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Haley N, Henderson D, Donner R, Wyckoff S, Merrett K, Tennant J, Hoover E, Love D, Kline E, Lehmkuhl A, Thomsen B. Management of chronic wasting disease in ranched elk: conclusions from a longitudinal three-year study. Prion 2020; 14:76-87. [PMID: 32033521 PMCID: PMC7009334 DOI: 10.1080/19336896.2020.1724754] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Chronic wasting disease is a fatal, horizontally transmissible prion disease of cervid species that has been reported in free-ranging and farmed animals in North America, Scandinavia, and Korea. Like other prion diseases, CWD susceptibility is partly dependent on the sequence of the prion protein encoded by the host's PRNP gene; it is unknown if variations in PRNP have any meaningful effects on other aspects of health. Conventional diagnosis of CWD relies on ELISA or IHC testing of samples collected post-mortem, with recent efforts focused on antemortem testing approaches. We report on the conclusions of a study evaluating the role of antemortem testing of rectal biopsies collected from over 570 elk in a privately managed herd, and the results of both an amplification assay (RT-QuIC) and conventional IHC among animals with a several PRNP genotypes. Links between PRNP genotype and potential markers of evolutionary fitness, including pregnancy rates, body condition, and annual return rates were also examined. We found that the RT-QuIC assay identified significantly more CWD positive animals than conventional IHC across the course of the study, and was less affected by factors known to influence IHC sensitivity - including follicle count and PRNP genotype. We also found that several evolutionary markers of fitness were not adversely correlated with specific PRNP genotypes. While the financial burden of the disease in this herd was ultimately unsustainable for the herd owners, our scientific findings and the hurdles encountered will assist future CWD management strategies in both wild and farmed elk and deer.
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Affiliation(s)
- N.J. Haley
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA,CONTACT N.J. Haley Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - D.M. Henderson
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - R. Donner
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - S. Wyckoff
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - K. Merrett
- Department of Microbiology and Immunology, College of Graduate Studies, Midwestern University, Glendale, AZ, USA
| | - J Tennant
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - E.A. Hoover
- Prion Research Center, Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - D. Love
- Colorado Department of Agriculture Animal Health Division, Broomfield, CO, USA
| | - E. Kline
- Colorado Department of Agriculture Animal Health Division, Broomfield, CO, USA
| | - A.D. Lehmkuhl
- National Veterinary Services Laboratories, United States Department of Agriculture, APHIS, VS, Ames, IA, USA
| | - B.V. Thomsen
- National Veterinary Services Laboratories, United States Department of Agriculture, APHIS, VS, Ames, IA, USA,Center for Veterinary Biologics, United States Department of Agriculture, APHIS, VS, Ames, IA, USA
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Fagerholm P, Lagali NS, Carlsson DJ, Merrett K, Griffith M. Corrigendum to “Corneal Regeneration Following Implantation of a Biomimetic Tissue-Engineered Substitute”. Clin Transl Sci 2014. [DOI: 10.1111/cts.12183] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Per Fagerholm
- Department of Ophthalmology; Linköping University Hospital; Linköping Sweden
| | - Neil S. Lagali
- Department of Ophthalmology; Linköping University Hospital; Linköping Sweden
| | - David J. Carlsson
- National Research Council of Canada; Ottawa Ontario Canada
- University of Ottawa Eye Institute; Ottawa Ontario Canada
| | | | - May Griffith
- University of Ottawa Eye Institute; Ottawa Ontario Canada
- Department of Cellular and Molecular Medicine; University of Ottawa; Ottawa Ontario Canada
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Ljunggren MK, Elizondo RA, Edin E, Olsen D, Merrett K, Lee CJ, Salerud G, Polarek J, Fagerholm P, Griffith M. Effect of Surgical Technique on Corneal Implant Performance. Transl Vis Sci Technol 2014; 3:6. [PMID: 24749003 DOI: 10.1167/tvst.3.2.6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 02/14/2014] [Indexed: 02/04/2023] Open
