Iron-loaded PLLA nanoparticles as highly efficient intracellular markers for visualization of mesenchymal stromal cells by MRI

Monitoring of the fate of cells after injection appears paramount for the further development of cell therapies. In this context magnetic resonance imaging (MRI) is increasing in relevance owing to its unique tissue visualization properties. For assessment of cell trafficking and homing, the cells have to be labeled to become MR visible. The rather low sensitivity of MRI demands dedicated intracellular markers with high payloads of MR contrast agents for ensuring sensitive detection of local cell aggregations. In the presented work the application of custom-designed nanometer-sized iron oxide loaded poly-(l-lactide) (iPLLA) nanoparticles was investigated. The particles were synthesized by the mini-emulsion process and evaluated for labeling of mesenchymal stromal cells (MSCs). The efficient cellular uptake and long intracellular retention times of the particles as well as their nontoxicity are demonstrated. The average cellular iron content was 55 pg iron per cell. Further incorporation of, for example, fluorescent dye enables the generation of multireporter particles, providing the great potential for multimodal imaging. The efficiency of these nanoparticles as MRI contrast agent was evaluated in vitro using relaxation rate mapping, yielding relaxivities r2 = 273.3, r2 (*) = 545.1 mm(-1) s(-1) at 3 T and r2 = 415.7, r2 (*) = 872.3 mm(-1) s(-1) at 11.7 T. The high r2 (*) relaxivity of the iPLLA nanoparticles enabled visualization of a single labeled cell in vitro at 50-µm spatial resolution. In vivo evaluation in a rat injury model revealed the potential of the iPLLA particles to efficiently label MSCs for MRI monitoring of ~20 000-40 000 injected cells at 11.7 T. In conclusion the presented work demonstrates the applicability of iPLLA particles as efficient intracellular marker for MSC labeling for monitoring the fate of the cells by MRI.

Effect of high-dose irradiation on human bone-marrow-derived mesenchymal stromal cells

Cell therapy using multipotent mesenchymal stromal cells (MSCs) is of high interest in various indications. As the pleiotropic effects mediated by MSCs rely mostly on their unique secretory profile, long-term persistence of ex-vivo-expanded cells in the recipient may not always be desirable. Irradiation is a routine procedure in transfusion medicine to prevent long-term persistence of nucleated cells and could therefore also be applied to MSCs. We have exposed human bone-marrow-derived MSCs to 30 or 60 Gy of γ-irradiation and assessed cell proliferation, clonogenicity, differentiation, cytokine levels in media supernatants, surface receptor profile, as well as expression of proto-oncogenes/cell cycle markers, self-renewal/stemness markers, and DNA damage/irradiation markers. Irradiated MSCs show a significant decrease in proliferation and colony-forming unit-fibroblasts. However, a subpopulation of surviving cells is able to differentiate, but is unable to form colonies after irradiation. Irradiated MSCs showed stable expression of CD73 and CD90 and absence of CD3, CD34, and CD45 during a 16-week follow-up period. We found increased vascular endothelial growth factor (VEGF) levels and a decrease of platelet-derived growth factor (PDGF)-AA and PDGF-AB/BB in culture media of nonirradiated cells. Irradiated MSCs showed an inverse pattern, that is, no increase of VEGF, and less consumption of PDGF-AA and PDGF-AB/BB. Interestingly, interleukin-6 (IL-6) levels increased during culture regardless of irradiation. Cells with lower sensitivity toward γ-irradiation showed positive β-galactosidase activity 10 days after irradiation. Gene expression of both irradiated and nonirradiated MSCs 13-16 weeks after irradiation with 60 Gy predominantly followed the same pattern; cell cycle regulators CDKN1A (p21) and CDKN2A (p16) were upregulated, indicating cell cycle arrest, whereas classical proto-oncogenes, respectively, and self-renewal/stemness markers MYC, TP53 (p53), and KLF4 were downregulated. In addition, DNA damage/irradiation markers ATM, ATR, BRCA1, CHEK1, CHEK2, MDC1, and TP53BP1 also mostly showed the same pattern of gene expression as high-dose γ-irradiation. In conclusion, we demonstrated the existence of an MSC subpopulation with remarkable resistance to high-dose γ-irradiation. Cells surviving irradiation retained their trilineage differentiation capacity and surface marker profile but changed their cytokine secretion profile and became prematurely senescent.

