Utilising silk fibroin membranes as scaffolds for the growth of tympanic membrane keratinocytes, and application to myringoplasty surgery.

BACKGROUND: Chronic tympanic membrane perforations can cause significant morbidity. The term myringoplasty describes the operation used to close such perforations. A variety of graft materials are available for use in myringoplasty, but all have limitations and few studies report post-operative hearing outcomes. Recently, the biomedical applications of silk fibroin protein have been studied. This material's biocompatibility, biodegradability and ability to act as a scaffold to support cell growth prompted an investigation of its interaction with human tympanic membrane keratinocytes. METHODS AND MATERIALS: Silk fibroin membranes were prepared and human tympanic membrane keratinocytes cultured. Keratinocytes were seeded onto the membranes and immunostained for a number of relevant protein markers relating to cell proliferation, adhesion and specific epithelial differentiation. RESULTS: The silk fibroin scaffolds successfully supported the growth and adhesion of keratinocytes, whilst also maintaining their cell lineage. CONCLUSION: The properties of silk fibroin make it an attractive option for further research, as a potential alternative graft in myringoplasty.

An improved method using densitometry for evaluating severity of laser photocoagulation induced CNV.

Laser photocoagulation induced choroidal neovascularization currently is the most effective model available for the study of this disease in terms of efficacy of new drugs and therapies. Previously, evaluating the extent of choroidal neovascularization using this model was time-consuming and required the use of experienced personnel. We describe a new method for simple and rapid evaluation of laser induced choroidal neovascularization using densitometry. Fluorescein angiograms of a laser photocoagulated rat eye were scanned into a computer. Densitometry software subsequently was used to calculate the severity of the laser lesions. The densitometry method proved effective for calculating the extent of laser induced choroidal neovascularization. In addition, this method was more rapid than visual evaluations and less likely to produce errors.

Dendrimer delivery of an anti-VEGF oligonucleotide into the eye: a long-term study into inhibition of laser-induced CNV, distribution, uptake and toxicity.

We have performed a long-term study into the use of a lipophilic amino-acid dendrimer to deliver an anti-vascular endothelial growth factor (VEGF) oligonucleotide (ODN-1) into the eyes of rats and inhibit laser-induced choroidal neovascularization (CNV). In addition, the uptake, distribution and retinal tolerance of the dendrimer plus oligonucleotide conjugates were examined. Analysis of fluorescein angiograms of laser photocoagulated eyes revealed that dendrimer plus ODN-1 significantly inhibited (P<0.05) the development of CNV for 4-6 months by up to 95% in the initial stages. Eyes similarly injected with ODN-1 alone showed no significant difference (P>0.05) in mean severity score at 2 months (2.86+/-0.09), 4 months (2.15+/-0.17) or 6 months (2.7+/-0.12) compared to the vehicle-injected controls. Furthermore, we showed that intravitreally injected ODN-1 tagged with 6-fam was absorbed by a wide area of the retina and penetrated all of the retinal cell layers to the retinal pigment epithelium. Ophthalmological examinations indicated that the dendrimers plus ODN-1 conjugates were well tolerated in vivo, which was later confirmed using immunohistochemistry, which showed no observable increase in antigens associated with inflammation. We conclude that the use of such dendrimers may provide a viable mechanism for the delivery of therapeutic oligonucleotides for the treatment of angiogenic eye diseases.

Purification, molecular cloning and heterologous expression of a glutathione S-transferase from the Australian sheep blowfly (Lucilia cuprina).

Three glutathione S-transferases from Lucilia cuprina (Australian sheep blowfly) pupae were purified by affinity chromatography and anion-exchange chromatography. One isoenzyme was composed of M(r)-24,800 subunits, and two isoenzymes had subunits of M(r) 23,900. The M(r)-23,900 subunits showed immunological identity and were immunologically distinct from the M(r)-24,800 subunits. All three enzymes were active with the substrate 1-chloro-2,4-dinitrobenzene and had low activity with 1,2-dichloro-4-nitrobenzene. A cDNA clone encoding a M(r)-23,900 subunit (LuGST1) was isolated and sequenced. The sequence has close similarities (> 81%) to that of GSTs from the fruitfly Drosophila melanogaster and Musca domestica (housefly). The deduced amino acid sequence of the Lu GST1 subunit showed no significant similarity to that of the mammalian GSTs to the Alpha, Mu and Pi classes, but shows some similarity (33%) over the first 100 residues with the rat subunit 12 Theta-class GST. Southern blots of genomic DNA hybridized with the LuGST1 cDNA identified many hybridizing fragments. Taken together, these data indicated that the L. cuprina genome contains multiple glutathione S-transferase genes.