Subconjunctivally implanted hydrogels for sustained insulin release to reduce retinal cell apoptosis in diabetic rats

Hisanori Imai, Gauri P. Misra, Linfeng Wu, Dileep R. Janagam, Thomas W. Gardner, Tao Lowe

Research output: Contribution to journalArticle

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Abstract

PURPOSE. Diabetic retinopathy (DR) is a leading cause of blindness in diabetic patients that involves early-onset retinal cell loss. Here, we report our recent work using subconjunctivally implantable hydrogels for sustained insulin release to the retina to prevent retinal degeneration. METHODS. The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide and a dextran macromer containing oligolactate-(2-hydroxyetheyl methacrylate) units. Insulin was loaded into the hydrogels during the synthesis. The ex vivo bioactivity of insulin released from the hydrogels was tested on fresh rat retinas using immunoprecipitation and immunoblotting to measure insulin receptor tyrosine and Akt phosphorylation. The biosafety and the effect on the blood glucose of the hydrogels were evaluated in rats 2 months after subconjunctival implantation. The release of insulin from the hydrogels was studied both in vitro in PBS (pH 7.4), and in vivo using confocal microscopy and RIA kit. The in vivo bioactivity of the released insulin was investigated in diabetic rats using DNA fragmentation method. RESULTS. The hydrogels could load insulin with approximately 98% encapsulation efficiency and continuously release FITC-insulin in PBS (pH = 7.4) at 37˚C for at least 5 months depending on their composition. Insulin lispro released from the hydrogels was biologically active by increasing insulin receptor tyrosine and Akt serine phosphorylation of ex vivo retinas. In vivo studies showed normal retinal histology 2 months post subconjunctival implantation. Insulin released from subconjunctivally implanted hydrogels could be detected in the retina by using confocal microscopy and RIA kit for 1 week. The implanted hydrogels with insulin lispro did not change the blood glucose level of normal and diabetic rats, but significantly reduced the DNA fragmentation of diabetic retinas for 1 week. CONCLUSIONS. The developed hydrogels have great potential to sustain release of insulin to the retina via subconjunctival implantation to minimize DR without the risk of hypoglycemia.

Original languageEnglish (US)
Pages (from-to)7839-7846
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume56
Issue number13
DOIs
StatePublished - Dec 1 2015

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Hydrogels
Insulin
Apoptosis
Retina
Insulin Lispro
Insulin Receptor
Diabetic Retinopathy
DNA Fragmentation
Confocal Microscopy
Tyrosine
Blood Glucose
Phosphorylation
Retinal Degeneration
Methacrylates
Blindness
Dextrans
Immunoprecipitation
Hypoglycemia
Immunoblotting
Serine

All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Subconjunctivally implanted hydrogels for sustained insulin release to reduce retinal cell apoptosis in diabetic rats. / Imai, Hisanori; Misra, Gauri P.; Wu, Linfeng; Janagam, Dileep R.; Gardner, Thomas W.; Lowe, Tao.

In: Investigative Ophthalmology and Visual Science, Vol. 56, No. 13, 01.12.2015, p. 7839-7846.

Research output: Contribution to journalArticle

Imai, Hisanori ; Misra, Gauri P. ; Wu, Linfeng ; Janagam, Dileep R. ; Gardner, Thomas W. ; Lowe, Tao. / Subconjunctivally implanted hydrogels for sustained insulin release to reduce retinal cell apoptosis in diabetic rats. In: Investigative Ophthalmology and Visual Science. 2015 ; Vol. 56, No. 13. pp. 7839-7846.
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abstract = "PURPOSE. Diabetic retinopathy (DR) is a leading cause of blindness in diabetic patients that involves early-onset retinal cell loss. Here, we report our recent work using subconjunctivally implantable hydrogels for sustained insulin release to the retina to prevent retinal degeneration. METHODS. The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide and a dextran macromer containing oligolactate-(2-hydroxyetheyl methacrylate) units. Insulin was loaded into the hydrogels during the synthesis. The ex vivo bioactivity of insulin released from the hydrogels was tested on fresh rat retinas using immunoprecipitation and immunoblotting to measure insulin receptor tyrosine and Akt phosphorylation. The biosafety and the effect on the blood glucose of the hydrogels were evaluated in rats 2 months after subconjunctival implantation. The release of insulin from the hydrogels was studied both in vitro in PBS (pH 7.4), and in vivo using confocal microscopy and RIA kit. The in vivo bioactivity of the released insulin was investigated in diabetic rats using DNA fragmentation method. RESULTS. The hydrogels could load insulin with approximately 98{\%} encapsulation efficiency and continuously release FITC-insulin in PBS (pH = 7.4) at 37˚C for at least 5 months depending on their composition. Insulin lispro released from the hydrogels was biologically active by increasing insulin receptor tyrosine and Akt serine phosphorylation of ex vivo retinas. In vivo studies showed normal retinal histology 2 months post subconjunctival implantation. Insulin released from subconjunctivally implanted hydrogels could be detected in the retina by using confocal microscopy and RIA kit for 1 week. The implanted hydrogels with insulin lispro did not change the blood glucose level of normal and diabetic rats, but significantly reduced the DNA fragmentation of diabetic retinas for 1 week. CONCLUSIONS. The developed hydrogels have great potential to sustain release of insulin to the retina via subconjunctival implantation to minimize DR without the risk of hypoglycemia.",
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T1 - Subconjunctivally implanted hydrogels for sustained insulin release to reduce retinal cell apoptosis in diabetic rats

