Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie
Department für Zahn-, Mund- und Kieferheilkunde

DFG-sponsored project / Cooperation with the Department of Thoracic and Cardiovascular Surgery – Generation of induced, pluripotent stem cells from jaw periosteal cells

The reconstruction of large bone resections with BTE products, e.g., for tumor patients, requires extremely high cell numbers. Unfortunately, the production of adequate cell yields is hampered by the occurrence of cell senescence and a decreased osteogenic potential of periosteal stem cells at higher passages. Additionally, primary JPCs exhibit under cultivation with fetal calf serum a high donor variability concerning their differentiation potential.

Although surface markers have been identified, which allow the enrichment of osteogenic progenitor cells from heterogeneous cell populations via fluorescence or magnetic activated cell sorting (FACS, MACS) [8, 16, 19], cell yields are often unsatisfactory because of low sorting efficiencies and high cell mortality.

The use of patient-specific induced pluripotent stem cells (iPSCs) from somatic cells could solve the above-mentioned problems. In the present study, we used for reprogramming of jaw periosteal cells an optimized self-replicating RNA construct containing a green fluorescent protein (GFP) encoding sequence to enable live monitoring of transfected cells. The subsequent differentiation from iPSCs to iMSCs might lead to the generation of a more homogeneous cell population, thus contributing to the standardization of the TE-process. 

(PhD student Felix Umrath, Doctoral student Sarah-Lena Frick)

Quality analysis of bone-specific matrix formed by JPCs under serum-containing versus –free culture conditions

The clinical application of in vitro developed tissue engineering constructs in humans makes a standardization of the manufacturing process necessary. In terms of biomaterials, the innovative 3D printing technology allows a high level of precision and uniformity of printing quality leading to standardized fabrication of 3D scaffold materials. However, material modification with functional bio-molecules for enhancement and controlling of cell function require a suitable detection/quantification method which is still lacking at present. At the same time, maturation of in vitro generated cell-material constructs has to be recorded step by step by quantitative live-imaging and monitoring for quality control. This should assure the success of the TE procedure and determine the optimal time point for construct implantation.
Jaw periosteal cells are able to form bone-specific matrix after stimulation with specific agents. Cell mineralization can be detected using histologic staining and quantification. However, no statements concerning the quality of the formed matrix can be done. Using the non-destructive Raman technology, fingerprint Raman spectra containing information about biochemical composition of the formed matrix can be generated, based on molecule vibrations. The biochemical characterization of mineralized tissues provides structural and functional information, which might help to classify and discriminate formation of poor quality bone tissue.

DFG sponsoring Differences in the biochemical composition of mineralized species formed by MSCA-1+ JPC-subpopulation under serum-containing and serum-free culture conditions were analyzed. Under serum-free culturing, MSCA-1+ JPCs form a more mature bone-like matrix which probably possesses less elastic properties due to a reduced collagen formation by the cells. [13]

In this study we combined atomic force microscopy with raman spectroscopy in order to characterize both mechanical and biochemical properties of the formed mineralized matrix, at the same time. For future clinical applications it is important to remove animal components from in vitro cell culture. Therefore, we compared mineralized cell monolayers under FCS- and hPL-supplementation and found evidence for a high-quality matrix under hPL-supplementation [15].

Identification and functionalization of an optimal scaffold for JPCs

AiF sponsoring Different degradable biomaterials will be tested for suitability for jaw periosteal cells [5].

In order to mimic a natural microenvironment on synthetically manufactured biomaterials, different strategies for biofunctionalization and immobilization will be chosen [9-12].