Netrin-1 prolongs skin graft survival by inducing the transformation of mesenchymal stem cells from pro-rejection to immune-tolerant phenotype.

OBJECTIVE: Mesenchymal stem cells (MSCs) induce allograft immune tolerance, but low efficacy severely limits their wide application. In this work, Netrin-1 was used to maintain MSC function in an IR environment to study its role in the immune tolerance induction of the allograft. MATERIALS AND METHODS: The experiments were divided into three groups: the control group, the IR group and the Netrin-1 group (Netrin-1 was added to MSC medium and then cultured for 48 h). After digestion, MSCs were mixed with TLR4 and TLR3 antibodies (BD), incubated for 20 min, and washed with Phosphate-Buffered Saline (PBS) three times. The mean fluorescence intensity (MFI) of TLR4 and TLR3 was detected by flow cytometry. Isolated lymphocytes were divided into four groups: the control group (no treatment), the MSC group (lymphocytes were co-cultured with MSCs in the control group), the rejection group (lymphocytes were co-cultured with MSCs in the IR group), and the Netrin-1 group (MSCs in the IR group) was stimulated by Netrin-1 for 48h. RESULTS: Our study found that compared with control mice, toll-like receptor (TLR3) expression in bone marrow MSCs decreased as the expression of TLR4 increased, the secretion of transforming growth factor-ß (TGF-ß) and interleukin-10 (IL-10) was reduced, while the secretion of IL-6 significantly increased in immune rejection (IR) mice. MSCs in IR mice promoted T-cell proliferation and reduced the ratio of Treg cells. Netrin-1 inhibited the pro-rejection effect of these MSCs, further inhibited T-cell proliferation and facilitated an increase in the ratio of Treg cells. The animal experiment results showed that MSC transplantation in the rejection group would shorten the mean survival time of the skin graft and induce the infiltration of lymphocytes. Netrin-1 prolonged the mean survival time of the skin graft by enhancing MSC function. The immunohistochemistry results showed that, compared with the rejection group, the T cell number in the skin graft significantly decreased in the Netrin-1 group. CONCLUSIONS: MSC can be divided into immune-tolerant and pro-rejection types in organ transplantation and Netrin-1 can induce the transformation of MSC from the pro-rejection to immune-tolerant type and markedly prolong the skin graft survival time.

[Correlation between diameter and primary closure rate by internal limiting membrane peeling and air tamponade in large idiopathic macular holes].

Objective: To analyze surgical outcomes by internal limiting membrane peeling and air tamponade in large idiopathic macular holes (IMHs) and the correlation between the minimal diameter and the primary closure rate. Methods: Retrospective study. A total of 282 patients (300 eyes) with IMHs larger than 400 µm who underwent vitrectomy and internal limiting membrane peeling in Beijing Tongren Hospital from July 2015 to January 2019 were enrolled, including 56 males (61 eyes) and 226 females (239 eyes) with an medium age of 65(62, 68) years. Before July 2016, gas tamponade was applied while after that, air tamponade was used. The minimal diameter of the IMH was measured. IMHs were divided into intervals every 50 µm by minimal diameter, and the primary closure rate of the two tamponades were compared between intervals by Chi-square test. The receiver operating characteristic (ROC) curve was drawn to show the correlation between the minimal diameter and the primary closure rate by air tamponde. Results: The mean minimal diameter of all the IMHs was (615.7±126.0)µm. In general, the primary closure rate was 91.7% (275/300), and the BCVA at last visit (0.5(0.3, 0.7)) improved significantly (P<0.001) comparing to the preoperative one (0.1(0.05, 0.2)). A total of 187 eyes with air tamponade exhibited a primary closure rate of 88.2%, which was significantly lower (P=0.005) than that with gas tamponade (97.3%). For IMHs with air tamponade, the optimal closure rate was 100% among all intervals; from the interval of (650, 700)µm on, the primary closure rates of every interval gradually decreased and were significantly lower than the optimal one (P<0.05) respectively; the ROC curve revealed that IMHs larger than 664.5 µm tended to exhibit a smaller chance of primary closure. For IMHs ≤650 µm, the two tamponades exhibited comparable primary closure rate (96.1% for air, 100.0% for gas, P=0.17), while for IMHs>650 µm, air tamponade (71.2%) presented significantly lower rate (93.5% for gas, P=0.002). IMHs ≤650 µm exhibited significantly better BCVA compared to those larger (P<0.01), no matter which tamponade was applied. In IMHs ≤650 µm, BCVA exhibited no significant difference between the two tamponades, so as in IMHs>650 µm. Conclusions: For IMHs with air tamponade, the minimal diameter is closely related to both the primary closure rate and the postoperative BCVA. IMHs>650 µm exhibited evidently poorer anatomical and functional outcomes compared with those ≤650 µm, which suggested that maybe other techniques for the internal limiting membrane could be applied to improve surgical outcomes for these large IMHs. (Chin J Ophthalmol, 2019, 55:739-746).

Cardiac arrhythmias are ameliorated by local inhibition of angiotensin formation and bradykinin degradation with the converting-enzyme inhibitor ramipril.

We investigated the influence of the angiotensin-converting enzyme (ACE) inhibitor ramipril on cardiac arrhythmias in guinea pigs and rats. Ramiprilat, the active moiety of ramipril, did not influence action potentials of isolated guinea-pig papillary muscle or rabbit sinus node, thereby excluding cellular electrophysiological evidence of anti-arrhythmic properties. Ramipril protected against cardiac arrhythmias induced by digoxin infusion in guinea pigs. This effect was comparable with that of lidocaine. In isolated perfused ischemic working rat hearts, angiotensin (ANG) I (3 x 10(-9) M/l) and ANG II (1 x 10(-9) M/l) aggravated reperfusion arrhythmias, accompanied by deterioration of cardiodynamic and metabolic events. Bradykinin (BK) (1 x 10(-10)-1 x 10(-8) M/l), in contrast, protected against reperfusion arrhythmias, which corresponded to an increase in energy-rich phosphates and glycogen stores and a decrease in lactate levels in myocardial tissue. Identical changes were seen in hearts from rats pretreated with ramipril (1 mg/kg PO) or perfused with ramiprilat (2.58 x 10(-7)-2.58 x 10(-5) M/l). Local ACE inhibition in these ischemic hearts antagonized ANG I but not ANG II effects and enhanced BK effects. The BK antagonist D-Arg-(Hyp2, Thi5,8, D-Phe7)BK abolished the beneficial effects of BK, ramipril, and ramiprilat. Increased concentrations of BK or ramiprilat were able to reverse the antagonism. The antiarrhythmic agent nicainoprol, a fast-sodium-channel blocking drug (class Ib), also protected isolated rat hearts against reperfusion arrhythmias, but was without beneficial effects on cardiac hemodynamics and biochemical parameters, in contrast to the ACE inhibitor. These results suggest that the beneficial effects of the ACE inhibitor ramipril on digoxin and reperfusion arrhythmias are not mediated by their direct actions on ionic channels in the cell membrane. It seems that other factors are responsible for its beneficial effects on reperfusion arrhythmias, cardiac function, and metabolism, which are associated with a reduction in ANG II generation and BK degradation by local ACE inhibition in the heart.