Phenotypic changes of Schwann cells on the proximal stump of injured peripheral nerve during repair using small gap conduit tube.

Dedifferentiation of Schwann cells is an important feature of the response to peripheral nerve injury and specific negative myelination regulators are considered to have a major role in this process. However, most experiments have focused on the distal nerve stump, where the Notch signaling pathway is strongly associated with Schwann cell dedifferentiation and repair of the nerve. We observed the phenotypic changes of Schwann cells and changes of active Notch signaling on the proximal stump during peripheral nerve repair using small gap conduit tubulization. Eighty rats, with right sciatic nerve section of 4 mm, were randomly assigned to conduit bridging group and control group (epineurium suture). Glial fibrillary acidic protein expression, in myelinating Schwann cells on the proximal stump, began to up-regulate at 1 day after injury and was still evident at 5 days. Compared with the control group, Notch1 mRNA was expressed at a higher level in the conduit bridging group during the first week on the proximal stump. Hes1 mRNA levels in the conduit bridging group significantly increased compared with the control group at 3, 5, 7 and 14 days post-surgery. The change of the Notch intracellular domain shared a similar trend as Hes1 mRNA expression. Our results confirmed that phenotypic changes of Schwann cells occurred in the proximal stump. The differences in these changes between the conduit tubulization and epineurium suture groups correlate with changes in Notch signaling. This suggests that active Notch signaling might be a key mechanism during the early stage of neural regeneration in the proximal nerve stump.

Effects of platelet-derived growth factor on chondrocyte proliferation, migration and apoptosis via regulation of GIT1 expression.

The formation of fibrocartilage, cartilaginous and bony calluses is vital for bone healing following a fracture. Fibroblasts, chondrocytes and osteoblasts are critical functional cells that are involved in these three processes, respectively. Platelet­derived growth factor (PDGF), a growth factor that is released from platelet particles and appears during the early stages at the site of fractures, is essential in bone healing via regulation of cell proliferation and differentiation. However, the effects of PDGF on the chondrocytes remain unclear. In the present study, PDGF promoted phosphorylation of Src and upregulated the expression level of G­protein­coupled receptor kinase interacting protein­1 (GIT1) according to the results of the cell culture of chondrocytes in vitro and western blotting. However, the effect of PDGF on the upregulation of GIT1 expression was mostly inhibited by the Src inhibitor, PP2. After knocking down GIT1 expression using siRNA, the phosphorylation of Src continued to be induced by PDGF, although the expression of GIT1 was inhibited. Furthermore, the results indicated that PDGF promoted chondrocyte proliferation and migration, however, the effect on cell apoptosis induction was suppressed after adding the Src inhibitor, PP2. Additionally, when knocking down GIT1 using siRNA, the expression level of GIT1 decreased, which is similar to the effect of the Src inhibitor, PP2. The current study demonstrates that PDGF may initially activate the phosphorylation of Src, and subsequently induce GIT1 expression to promote chondrocyte proliferation and migration, but suppress cell apoptosis.

Pulsed electrical stimulation protects neurons in the dorsal root and anterior horn of the spinal cord after peripheral nerve injury.

Most studies on peripheral nerve injury have focused on repair at the site of injury, but very few have examined the effects of repair strategies on the more proximal neuronal cell bodies. In this study, an approximately 10-mm-long nerve segment from the ischial tuberosity in the rat was transected and its proximal and distal ends were inverted and sutured. The spinal cord was subjected to pulsed electrical stimulation at T10 and L3, at a current of 6.5 mA and a stimulation frequency of 15 Hz, 15 minutes per session, twice a day for 56 days. After pulsed electrical stimulation, the number of neurons in the dorsal root ganglion and anterior horn was increased in rats with sciatic nerve injury. The number of myelinated nerve fibers was increased in the sciatic nerve. The ultrastructure of neurons in the dorsal root ganglion and spinal cord was noticeably improved. Conduction velocity of the sciatic nerve was also increased. These results show that pulsed electrical stimulation protects sensory neurons in the dorsal root ganglia as well as motor neurons in the anterior horn of the spinal cord after peripheral nerve injury, and that it promotes the regeneration of peripheral nerve fibers.

Integrin-ß1 regulates chondrocyte proliferation and apoptosis through the upregulation of GIT1 expression.

