Regeneration of long-distance peripheral nerve defects after delayed reconstruction in healthy and diabetic rats is supported by immunomodulatory chitosan nerve guides.

BACKGROUND: Delayed reconstruction of transection or laceration injuries of peripheral nerves is inflicted by a reduced regeneration capacity. Diabetic conditions, more frequently encountered in clinical practice, are known to further impair regeneration in peripheral nerves. Chitosan nerve guides (CNGs) have recently been introduced as a new generation of medical devices for immediate peripheral nerve reconstruction. Here, CNGs were used for 45 days delayed reconstruction of critical length 15 mm rat sciatic nerve defects in either healthy Wistar rats or diabetic Goto-Kakizaki rats; the latter resembling type 2 diabetes. In short and long-term investigations, we comprehensively analyzed the performance of one-chambered hollow CNGs (hCNGs) and two-chambered CNGs (CFeCNGs) in which a chitosan film has been longitudinally introduced. Additionally, we investigated in vitro the immunomodulatory effect provided by the chitosan film. RESULTS: Both types of nerve guides, i.e. hCNGs and CFeCNGs, enabled moderate morphological and functional nerve regeneration after reconstruction that was delayed for 45 days. These positive findings were detectable in generally healthy as well as in diabetic Goto-Kakizaki rats (for the latter only in short-term studies). The regenerative outcome did not reach the degree as recently demonstrated after immediate reconstruction using hCNGs and CFeCNGs. CFeCNG-treatment, however, enabled tissue regrowth in all animals (hCNGs: only in 80% of animals). CFeCNGs did further support with an increased vascularization of the regenerated tissue and an enhanced regrowth of motor axons. One mechanism by which the CFeCNGs potentially support successful regeneration is an immunomodulatory effect induced by the chitosan film itself. Our in vitro results suggest that the pro-regenerative effect of chitosan is related to the differentiation of chitosan-adherent monocytes into pro-healing M2 macrophages. CONCLUSIONS: No considerable differences appear for the delayed nerve regeneration process related to healthy and diabetic conditions. Currently available chitosan nerve grafts do not support delayed nerve regeneration to the same extent as they do after immediate nerve reconstruction. The immunomodulatory characteristics of the biomaterial may, however, be crucial for their regeneration supportive effects.

Activation of extracellular-signal-regulated kinase-1/2 precedes and is required for injury-induced Schwann cell proliferation.

Activation of extracellular-signal-regulated kinase-1/2 (Erk1/2) by phosphorylation to p-Erk1/2, and proliferation of Schwann cells were investigated in the rat sciatic nerve by immunohistochemistry. Axotomy in vivo and culturing of nerve segments in vitro resulted in a rapid (30 min) increase of p-Erk1/2 in Schwann cells with peaks at 2 and 24 h. Proliferation measured by bromodeoxy uridine incorporation and immunostaining in vivo and in vitro 48 h after axotomy showed an increase in Schwann cell proliferation at the sites of Erk1/2 activation. The Erk1/2 inhibitor U0126 inhibited both the increase in p-Erk1/2 and the bromodeoxy uridine incorporation. We suggest that an increase in p-Erk1/2 is required for nerve injury-induced proliferation of Schwann cells.

Ca2+ involvement in activation of extracellular-signal-regulated-kinase 1/2 and m-calpain after axotomy of the sciatic nerve.

