal, proliferation and differentiation of limbal stem cells are regulated by the DNp63 (a, b and g), C/EBPd and Bmi1 transcription factors. Cultivated limbal stem cells generate sheets of corneal epithelium suitable for clinical application. We report long-term clinical results obtained in an homogeneous group of 154 patients presenting with corneal opacification and visual loss due to chemical and thermal burn-dependent limbal stem cell deficiency. The corneal epithelium and the visual acuity of these patients have been restored by grafts of autologous cultured limbal keratinocytes. In post hoc analyses, success was associated with the percentage of p63-bright holoclone-forming stem cells in culture. Graft failure was also associated with the type of initial ocular damage and postoperative complications. Mutations in genes encoding the basement membrane component laminin 5 (LAM5) cause junctional epidermolysis bullosa (JEB), a devastating and often fatal skin adhesion disorder. Epidermal stem cells transduced with a retroviral vector expressing the b3 cDNA can generate genetically corrected cultured epidermal grafts able to permanently restore the skin of patients affected by LAM5-b3-deficient JEB. The implication of these results for the gene therapy of different genetic skin diseases will be discussed.
Divide and conquer – Synthetic Biology of Cell Division
Tuesday July 23, 09.00
In recent years, biophysics has accumulated an impressive selection of novel techniques to analyze biological systems with ultimate sensitivity and precision. Single molecule imaging, tracking and manipulation have enabled us to unravel biological phenomena with unprecedented analytical power, and to come closer to revealing fundamental features of biological self-organization. The power of physics has always been the reductionist approach, i.e. the possibility to define an appropriate subsystem simple enough to be quantitatively modeled and described, but complex enough to retain the essential features of its real counterpart. Transferring this approach into biology has so far been extremely challenging, because most “modern” biological systems usually comprise so many modules and elements, many of them still awaiting to be functionally resolved, that it is a risky task to define truly essential ones. Nevertheless, the strive for identifying minimal biological systems, particularly of subcellular structures or modules, has in the past years been very successful, and crucial in vitro experiments with reduced complexity can nowadays be performed, e.g., on reconstituted cytoskeleton and membrane systems. As a particularly exciting example for the power of minimal systems, self-organization of essential proteins of the bacterial cell division machinery could be shown in a simple assay, consisting of only two protein species, an energy source, and a membrane. In my talk, I will discuss some recent results of our work on membrane-based emergent systems, using single molecule optics and biological reconstitution assays. I will further discuss the perspective of assembling a minimal system to reconstitute bacterial cell division.