Chondrocytes play a critical role in the repair process of osteoarthritis, which is also known as degenerative arthritis. Integrins, as the key family of cell surface receptors, are responsible for the regulation of chondrocyte proliferation, differentiation, survival and apoptosis through the recruitment and activation of downstream adaptor proteins. Moreover, G-protein-coupled receptor kinase interacting protein-1 (GIT1) exerts its effects on cell proliferation and migration through interaction with various cytokines. It has been previously suggested that GIT1 acts as a vital protein downstream of the integrin-mediated pathway. In the present study, we investigated the effects of integrin-ß1 on cell proliferation and apoptosis, as well as the underlying mechanisms in chondrocytes in vitro. Following transfection with a vector expressing integrin-ß1, our results revealed that the overexpression of integrin-ß1 enhanced GIT1 expression, whereas the knockdown of integrin-ß1 by siRNA suppressed GIT1 expression. However, no significant effect was observed on integrin-ß1 expression following the enforced overexpression of GIT1, which suggests that GIT1 is localized downstream of integrin-ß1. In other words, integrin-ß1 regulates the expression of GIT1. Furthermore, this study demonstrated that integrin-ß1 and GIT1 increased the expression levels of aggrecan and type II collagen, thus promoting chondrocyte proliferation; however, they inhibited chondrocyte apoptosis. Taken together, our data demonstrate that integrin-ß1 plays a vital role in chondrocyte proliferation, differentiation and apoptosis. GIT1 exerts effects similar to those of integrin-ß1 and is a downstream target of integrin-ß1.

Role of recombinant plasmid pEGFP-N1-IGF-1 transfection in alleviating osteoporosis in ovariectomized rats.

Decreased levels of serum insulin-like growth factor-1 (IGF-1) have been proven to cause osteoporosis. Gene transfer of IGF-1 offers an attractive technology to treat skeletal metabolic disorders including osteoporosis, but the viral vectors are limited by their high antigenicity and immune response. Our purpose was to investigate the expression of a non-invasive vector, recombinant plasmid enhanced green fluorescent protein-N1 (pEGFP-N1) that transferred IGF-1 gene into ovariectomized (OVX) rats in vivo and evaluate the effect of this therapy on osteoporosis. OVX or sham operations were performed in 60 female, 7-month-old unmated SD rats. 12 weeks after OVX operation, the vectors were transfected to the 10-month-old rats and experimental data were detected from 48 h to 7 week after transfection. Our results showed that remarkable expression of fluorescence and serum IGF-1 was observed in the rats transfected by recombinant plasmids, indicating that IGF-1 gene was successfully transferred to OVX rats by injecting the vector through hydrodynamic method via the tail vein. The bone metabolism index including serum alkaline phosphatase, the histomorphometric parameters of lumbar vertebra including trabecular area percentage, trabecular thickness, trabecular number and trabecular separation, and the bone mineral density (BMD) and biomechanical parameters of lumbar vertebra including BMD, maximum condensing force, crushing strength in OVX rats transfected by pEGFP-N1-IGF-1 were improved remarkably compared with OVX+pEGFP-N1 rats, indicating that the transfection of recombinant plasmid pEGFP-N1-IGF-1 played a significant role in alleviating osteoporosis in rats induced by OVX. This encouraged a potential approach of IGF-1 gene therapy to the treatment of osteoporosis.

Management of lumbosacropelvic fracture-dislocation using lumbo-iliac internal fixation.

OBJECTIVE: Traumatic lumbosacropelvic fracture-dislocation is a rare but potentially serious injury. Conventional methods like lumbosacral fixation used to treat such injuries often result in suboptimal outcome secondary to complications like pseudoarthroses, sagittal imbalance and hardware failure. In this study, we retrospectively analysed the clinical features and management for this trauma using lumbo-iliac fixation. METHODS: Eight patients (6 male, 2 female; 21-52 years old, mean: 38.4) with traumatic lumbosacropelvic fracture-dislocation were surgically managed by lumbo-iliac internal fixation after lumbosacral decompression. Patients were followed up for 24-40 months (mean: 31.6). American Spine Injury Association (ASIA) scores were measured before surgery and at the last follow-up, and statistically analysed. RESULTS: After surgery, all patients experienced improved sensory and motor performance. Six patients showed recovery of bowel and bladder functions. Immediately after lumbo-iliac fixation, all patients could turn in bed without assistance. Lumbosacral alignment was restored immediately after surgery and no dislocation was observed during follow-up. Radiography indicated excellent integration between the autograft and the vertebrae. After surgery, no patient experienced neurological deterioration. CONCLUSION: Our experience with these cases suggests that early surgical decompression and posterior lumbo-iliac internal fixation can effectively restore spinal alignment, stabilise the spine, and improve neurological symptoms for this complex trauma.

[Efficacy and safety of olmesartan medoxomil versus losartan potassium in Chinese patients with mild to moderate essential hypertension].

