Role of Trichocytic Keratins in Anti‐Neuroinflammatory Effects After Spinal Cord Injury

Abstract

Shifting microglia/macrophages to M2 anti-inflammatory phenotype is considered a pivotal therapeutic target for spinal cord injury (SCI). Keratin extracted from human hair exhibits anti-inflammatory properties. However, the differences among the 17 types of human hair keratins and their mechanisms of anti-inflammation remain poorly understood. In this study, the anti-inflammatory activity of 17 human hair keratins using a recombinant synthesis approach is explored. Distinct activities of microglia/macrophage phenotype modulation of 17 keratins are found through qRT-PCR analysis, and recombinant keratin 33A (RK33A) and RK35 display superior anti-inflammatory efficiency compared to other keratins. Immunofluorescence and flow cytometry reveals a significant effect of RK33A on the regulation of microglia/macrophages into an anti-inflammatory M2 phenotype. Subsequently, recombinant keratin 33A nanofiber (RKNF33A) is fabricated to evaluate its in vivo anti-inflammatory and nerve regeneration properties using the rat T9 spinal cord lateral hemisection model. The optimized keratin-based nanofiber shows outstanding performance in enhancing M2 polarization, reducing glial scarring, promoting nerve regeneration, and improving locomotor function recovery in SCI rats. Moreover, it is preliminarily found that RK33A regulates M2 microglia/macrophage polarization by upregulating the PI3K/AKT/mTOR signaling pathway. Together, this study reveals that trichocytic keratins exhibit distinct anti-inflammatory properties, providing a prospective treatment for SCI by modulating microglia/macrophage polarization.

Functional Polyphenol-Based Nanoparticles Boosted the Neuroprotective Effect of Riluzole for Acute Spinal Cord Injury

“…M1 microglia/macrophages (specific marker CD86) in the proinflammatory state could kill nearby cells and hinder cell proliferation by secreting cytokines such as interleukin-1b (IL-1β), tumor necrosis factor-α (TNF-α), IL-6, etc. On the contrary, M2 microglia/macrophages (specific marker CD206) represent the anti-inflammatory state by secreting cytokines such as transforming growth factor beta (TGF-β) and IL-10, which promote cell activation and tissue growth. , The effective transformation between microglia/macrophages M1 and M2 plays a vital role in neuroinflammation related pathological processes . Thus, microglial BV2 cells were selected to study the response of microglia/macrophages treated with Ri@EGCG-2 NPs and LPS (500 ng/mL), which could stimulate microglia/macrophages to polarize to the M1 phenotype and reduce the M2 phenotype.…”

“…On the contrary, M2 microglia/macrophages (specific marker CD206) represent the anti-inflammatory state by secreting cytokines such as transforming growth factor beta (TGF-β) and IL-10, which promote cell activation and tissue growth. 11,50 The effective transformation between microglia/macrophages M1 and M2 plays a vital role in neuroinflammation related pathological processes. 51 Thus, microglial BV2 cells were selected to study the response of microglia/macrophages treated with Ri@ through reducing M1 polarization and increasing M2 polarization.…”

“…Traumatic spinal cord injury (SCI) is a ruinous neuropathological condition in the central nervous system (CNS) that is caused by external violence, tumors, and hemorrhages. − Because of intractable therapy processes and the limited regenerative capacity of CNS, patients usually suffer long-term dysfunction and disability, causing a huge economic burden to families and society. , Therefore, there is an urgent requirement to develop effective neuroprotective strategies to improve the prognosis for SCI patients with complex pathological process. , After the initial mechanical destruction of spinal cord tissue, subsequent neuroinflammation, excess reactive oxygen species (ROS), increased glutamate (Glu), disordered ion channel, and other abnormal pathological processes would further aggravate tissue damage and inhibit nerve repair. , Owing to the uncontrollability of the primary injury, the development of highly efficient neuroprotective agents targeting all the above secondary injuries has been considered as the most promising treatment option for reducing the severity of injury and promoting functional recovery. − …”

Robust and Multifunctional Nanoparticles Assembled from Natural Polyphenols and Metformin for Efficient Spinal Cord Regeneration

“…1−3 After SCI caused by primary violence, a harsh microenvironment caused by oxidative stress and neuroinflammation storms usually plays a dominant role in the subsequent injury, including neuron loss, demyelination, and axon dieback, which further exacerbates neurological dysfunction. 2,4,5 Inhibiting the release of pro-inflammatory factors and effectively removing reactive oxygen species (ROS) after the injury have been regarded as an efficient way to reduce neuronal apoptosis and axon demyelination, achieving excellent neuroprotective effects. 4−7 However, the harsh microenvironment at the injury site has limited potential to mobilize the innate regeneration of the spinal cord, which cannot achieve satisfactory results in repairing damaged structures and promoting the recovery of motor function in SCI animal models.…”

“…Spinal cord injury (SCI) is a destructive neuropathological disease of neural circuitry and connectivity caused by external violence, tumor, and other factors, leading to loss of autonomic regulation, intestinal dysfunction, and permanent sensory and motor dysfunction. − After SCI caused by primary violence, a harsh microenvironment caused by oxidative stress and neuroinflammation storms usually plays a dominant role in the subsequent injury, including neuron loss, demyelination, and axon dieback, which further exacerbates neurological dysfunction. ,, Inhibiting the release of pro-inflammatory factors and effectively removing reactive oxygen species (ROS) after the injury have been regarded as an efficient way to reduce neuronal apoptosis and axon demyelination, achieving excellent neuroprotective effects. − However, the harsh microenvironment at the injury site has limited potential to mobilize the innate regeneration of the spinal cord, which cannot achieve satisfactory results in repairing damaged structures and promoting the recovery of motor function in SCI animal models. , Therefore, given the limited regenerative capability after SCI, the strategy of simply remodeling the harsh microenvironment after injury may not promote significant neural regeneration and function restoration efficiently, and further considerations are highly desirable to address the challenge.…”