Attenuation of Robust Glial Scar Formation Facilitates Functional Recovery in Animal Models of Chronic Nerve Compression Injury

Administration of methylprednisolone do not affect the spinal scar component of spinal cord injury

OBJECTIVE

The aim of this study is to evaluate the impact of methylprednisolone (MP) on scar composition following spinal cord injury (SCI).

DESIGN

A total of 40 adult Sprague Dawley rats underwent right hemisection injuries to the spinal cord.

INTERVENTIONS

The rats were randomly divided into two groups: the vehicle group and the MP group. In the MP group, rats received intraperitoneal injections of MP at a dose of 30 mg/kg for 7 consecutive days, while the vehicle group received intraperitoneal injections of saline as a control. Weekly assessments of hindlimb performance in the rat models were conducted using the Basso-Beattie-Bresnahan test (BBB) score and the horizontal ladder-walking test. Changes in scar components were identified through immunofluorescence staining, and an axonal regeneration assay was employed to evaluate regrowth under inhibitory conditions.

RESULTS

The administration of MP led to a significant improvement in BBB scores compared to the control group at 7 days post-injury, although this improvement was not consistent. Furthermore, rats in the MP group did not demonstrate progressive improvement in horizontal ladder walking. Notably, there were no significant changes in the content of scar components in the injured area following MP treatment, and the axon length of neurons treated with MP did not exhibit significant extension compared to the vehicle group.

CONCLUSIONS

Our findings indicate that the administration of MP does not effectively enhance hindlimb motor function or promote neuronal axon growth within a scarred environment after SCI.

Model-based parcellation of diffusion MRI of injured spinal cord predicts hand use impairment and recovery in squirrel monkeys

A mathematical model-based parcellation of magnetic resonance diffusion tensor images (DTI) has been developed to quantify progressive changes in three types of tissues - grey (GM), white matter (WM), and damaged spinal cord tissue, along with behavioral assessments over a 6 month period following targeted spinal cord injuries (SCI) in monkeys. Sigmoid Gompertz function based fittings of DTI metrics provide early indicators that correlate with, and predict, recovery of hand grasping behavior. Our three tissue pool model provided unbiased, data-driven segmentation of spinal cord images and identified DTI metrics that can serve as reliable biomarkers of severity of spinal cord injuries and predictors of behavioral outcomes.

Diagnosis and treatment of meralgia paresthetica between 2005 and 2018: a national cohort study

The prevalence of meralgia paresthetica (MP), which is caused by compression of the lateral femoral cutaneous nerve (LFCN), has been increasing over recent decades. Since guidelines and large-scale studies are lacking, there are substantial regional differences in diagnostics and management in MP care. Our study aims to report on current diagnostic and therapeutic strategies as well as time trends in clinical MP management in Germany. Patients hospitalized in Germany between January 1, 2005, and December 31, 2018, with MP as their primary diagnosis were identified using the International Classification of Disease (ICD-10) code G57.1 and standardized operations and procedures codes (OPS). A total of 5828 patients with MP were included. The rate of imaging studies increased from 44% in 2005 to 79% in 2018 (p < 0.001) and that of non-imaging diagnostic studies from 70 to 93% (p < 0.001). Among non-imaging diagnostics, the rates of evoked potentials and neurography increased from 20%/16% in 2005 to 36%/23% in 2018 (p < 0.001, respectively). Rates of surgical procedures for MP decreased from 53 to 37% (p < 0.001), while rates of non-surgical procedures increased from 23 to 30% (p < 0.001). The most frequent surgical interventions were decompressive procedures at a mean annual rate of 29% (± 5) throughout the study period, compared to a mean annual rate of 5% (± 2) for nerve transection procedures. Between 2005 and 2018, in-hospital MP care in Germany underwent significant changes. The rates of imaging, evoked potentials, neurography, and non-surgical management increased. The decompression of the LFCN was substantially more frequent than that of the LFCN transection, yet both types of intervention showed a substantial decrease in in-hospital prevalence over time.

Treatment of idiopathic meralgia paresthetica – is there reliable evidence yet?

OBJECTIVE

Meralgia paresthetica is a common condition that is usually diagnosed by its classical clinical presentation and by exclusion of a spinal origin of pain, sensory loss, and/or paresthesias in the anterolateral thigh. Treatment modalities include conservative management, local injections, and surgical therapy. To date, no level 1 evidence exists about treatment options for idiopathic meralgia paresthetica. This review article aims to give a structured overview of epidemiology, history, anatomy, diagnostics, and treatment. It focuses on the existing literature and current developments in clinical management.

METHODS

A literature search on PubMed/MEDLINE was performed on 20 December 2021, yielding 1412 results. Abstracts were screened and classified in terms of epidemiology, anatomy, diagnostics, and treatment.

