Mitomycin-C Induces the Apoptosis of Human Tenon’s Capsule Fibroblast by Activation ofc-JunN-Terminal Kinase 1 and Caspase-3 Protease

Noncontact Conjunctiva: A Better Mitomycin C Application Site for Trabeculectomy

INTRODUCTION

Bleb scarring is the most important complication of trabeculectomy. Changing the application position of mitomycin C (MMC) during trabeculectomy might affect the surgery outcome. Our aim is to compare the effectiveness and safety of intraocular pressure (IOP) lowering in two different application sites of mitomycin in trabeculectomy.

METHODS

This retrospective trial compared the surgical outcomes of 177 eyes that underwent trabeculectomy with adjunctive mitomycin C. In 70 eyes, an MMC-soaked sponge was applied under the scleral flap without touching Tenon's capsule. In 107 eyes, an MMC-soaked sponge was applied under the scleral flap covered by Tenon's capsule. Outcome measures were the IOP, best-corrected visual acuity (BCVA), success rates, and incidence of complications.

RESULTS

Within both groups, a highly significant IOP reduction was seen during follow-up. The effectiveness in reducing IOP and the change in best-corrected visual acuity (BCVA) were similar between the two groups. Thin-walled blebs and postoperative hypotony were seen more often when MMC-soaked sponges were applied under the scleral flap covered by Tenon's capsule (P = 0.008 and P = 0.012, respectively). There was no significant difference in BCVA or other complications in either group.

CONCLUSION

Since the effectiveness of IOP reduction was similar between both groups and with a low incidence of thin-walled blebs and hypotony, the subscleral application without touching Tenon's capsule seems to be the safer application site of MMC during trabeculectomy.

Substance P, a Neuropeptide, Promotes Wound Healing via Neurokinin-1 Receptor

Substance P (SP), an endogenous neuropeptide, mediates intracellular signaling, mainly through a tachykinin receptor. The tachykinin receptors family consists of neurokinin-1 (NK-1), neurokinin-2 (NK-2), and neurokinin-3 receptors. Our previous studies on SP have shown its wound healing potentials. But the exact mechanism of wound healing by SP is not exactly known. In view of this, the present study was aimed at evaluating the in vitro wound healing effect of SP alone and in the presence of NK-1, NK-2, and both receptor antagonists. Scratch assay, transwell assay, and tumor growth factor-beta 1 (TGF-β1) assay were performed on buffalo fetal fibroblast culture. The cotreatment of fibroblast cultures with SP alone during the 24 h caused the significant proliferation and migrations of cells in both horizontal and vertical directions. The SP in the presence of spantide II (NK-1 antagonist) failed to stimulate this migration. The treatment of cells with SP in the presence of NK-2 antagonist treatment also showed a significant reduction of migration of cells with respect to SP treatment alone. The SP in the presence of both NK-1 and NK-2 antagonists failed to stimulate the horizontal migration of cells and most of the ineffectiveness of SP was observed in this combination. The TGF-β1 levels were significantly higher in the supernatants of cells that were exposed to SP alone. All other treatments have significantly lower TGF-β1 levels than SP alone treatment. It is concluded that different actions on fibroblast cells by SP were mainly mediated through the NK-1 receptor.

Effects of Regorafenib, a Multi-Kinase Inhibitor, on Conjunctival Scarring in a Canine Filtration Surgery Model in Comparison with Mitomycin-C

Regorafenib eye drops were developed for treating age-related macular degeneration. This study aimed to investigate the effects of this multi-kinase inhibitor on intraocular pressure (IOP), bleb formation, and conjunctival changes in a canine filtration surgery model. Glaucoma filtration surgery models were created in 24 eyes of 24 beagles. In experiment 1 (Ex 1), regorafenib eye drops (regorafenib group: n = 6) or a vehicle (control group, n = 6) were instilled twice daily for 4 weeks postoperatively. In experiment 2 (Ex 2), regorafenib eye drops were instilled as in Ex 1 (regorafenib group: n = 6) for 12 weeks while conventional intraoperative mitomycin-C (MMC) was utilized (MMC group: n = 6), In Ex 1, only the regorafenib group showed significant IOP reduction with a significantly higher bleb score. Subconjunctival area, collagen density, vessels, and cells showing proliferation and differentiation were lower in subconjunctival tissue in the regorafenib group. In Ex 2, no significant difference was found in IOP reduction and bleb formation between the regorafenib and MMC groups; bleb walls were significantly thicker and collagen density and vessels were higher in the regorafenib group; and no differences were observed in the above-mentioned cells. Thus, regorafenib might be a better alternative to MMC for creating thicker and less ischemic blebs in glaucoma filtration surgery.