AU - Imai, Hisanori

AU - Misra, Gauri P.

AU - Wu, Linfeng

AU - Janagam, Dileep R.

AU - Gardner, Thomas W.

AU - Lowe, Tao

PY - 2015/12/1

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N2 - PURPOSE. Diabetic retinopathy (DR) is a leading cause of blindness in diabetic patients that involves early-onset retinal cell loss. Here, we report our recent work using subconjunctivally implantable hydrogels for sustained insulin release to the retina to prevent retinal degeneration. METHODS. The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide and a dextran macromer containing oligolactate-(2-hydroxyetheyl methacrylate) units. Insulin was loaded into the hydrogels during the synthesis. The ex vivo bioactivity of insulin released from the hydrogels was tested on fresh rat retinas using immunoprecipitation and immunoblotting to measure insulin receptor tyrosine and Akt phosphorylation. The biosafety and the effect on the blood glucose of the hydrogels were evaluated in rats 2 months after subconjunctival implantation. The release of insulin from the hydrogels was studied both in vitro in PBS (pH 7.4), and in vivo using confocal microscopy and RIA kit. The in vivo bioactivity of the released insulin was investigated in diabetic rats using DNA fragmentation method. RESULTS. The hydrogels could load insulin with approximately 98% encapsulation efficiency and continuously release FITC-insulin in PBS (pH = 7.4) at 37˚C for at least 5 months depending on their composition. Insulin lispro released from the hydrogels was biologically active by increasing insulin receptor tyrosine and Akt serine phosphorylation of ex vivo retinas. In vivo studies showed normal retinal histology 2 months post subconjunctival implantation. Insulin released from subconjunctivally implanted hydrogels could be detected in the retina by using confocal microscopy and RIA kit for 1 week. The implanted hydrogels with insulin lispro did not change the blood glucose level of normal and diabetic rats, but significantly reduced the DNA fragmentation of diabetic retinas for 1 week. CONCLUSIONS. The developed hydrogels have great potential to sustain release of insulin to the retina via subconjunctival implantation to minimize DR without the risk of hypoglycemia.

AB - PURPOSE. Diabetic retinopathy (DR) is a leading cause of blindness in diabetic patients that involves early-onset retinal cell loss. Here, we report our recent work using subconjunctivally implantable hydrogels for sustained insulin release to the retina to prevent retinal degeneration. METHODS. The hydrogels are synthesized by UV photopolymerization of N-isopropylacrylamide and a dextran macromer containing oligolactate-(2-hydroxyetheyl methacrylate) units. Insulin was loaded into the hydrogels during the synthesis. The ex vivo bioactivity of insulin released from the hydrogels was tested on fresh rat retinas using immunoprecipitation and immunoblotting to measure insulin receptor tyrosine and Akt phosphorylation. The biosafety and the effect on the blood glucose of the hydrogels were evaluated in rats 2 months after subconjunctival implantation. The release of insulin from the hydrogels was studied both in vitro in PBS (pH 7.4), and in vivo using confocal microscopy and RIA kit. The in vivo bioactivity of the released insulin was investigated in diabetic rats using DNA fragmentation method. RESULTS. The hydrogels could load insulin with approximately 98% encapsulation efficiency and continuously release FITC-insulin in PBS (pH = 7.4) at 37˚C for at least 5 months depending on their composition. Insulin lispro released from the hydrogels was biologically active by increasing insulin receptor tyrosine and Akt serine phosphorylation of ex vivo retinas. In vivo studies showed normal retinal histology 2 months post subconjunctival implantation. Insulin released from subconjunctivally implanted hydrogels could be detected in the retina by using confocal microscopy and RIA kit for 1 week. The implanted hydrogels with insulin lispro did not change the blood glucose level of normal and diabetic rats, but significantly reduced the DNA fragmentation of diabetic retinas for 1 week. CONCLUSIONS. The developed hydrogels have great potential to sustain release of insulin to the retina via subconjunctival implantation to minimize DR without the risk of hypoglycemia.

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