OBJECTIVE: To evaluate the efficacy and safety of olmesartan medoxomil compared with losartan potassium in patients with mild to moderate essential hypertension. METHOD: This is a randomized, double-blind, double-dummy, active-controlled, parallel, multi-center study. After a 2-week placebo run-in period, a total of 287 eligible subjects were randomized at 1:1 ratio to receive olmesartan medoxomil 20 mg or losartan potassium 50 mg, once daily for 8 weeks. The blood pressure was assessed after 4 weeks treatment. If the subject's seating diastolic blood pressure (SeDBP) was still >or=90 mm Hg, the dosage was doubled for another 4 weeks; for those subjects whose SeDBP was <90 mm Hg after 4-week treatment, the initial dosage remained unchanged and the treatment continued until completion of the study. RESULTS: (1) The mean trough reduction in SeDBP from baseline in olmesartan group was significantly greater than that in losartan group after 4 weeks (11.72 mm Hg vs 9.23 mm Hg, P=0.004) and 8 weeks treatment (12.94 mm Hg vs 11.01 mm Hg, P=0.035). (2) The number and percentage of responders in olmesartan group (81, 65.3%) were statistically higher than those (68, 52.7%) in losartan group (P=0.028) after 4 weeks treatment and were similar between the two groups after 8 weeks treatment (P>0.05). (3) Individual and overall trough/peak ratios of DBP and SBP in 24-hour ambulatory blood pressure monitoring were higher in olmesartan group than losartan group. The hypotensive effect of olmesartan was more durable than losartan at 24 hour interval. (4) The incidence of study drug-related adverse events (AEs) in olmesartan group (10.5%) was similar as that in losartan group (13.9%, P>0.05). Most of these AEs were mild and transient. CONCLUSION: This study shows that olmesartan medoxomil, at oral dose of 20 mg-40 mg once daily was effective and safe for hypertension treatment and the hypotensive effect was superior to losartan potassium (50 mg-100 mg once daily).

[Effects of tea polyphennols on hepatic lipase activity in rabbits with fatty liver].

OBJECTIVE: To investigate the relationship between hepatic lipase activity and fatty degeneration of hepatocytes and explore the effects of tea polyphennols (TP) on the changes of hepatic lipase (HL) activity in rabbits with fatty liver. METHODS: According to serum cholesterol and triglyceride (TC) levels, 19 rabbits were divided into fatty liver group (FL, n=6) fed with high cholesterol diet, TP group (n=7) fed with high cholesterol diet and 20mug/g/d tea polyphennols everyday orally, control group (n=6) fed with normal diet. After 8 weeks, the levels of serum TC, HL activity, HL activity and malondildehyde (MDA) in hepatic tissue were detected, and the pathomorphology of hepatic tissue were determined in all rabbits. RESULTS: The fatty degeneration of hepatocyts in FL group was more severe than that in TP and control group. The serum TC level in TP group (16.87 6.58) mmol/L was higher than that (1.11 0.82) mmol/L in control group (t=5.786, p<0.05), but lower than that (28.49 5.99) mmol/L in FL group (t=3.968, p<0.05). The serum low density lipoprotein-cholesterol level in Tp group (5.10 4.19) mmol/L also higher than that (0.71 1.14) mmol/L in control group (t=3.763, p<0.05), but lower than that (12.15 1.95) mmol/L in FL group (t=2.478, p<0.05). The number of positive dots presenting HL activity level in 100 square micron, hepatic tissue in TP group (3.24 0.17) was higher than that (1.76 0.10) in FL group (t=-3.153, p<0.05), but lower than that (4.14 0.05) in control group (t=-2.902, p<0.05). The levels of MDA in hepatic tissue in TP group (44.66 26.18) nmol/mg was significantly lower than that (75.58 29.88) nmol/mg in FL group (t=2.261, p<0.05), but no evidently different from that (43.64 16.95) nmol/mg in control group. The plasma HL activity was no difference among the three groups. CONCLUSION: The HL activity in hepatic tissue with fatty degeneration of hepatocytes was lower than that in normal liver. Tea polyphennols can increase HL activity in hepatic tissue and protect hepatocytes from fatty degeneration.

[Effect of Erigeron breviscapus injection on ventricular and vascular remodeling in spontaneous hypertension rats].

OBJECTIVE: To observe the ventricular and vascular remodeling reversal effect of Erigeron breviscapus injection (EBI), a protein kinase C inhibitor, in spontaneous hypertension rats (SHR). METHODS: Twenty-four SHR were divided into 4 groups, they were treated respectively with EBI, Fosinopril, Enalapril and normal saline 10 mg/kg per day by intraperitoneal injection for 8 weeks. Systolic blood pressure (SBP), ventricular weight index (VWI) and protein kinase C (PKC) activity in myocardial cells were determined, ultrastructural changes of heart and vessel were observed by polaroscope and transmission electron microscope, and the area and content of myocardial interstitial collagen (MIC) were determined by image analyzer system. RESULTS: The left ventricular hypertrophy was regressed to certain degree after EBI, Fosinopril and Enalapril treatment, but no significant change in heart rate and right VWI was found. Fosinopril and Enalapril were superior to EBI in lowering SBP and left VWI, and EBI was more obvious in improving myocardial ultrastructure such as hypertrophy and degeneration. All the 3 drugs could improve the MIC and vascular remodeling, the MIC area, content and collagen volume fraction in the EBI group were lowered after treatment, as compared with those in the control group, but comparison between the three groups showed no significant difference. The 3 drugs could reduce the PKC activity in myocardial cell membrane, and EBI showed the effect more significant than that of the other two (P < 0.05). CONCLUSION: EBI could reverse the myocardial, interstitial and vascular remodeling, improve the rigidness of cardiac muscle, thus, has protective effect on heart.