Recommendations for the management of elevated intraocular pressure due to bleb fibrosis after XEN gel stent implantation

Surgical management of glaucoma offers a means of effective disease control. A gel stent that facilitates drainage to the subconjunctival space offers intraocular pressure (IOP) reduction similar to traditional glaucoma filtering surgeries in a less invasive manner. However, like all subconjunctival filtering procedures that result in a bleb, fibrosis can present as a cause of elevated IOP. The following proposed techniques and recommendations for managing elevated IOP due to bleb fibrosis after gel stent implantation are based on the clinical experience of the authors. The goal of this paper is to improve outcomes following gel stent surgery by providing guidance on assessment of bleb function and strategies for bleb enhancement.

Potential Role of Cytochrome c and Tryptase in Psoriasis and Psoriatic Arthritis Pathogenesis: Focus on Resistance to Apoptosis and Oxidative Stress

Psoriasis (PsO) is an autoimmune disease characterized by keratinocyte proliferation, chronic inflammation and mast cell activation. Up to 42% of patients with PsO may present psoriatic arthritis (PsA). PsO and PsA share common pathophysiological mechanisms: keratinocytes and fibroblast-like synoviocytes are resistant to apoptosis: this is one of the mechanism facilitating their hyperplasic growth, and at joint level, the destruction of articular cartilage, and bone erosion and/or proliferation. Several clinical studies regarding diseases characterized by impairment of cell death, either due to apoptosis or necrosis, reported cytochrome c release from the mitochondria into the extracellular space and finally into the circulation. The presence of elevated cytochrome c levels in serum has been demonstrated in diseases as inflammatory arthritis, myocardial infarction and stroke, and liver diseases. Cytochrome c is a signaling molecule essential for apoptotic cell death released from mitochondria to the cytosol allowing the interaction with protease, as the apoptosis protease activation factor, which lead to the activation of factor-1 and procaspase 9. It has been demonstrated that this efflux from the mitochondria is crucial to start the intracellular signaling responsible for apoptosis, then to the activation of the inflammatory process. Another inflammatory marker, the tryptase, a trypsin-like serine protease produced by mast cells, is released during inflammation, leading to the activation of several immune cells through proteinase-activated receptor-2. In this review, we aimed at discussing the role played by cytochrome c and tryptase in PsO and PsA pathogenesis. To this purpose, we searched pathogenetic mechanisms in PUBMED database and review on oxidative stress, cytochrome c and tryptase and their potential role during inflammation in PsO and PsA. To this regard, the cytochrome c release into the extracellular space and tryptase may have a role in skin and joint inflammation.

Modulation of Fibroblasts in Conjunctival Wound Healing

Modulating conjunctival wound healing has the potential to improve outcomes after glaucoma filtration surgery and for several ocular disorders, including ocular cicatrial pemphigoid, vernal keratoconjunctivitis, and pterygium. Although anti-inflammatories and antimetabolites have been used with success, these nonspecific agents are not without their complications. The search for novel and more targeted means to control conjunctival fibrosis without such limitations has brought much attention to the regulation of fibroblast proliferation, differentiation, extracellular matrix production, and apoptosis. This review provides an update on where we stand with current antifibrotic agents and outlines the strategies that novel agents use, as they evolve from the bench to the bedside.

