Oral fibroblasts rescue osteogenic differentiation of mesenchymal stem cells after exposure to Zoledronic acid in a paracrine effect.

Background: Medication-related osteonecrosis of the jaw is a serious complication that develops in oncologic patients treated with Zoledronic acid. Although used for over 30 years, the influence of Zoledronic acid on bone has been thoroughly investigated, mainly on osteoclasts. While decreasing osteoclast differentiation and function, for many years it was thought that Zoledronic acid increased osteoblast differentiation, thus increasing bone volume. Moreover, despite the influence of soft tissue on the bone healing process, the impact of zoledronic acid on the interaction between soft tissue and bone was not investigated. Aim: Our goal was to investigate the influence of Zoledronic Acid and soft tissue cells on osteogenic differentiation of mesenchymal stem cells (MSCs). Materials and methods: Osteogenic differentiation of MSCs was examined after exposure to Zoledronic Acid. To determine the influence of soft tissue cells on MSCs' osteogenic differentiation, conditioned media from keratinocytes and oral fibroblasts were added to osteogenic medium supplemented with Zoledronic Acid. Proteomic composition of keratinocytes' and fibroblasts' conditioned media were analyzed. Results: Zoledronic Acid decreased osteogenic differentiation of MSCs by seven-fold. The osteogenic differentiation of MSCs was restored by the supplementation of fibroblasts' conditioned medium to osteogenic medium, despite Zoledronic acid treatment. Five osteogenic proteins involved in the TGFß pathway were exclusively identified in fibroblasts' conditioned medium, suggesting their role in the rescue effect. Conclusion: Oral fibroblasts secrete proteins that enable osteogenic differentiation of MSCs in the presence of Zoledronic Acid.

Endothelial Progenitor Cells Promote Osteosarcoma Progression and Invasiveness via AKT/PI3K Signaling.

BACKGROUND: Osteosarcoma (OS) mortality is attributed to lung metastases. Endothelial progenitor cells (EPCs) mediate the angiogenic switch in several cancers. The spatial proximity between EPCs and OS in the bone led to the hypothesis that EPCs-osteosarcoma interactions may possibly promote OS progression and aggressiveness. METHODS: A PI3K inhibitor, Bevacizumab (an anti-VEGF-A antibody), and an anti-FGF2 antibody were added to the EPCs' conditioned medium (EPC-CM), and their impacts on OS cell (U2-OS and 143B) proliferation, migration, invasion, MMP9 expression, and AKT phosphorylation were determined. The autocrine role of VEGF-A was assessed using Bevacizumab treatment and VEGF-A silencing in OS cells. Toward this end, an orthotopic mouse OS model was established. Mouse and human tumors were immunolabeled with antibodies to the abovementioned factors. RESULTS: EPC-CM enhanced osteosarcoma MMP9 expression, invasiveness, and migration via the PI3K/AKT pathway. The addition of Bevacizumab and an anti-FGF2 antibody to the EPC-CM diminished OS cell migration. The autocrine role of VEGF-A was assessed using Bevacizumab and VEGF-A silencing in OS cells, resulting in decreased AKT phosphorylation and, consequently, diminished invasiveness and migration. Consistently, OS xenografts in mice displayed high VEGF-A and FGF2 levels. Remarkably, lung metastasis specimens derived from OS patients exhibited marked immunolabeling of CD31, VEGF-A, and FGF2. Conclusions: EPCs promote OS progression not only by physically incorporating into blood vessels, but also by secreting cytokines, which act via paracrine signaling. EPCs induced in vitro MMP9 overexpression, invasion, and migration. Additional animal studies are warranted to further expand these results. These findings may pave the way toward the development of novel EPCs-targeted therapeutics aimed at blocking OS metastasis.

Implanted synthetic cells trigger tissue angiogenesis through de novo production of recombinant growth factors.

Progress in bottom-up synthetic biology has stimulated the development of synthetic cells (SCs), autonomous protein-manufacturing particles, as dynamic biomimetics for replacing diseased natural cells and addressing medical needs. Here, we report that SCs genetically encoded to produce proangiogenic factors triggered the physiological process of neovascularization in mice. The SCs were constructed of giant lipid vesicles and were optimized to facilitate enhanced protein production. When introduced with the appropriate genetic code, the SCs synthesized a recombinant human basic fibroblast growth factor (bFGF), reaching expression levels of up to 9⋅106 protein copies per SC. In culture, the SCs induced endothelial cell proliferation, migration, tube formation, and angiogenesis-related intracellular signaling, confirming their proangiogenic activity. Integrating the SCs with bioengineered constructs bearing endothelial cells promoted the remodeling of mature vascular networks, supported by a collagen-IV basement membrane-like matrix. In vivo, prolonged local administration of the SCs in mice triggered the infiltration of blood vessels into implanted Matrigel plugs without recorded systemic immunogenicity. These findings emphasize the potential of SCs as therapeutic platforms for activating physiological processes by autonomously producing biological drugs inside the body.

Advanced human-relevant in vitro pulmonary platforms for respiratory therapeutics.

Over the past years, advanced in vitro pulmonary platforms have witnessed exciting developments that are pushing beyond traditional preclinical cell culture methods. Here, we discuss ongoing efforts in bridging the gap between in vivo and in vitro interfaces and identify some of the bioengineering challenges that lie ahead in delivering new generations of human-relevant in vitro pulmonary platforms. Notably, in vitro strategies using foremost lung-on-chips and biocompatible "soft" membranes have focused on platforms that emphasize phenotypical endpoints recapitulating key physiological and cellular functions. We review some of the most recent in vitro studies underlining seminal therapeutic screens and translational applications and open our discussion to promising avenues of pulmonary therapeutic exploration focusing on liposomes. Undeniably, there still remains a recognized trade-off between the physiological and biological complexity of these in vitro lung models and their ability to deliver assays with throughput capabilities. The upcoming years are thus anticipated to see further developments in broadening the applicability of such in vitro systems and accelerating therapeutic exploration for drug discovery and translational medicine in treating respiratory disorders.