Medical Student University of California, Davis Garden Grove, California, United States
Introduction: Spinal cord injury (SCI) is a devastating condition that leads to life-long disability, affecting patients and their families. It has been shown that placental mesenchymal stem cells (PMSCs) and PMSC-extracellular vesicles (EVs) demonstrate significant neuroprotective and neuroregenerative potential for the treatment of SCI. PMSC-EVs are preferable to PMSC cell-based therapy because they are immunomodulatory rather than proliferative, easily, and stably stored for off-the-shelf use, and more suitable for non-operative administration. Athough PMSC-EVs can be injected, they require additional modification to reach sufficient biodistribution in the spinal cord. Conjugating PMSC-EVs to CAQK (cysteine-alanine-glutamine-lysine), an intravenous platform drug delivery system that carries neurotherapeutics directly to the site of SCI, could overcome this challenge. We hypothesize that conjugation of CAQK to the surfaces of PMSC-EVs will increase their accumulation within injured spinal tissue, and improve neuroprotective effect in vitro compared to unmodified PMSC-EVs.
Methods: Click chemistry was utilized to conjugate PMSC-EVs with CAQK. The conjugated product underwent super-resolution imaging to confirm its successful synthesis and structural integrity. A neuroprotection assay was conducted to evaluate and compare the anti-apoptotic effects of among three groups: CAQK alone, PMSC-EVs alone, and the CAQK-conjugated PMSC-EVs. Furthermore, live animal imaging was performed using a rodent SCI model following intravenous administration of each group to assess distribution, targeting efficiency, and therapeutic potential in vivo.
Results: Click chemistry was successfully employed to conjugate PMSC-EVs with CAQK, as confirmed through super-resolution imaging. In vitro analyses demonstrated that the conjugated PMSC-EVs exhibited significantly enhanced anti-apoptotic effects compared to either CAQK or PMSC-EVs alone. In vivo live animal imaging revealed increased localization of PMSC-EVs when conjugated with CAQK compared to IV administration of CAQK alone, highlighting the targeted delivery and potential therapeutic advantage of the conjugated complex.
Conclusion : The conjugation of PMSC-EVs with CAQK via click chemistry results in enhanced neuroprotective effects in vitro compared to their individual components. Furthermore, CAQK conjugation facilitates targeted localization of PMSC-EVs to the SCI sites following intravenous administration, highlighting its potential for improved therapeutic efficacy of PMSC-EVs.
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