Mitomycin C induces apoptosis in human epidural scar fibroblasts after surgical decompression for spinal cord injury

Numerous studies have shown that topical application of mitomycin C after surgical decompression effectively reduces scar adhesion. However, the underlying mechanisms remain unclear. In this study, we investigated the effect of mitomycin C on the proliferation and apoptosis of human epidural scar fibroblasts. Human epidural scar fibroblasts were treated with various concentrations of mitomycin C (1, 5, 10, 20, 40 μg/mL) for 12, 24 and 48 hours. Mitomycin C suppressed the growth of these cells in a dose- and time-dependent manner. Mitomycin C upregulated the expression levels of Fas, DR4, DR5, cleaved caspase-8/9, Bax, Bim and cleaved caspase-3 proteins, and it downregulated Bcl-2 and Bcl-xL expression. In addition, inhibitors of caspase-8 and caspase-9 (Z-IETD-FMK and Z-LEHD-FMK, respectively) did not fully inhibit mitomycin C-induced apoptosis. Furthermore, mitomycin C induced endoplasmic reticulum stress by increasing the expression of glucose-regulated protein 78, CAAT/enhancer-binding protein homologous protein (CHOP) and caspase-4 in a dose-dependent manner. Salubrinal significantly inhibited the mitomycin C-induced cell viability loss and apoptosis, and these effects were accompanied by a reduction in CHOP expression. Our results support the hypothesis that mitomycin C induces human epidural scar fibroblast apoptosis, at least in part, via the endoplasmic reticulum stress pathway.

A dual-targeting approach to inhibit Brucella abortus replication in human cells

Brucella abortus is an intracellular bacterial pathogen and an etiological agent of the zoonotic disease known as brucellosis. Brucellosis can be challenging to treat with conventional antibiotic therapies and, in some cases, may develop into a debilitating and life-threatening chronic illness. We used multiple independent assays of in vitro metabolism and intracellular replication to screen a library of 480 known bioactive compounds for novel B. abortus anti-infectives. Eighteen non-cytotoxic compounds specifically inhibited B. abortus replication in the intracellular niche, which suggests these molecules function by targeting host cell processes. Twenty-six compounds inhibited B. abortus metabolism in axenic culture, thirteen of which are non-cytotoxic to human host cells and attenuate B. abortus replication in the intracellular niche. The most potent non-cytotoxic inhibitors of intracellular replication reduce B. abortus metabolism in axenic culture and perturb features of mammalian cellular biology including mitochondrial function and receptor tyrosine kinase signaling. The efficacy of these molecules as inhibitors of B. abortus replication in the intracellular niche suggests “dual-target” compounds that coordinately perturb host and pathogen are promising candidates for development of improved therapeutics for intracellular infections.

Hypoxia-inducible factor-1α antagonizes the hypoxia-mediated osteoblast cell viability reduction by inhibiting apoptosis

Bone fracture is accompanied with poor oxygen supply and nutrient deficiency in the local fracture site, and oxygen supply is an important factor that can affect fracture healing. Hypoxia-inducible factor-1 (HIF-1) plays a key role in the regulation of oxygen homeostasis. HIF-1α is rapidly upregulated in response to hypoxia and antagonizes hypoxia-induced apoptosis. In the present study, the viability of an osteoblast cell line, MC3T3-E1, and the expression of HIF-1α protein in the MC3T3-E1 cells was examined under hypoxic conditions. The HIF-1α level was then manipulated and the reduction in the viability of the MC3T3-E1 cells in response to the hypoxia was re-evaluated. In addition, the regulation of HIF-1α in the adaptation of MC3T3-E1 cells to hypoxia was explored. The results showed that the viability of MC3T3-E1 cells decreased and the expression of HIF-1α protein increased under hypoxic conditions. Furthermore, the reduction in the viability of MC3T3-E1 cells post-hypoxia was attenuated by HIF-1α overexpression, while HIF-1α-knockdown by small interfering RNA enhanced the hypoxia-induced decrease in cell viability. It was additionally found that the forced expression of HIF-1α inhibited the hypoxia-induced cell apoptosis. These findings indicate that the forced expression of HIF-1α inhibits hypoxia-induced apoptosis and thus attenuates the hypoxia-induced decrease in cell viability.

Improving patient outcomes following glaucoma surgery: state of the art and future perspectives

Of all the treatments currently used to lower intraocular pressure in glaucoma patients, filtration surgery is known to be the most effective. However, in a significant percentage of cases, the constructed channel closes due to excessive scar formation, resulting in surgical failure. The process of postoperative wound healing is characterized by the coagulative and inflammatory phase, followed by the proliferative and repair phase, and finally the remodeling phase. Perioperative antimitotic agents, such as mitomycin C and 5-fluorouracil, are known to modulate the process of wound healing and to improve surgical outcome, but they carry a risk of vision-threatening complications. New alternative strategies to prevent filtration failure, such as inhibition of transforming growth factor-β, vascular endothelial growth factor, and placental growth factor, have shown promising results in the improvement of surgical success. However, it remains necessary to broaden the therapeutic approach by focusing on combined therapies and on extended drug delivery.