Necrosis associated factors (S100A4 and uric acid) promote accumulation of MSCs which induce IL10+/IDO+ lymphocytes (TUM7P.949)

Necrosis with subsequent release of damage-associated molecular patterns (DAMPs) is a characteristic feature of advanced solid tumors. DAMPs impact the tumor-microenvironment stimulating tumor-associated cells like mesenchymal stromal cells (MSCs). Tumor-infiltrating-MSCs are associated with tumor progression and metastasis. Oxidized DAMPs lose their stimulatory capacity on MSCs. As a DAMP-member S100A4 is sensitive to oxidation while uric acid (UA) acts as an antioxidant. We tested these two DAMP-members separately and in combination for their biologic activity on MSCs. S100A4 and UA showed a dose-dependent chemotactic activity on MSCs with synergistic effects when both DAMPs were combined. Substituting for UA, alternative antioxidants (Vitamin-C, dithiothreitol, and acetylcystein) had also a comparable synergistic effect on the chemotactic activity of S100A4, emphasizing the reducing potential of UA being responsible for the observed synergy. Yet, S100A4 and UA inhibited MSC proliferation without impacting their viability. Nevertheless, in the presence of S100A4 or UA, MSCs gained immunosuppressive capacities by inducing IL-10 and indoleamine dioxygenase expressing lymphocytes. We characterized S100A4 and UA as necrosis-associated factors playing a crucial role within MSC biology and thus immunoregulation. Our results have implications for therapeutic approaches targeting the tumor microenvironment and addressing the immunosuppressive nature of necrotic tumor.

[Surgical therapy of oropharyngeal carcinoma within the scope of interdisciplinary tumor surgery]

BACKGROUND

The results of the surgical therapy of patients with extensive squamous cell carcinoma of the oropharynx and their lymph node metastasis, postoperative follow-up, and rehabilitation depend on the collaboration between ear, nose, and throat surgeons and maxillofacial surgeons. Modern reconstruction techniques permit single-session surgical treatment with a reduced period of hospitalization. The most important therapeutic aim is to improve patient well-being.

PATIENTS

Over a period of two years, 45 patients underwent the same surgical procedure. These patients were all in stages III or IV of their disease.

RESULTS

This procedure consists of a temporary lateral osteotomy of the mandible with or without resection of the mandible, to provide broad exposure of the tumor of the oropharynx. Apart from the broad exposure, the advantage of this surgical method lies in simple reconstruction using a pedicled and microanastomosed flap. Internal fixation with six and four-hole titanium plates is a reliable method for restoring the stability of the mandible. In six patients, complications occurred in connection with the plate fixation. In four patients, we observed osteomyelitis of the fragment fissure or sequestration. Plate fracture and pseudarthrosis occurred in one patient each.

CONCLUSIONS

In our clinical experience, the microvascular anastomosed radial flap proved to be the ideal free soft tissue transplant. One of its primary advantages is its plasticity and hence good post-therapeutic functional results. The jejunal flap has become less significant them the radial flap; the advantage of mucous membrane transfer is lost after radiation and a corresponding postoperative interval. In patients with large, voluminous defects, the use of myocutaneous flaps, especially from the latissimus dorsi, is still justified.

[Desmodont remains after tooth extraction in digital image processing]

Breakage of the dentoalveolar gomphosis during tooth extraction results in varying amounts of desmodont remaining at the surface of the root. By dying the remnants of desmodont with toluidine blue, the surface of the root can be made accessible to computerized optical analysis. After clinically induced extraction of 102 human teeth, and after the loosening of 24 sheep teeth by mechanical vibration, the remaining area of desmodont was compared to that of the entire surface. Except in one case, no parameters were found to influence the amount of desmodont. However, tooth extraction in sheep previously treated with ultrasound or low-frequency vibrations demonstrate more desmodont-free areas.

[Contribution to the standardization of intraoral radiography technics]

Many practices are available for placing a dental radiographic film in the mouth. A uniform system is proposed to make the best of the advantages offered by the standarization of the intra-oral X-ray technique.

[Mandibular refractures]

The portion of individuals with mandibular refractures in traumatized patients is but small. During a period of more than 10 years, 16 male patients presented once more with a mandibular fracture. In five of these patients, the mandibular fracture was a true refracture. Apart from problems by which experts are confronted in such cases, special attention is given to the epileptic who is at risk of trauma.

[Intraosseous screw splinting of mandibular fragments]

Fractures in the frontal region of the mandible may be treated by intra-ossal splinting without the risk of injuring nerves or vessels. Function-stable fixation of the reposited fragments was achieved in 15 patients by means of a transfragmental screw with metric thread. The advantages of this procedure consist in the easy removability of the material and the superfluidity of new developments of material or instruments. As the possibility of early functional treatment prevents the late impairment of the articular function, this procedure is particularly indicated in case of concurrent paramedian and articular fractures.