Surface-Functionalized Stem Cell-Derived Extracellular Vesicles for Vascular Elastic Matrix Regenerative Repair.

Extracellular vesicles (EVs) are nanosized vesicles that carry cell-specific biomolecular information. Our previous studies showed that adult human bone marrow mesenchymal stem cell (BM-MSC)-derived EVs provide antiproteolytic and proregenerative effects in cultures of smooth muscle cells (SMCs) derived from an elastase-infused rat abdominal aortic aneurysm (AAA) model, and this is promising toward their use as a therapeutic platform for naturally irreversible elastic matrix aberrations in the aortic wall. Since systemically administered EVs poorly home into sites of tissue injury, disease strategies to improve their affinity toward target tissues are of great significance for EV-based treatment strategies. Toward this goal, in this work, we developed a postisolation surface modification strategy to target MSC-derived EVs to the AAA wall. The EVs were surface-conjugated with a short, synthetic, azide-modified peptide sequence for targeted binding to cathepsin K (CatK), a cysteine protease overexpressed in the AAA wall. Conjugation was performed using a copper-free click chemistry method. We determined that such conjugation improved EV uptake into cultured aneurysmal SMCs in culture and their binding to the wall of matrix injured vessels ex vivo. The proregenerative and antiproteolytic effects of MSC-EVs on cultured rat aneurysmal SMCs were also unaffected following peptide conjugation. From this study, it appears that modification with short synthetic peptide sequences seems to be an effective strategy for improving the cell-specific uptake of EVs and may be effective in facilitating AAA-targeted therapy.

Stem Cell Based Approaches to Modulate the Matrix Milieu in Vascular Disorders.

The extracellular matrix (ECM) represents a complex and dynamic framework for cells, characterized by tissue-specific biophysical, mechanical, and biochemical properties. ECM components in vascular tissues provide structural support to vascular cells and modulate their function through interaction with specific cell-surface receptors. ECM-cell interactions, together with neurotransmitters, cytokines, hormones and mechanical forces imposed by blood flow, modulate the structural organization of the vascular wall. Changes in the ECM microenvironment, as in post-injury degradation or remodeling, lead to both altered tissue function and exacerbation of vascular pathologies. Regeneration and repair of the ECM are thus critical toward reinstating vascular homeostasis. The self-renewal and transdifferentiating potential of stem cells (SCs) into other cell lineages represents a potentially useful approach in regenerative medicine, and SC-based approaches hold great promise in the development of novel therapeutics toward ECM repair. Certain adult SCs, including mesenchymal stem cells (MSCs), possess a broader plasticity and differentiation potential, and thus represent a viable option for SC-based therapeutics. However, there are significant challenges to SC therapies including, but not limited to cell processing and scaleup, quality control, phenotypic integrity in a disease milieu in vivo, and inefficient delivery to the site of tissue injury. SC-derived or -inspired strategies as a putative surrogate for conventional cell therapy are thus gaining momentum. In this article, we review current knowledge on the patho-mechanistic roles of ECM components in common vascular disorders and the prospects of developing adult SC based/inspired therapies to modulate the vascular tissue environment and reinstate vessel homeostasis in these disorders.

ALPPL2 Aptamer-Mediated Targeted Delivery of 5-Fluoro-2'-Deoxyuridine to Pancreatic Cancer.

Nucleoside analogues are the most promising drugs for the treatment of pancreatic cancer to date. However, their use is often limited due to toxic side effects. Aptamer-mediated targeted delivery of these drugs to cancer cells could maximize their effectiveness and concomitantly minimize the toxic side effects by reducing uptake into normal cells. Previously, we identified a pancreatic cancer-specific, nuclease-resistant RNA aptamer, SQ2, which binds to alkaline phosphatase placental-like 2 (ALPPL2), a putative biomarker for pancreatic cancer. In this study, we demonstrate that the aptamer can be internalized into pancreatic cancer cells and can thus be used for the targeted delivery of therapeutics. Using the aptamer as a ligand, we established that glycophosphatidylinositol-anchored ALPPL2 is internalized by the cells through clathrin-independent and caveolae-dependent or dynamin-mediated cell-type-dependent pathways. Finally, we show that SQ2 can deliver nucleoside drug 5-fluoro-2'-deoxyuridine specifically to ALPPL2-expressing pancreatic cancer cells, inhibiting cell proliferation.