Prostaglandin D(2) induces apoptosis of human osteoclasts through ERK1/2 and Akt signaling pathways

In a recent study we have shown that prostaglandin D2 (PGD2) induces human osteoclast (OC) apoptosis through the activation of the chemoattractant receptor homologous molecule expressed on T-helper type 2 cell (CRTH2) receptor and the intrinsic apoptotic pathway. However, the molecular mechanisms underlying this response remain elusive. The objective of this study is to investigate the intracellular signaling pathways mediating PGD2-induced OC apoptosis. OCs were generated by in vitro differentiation of human peripheral blood mononuclear cells (PBMCs), and then treated with or without the selective inhibitors of mitogen-activated protein kinase-extracellular signal-regulated kinase (ERK) kinase, (MEK)-1/2, phosphatidylinositol3-kinase (PI3K) and NF-κB/IκB kinase-2 (IKK2) prior to the treatments of PGD2 as well as its agonists and antagonists. Fluorogenic substrate assay and immunoblotting were performed to determine the caspase-3 activity and key proteins involved in Akt, ERK1/2 and NF-κB signaling pathways. Treatments with both PGD2 and a CRTH2 agonist decreased ERK1/2 (Thr202/Tyr204) and Akt (Ser473) phosphorylation, whereas both treatments increased β-arrestin-1 phosphorylation (Ser412) in the presence of naproxen, which was used to eliminate endogenous prostaglandin production. In the absence of naproxen, treatment with a CRTH2 antagonist increased both ERK1/2 and Akt phosphorylations, and reduced the phosphorylation of β-arrestin-1. Treatment of OCs with a selective MEK-1/2 inhibitor increased caspase-3 activity and OC apoptosis induced by both PGD2 and a CRTH2 agonist. Moreover, a CRTH2 antagonist diminished the selective MEK-1/2 inhibitor-induced increase in caspase-3 activity in the presence of endogenous prostaglandins. In addition, treatment of OCs with a selective PI3K inhibitor decreased ERK1/2 (Thr202/Tyr204) phosphorylation caused by PGD2, whereas increased ERK1/2 (Thr202/Tyr204) phosphorylation by a CRTH2 antagonist was attenuated with a PI3K inhibitor treatment. The DP receptor was not implicated in any of the parameters evaluated. Treatment of OCs with PGD2 as well as its receptor agonists and antagonists did not alter the phosphorylation of RelA/p65 (Ser536). Moreover, the caspase-3 activity was not altered in OCs treated with a selective IKK2/NF-κB inhibitor. In conclusion, endogenous or exogenous PGD2 induces CRTH2-dependent apoptosis in human differentiated OCs; β-arrestin-1, ERK1/2, and Akt, but not IKK2/NF-κB are probably implicated in the signaling pathways of this receptor in the model studied.

Antifibrotic effect of pirfenidone on human pterygium fibroblasts

OBJECTIVE

The effects of pirfenidone were investigated on cultured human pterygium fibroblasts (HPFs).

METHODS

HPFs were obtained from pterygium surgery and subjected to primary culture. After treatment with 0.5, 1.0 or 1.5 mg/mL pirfenidone, MTT and cell migration assays were performed, and procollagen secretion and TGF-β expression were measured by Western blotting and immunofluorescence analysis.

RESULTS

Pirfenidone had a significant inhibitory effect on HPF proliferation, migration and collagen synthesis. There were no differences between the cells treated with 0.5, 1.0 and 1.5 mg/mL pirfenidone and the controls in the MTT assay. After 48 h of treatment with 1.0 or 1.5 mg/mL pirfenidone, TGF-β expression was significantly decreased.

CONCLUSIONS

These findings demonstrate that pirfenidone inhibits the proliferation, migration and procollagen secretion of HPFs at nontoxic concentrations by decreasing TGF-β expression. Thus, pirfenidone may be considered as a safe adjuvant for pterygium surgery to prevent recurrence.

