Date of Award
Summer 9-7-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Peripheral artery disease (PAD) is a widespread atherosclerotic disorder affecting more than 200 million people globally, with critical limb ischemia (CLI) being its most severe manifestation. Stem cell therapy has been a promising CLI treatment, but the harsh conditions in an ischemic limb, such as hypoxia, high reactive oxygen species (ROS) stress, and the lack of a support matrix, trophic factors, and nutrients, all compromise therapeutic efficacy by reducing the survival rate or function of transplanted cells. This thesis presents various biomaterial systems designed for stem cell and drug delivery to improve the cell microenvironment and promote angiogenesis and myogenesis in ischemic limbs. Its four chapters describe the development and testing, both in vitro and in vivo, of therapeutic systems using polymer-derived biomaterials, drugs, and/or stem cells. Chapter 2 describes a therapeutic system for treating critical limb ischemia (CLI), consisting of a biodegradable and thermosensitive hydrogel (pNHA), oxygen release microspheres (ORMs), and mesenchymal stromal cells (MSCs). The ORMs were conjugated by catalase to produce and release oxygen from loaded H2O2 for up to 14 days, without increasing reactive oxygen species (ROS) pressure. This system can increase the oxygen content to promote the MSC paracrine effect, which enhances cell survival. In vivo studies demonstrate that this system promotes cell survival, proliferation, and the paracrine effect, regulates inflammation, and accelerates angiogenesis and myogenesis. In Chapter 3, an N-cadherin mimic peptide, HAV, was conjugated to the thermosensitive and biodegradable hydrogel poly(NIPAAm-co-MAPEG-co-AOLA-co-NAS) (pNMAN) (Gel). This HAV-functionalized hydrogel (Gel-HAV) increases the expression of N-cadherin in engrafted induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs), promoting cell-matrix interaction, cell survival, and the paracrine effect under hypoxic conditions. The delivery of Gel-HAV/MSC also significantly improves ischemic limb tissue regeneration. In Chapter 4, the cell membrane repair-related protein TRIM72 is modified with an ischemia-targeted peptide, IMTP, and an MMP2 substrate sequence to create engineered TRIM72 protein (ETRIM72). Platelet membrane-coated ETRIM72 nanoparticles (ETRIM72 NP) and oxygen release nanoparticles (O2 NP) were then delivered to diabetic mice with CLI. This system increased oxygen tension and improved cell membrane repair, reducing cell death and improving cell proliferation and significantly accelerating tissue regeneration without the use of stem cells. In Chapter 5, an ischemia-targeted PLGA nanoparticle is used to encapsulate a GDH1 inhibitor, R162, and an antioxidant peptide, SS-31, to increase the glutamine concentration, decrease the ROS content, and regulate the M1 macrophage secretion in cells. This system shows great potential for clinical use. The co-treatment using R162 NP (RNP) and SS-31 NP (SNP) in diabetic CLI mice successfully promoted ischemic tissue angiogenesis or myogenesis.
Language
English (en)
Chair
Jianjun Guan