Abstract
PURPOSE Our aim was to determine the effect of a surgical technique on biomaterial implant performance, specifically graft retention. METHODS Twelve mini pigs were implanted with cell-free, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) cross-linked recombinant human collagen type III (RHCIII) hydrogels as substitutes for donor corneal allografts using overlying sutures with or without human amniotic membrane (HAM) versus interrupted sutures with HAM. The effects of the retention method were compared as well as the effects of collagen concentration (13.7% to 15% RHCIII). RESULTS All implanted corneas showed initial haze that cleared with time, resulting in corneas with optical clarity matching those of untreated controls. Biochemical analysis showed that by 12 months post operation, the initial RHCIII implants had been completely remodeled, as type I collagen, was the major collagenous protein detected, whereas no RHCIII could be detected. Histological analysis showed all implanted corneas exhibited regeneration of epithelial and stromal layers as well as nerves, along with touch sensitivity and tear production. Most neovascularization was seen in corneas stabilized by interrupted sutures. CONCLUSIONS This showed that the surgical technique used does have a significant effect on the overall performance of corneal implants, overlying sutures caused less vascularization than interrupted sutures. TRANSLATIONAL RELEVANCE Understanding the significance of the suturing technique can aid the selection of the most appropriate procedure when implanting artificial corneal substitutes. The same degree of regeneration, despite a higher collagen content indicates that future material development can progress toward stronger, more resistant implants.
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Affiliation(s)
- Monika Kozak Ljunggren
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Rodolfo A Elizondo
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Elle Edin
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - David Olsen
- FibroGen Incorporated, San Francisco, CA, USA
| | - Kimberley Merrett
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden ; Ottawa Hospital Research Institute-Vision Programme, Ottawa, Ontario, Canada
| | - Chyan-Jang Lee
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden ; Ottawa Hospital Research Institute-Vision Programme, Ottawa, Ontario, Canada
| | - Göran Salerud
- Integrative Regenerative Medicine Centre and Department of Biomedical Engineering, Linköping University, Linköping, Sweden
| | | | - Per Fagerholm
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - May Griffith
- Integrative Regenerative Medicine Centre and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden ; Ottawa Hospital Research Institute-Vision Programme, Ottawa, Ontario, Canada
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Koh LB, Islam MM, Mitra D, Noel CW, Merrett K, Odorcic S, Fagerholm P, Jackson WB, Liedberg B, Phopase J, Griffith M. Correction: Koh, L.B., et al. Epoxy Cross-Linked Collagen and Collagen-Laminin Peptide Hydrogels as Corneal Substitutes. J. Funct. Biomater. 2013, 4, 162-177. J Funct Biomater 2014. [PMCID: PMC4030903 DOI: 10.3390/jfb5010027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Affiliation(s)
- Li Buay Koh
- Integrative Regenerative Medicine Center, Department of Physics, Chemistry and Biology, Linköping University, SE 581 83 Linköping, Sweden; E-Mails: (L.B.K.); (J.P.)
| | - Mohammad Mirazul Islam
- Swedish Nanoscience Center, Karolinska Institute, 171 77 Stockholm, Sweden; E-Mail:
- Integrative Regenerative Medicine Center & Department of Clinical and Experimental Medicine, Cell Biology Building, Linköping University, SE 581 85 Linköping, Sweden; E-Mails: (K.M.); (P.F.)
| | - Debbie Mitra
- Ottawa Hospital Research Institute, University of Ottawa Eye Institute, 501 Smyth Rd. Ottawa, ON K1H 8L6, Canada; E-Mails: (D.M.); (C.W.N.); (S.O.); (W.B.J.)
| | - Christopher W. Noel
- Ottawa Hospital Research Institute, University of Ottawa Eye Institute, 501 Smyth Rd. Ottawa, ON K1H 8L6, Canada; E-Mails: (D.M.); (C.W.N.); (S.O.); (W.B.J.)
| | - Kimberley Merrett
- Integrative Regenerative Medicine Center & Department of Clinical and Experimental Medicine, Cell Biology Building, Linköping University, SE 581 85 Linköping, Sweden; E-Mails: (K.M.); (P.F.)