Dose-dependent effect of mitomycin C on human vocal fold fibroblasts

BACKGROUND

The purpose of this study was to evaluate in vitro cytotoxicity and antifibrotic effects of mitomycin C on normal and scarred human vocal fold fibroblasts.

METHODS

Fibroblasts were subjected to mitomycin C treatment at 0.2, 0.5, or 1 mg/mL, or serum control. Cytotoxicity, immunocytochemistry, and Western blot for collagen I/III were performed at days 0, 1, 3, and 5.

RESULTS

Significant decreases in live cells were measured for mitomycin C-treated cells on days 3 and 5 for all doses. Extracellular staining of collagen I/III was observed in mitomycin C-treated cells across all doses and times. Extracellular staining suggests apoptosis with necrosis, compromising the integrity of cell membranes and release of cytosolic proteins into the extracellular environment. Western blot indicates inhibition of collagen at all doses except 0.2 mg/mL at day 1.

CONCLUSION

A total of 0.2 mg/mL mitomycin C may provide initial and transient stimulation of collagen for necessary repair to damaged tissue without the long-term risk of fibrosis.

Effect of mitomycin on normal dermal fibroblast and HaCat cell: an in vitro study

OBJECTIVE

To evaluate the effects of mitomycin on the growth of human dermal fibroblast and immortalized human keratinocyte line (HaCat cell), particularly the effect of mitomycin on intracellular messenger RNA (mRNA) synthesis of collagen and growth factors of fibroblast.

METHODS

The normal dermal fibroblast and HaCat cell were cultured in vitro. Cell cultures were exposed to 0.4 and 0.04 mg/ml of mitomycin solution, and serum-free culture medium was used as control. The cellular morphology change, growth characteristics, cell proliferation, and apoptosis were observed at different intervals. For the fibroblasts, the mRNA expression changes of transforming growth factor (TGF)-β1, basic fibroblast growth factor (bFGF), procollagen I, and III were detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The cultured normal human skin fibroblast and HaCat cell grew exponentially. A 5-min exposure to mitomycin at either 0.4 or 0.04 mg/ml caused marked dose-dependent cell proliferation inhibition on both fibroblasts and HaCat cells. Cell morphology changed, cell density decreased, and the growth curves were without an exponential phase. The fibroblast proliferated on the 5th day after the 5-min exposure of mitomycin at 0.04 mg/ml. Meanwhile, 5-min application of mitomycin at either 0.04 or 0.4 mg/ml induced fibroblast apoptosis but not necrosis. The apoptosis rate of the fibroblast increased with a higher concentration of mytomycin (p<0.05). A 5-min exposure to mitomycin at 0.4 mg/ml resulted in a marked decrease in the mRNA production of TGF-β1, procollagen I and III, and a marked increase in the mRNA production of bFGF.

CONCLUSIONS

Mitomycin can inhibit fibroblast proliferation, induce fibroblast apoptosis, and regulate intracellular protein expression on mRNA levels. In addition, mitomycin can inhibit HaCat cell proliferation, so epithelial cell needs more protecting to avoid mitomycin's side effect when it is applied clinically.

Endoplasmic reticulum stress signaling is involved in mitomycin C (MMC)-induced apoptosis in human fibroblasts via PERK pathway

Endoplasmic reticulum (ER) stress-mediated cell apoptosis has been implicated in various cell types, including fibroblasts. Previous studies have shown that mitomycin C (MMC)-induced apoptosis occurs in fibroblasts, but the effects of MMC on ER stress-mediated apoptosis in fibroblasts have not been examined. Here, MMC-induced apoptosis in human primary fibroblasts was investigated by exposing cells to a single dose of MMC for 5 minutes. Significant inhibition of cell proliferation and increased apoptosis were observed using a cell viability assay, Annexin V/propidium iodide double staining, cell cycle analysis, and TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) staining. Upregulation of proapoptotic factors, including cleaved caspase-3 and poly ADP-ribose polymerase (PARP), was detected by Western blotting. MMC-induced apoptosis was correlated with elevation of 78-kDa glucose-regulated protein (GRP78) and C/EBP homologous protein (CHOP), which are hallmarks of ER stress. Three unfolded protein response (UPR) sensors (inositol-requiring enzyme 1, IRE1; activating transcription factor 6, ATF6; and PKR-like ER kinase, PERK) and their downstream signaling pathways were also activated. Knockdown of CHOP attenuated MMC-induced apoptosis by increasing the ratio of BCL-2/BAX and decreasing BIM expression, suggesting that ER stress is involved in MMC-induced fibroblast apoptosis. Interestingly, knockdown of PERK significantly decreased ER stress-mediated apoptosis by reducing the expression of CHOP, BIM and cleaved caspase-3. Reactive oxygen species (ROS) scavenging also decreased the expression of GRP78, phospho-PERK, CHOP, and BIM. These results demonstrate that MMC-induced apoptosis is triggered by ROS generation and PERK activation.

