HSPB2 facilitates neural regeneration through autophagy for sensorimotor recovery after traumatic brain injury

Autophagy is a promising target for promoting neural regeneration, which is essential for sensorimotor recovery following traumatic brain injury (TBI). Whether neuronal heat shock protein B2 (HSPB2), a small molecular heat shock protein, reduces injury and promotes recovery following TBI remains unclear. In this study, we demonstrated that HSPB2 was significantly increased in the neurons of a TBI mouse model, patients, and primary neuron cultures subjected to oxygen/glucose deprivation and reperfusion treatment. Upon creating a tamoxifen-induced neuron-specific HSPB2 overexpression transgenic mouse model, we found that elevated HSPB2 levels promoted long-term sensorimotor recovery and alleviated tissue loss after TBI. We also demonstrated that HSPB2 enhanced white matter structural and functional integrity, promoted central nervous system (CNS) plasticity, and accelerated long-term neural remodeling. Moreover, we found that autophagy occurred around injured brain tissues in patients, and the pro-regenerative effects of HSPB2 relied on its autophagy-promoting function. Mechanistically, HSPB2 may regulate autophagy possibly by forming the HSPB2/BCL2-associated athanogene 3/sequestosome-1 complex to facilitate the clearance of erroneously accumulated proteins in the axons. Treatment with the autophagy inhibitor chloroquine during the acute stage or delayed induction of HSPB2 remarkably impeded HSPB2’s long-term reparative function, indicating the importance of acute-stage autophagy in long-term neuro-regeneration. Our findings highlight the beneficial role of HSPB2 in neuro-regeneration and functional recovery following acute CNS injury, thereby emphasizing the therapeutic potential of autophagy regulation for enhancing neuro-regeneration.


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To assess tissue loss, 10 serial sections with an interval of 11 sections were NeuN immunostained to calculate  166 flexion between 22.5° and 45° from vertical was rated 3 (moderate), and flexion of the torso at 45° or more 167 and with/or without grasping of the hindlimbs by forelimbs was given a rating of 4 (severe).

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The foot fault test (grid-walking test) was performed as described previously (5)

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The Morris water maze test was carried out 29-34 days following TBI to evaluate spatial cognitive functions 180 as described previously(6). Briefly, in the learning stage (day 29-33), a square platform (11 × 11 cm 2 ) was 181 submerged 2 cm beneath the water surface in a circular pool (diameter = 109 cm) filled with opaque water.

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Mice were placed into the pool at one of the four locations and given 60 seconds to locate the hidden platform.

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At the end of each trial, the mouse was placed on the platform or allowed to stay on the platform for 30 s 184 with prominent spatial cues displayed around the room.

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Compound action potentials (CAPs) in the external capsule were recorded as previously described (7). Mice 207 were anesthetized with isoflurane and were decapitated to remove the brains rapidly. A 350-μm coronal brain 208 slice was prepared using a vibratome (1200s, Leica). Slices were transferred to artificial cerebrospinal fluid 209 (aCSF) saturated with 95% O2+5% CO2 mixture at 32°C for 0.5 h then at room temperature for 1 h for 210 recovery. The aCSF contained 124 mM NaCl, 2.5 mM KCl, 2 mM CaCl2, 1 mM NaH2PO4, 24 mM NaHCO3,   Figure