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Axonal regeneration plays an important role in functional recovery after nervous system damage. However, after axonal injury in mammals, regeneration is often poor. The deletion of Kruppel-like factor-4 (Klf4) has been shown to promote axonal regeneration in retinal ganglion cells. However, the effects of Klf4 deletion on the corticospinal tract and peripheral nervous system are unknown. In this study, using a mouse model of sciatic nerve injury, we show that the expression of Klf4 in dorsal root ganglion sensory neurons was significantly reduced after peripheral axotomy, suggesting that the regeneration of the sciatic nerve is associated with Klf4. In vitro, dorsal root ganglion sensory neurons with Klf4 knockout exhibited significantly enhanced axonal regeneration. Furthermore, the regeneration of the sciatic nerve was enhanced in vivo following Klf4 knockout. Finally, AAV-Cre virus was used to knockout the Klf4 gene in the cortex. The deletion of Klf4 enhanced regeneration of the corticospinal tract in mice with spinal cord injury. Together, our findings suggest that regulating KLF4 activity in neurons is a potential strategy for promoting axonal regeneration and functional recovery after nervous system injury. This study was approved by the Animal Ethics Committee at Soochow University, China (approval No. SUDA20200316A01).

While axon regeneration is a key determinant of functional recovery of the nervous system after injury, it is often poor in the mature nervous system. Influx of extracellular calcium (Ca2+ ) is one of the first phenomena that occur following axonal injury, and calcium/calmodulin-dependent protein kinase II (CaMKII), a target substrate for calcium ions, regulates the status of cytoskeletal proteins such as F-actin. Herein, we found that peripheral axotomy activates CaMKII in dorsal root ganglion (DRG) sensory neurons, and inhibition of CaMKII impairs axon outgrowth in both the peripheral and central nervous systems (PNS and CNS, respectively). Most importantly, we also found that the activation of CaMKII promotes PNS and CNS axon growth, and regulatory effects of CaMKII on axon growth occur via affecting the length of the F-actin. Thus, we believe our findings provide clear evidence that CaMKII is a critical modulator of mammalian axon regeneration.

Background and Aims To describe the clinical features, renal pathology findings and prognosis in patients with mixed cryoglobulinemic glomerulonephritis (Gn) caused by hepatitis B virus (HBV) infection. Method This was a retrospective study including seven Chinese patients with HBV infection associated mixed cryoglobulinemic Gn in a tertiary referral hospital from April, 2016 to March, 2019. The demographic, clinical, pathological characteristics, treatment and follow-up data were collected and analyzed. Results Age at renal biopsy was 47±12 years, including three females and four males. 24hUP was 5.6(3.0, 6.6)g/d and five cases presented with nephrotic syndrome. The median baseline eGFR(CKD-EPI) was 23.5(20.2, 46.3) ml/min per 1.73m2. The extrarenal manifestations were: purpura (n=6), arthralgia (n=1), peripheral neuropathy (n=1), and cardiomyopathy (n=1). Six cases had type II cryoglobulinemia with IgMκ, the other one had type III. The median cryocrit was 4.0 (1.0, 15.0) %, rheumatoid factor was 368(117, 733) IU/ml, C3 was 0.48(0.41, 0.57) g/L, C4 was 0.013(0.003, 0.118) g/L. Renal pathologic findings on light microscopy: endocapillary proliferative Gn (n=3), membranoproliferative Gn (n=3), and mesangial proliferative glomerulonephritis(n=1). Hyaline thrombi were seen in four cases, while crescents were found in two cases. On immunofluorescence microscopy, the predominant types of immunoglobulin deposits were: IgM(n=5), IgA(n=1), and codominance of IgG and IgA(n=1). HBsAg and HBcAg deposits were found in only one case. Ultrastructural studies showed granular subendothelial and mesangial electron-dense deposits in all patients and organized microtubules was seen in only one case. All patients received antiviral medication (entecavir, n=6; lamivudine, n=1). They were given corticosteroid alone(n=2) or combined with cyclophosphamide(n=4) or mycophenolate mofetil(n=1). Two patients received plasmapheresis. The median follow-up time were 18 (6, 37) months. One patient died from pneumonia, and one progressed to end stage of renal disease (ESRD). At endpoint of follow-up, 24hUP was 2.1 (0.8-5.2) g/d, and eGFR (CKD-EPI) was 55.3 (20.7, 111.8) ml/min per 1.73m2. Conclusion Mixed cryoglobulinemic Gn should be screened for HBV etiologies, especially in HBV-endemic country. Endocapillary proliferative Gn was the common pathologic type, as well as membranoproliferative Gn. Diagnosis and treatment in early stage benefit patients’ renal outcome. Long-term prognosis should be investigated in further studies.

While axon regeneration is a key determinant of functional recovery of the nervous system after injury, it is often poor in the mature nervous system. Influx of extracellular calcium (Ca2+) is one of the first phenomena that occur following axonal injury, and calcium/calmodulin-dependent protein kinase (CaMKII), a target protein for calcium ions, regulates the status of cytoskeletal proteins such as F-actin. Herein, we found that peripheral axotomy activates CaMKII in dorsal root ganglion (DRG) sensory neurons, and inhibition of CaMKII impairs axon growth in both the peripheral and central nervous systems (PNS and CNS, respectively). Most importantly, we also found that activation of CaMKII promotes PNS and CNS axon growth, and regulatory effects of CaMKII on axon growth occur via affecting the length of the F-actin. Thus, we believe our findings provide clear evidence that CaMKII is a critical modulator of mammalian axon regeneration.