Harnessing the Angiogenic Potential of Stem Cell-Derived Exosomes for Vascular Regeneration.

Mesenchymal stem cells (MSCs) are known to display important regenerative properties through the secretion of proangiogenic factors. Recent evidence pointed at the key role played by exosomes released from MSCs in this paracrine mechanism. Exosomes are key mediators of intercellular communication and contain a cargo that includes a modifiable content of microRNA (miRNA), mRNA, and proteins. Since the biogenesis of the MSCs-derived exosomes is regulated by the cross talk between MSCs and their niche, the content of the exosomes and consequently their biological function are dependent on the cell of origin and the physiologic or pathologic status of their microenvironment. Recent preclinical studies revealed that MSCs-derived exosomes have a critical implication in the angiogenic process since the use of exosomes-depleted conditioned medium impaired the MSCs angiogenesis response. In this review, we discuss the current knowledge related to the angiogenic potential of MSCs-exosomes and methods to enhance their biological activities for improved vascular regeneration. The current gain of insight in exosomes studies highlights the power of combining cell based therapies and their secreted products in therapeutic angiogenesis.

Osteosarcoma cells as carriers to allow antitumor activity of canine oncolytic adenovirus in the presence of neutralizing antibodies.

Osteosarcoma (OSA) is the most common bone tumor affecting the dog. The veterinary options for therapeutic management of OSA are limited and prognosis for such patients is poor. Oncolytic adenoviruses are attractive tools for experimental therapeutics as they can replicate and spread within tumors to directly induce tumor destruction. However, a major impediment to systemic oncolytic adenoviruses injection is the presence of pre-existing neutralizing antibodies (Nabs). In this study, we investigated the effect of a replication-selective canine adenovirus (OCCAV) to treat OSA in the presence of Nabs and the use of canine OSA cells as carrier vehicles for evading Nabs. Our systemic biodistribution data indicated that canine tumor cells could successfully reach the tumor site and deliver OCCAV to tumor cells in an immunized mice model. Furthermore, the use of carrier cells also reduced adenovirus uptake by the liver. Importantly, OCCAV alone was not effective to control tumor growth in a pre-immunized xenograft mouse model. On the contrary, systemic antitumoral activity of carrier-cell OCCAV was evident even in the presence of circulating antibodies, which is a relevant result from a clinical point of view. These findings are of direct translational relevance for the future design of canine clinical trials.