Prostaglandin D2 induces apoptosis of human osteoclasts by activating the CRTH2 receptor and the intrinsic apoptosis pathway

Prostaglandin D(2) (PGD(2)) is a lipid mediator synthesized from arachidonic acid that directly activates two specific receptors, the D-type prostanoid (DP) receptor and chemoattractant receptor homologous molecule expressed on T-helper type 2 cells (CRTH2). PGD(2) can affect bone metabolism by influencing both osteoblast and osteoclast (OC) functions, both cells involved in bone remodeling and in in vivo fracture repair as well. The objective of the present study was to determine the effects of PGD(2), acting through its two specific receptors, on human OC apoptosis. Human OCs were differentiated in vitro from peripheral blood mononuclear cells in the presence of receptor activator for nuclear factor κB ligand (RANKL) and macrophage-colony stimulating factor (M-CSF), and treated with PGD(2), its specific agonists and antagonists. Treatment with PGD(2) for 24hours in the presence of naproxen (10μM) to inhibit endogenous prostaglandin production increased the percentage of apoptotic OCs in a dose-dependent manner, as did the specific CRTH2 agonist compound DK-PGD(2) but not the DP agonist compound BW 245C. In the absence of naproxen, the CRTH2 antagonist compound CAY 10471 reduced OC apoptosis rate but the DP antagonist BW A868C had no effect. The induction of PGD(2)-CRTH2 dependent apoptosis was associated with the activation of caspase-9, but not caspase-8, leading to caspase-3 cleavage. These data show that PGD(2) induces human OC apoptosis through activation of CRTH2 and the apoptosis intrinsic pathway.

Different fibroblast subpopulations of the eye: a therapeutic target to prevent postoperative fibrosis in glaucoma therapy

The aim of this study is the characterization of fibroblasts mainly responsible for fibrosis processes associated with trabeculectomy or microstent implantation for glaucoma therapy. Therefore we isolated human primary fibroblasts from choroidea, sclera, Tenon capsule, and orbital fat tissues. These fibroblast subpopulations were analysed in vitro for expression of the extracellular matrix components which are responsible for postoperative scarring in glaucoma therapy. For scarring the proteins of the collagen family are predominant and so we focused on the expression of collagen I, collagen III and collagen VI in every fibroblast subpopulation. Also, the extracellular matrix protein fibronectin which crosslinks collagen fibres or other extracellular matrix components and cell surfaces, was analyzed. Collagen I, III and VI were prominent in every fibroblast subpopulation. The highest amounts of collagen III were found in hCF and hOF, whereas the signal in hSF and hTF was negligible. Additionally, there is a link between scarring processes and proliferating potential of fibroblasts, in case of microstent implantation triggered through the infiltration of inflammatory cells. Thus we analyzed fibroblast subpopulations for the presence of TGF-β1 which is one of the most important cytokines involved in proliferation processes. TGF-β1 was prominent in all fibroblast subpopulations with lowest expression in hCF cultures. To prevent postoperative fibroblast proliferation we analyzed in vitro the proliferation-inhibitors paclitaxel and mitomycin C which are potential candidates in drug eluting drainage systems on ocular fibroblast subpopulations. These inhibitors arrest fibroblast proliferation and viability, being, however, not very specific and have a cytotoxic potential also on healthy tissues surrounding the microstent outflow area. Significant differences in protein synthesis of fibroblasts subpopulations which could be specific targets for inhibition may help to find out fibroblast specific inhibitors to prevent postoperative scarring and could prevent patients from secondary surgery after microstent implantation.