- Ottawa Hospital Research Institute, University of Ottawa Eye Institute, 501 Smyth Rd. Ottawa, ON K1H 8L6, Canada; E-Mails: (D.M.); (C.W.N.); (S.O.); (W.B.J.)
| | - Silvia Odorcic
- Ottawa Hospital Research Institute, University of Ottawa Eye Institute, 501 Smyth Rd. Ottawa, ON K1H 8L6, Canada; E-Mails: (D.M.); (C.W.N.); (S.O.); (W.B.J.)
| | - Per Fagerholm
- Integrative Regenerative Medicine Center & Department of Clinical and Experimental Medicine, Cell Biology Building, Linköping University, SE 581 85 Linköping, Sweden; E-Mails: (K.M.); (P.F.)
| | - William Bruce Jackson
- Ottawa Hospital Research Institute, University of Ottawa Eye Institute, 501 Smyth Rd. Ottawa, ON K1H 8L6, Canada; E-Mails: (D.M.); (C.W.N.); (S.O.); (W.B.J.)
| | - Bo Liedberg
- Center for Biomimetic Sensor Science, Nanyang Technological University, Research Technoplaza, Story 6, 50 Nanyang Drive, Singapore 637553; E-Mail:
| | - Jaywant Phopase
- Integrative Regenerative Medicine Center, Department of Physics, Chemistry and Biology, Linköping University, SE 581 83 Linköping, Sweden; E-Mails: (L.B.K.); (J.P.)
| | - May Griffith
- Swedish Nanoscience Center, Karolinska Institute, 171 77 Stockholm, Sweden; E-Mail:
- Integrative Regenerative Medicine Center & Department of Clinical and Experimental Medicine, Cell Biology Building, Linköping University, SE 581 85 Linköping, Sweden; E-Mails: (K.M.); (P.F.)
- Author to whom correspondence should be addressed; E-Mail:
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Fagerholm P, Lagali NS, Ong JA, Merrett K, Jackson WB, Polarek JW, Suuronen EJ, Liu Y, Brunette I, Griffith M. Stable corneal regeneration four years after implantation of a cell-free recombinant human collagen scaffold. Biomaterials 2013; 35:2420-7. [PMID: 24374070 DOI: 10.1016/j.biomaterials.2013.11.079] [Citation(s) in RCA: 201] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 11/26/2013] [Indexed: 12/16/2022]
Abstract
We developed cell-free implants, comprising carbodiimide crosslinked recombinant human collagen (RHC), to enable corneal regeneration by endogenous cell recruitment, to address the worldwide shortage of donor corneas. Patients were grafted with RHC implants. Over four years, the regenerated neo-corneas were stably integrated without rejection, without the long immunosuppression regime needed by donor cornea patients. There was no recruitment of inflammatory dendritic cells into the implant area, whereas, even with immunosuppression, donor cornea recipients showed dendritic cell migration into the central cornea and a rejection episode was observed. Regeneration as evidenced by continued nerve and stromal cell repopulation occurred over the four years to approximate the micro-architecture of healthy corneas. Histopathology of a regenerated, clear cornea from a regrafted patient showed normal corneal architecture. Donor human cornea grafted eyes had abnormally tortuous nerves and stromal cell death was found. Implanted patients had a 4-year average corrected visual acuity of 20/54 and gained more than 5 Snellen lines of vision on an eye chart. The visual acuity can be improved with more robust materials for better shape retention. Nevertheless, these RHC implants can achieve stable regeneration and therefore, represent a potentially safe alternative to donor organ transplantation.
