Tiny vesicles show potential to revolutionize treatment for diabetic limb ischemia, addressing a serious complication related to diabetes.
Researchers are exploring new avenues to tackle diabetic limb ischemia, which is characterized by decreased blood flow to the legs and feet. This condition, unfortunately, leads to severe complications such as chronic pain, the formation of stubborn ulcers, and, most alarmingly, limb amputations. Statistics reveal it as the leading cause of non-traumatic amputations, with affected individuals facing significantly heightened risks.
For individuals suffering from diabetic limb ischemia, the stakes are high with elevated chances of cardiovascular events, estimated to be 20%-30% higher than those without this condition. The alarming reality is these patients are also 14 times more likely to face amputation compared to individuals with other artery diseases.
“Our primary motivation is to find a safer, non-surgical option for diabetic limb ischemia patients who often suffer from restricted blood flow and tissue damage,” stated Xing Zhang, a researcher from the Department of Vascular Surgery at Shanghai Ninth People’s Hospital, China's highly regarded healthcare institution. According to Zhang, current treatment methods, which largely involve surgery or medication, come with risks and sometimes fail to deliver the desired effectiveness.
Zhang and his team have dedicated the past ten years to researching stem cell therapies for vascular diseases. Along the way, they encountered several challenges, including immune rejection, the potential for tumors, ethical concerns surrounding the use of stem cells, and inconsistent survival rates of transplanted cells. These hurdles prompted them to seek out alternative therapies.
Turning to Extracellular Vesicles
An innovative approach is gaining traction: extracellular vesicles. These microvesicles, which are lipid-bound particles released by nearly all cell types, serve as natural carriers of biomolecules. The research team advocates for extracellular vesicle transplantation, particularly focusing on exosome transplantation, which boasts several advantages over traditional stem cell transplants.
A pivotal part of this approach involves identifying specific proteins or genes capable of guiding the vesicles and enhancing their therapeutic efficacy. By targeting certain receptors or pathways, researchers can instruct the vesicles to ferry their biologically active cargo—such as therapeutic molecules or genetic material—exactly to the location where it's needed most. This precision is key to boosting the effectiveness of the therapy and minimizing unwanted side effects.
Recent studies highlight the role of Netrin1, a protein recognized for its protective effects within the cardiovascular system. It promotes blood vessel growth, fosters cell survival, and mitigates inflammation, all of which are significant factors affected by diabetic limb ischemia. “Netrin1 has primarily been studied for its role in nervous system development, especially with guiding nerve cells,” explained Xinwu Lu, director of the Department of Vascular Surgery at the same hospital as Zhang. “It hasn’t been commonly linked to conditions like diabetic limb ischemia, which involves complex issues like restricted blood flow, immune responses, and inflammation.”
Despite its known benefits, the specific actions of Netrin1 related to diabetic limb ischemia are still unclear, inspiring the team to investigate its potential as both a biomarker and therapeutic target.
Initial Promising Findings
The researchers started by measuring Netrin1 levels within blood and tissue samples from diabetic limb ischemia patients, comparing these against samples from individuals suffering from acute arterial embolism—a condition affecting the arteries. "Our findings indicated significantly lower Netrin1 levels among diabetic limb ischemia patients compared to our control group," said Zhijue Xu, who is working as assistant researcher at Shanghai Jiao Tong University. This discrepancy suggests decreased Netrin1 levels could contribute to disease progression and encourages the team to explore its therapeutic potential.
The ultimate objective? Use genetically modified stem cells derived from adipose (fat) tissue to produce higher levels of Netrin1. These modified cells release exosomes—tiny vesicles—rich with Netrin1 as part of their normal cellular activities.
“Exosomes were collected via differential ultracentrifugation, which separates them based on size and density,” the research team specified. The purified exosomes were then injected directly where blood flow was compromised, which allows it to assist the body’s healing processes by improving blood flow and promoting tissue repair.
Enhancing Healing Capacities
Initial laboratory tests indicate Netrin1-enriched exosomes offer superior performance compared to standard exosomes derived from adipose-derived stem cells. “This is primarily because Netrin1 activates specific pathways within cells, enabling them to endure challenging conditions more effectively,” Yihong Jiang, another researcher engaged with the project, noted.
The dual action of Netrin1 — boosting protective effects and stimulating the growth of blood vessels — leads to significant enhancements in the healing capacity of tissues afflicted by diabetic limb ischemia. One of the primary factors driving this success is the activation of two cellular pathways associated with cell survival and repair. “One pathway promotes angiogenesis, thereby improving blood flow to damaged tissues; the other accelerates cell growth and renewal,” Jiang elaborated. “The activation mediated by Netrin1-enriched exosomes acts as a protective ‘shield’ for blood vessel cells, facilitating quicker recovery and restoration of compromised tissues.”
Unlike more invasive interventions, such as stent placements or bypass surgeries, the Netrin1-enriched exosomes present themselves as promising non-surgical options, enabling the body to heal naturally and restore appropriate blood flow to the affected limbs.
Nevertheless, significant hurdles remain before this approach can be employed clinically. “Initially, we must devise effective delivery systems to guarantee the exosomes maintain stability and perform optimally within the body,” Xinwu cautioned. “Producing sufficient quantities of high-quality exosomes is equally important, ensuring every batch consistently demonstrates the necessary efficacy and purity.”
Extensive clinical trials are necessary to solidify the therapy's long-term safety and efficacy for patients experiencing diabetic limb ischemia. An additional avenue for patient care may involve monitoring blood levels of Netrin1 to identify at-risk patients early, facilitating timely interventions before the onset of serious complications.
“The next steps entail conducting larger animal studies to validate the safety and efficacy of Netrin1-enriched exosomes,” Xinwu added. “Should these studies yield promising outcomes, we plan to proceed with preliminary human trials. Simultaneously, we are focusing on optimizing exosome delivery to guarantee their stability and effective targeting.”
“At the end of the day, our ultimate mission is to usher this innovative therapy from the lab to clinical practice, granting diabetic limb ischemia patients access to safe and non-invasive treatment options.”
Reference: Zhijue Xu, Xing Zhang, Xinwu Lu, et al., "Netrin1-Enriched Exosomes From Genetically Modified ADSCs as a Novel Treatment for Diabetic Limb Ischemia," Advanced Healthcare Materials (2024). DOI: 10.1002/adhm.202403521
