ALG-bFGF Hydrogel Inhibiting Autophagy Contributes to Protection of Blood–Spinal Cord Barrier Integrity via PI3K/Akt/FOXO1/KLF4 Pathway After SCI

Abstract

Promoting blood–spinal cord barrier (BSCB) repair at the early stage plays a crucial role in treatment of spinal cord injury (SCI). Excessive activation of autophagy can prevent recovery of BSCB after SCI. Basic fibroblast growth factor (bFGF) has been shown to promote BSCB repair and locomotor function recovery in SCI. However, the therapeutic effect of bFGF via direct administration on SCI is limited because of its rapid degradation and dilution at injury site. Based on these considerations, controlled release of bFGF in the lesion area is becoming an attractive strategy for SCI repair. At present, we have designed a sustained-release system of bFGF (called ALG-bFGF) using sodium alginate hydrogel, which is able to load large amounts of bFGF and suitable for in situ administration of bFGF in vivo. Here, traumatic SCI mice models and oxygen glucose deprivation (OGD)–stimulated human brain microvascular endothelial cells were performed to explore the effects and the underlying mechanisms of ALG-bFGF in promoting SCI repair. After a single in situ injection of ALG-bFGF hydrogel into the injured spinal cord, sustained release of bFGF from ALG hydrogel distinctly prevented BSCB destruction and improved motor functional recovery in mice after SCI, which showed better therapeutic effect than those in mice treated with bFGF solution or ALG. Evidences have demonstrated that autophagy is involved in maintaining BSCB integrity and functional restoration in animals after SCI. In this study, SCI/OGD exposure–induced significant upregulations of autophagy activation-related proteins (Beclin1, ATG5, LC3II/I) were distinctly decreased by ALG-bFGF hydrogel near the baseline and not less than it both in vivo and in vitro, and this inhibitory effect contributed to prevent BSCB destruction. Finally, PI3K inhibitor LY294002 and KLF4 inhibitor NSC-664704 were applied to further explore the underlying mechanism by which ALG-bFGF attenuated autophagy activation to alleviate BSCB destruction after SCI. The results further indicated that ALG-bFGF hydrogel maintaining BSCB integrity by inhibiting autophagy activation was regulated by PI3K/Akt/FOXO1/KLF4 pathway. In summary, our current study revealed a novel mechanism by which ALG-bFGF hydrogel improves BSCB and motor function recovery after SCI, providing an effective therapeutic strategy for SCI repair.

Engineered Basic Fibroblast Growth Factor Specifically Bonded with Injectable Extracellular Matrix Hydrogel for the Functional Restoration of Cerebral Ischemia in Rats

“…6 B and F). It was reported that bFGF could regulate junction proteins of the microvascular barrier and decrease the permeability of BBB or blood spine cord barrier in the brain or spine cord, respectively [ 15 , 23 , 24 ].The major tight junction protein ZO-1 was detected to measure the effect of bFGF on the BBB of the ischemic brain. The results showed that the mean fluorescence intensity of ZO-1 in the EBP-bFGF/ECM group (74.5 ± 11.7) was typically higher than that in the bFGF/ECM group (45.7 ± 11.5; P < 0.001), ECM group (31.6 ± 4.2; P < 0.001), and PBS group (30.0 ± 4.2; P < 0.001), which the tight junction was more compact than other 3 groups (Fig.…”

Erythropoietin Activates Autophagy to Regulate Apoptosis and Angiogenesis of Periodontal Ligament Stem Cells via the Akt/ERK1/2/BAD Signaling Pathway under Inflammatory Microenvironment

“…p-Erk1/2 and p-BAD changed following the change of phosphorylated Akt. VEGF-a, FGF-2, and IGF-1 levels may be regulated by p-Erk1/2 [ 68 ]; Bax/Bcl2 ratio may be relevant to p-BAD [ 69 ]; Beclin1 and LC3B may be targeted by Akt [ 70 ]. Additionally, some researchers also found that expression of LC3 and Erk/p-Erk played a vital role in the regulation of dental pulp stem cell inflammation, suggesting that the prompt LC3 and p-Erk rescued autophagy, which was consistent with our results [ 71 ].…”

Immunopathology of herpes simplex virus‐associated neuroinflammation: Unveiling the mysteries

“…It functions closely with neurons, astrocytes, and pericytes, forming what is known as the neurovascular unit (NVU) 89 . The BBB's primary role is to safeguard the spinal parenchyma by serving as a barrier that restricts the entry of harmful circulating molecules, immune cells, and inflammatory agents into the spinal cord 90 . In the context of HSV infection, the BBB is of utmost importance, as it acts as a critical defence mechanism preventing the virus from entering the brain and inciting neuroinflammation.…”

“…The maintenance of BBB integrity is essential. HSV‐induced neuroinflammation can compromise the BBB's function and structure, resulting in the loss of neural tissue and affecting the responsiveness to neuroprotective medications 89,90 . Therefore, it is imperative to prioritise preserving BBB integrity, especially in HSV infection, as it plays a pivotal role in averting neuroinflammation and its associated complications.…”