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Affiliation(s)
- Per Fagerholm
- Integrative Regenerative Medicine Centre, Dept. of Clinical and Experimental Medicine, Cell Biology Bldg. - Level 10, Linköping University, SE-581 85 Linköping, Sweden
| | - Neil S Lagali
- Integrative Regenerative Medicine Centre, Dept. of Clinical and Experimental Medicine, Cell Biology Bldg. - Level 10, Linköping University, SE-581 85 Linköping, Sweden
| | - Jeb A Ong
- Department of Ophthalmology, Maisonneuve-Rosemont Hospital, 5415 Boulevard de L'Assomption, Montreal, QC, H1T 2M4, Canada
| | - Kimberley Merrett
- Integrative Regenerative Medicine Centre, Dept. of Clinical and Experimental Medicine, Cell Biology Bldg. - Level 10, Linköping University, SE-581 85 Linköping, Sweden; Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | - W Bruce Jackson
- Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | - James W Polarek
- FibroGen, Inc. 409 Illinois Street, San Francisco, CA 94158, USA
| | - Erik J Suuronen
- Division of Cardiac Surgery, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7, Canada
| | - Yuwen Liu
- CooperVision Inc., 5870 Stoneridge Drive, Suite 1, Pleasanton, CA 94588, USA
| | - Isabelle Brunette
- Department of Ophthalmology, Maisonneuve-Rosemont Hospital, 5415 Boulevard de L'Assomption, Montreal, QC, H1T 2M4, Canada
| | - May Griffith
- Integrative Regenerative Medicine Centre, Dept. of Clinical and Experimental Medicine, Cell Biology Bldg. - Level 10, Linköping University, SE-581 85 Linköping, Sweden; FibroGen, Inc. 409 Illinois Street, San Francisco, CA 94158, USA.
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Abstract
Human recombinant collagen can be cross-linked with a variety of chemical cross-linking agents. Cross-linking methods can be tuned to confer collagen-based scaffolds with specific physical properties, improved antigenicity and thermal stability without impeding the ability of the material to integrate into the surrounding tissue and to promote regeneration. Here, we describe a method to cross-link human recombinant collagen using a water soluble carbodiimide. Carbodiimides are referred to as zero-length cross-linking agents as they are not incorporated into the final cross-link and thus pose minimal risk with respect to cytotoxicity. The resulting collagen-based scaffold possesses properties comparable to that of the human cornea and is thus suitable for use as a corneal substitute.
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Ahn JI, Kuffova L, Merrett K, Mitra D, Forrester JV, Li F, Griffith M. Crosslinked collagen hydrogels as corneal implants: effects of sterically bulky vs. non-bulky carbodiimides as crosslinkers. Acta Biomater 2013; 9:7796-805. [PMID: 23619290 DOI: 10.1016/j.actbio.2013.04.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 03/05/2013] [Accepted: 04/08/2013] [Indexed: 02/08/2023]
Abstract
We have previously shown that recombinant human collagen can be crosslinked with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) to fabricate transparent hydrogels possessing the shape and dimensions of the human cornea. These corneal implants have been tested in a Phase I human clinical study. Although these hydrogels successfully promoted corneal tissue and nerve regeneration, the gelling kinetics were difficult to control during the manufacture of the implants. An alternative carbodiimide capable of producing hydrogels of similar characteristics as EDC in terms of strength and biocompatibility, but with a longer gelation time would be a desirable alternative. Here, we compared the crosslinking kinetics and properties of hydrogels crosslinked with a sterically bulky carbodiimide, N-Cyclohexyl-N'-(2-morpholinoethyl) carbodiimide metho-p-toluenesulfonate (CMC), with that of EDC. CMC crosslinking was possible at ambient temperature whereas the EDC reaction was too rapid to control and had to be carried out at low temperatures. The highest tensile strength obtained using optimized formulations were equivalent, although CMC crosslinked hydrogels were found to be stiffer. The collagenase resistance of CMC crosslinked hydrogels was superior to that of EDC crosslinked hydrogels while biocompatibility was similar. We are also able to substitute porcine collagen with recombinant human collagen and show that the in vivo performance of both resulting hydrogels as full-thickness corneal implants is comparable in a mouse model of an orthotopic corneal graft. In conclusion, CMC is a viable alternative to EDC as a crosslinker for collagen-based biomaterials for use as corneal implants, and potentially for use in other tissue engineering applications.