RESULTS

High-quality observational data that was included in recent meta-analyses showed satisfactory results for conservative management, injections, and surgical decompression or neurectomy, but there is some major methodological criticism. For idiopathic meralgia paresthetica, the results of surgical decompression have never been compared to those of neurectomy in a randomized setup. The only study protocol published so far does not consider any extended decompression techniques (dynamic, circumferent, proximal, and distal to the inguinal ligament). A multicenter, prospective design has never been proposed.

DISCUSSION

Reliable high-quality evidence on the treatment of idiopathic meralgia paresthetica is lacking at the current state, and challenges in clinical decision-making remain.

5-Fluorouracil reduces the fibrotic scar via inhibiting matrix metalloproteinase 9 and stabilizing microtubules after spinal cord injury

AIMS

Fibrotic scars composed of a dense extracellular matrix are the major obstacles for axonal regeneration. Previous studies have reported that antitumor drugs promote neurofunctional recovery.

METHODS

We investigated the effects of 5-fluorouracil (5-FU), a classical antitumor drug with a high therapeutic index, on fibrotic scar formation, axonal regeneration, and functional recovery after spinal cord injury (SCI).

RESULTS

5-FU administration after hemisection SCI improved hind limb sensorimotor function of the ipsilateral hind paws. 5-FU application also significantly reduced the fibrotic scar formation labeled with aggrecan and fibronectin-positive components, Iba1⁺ /CD11b⁺ macrophages/microglia, vimentin, chondroitin sulfate proteoglycan 4 (NG2/CSPG4), and platelet-derived growth factor receptor beta (PDGFRβ)⁺ pericytes. Moreover, 5-FU treatment promoted stromal cells apoptosis and inhibited fibroblast proliferation and migration by abrogating the polarity of these cells and reducing matrix metalloproteinase 9 expression and promoted axonal growth of spinal neurons via the neuron-specific protein doublecortin-like kinase 1 (DCLK1). Therefore, 5-FU administration impedes the formation of fibrotic scars and promotes axonal regeneration to further restore sensorimotor function after SCI.

Efficacy of direct anterior approach combined with direct posterior approach in Pipkin IV femoral head fractures

Objective

The study aimed to explore the efficacy of direct anterior approach combined with direct posterior approach in Pipkin IV femoral head fractures.

Methods

The study enrolled 64 patients with Pipkin IV femoral head fractures who were treated at our hospital between March 2019 and April 2020. They were assigned to the control group and the study group using the random number table method with 32 patients in each group and received treatment by the direct anterior approach and treatment by the direct anterior approach combined with the direct posterior approach. The operative time, intraoperative estimated blood loss, postoperative drainage time, drainage volume, time to partial and full weight-bearing, total length of hospital stay and the levels of hemoglobin (Hb) and hematocrit (Hct) in the two groups were compared, and severity of pain and hip function at different time points postoperatively were observed, and the occurrences of complications were compared.

Results

There was no statistical difference in the operative time and intraoperative estimated blood loss between the two groups (P > 0.05). Compared with the control group, the study group had shorter postoperative drainage time, lower drainage volume, shorter time to partial and full weight-bearing, and shorter total length of hospital stay, and the difference was statistically different (P < 0.05). There was no significant difference in Hb and Hct levels between the two groups before surgery (P > 0.05). The levels of Hb and Hct in both groups at postoperative day (POD) 1 were lower than those before surgery, and the levels of Hb and Hct in the study group were significantly higher than those in the control group (P < 0.05). Compared with the control group, the study group had significantly less severe pain at POD 1 and 7 and 1, 3 and 6 months postoperatively (P < 0.05). Compared with the control group, the study group had significantly better hip function at 3, 6 and 12 months postoperatively (P < 0.05). All patients were followed up for 12 months, and 1 case of ectopic ossification appeared in both groups 3 months postoperatively, both Brooker grade I. No special treatment was provided as it did not interfere with the mobility of the hip and caused no apparent discomfort in the patients. In the current study, no incision infection, ischemic necrosis of the femoral head, breakage of the internal fixation device, fracture nonunion and loss of fracture reduction and other complications were reported in any patients.

Conclusion

Direct anterior approach combined with direct posterior approach in Pipkin IV femoral head fractures does not increase operative time and intraoperative estimated blood loss but can lessen severity of pain and promote functional recovery of the hip, leading to a favorable prognosis while not increasing the incidence of complications.