The Apaf-1-binding protein Aven is cleaved by Cathepsin D to unleash its anti-apoptotic potential

The anti-apoptotic molecule Aven was originally identified in a yeast two-hybrid screen for Bcl-x(L)-interacting proteins and has also been found to bind Apaf-1, thereby interfering with Apaf-1 self-association during apoptosome assembly. Aven is expressed in a wide variety of adult tissues and cell lines, and there is increasing evidence that its overexpression correlates with tumorigenesis, particularly in acute leukemias. The mechanism by which the anti-apoptotic activity of Aven is regulated remains poorly understood. Here we shed light on this issue by demonstrating that proteolytic removal of an inhibitory N-terminal Aven domain is necessary to activate the anti-apoptotic potential of the molecule. Furthermore, we identify Cathepsin D (CathD) as the protease responsible for Aven cleavage. On the basis of our results, we propose a model of Aven activation by which its N-terminal inhibitory domain is removed by CathD-mediated proteolysis, thereby unleashing its cytoprotective function.

Mitomycin C: a promising agent for the treatment of canine corneal scarring

OBJECTIVE

To evaluate the safety and efficacy of mitomycin C (MMC) in prevention of canine corneal scarring.

METHODS

With an in vitro approach using healthy canine corneas, cultures of primary canine corneal fibroblasts or myofibroblasts were generated. Primary canine corneal fibroblasts were obtained by growing corneal buttons in minimal essential medium supplemented with 10% fetal bovine serum. Canine corneal myofibroblasts were produced by growing cultures in serum-free medium containing transforming growth factor β1 (1 ng/mL). Trypan blue assay and phase-contrast microscopy were used to evaluate the toxicity of three doses of MMC (0.002%, 0.02% and 0.04%). Real-time PCR, immunoblot, and immunocytochemistry techniques were used to determine MMC efficacy to inhibit markers of canine corneal scarring.

RESULTS

A single 2-min treatment of 0.02% or less MMC did not alter canine corneal fibroblast or keratocyte phenotype, viability, or growth. The 0.02% dose substantially reduced myofibroblast formation (up to 67%; P < 0.001), as measured by the change in RNA and protein expression of fibrosis biomarkers (α-smooth muscle actin and F-actin).

CONCLUSION

This in vitro study suggests that a single 2-min 0.02% MMC treatment to the canine corneal keratocytes is safe and may be useful in decreasing canine corneal fibrous metaplasia. In vivo studies are warranted.

Regulation of Tenon's capsule fibroblast cell proliferation by the opioid growth factor and the opioid growth factor receptor axis

PURPOSE

Glaucoma filtration surgery often fails because of the fibrotic reaction from Tenon's capsule fibroblasts (TCFs). This study examined whether the interaction of the opioid growth factor (OGF) [Met(5)]-enkephalin with its receptor (OGFr) is a regulator of TCF proliferation.

METHODS

The presence of OGF and its receptor (OGFr) was determined in rabbit TCFs (RTCFs) by immunocytochemistry. The kinetics of OGFr were established in receptor binding assays. The ability of OGF to inhibit RTCF proliferation was assessed with dose-response, receptor mediation, and reversibility studies. Dependence on OGF and OGFr was ascertained by antibody neutralization and siRNA studies, respectively. The mechanism of action of the OGF-OGFr axis on survival (apoptosis, necrosis) and DNA synthesis of RTCFs was elucidated.

RESULTS

OGF and OGFr were detected in RTCF cells, and specific and saturable binding to OGFr was recorded. Exogenous OGF had a dose-dependent, reversible, and receptor-mediated inhibitory effect on cell proliferation. Endogenous OGF was found to be constitutively produced and tonically active in cell replication, with neutralization of this peptide causing acceleration of cell proliferation. The silencing of OGFr by using siRNA technology stimulated cell replication, validating OGFr's integral role. The mechanism of OGF-OGFr action was not related to cell survival, but rather to DNA synthesis-specifically, the cyclin-dependent kinase inhibitory pathway. Knockdown of p16 or p21 eliminated OGF's inhibitory effect on growth.

CONCLUSIONS

The OGF-OGFr system is a native biological regulator of cell proliferation in RTCFs and may offer a means of improving the success of glaucoma filtration surgery in a safe and nontoxic manner.

