Exosomes as emerging mediators and therapeutic vehicles in painful diabetic neuropathy: From pathophysiology to clinical translation

Table 5 Exosomes as therapeutic vehicles in painful diabetic neuropathy

Category	Agent/approach	Mechanism of action/key cargo	Therapeutic outcomes/advantages	Evidence density/quality
Therapeutic rationale	Exosomes (general)	CD47 “don’t eat me” signal; natural barrier traversal; multi-molecular cargo delivery; surface engineerability	Bypasses limitations of single-agent drugs; non-genomic; immunologically well-tolerated; protects labile cargo	Conceptual/mechanistic rationale – not outcome-specific
Leading platform	MSC-derived exosomes	Cargo: BDNF, NGF, NT-3, GDNF, VEGF, HGF, HSP70/90, miR-146a, miR-223, let-7 family, miR-132-3p, miR-21-5p. Action: PI3K-Akt/MAPK-ERK activation; TLR4/NF-κB suppression; macrophage M2 polarization	Improves nerve conduction velocity (30%-60%), IENFD (35%-80%), and behavioral pain thresholds (40%-70%); reduces endoneurial TNF-α, IL-1β, iNOS; promotes structural regeneration	High – multi-study preclinical evidence base using consistent, composite functional/electrophysiological/behavioral outcome batteries
Preconditioning strategies	Hypoxic	Enriches HIF-1α products (VEGF, EPO, miR-210)	Enhanced endoneurial vascular restoration	Moderate – mechanistic enrichment data; outcome reported qualitatively
	Inflammatory	Augments anti-inflammatory miR-146a and let-7b content.	Enhanced anti-inflammatory effect	Moderate – mechanistic enrichment data; outcome reported qualitatively
	Neurotrophic	Increases neurotrophic protein cargo	Enhanced DRG neuroprotection	Moderate – mechanistic enrichment data; outcome reported qualitatively
Engineering for targeted delivery	Surface engineering	RVG peptide fusion (targets neuronal nAChRs); PEGylation	Increased DRG/peripheral nerve accumulation; extended circulation half-life (2-4 x)	Moderate-high – quantified pharmacokinetic data (half-life), but limited PDN-specific functional endpoint data
	Cargo engineering	Electroporation (miRNA/siRNA); passive incubation (curcumin); parent cell genetic engineering (lactadherin C1C2 fusion)	Overcomes bioavailability limits (e.g., curcumin); enables scalable, enriched cargo production	Moderate – proof-of-concept delivery data; outcome reported qualitatively
Mechanistically targeted cargo	let-7a mimic	Suppresses HMGA2-driven Nav1.7 transcription	Reduces ectopic discharge and mechanical allodynia without cardiac side effects	Moderate – single-mechanism preclinical study; qualitative behavioral outcome
	Anti-TRPV1 siRNA	RVG-targeted knockdown of TRPV1	Sustained reduction of thermal hyperalgesia from a single injection	Moderate – single-mechanism preclinical study; qualitative behavioral outcome
	MiR-146a-5p mimic	Reduces NF-κB activation and pro-inflammatory cytokines	Decreased endoneurial macrophage infiltration; improved nerve conduction and IENFD	Moderate – qualitative directional outcome; not consolidated into a quantified range
	Combined Cargo (let-7b-5p + miR-146a-5p)	Synergistic targeting of peripheral sensitization and neuroinflammation	Outperforms single-cargo preparations; demonstrates multiplex therapeutic advantage	Moderate – comparative (vs single-cargo) data; outcome reported qualitatively
	IL-4-stimulated macrophage exosomes	Enriched in IL-10, TGF-β, miR-124	Suppresses microglial activation; restores KCC2 expression; reverses central sensitization	Moderate – proof-of-concept central-mechanism study; qualitative outcome
	Exosomal curcumin	Suppresses NF-κB activation	Superior anti-inflammatory efficacy vs free curcumin	Moderate – direct comparative study; qualitative outcome
Alternative cell sources	Healthy Schwann cell-derived exosomes	Full physiological complement of neurotrophic cargo	Restores axonal mitochondrial function and IENFD more effectively than recombinant factors	Low-moderate – limited to comparison against single recombinant factors; no consolidated quantitative range or multi-domain (functional + electrophysiological + behavioral) outcome battery equivalent to MSC-derived exosome data
	Plant-derived nanoparticles (ginger)	Enriched in phosphatidic acids and 6-gingerol	Attenuates NF-κB signaling and mechanical hyperalgesia; oral delivery possible; scalable and non-immunogenic	Low – limited to a single identified preclinical study; no IENFD, nerve conduction velocity, or quantified behavioral threshold data available; should be regarded as an early proof-of-concept signal rather than a validated efficacy estimate

MSC: Mesenchymal stem cell; BDNF: Brain-derived neurotrophic factor; NGF: Nerve growth factor; NT-3: Neurotrophin-3; GDNF: Glial cell line-derived neurotrophic factor; VEGF: Vascular endothelial growth factor; HGF: Hepatocyte growth factor; HSP: Heat shock protein; PI3K-Akt: Phosphatidylinositol 3-kinase-protein kinase B; MAPK-ERK: Mitogen-activated protein kinase-extracellular signal-regulated kinase; TLR4: Toll-like receptor 4; NF-κB: Nuclear factor kappa B; IENFD: Intraepidermal nerve fiber density; TNF-α: Tumor necrosis factor-alpha; IL: Interleukin; iNOS: Inducible nitric oxide synthase; HIF-1α: Hypoxia-inducible factor 1-alpha; DRG: Dorsal root ganglion; RVG: Rabies virus glycoprotein; nAChRs: Nicotinic acetylcholine receptors; PEGylation: Polyethylene glycol conjugation; miRNAs: MicroRNAs; siRNA: Small interfering RNA; HMGA2: High mobility group AT-hook 2; TRPV1: Transient receptor potential vanilloid 1; KCC2: Potassium-chloride cotransporter 2; TGF-β: Transforming growth factor-β; PDN: Painful diabetic neuropathy; EPO: Erythropoietin.