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Hackett JM, Lagali N, Merrett K, Edelhauser H, Sun Y, Gan L, Griffith M, Fagerholm P. Biosynthetic corneal implants for replacement of pathologic corneal tissue: performance in a controlled rabbit alkali burn model. Invest Ophthalmol Vis Sci 2011; 52:651-7. [PMID: 20847116 DOI: 10.1167/iovs.10-5224] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
PURPOSE To evaluate the performance of structurally reinforced, stabilized recombinant human collagen-phosphorylcholine (RHCIII-MPC) hydrogels as corneal substitutes in a rabbit model of severe corneal damage. METHODS One eye each of 12 rabbits received a deep corneal alkali wound. Four corneas were implanted with RHCIII-MPC hydrogels. The other eight control corneas were implanted with either allografts or a simple cross-linked RHCIII hydrogel. In all cases, 6.25 mm diameter, 350 μm thick buttons were implanted by anterior lamellar keratoplasty to replace damaged corneal tissue. Implants were followed for nine months by clinical examination and in vivo confocal microscopy, after which implanted corneas were removed and processed for histopathological and ultrastructural examination. RESULTS Alkali exposure induced extensive central corneal scarring, ocular surface irregularity, and neovascularization in one case. All implants showed complete epithelial coverage by four weeks postoperative, but with accompanying suture-induced vascularization in 6 out of 12 cases. A stable, stratified epithelium with hemidesmosomal adhesion complexes regenerated over all implants, and subbasal nerve regeneration was observed in allograft and RHCIII-MPC implants. Initially acellular biosynthetic implants were populated with host-derived keratocytes as stromal haze subsided and stromal collagen was remodeled. Notably, RHCIII-MPC implants exhibited resistance to vascular ingrowth while supporting endogenous cell and nerve repopulation. CONCLUSIONS Biosynthetic implants based on RHC promoted cell and nerve repopulation in alkali burned rabbit eyes. In RHCIII-MPC implants, evidence of an enhanced resistance to neovascularization was additionally noted.
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Fagerholm P, Lagali NS, Merrett K, Jackson WB, Munger R, Liu Y, Polarek JW, Söderqvist M, Griffith M. A biosynthetic alternative to human donor tissue for inducing corneal regeneration: 24-month follow-up of a phase 1 clinical study. Sci Transl Med 2010; 2:46ra61. [PMID: 20739681 DOI: 10.1126/scitranslmed.3001022] [Citation(s) in RCA: 269] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Corneas from human donors are used to replace damaged tissue and treat corneal blindness, but there is a severe worldwide shortage of donor corneas. We conducted a phase 1 clinical study in which biosynthetic mimics of corneal extracellular matrix were implanted to replace the pathologic anterior cornea of 10 patients who had significant vision loss, with the aim of facilitating endogenous tissue regeneration without the use of human donor tissue. The biosynthetic implants remained stably integrated and avascular for 24 months after surgery, without the need for long-term use of the steroid immunosuppression that is required for traditional allotransplantation. Corneal reepithelialization occurred in all patients, although a delay in epithelial closure as a result of the overlying retaining sutures led to early, localized implant thinning and fibrosis in some patients. The tear film was restored, and stromal cells were recruited into the implant in all patients. Nerve regeneration was also observed and touch sensitivity was restored, both to an equal or to a greater degree than is seen with human donor tissue. Vision at 24 months improved from preoperative values in six patients. With further optimization, biosynthetic corneal implants could offer a safe and effective alternative to the implantation of human tissue to help address the current donor cornea shortage.
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Affiliation(s)
- Per Fagerholm
- Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Cell Biology Building, Level 10, SE-581 83 Linköping, Sweden
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Fagerholm P, Lagali NS, Carlsson DJ, Merrett K, Griffith M. Corneal regeneration following implantation of a biomimetic tissue-engineered substitute. Clin Transl Sci 2010; 2:162-4. [PMID: 20443883 DOI: 10.1111/j.1752-8062.2008.00083.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Per Fagerholm
- Department of Ophthalmology, Linköping University Hospital, 58185 Linköping, Sweden.