Mitomycin C-polyethylene glycol controlled-release film inhibits collagen secretion and induces apoptosis of fibroblasts in the early wound of a postlaminectomy rat model

BACKGROUND CONTEXT

Recovery from spine surgery is usually accompanied with the development of epidural scar adhesions from the abnormal proliferation of fibroblast and extracellular matrix-related metabolism. Polyethylene glycol (PEG) could alleviate the postsurgical adhesion formation with still leaving a gap between the sheet and the dura. However, PEG film could not function as a three-dimensional barrier to prevent adhesion completely. Mitomycin C (MMC) could also reduce the scar formation after surgery, but cytotoxicity and the administrative pathway prevent its application.

PURPOSE

Our purpose was to design and attest the role of new delivery system MMC-PEG controlled-release film in preventing the epidural scar adhesions after laminectomy in the rat model.

STUDY DESIGN/SETTING

A total laminectomy of L1 in the rat model was used to assess epidural fibrosis between and around the spinal nerves using a histochemistry assessment along with flow cytometry analysis.

PATIENT SAMPLE

The sample comprises 64 adult male Sprague-Dawley rats.

OUTCOME MEASURES

The outcome measures are macroscopic evaluation, histological analysis, and flow cytometry analysis.

METHODS

Lumbar laminectomies at L1 and L2 with a L1-L2 disc injury were performed on 64 adult male Sprague-Dawley rats. The rats were then randomized into four groups. In Group I, 25 mg PEG film was applied on the dura mater in the laminectomy area before the layers were sutured. In Group II, a cotton pad soaked with 0.05% MMC solution was kept on the laminectomy area for 5 minutes. In Group III, 25 mg PEG film containing 0.01% MMC was implanted on the laminectomy area. In Group IV, the laminectomy area was flushed with saline before wound closure. The rats were sacrificed 4 weeks after the operation. Macroscopic evaluation and histological analysis of epidural scar adhesion with the hematoxylin and eosin stain and Masson stain were used followed by the quantification of hydroxyproline (Hyp) and flow cytometry analysis of the apoptosis of fibroblasts in the scar tissues.

RESULTS

The recovery of all rats was uneventful after the operations. In the laminectomy sites of rats treated with MMC or MMC-PEG, the dura mater was clean without any evident adhesion or membrane. Collagen tissue hyperplasia significantly decreased in the MMC- or MMC-PEG-treated models. Accordingly, Hyp concentration was significantly reduced in these two groups compared with saline-control group. In addition, the apoptosis of fibroblasts, however, was significantly elevated in the MMC or MMC-PEG group compared with the saline-control group.

CONCLUSIONS

These results demonstrate that the treatment of postlaminectomy wounds with MMC-PEG film reduces the severity of adhesion by decreasing the concentration of Hyp and increasing the apoptosis of fibroblasts.

Mitomycin C in corneal refractive surgery

Mitomycin C has played a deciding role in the current revival of excimer laser surface ablation techniques. We review the literature regarding mechanism of action of mitomycin C, histological effects on the cornea, and indications, dose, exposure time, and toxicity of mitomycin C in corneal refractive surgery. Mitomycin C is an alkylating agent with cytotoxic and antiproliferative effects that reduces the myofibroblast repopulation after laser surface ablation and, therefore, reduces the risk of postoperative corneal haze. It is used prophylactically to avoid haze after primary surface ablation and therapeutically to treat pre-existing haze. There is no definite evidence that establishes an exact diopter limit or ablation depth at which to apply prophylactic mitomycin C. It is usually applied at a concentration of 0.2mg/ml (0.02%) for 12 to 120 seconds over the ablated stroma, although some studies suggest that lower concentrations (0.01%, 0.002%) could also be effective in preventing haze when treating low to moderate myopia. This dose of mitomycin C has not been associated with any clinically relevant epithelial corneal toxicity. Its effect on the endothelium is more controversial: two studies report a decrease in endothelial cell density, but the majority of reports suggest that the endothelium is not altered. Regarding mitomycin C's effect on keratocyte population, although animal studies report keratocyte depletion after its use, longer follow-up suggested that the initial keratocyte depletion does not persist over time.