Potential of electrospun cationic BSA fibers to guide osteogenic MSC differentiation via surface charge and fibrous topography

Large or complex bone fractures often need clinical treatments for sufficient bone repair. New treatment strategies have pursued the idea of using mesenchymal stromal cells (MSCs) in combination with osteoinductive materials to guide differentiation of MSCs into bone cells ensuring complete bone regeneration. To overcome the challenge of developing such materials, fundamental studies are needed to analyze and understand the MSC behavior on modified surfaces of applicable materials for bone healing. For this purpose, we developed a fibrous scaffold resembling the bone/bone marrow extracellular matrix (ECM) based on protein without addition of synthetic polymers. With this biomimetic in vitro model we identified the fibrous structure as well as the charge of the material to be responsible for its effects on MSC differentiation. Positive charge was introduced via cationization that additionally supported the stability of the scaffold in cell culture, and acted as nucleation point for mineralization during osteogenesis. Furthermore, we revealed enhanced focal adhesion formation and osteogenic differentiation of MSCs cultured on positively charged protein fibers. This pure protein-based and chemically modifiable, fibrous ECM model allows the investigation of MSC behavior on biomimetic materials to unfold new vistas how to direct cells’ differentiation for the development of new bone regenerating strategies

A parallelized, perfused 3D triculture model of leukemia for in vitro drug testing of chemotherapeutics

Leukemia patients undergo chemotherapy to combat the leukemic cells (LCs) in the bone marrow. During therapy not only the LCs, but also the blood-producing hematopoietic stem and progenitor cells (HSPCs) may be destroyed. Chemotherapeutics targeting only the LCs are urgently needed to overcome this problem and minimize life-threatening side-effects. Predictive in vitro drug testing systems allowing simultaneous comparison of various experimental settings would enhance the efficiency of drug development. Here, we present a three-dimensional (3D) human leukemic bone marrow model perfused using a magnetic, parallelized culture system to ensure media exchange. Chemotherapeutic treatment of the acute myeloid leukemia cell line KG-1a in 3D magnetic hydrogels seeded with mesenchymal stem/stromal cells (MSCs) revealed a greater resistance of KG-1a compared to 2D culture. In 3D tricultures with HSPCs, MSCs and KG-1a, imitating leukemic bone marrow, HSPC proliferation decreased while KG-1a cells remained unaffected post treatment. Non-invasive metabolic profiling enabled continuous monitoring of the system. Our results highlight the importance of using biomimetic 3D platforms with proper media exchange and co-cultures for creating in vivo-like conditions to enable in vitro drug testing. This system is a step towards drug testing in biomimetic, parallelized in vitro approaches, facilitating the discovery of new anti-leukemic drugs

Iron Nanoparticle Composite Hydrogels for Studying Effects of Iron Ion Release on Red Blood Cell In Vitro Production

Growing numbers of complex surgical interventions increase the need for blood transfusions, which cannot be fulfilled by the number of donors. Therefore, the interest in producing erythrocytes from their precursors—the hematopoietic stem and progenitor cells (HSPCs)—in laboratories is rising. To enable this, in vitro systems are needed, which allow analysis of the effects of essential factors such as iron on erythroid development. For this purpose, iron ion-releasing systems based on poly(ethylene glycol) (PEG)–iron nanocomposites are developed to assess if gradual iron release improves iron bioavailability during in vitro erythroid differentiation. The nanocomposites are synthesized using surfactant-free pulsed laser ablation of iron directly in the PEG solution. The iron concentrations released from the material are sufficient to influence in vitro erythropoiesis. In this way, the production of erythroid cells cultured on flat PEG–iron nanocomposite hydrogel pads can be enhanced. In contrast, erythroid differentiation is not enhanced in the biomimetic macroporous 3D composite scaffolds, possibly because of local iron overload within the pores of the system. In conclusion, the developed iron nanoparticle-PEG composite hydrogel allows constant iron ion release and thus paves the way (i) to understand the role of iron during erythropoiesis and (ii) toward the development of biomaterials with a controlled iron release for directing erythropoiesis in culture

Biomimetic 3D in vitro model of biofilm triggered osteomyelitis for investigating hematopoiesis during bone marrow infections

In this work, we define the requirements for a human cell-based osteomyelitis model which overcomes the limitations of state of the art animal models. Osteomyelitis is a severe and difficult to treat infection of the bone that develops rapidly, making it difficult to study in humans. We have developed a 3D in vitro model of the bone marrow, comprising a macroporous material, human hematopoietic stem and progenitor cells (HSPCs) and mesenchymal stromal cells (MSCs). Inclusion of biofilms grown on an implant into the model system allowed us to study the effects of postoperative osteomyelitis-inducing bacteria on the bone marrow. The bacteria influenced the myeloid differentiation of HSPCs as well as MSC cytokine expression and the MSC ability to support HSPC maintenance. In conclusion, we provide a new 3D in vitro model which meets all the requirements for investigating the impact of osteomyelitis. Statement of Significance: Implant-associated osteomyelitis is a persistent bacterial infection of the bone which occurs in many implant patients and can result in functional impairments or even entire loss of the extremity. Nevertheless, surprisingly little is known on the triangle interaction between implant material, bacterial biofilm and affected bone tissue. Closing this gap of knowledge would be crucial for the fundamental understanding of the disease and the development of novel treatment strategies. For this purpose, we developed the first biomaterial-based system that is able to mimic implant-associated osteomyelitis outside of the body, thus, opening the avenue to study this fatal disease in the laboratory