Experimental Methods to Simulate and Evaluate Postsurgical Peripheral Nerve Scarring

As a consequence of trauma or surgical interventions on peripheral nerves, scar tissue can form, interfering with the capacity of the nerve to regenerate properly. Scar tissue may also lead to traction neuropathies, with functional dysfunction and pain for the patient. The search for effective antiadhesion products to prevent scar tissue formation has, therefore, become an important clinical challenge. In this review, we perform extensive research on the PubMed database, retrieving experimental papers on the prevention of peripheral nerve scarring. Different parameters have been considered and discussed, including the animal and nerve models used and the experimental methods employed to simulate and evaluate scar formation. An overview of the different types of antiadhesion devices and strategies investigated in experimental models is also provided. To successfully evaluate the efficacy of new antiscarring agents, it is necessary to have reliable animal models mimicking the complications of peripheral nerve scarring and also standard and quantitative parameters to evaluate perineural scars. So far, there are no standardized methods used in experimental research, and it is, therefore, difficult to compare the results of the different antiadhesion devices.

Is Decorin a Promising New Agent for Facial Nerve Regeneration? An Experimental Study

OBJECTIVE

The aim of this study was to investigate the effects of systemic administration of decorin (DC) on facial nerve (FN) regeneration.

METHODS

A total of 32 female albino Wistar rats were divided into 4 groups: control (C) group: no bilateral FN neurorrhaphy (B-FNN), no DC application, sham-operated group: B-FNN without DC application, DC group: DC application without B-FNN, and B-FNN + DC group: B-FNN and DC application. Nerve conduction studies were performed before and after skin incisions at 1st, 3rd, 5th, and 7th weeks in all groups. The amplitude and latency of compound muscle action potentials were recorded. FN samples were obtained and were investigated under light microscopy and immunohistochemical staining. The nerve and axon diameter, number of axons, H score, Schwann cell proliferation, and myelin and axonal degeneration were recorded quantitatively.

RESULTS

In the sham group, the 3rd and 5th postoperative week, amplitude values were significantly lower than those of the B-FNN + DC group (p < 0.05). Nerve diameters were found to be significantly larger in the sham, DC, and B-FNN + DC groups than in the C group (p < 0.05). The number of axons, the axon diameter, and the H scores were found to be significantly higher in the B-FNN + DC group than in the sham group (p < 0.05). The Schwann cell proliferation, myelin degeneration, and axonal degeneration scores were significantly lower in the B-FNN + DC group than in the sham group (p < 0.05).

CONCLUSION

Electrophysiological and histopathological evaluation revealed the potential benefits provided by DC. This agent may increase FN regeneration.

RGC-32 regulates reactive astrocytosis and extracellular matrix deposition in experimental autoimmune encephalomyelitis

Extracellular matrix (ECM) deposition in active demyelinating multiple sclerosis (MS) lesions may impede axonal regeneration and can modify immune reactions. Response gene to complement (RGC)-32 plays an important role in the mediation of TGF-β downstream effects, but its role in gliosis has not been investigated. To gain more insight into the role played by RGC-32 in gliosis, we investigated its involvement in TGF-β-induced ECM expression and the upregulation of the reactive astrocyte markers α-smooth muscle actin (α-SMA) and nestin. In cultured neonatal rat astrocytes, collagens I, IV, and V, fibronectin, α-SMA, and nestin were significantly induced by TGF-β stimulation, and RGC-32 silencing resulted in a significant reduction in their expression. Using astrocytes isolated from RGC-32 knock-out (KO) mice, we found that the expression of TGF-β-induced collagens I, IV, and V, fibronectin, and α-SMA was significantly reduced in RGC-32 KO mice when compared with wild-type (WT) mice. SIS3 inhibition of Smad3 phosphorylation was also associated with a significant reduction in RGC-32 nuclear translocation and TGF-β-induced collagen I expression. In addition, during experimental autoimmune encephalomyelitis (EAE), RGC-32 KO mouse astrocytes displayed an elongated, bipolar phenotype, resembling immature astrocytes and glial progenitors whereas those from WT mice had a reactive, hypertrophied phenotype. Taken together, our data demonstrate that RGC-32 plays an important role in mediating TGF-β-induced reactive astrogliosis in EAE. Therefore, RGC-32 may represent a new target for therapeutic intervention in MS.

Peripheral nerve injury, scarring, and recovery

Peripheral nerve injuries (PNI) resulting from trauma can be severe and permanently debilitating. Despite the armamentarium of meticulous microsurgical repair techniques that includes direct repair, grafting of defects with autograft nerve, and grafting with cadaveric allografts, approximately one-third of all PNI demonstrate incomplete recovery with poor restoration of function. This may include total loss or incomplete recovery of motor and/or sensory function, chronic pain, muscle atrophy, and profound weakness, which can result in lifelong morbidity. Much of this impaired nerve healing can be attributed to perineural scarring and fibrosis at the site of injury and repair. To date, this challenging clinical problem has not been adequately addressed. In this review, we summarize the existing literature surrounding biological aspects of perineural fibrosis following PNI, detail current strategies to limit nerve scarring, present our own work developing reliable nerve injury models in animal studies, and discuss potential future studies which may ultimately lead to new therapeutic strategies.