Detailed mechanisms behind regeneration after nerve injury, in particular signal transduction and the fate of Schwann cells (SCs), are poorly understood. Here, we investigated axotomy-induced activation of extracellular-signal-regulated kinase-1/2 (ERK1/2; important for proliferation) and m-calpain in vitro, and the relation to Ca2+ deletion and Schwann cell proliferation and death after rat sciatic nerve axotomy. Nerve segments were cultured for up to 72 hours with and without ethylene glycol-bis(ß-aminoethyl ether)-N, N, N', N'-tetraacetic acid (EGTA). In some experiments, 5-bromo-2'-deoxyuridine (BrdU) was added during the last 24 hours to detect proliferating cells and propidium iodide (PI) was added at the last hour to detect dead and/or dying cells. Immunohistochemistry of sections of the cultured nerve segments was performed to label m-calpain and the phosphorylated and activated form of ERK1/2. The experiments revealed that immunoreactivity for p-ERK1/2 increased with time in organotypically cultured SCs. p-ERK1/2 and m-calpain were also observed in axons. A significant increase in the number of dead or dying SCs was observed in nerve segments cultured for 24 hours. When deprived of Ca2+, activation of axonal m-calpain was reduced, whereas p-ERK1/2 was increased in SCs. Ca2+ deprivation also significantly reduced the number of proliferating SCs, and instead increased the number of dead or dying SCs. Ca2+ seems to play an important role in activation of ERK1/2 in SCs and in SC survival and proliferation. In addition, extracellular Ca2+ levels are also required for m-calpain activation and up-regulation in axons. Thus, regulation of Ca2+ levels is likely to be a useful method to promote SC proliferation.

Nerve injury-induced c-Jun activation in Schwann cells is JNK independent.

We investigated (a) if activation of the mitogen activated protein kinase (MAPK) pathway was linked to the stress activated protein kinase (SAPK) pathway and (b) if JNK was required for activation of c-Jun in Schwann cells of rat sciatic nerve following injury. To this aim, ERK1/2 and the transcription factors c-Jun and ATF-3 were studied by immunohistochemistry in segments of transected nerves. We utilized pharmacological inhibitors of both signal transduction pathways in vitro to determine the effects on downstream signalling events, such as c-Jun activation, and on Schwann cell survival and proliferation. A transection induces c-Jun and ATF-3 transcription in Schwann cells. These events are followed by Schwann cell activation of c-Jun in the injured nerve. The MAPK inhibitor U0126 blocked ERK1/2 activation and reduced Schwann cell proliferation as well as induction of c-Jun transcription. The JNK inhibitor SP600125 reduced Schwann cell proliferation, but did not affect the expression of ERK1/2 or injury-induced increases in c-Jun or ATF-3 levels. Importantly, nerve injury induces Schwann cell activation of c-Jun by phosphorylation, which, in contrast to in sensory neurons, is JNK independent. MAP kinases, other than JNK, can potentially activate c-Jun in Schwann cells following injury; information that is crucial to create new nerve reconstruction strategies.

Injury-induced activation of ERK 1/2 in the sciatic nerve of healthy and diabetic rats.

Phosphorylation of extracellular-signal-regulated kinase 1/2 (p-ERK 1/2) was investigated by immunohistochemistry at 30 min, 1 h, and 48 h after nerve transection in the sciatic nerve of healthy and diabetic [streptozotocin (STZ)-induced diabetes mellitus and BioBreeding (BB; i.e. DR.lyp/lyp or BBDP)] rats. Transection injury increased the intensity of p-ERK 1/2 in nerve stumps at all time points. Staining was confined to Schwann cells with occasional faint staining in single axons. In diabetic rats, a lower intensity of p-ERK 1/2 was found at 1 and 48 h in the distal and proximal nerve stumps compared with healthy rats. STZ-induced diabetic rats were not different from BB rats. p-ERK 1/2 is activated differentially in Schwann cells after nerve injury in diabetic rats, whereas activation in STZ-induced diabetic rats did not differ from BB rats.

Outpatient transfusion practice and factors leading to inpatient transfusion in a pediatric hematology/oncology program.

Oral mucositis continues to be a common and debilitating side effect of the conditioning regimens that use high-dose chemotherapy with or without radiation for pediatric bone marrow transplantation. Limited interventions have demonstrated success in preventing or treating it. Administration of glutamine, which is a nitrogen-rich amino acid found in the body, has emerged as a possible method of preventing oral mucositis in patients undergoing bone marrow transplantation. Numerous studies have looked at the effects of oral glutamine supplementation during bone marrow transplant. The purpose of this article is to describe glutamine and how it functions, review the literature regarding the use of oral glutamine in the prevention of oral mucositis in bone marrow transplantion, discuss the administration concerns related to the pediatric setting, and stress the importance of the nurse's role at the bedside. Nurses working in pediatric bone marrow transplant play a key role in the assessment of oral mucositis, administration of oral glutamine, and education of the patient and family.