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Bareiss B, Ghorbani M, Li F, Blake JA, Scaiano JC, Zhang J, Deng C, Merrett K, Harden JL, Diaz-Mitoma F, Griffith M. Controlled Release of Acyclovir Through Bioengineered Corneal Implants with Silica Nanoparticle Carriers~!2009-08-29~!2010-01-05~!2010-03-18~! ACTA ACUST UNITED AC 2010. [DOI: 10.2174/1875043501003010010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Bareiss B, Merrett K, Deng C, Harden J, Li F, Diaz-Mitoma F, Griffith M. O59 Corneal substitutes with anti-microbial peptides for ocular HSV treatment. Int J Antimicrob Agents 2009. [DOI: 10.1016/s0924-8579(09)70206-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Merrett K, Fagerholm P, McLaughlin CR, Dravida S, Lagali N, Shinozaki N, Watsky MA, Munger R, Kato Y, Li F, Marmo CJ, Griffith M. Tissue-engineered recombinant human collagen-based corneal substitutes for implantation: performance of type I versus type III collagen. Invest Ophthalmol Vis Sci 2008; 49:3887-94. [PMID: 18515574 DOI: 10.1167/iovs.07-1348] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To compare the efficacies of recombinant human collagens types I and III as corneal substitutes for implantation. METHODS Recombinant human collagen (13.7%) type I or III was thoroughly mixed with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide. The final homogenous solution was either molded into sheets for in vitro studies or into implants with the appropriate corneal dimensions for transplantation into minipigs. Animals with implants were observed for up to 12 months after surgery. Clinical examinations of the cornea included detailed slit lamp biomicroscopy, in vivo confocal microscopy, and fundus examination. Histopathologic examinations were also performed on corneas harvested after 12 months. RESULTS Both cross-linked recombinant collagens had refractive indices of 1.35, with optical clarity similar to that in human corneas. Their chemical and mechanical properties were similar, although RHC-III implants showed superior optical clarity. Implants into pig corneas over 12 months show comparably stable integration, with regeneration of corneal cells, tear film, and nerves. Optical clarity was also maintained in both implants, as evidenced by fundus examination. CONCLUSIONS Both RHC-I and -III implants can be safely and stably integrated into host corneas. The simple cross-linking methodology and recombinant source of materials makes them potentially safe and effective future corneal matrix substitutes.
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Lagali N, Griffith M, Fagerholm P, Merrett K, Huynh M, Munger R. Innervation of tissue-engineered recombinant human collagen-based corneal substitutes: a comparative in vivo confocal microscopy study. Invest Ophthalmol Vis Sci 2008; 49:3895-902. [PMID: 18408185 DOI: 10.1167/iovs.07-1354] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To compare reinnervation in recombinant human collagen-based corneal substitutes with allografts during a 1-year postimplantation follow-up period in pigs. A retrospective comparison to innervation in porcine collagen-based biosynthetic grafts was also performed. METHODS Pigs received a corneal allograft or a substitute made of either recombinant human type-I or -III collagen. In vivo confocal microscopic examination of the central cornea of surgical and untouched control eyes before surgery and at 2, 6, and 12 months after surgery was performed to quantify the number, density, and diameter of nerves at various corneal depths. RESULTS By 12 months after surgery, the number and density of regenerated nerves in the anterior and deep anterior corneal stroma recovered to preoperative and control levels in both types of substitute grafts and in the allografts. In the subepithelial and subbasal regions, however, significantly fewer nerves were detected relative to those in control subjects at 12 months, regardless of graft type (P < 0.05), similar to the behavior of porcine collagen-based biosynthetic grafts. An absence of thick stromal nerve trunks (diameter, >10 mum) in all grafts, irrespective of material type, indicated that nerve regeneration in grafts was accompanied by persistent morphologic changes. CONCLUSIONS Nerve regeneration in recombinant human collagen-based biosynthetic corneal grafts proceeded similarly to that in allograft tissue, demonstrating the suitability of recombinant human collagen constructs as nerve-friendly corneal substitutes. Furthermore, only minor differences were noted between type-I and -III collagen grafts, indicating an insensitivity of nerve regeneration to initial collagen type.
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Affiliation(s)
- Neil Lagali
- University of Ottawa Eye Institute, Ottawa, Ontario, Canada
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Liu W, Merrett K, Griffith M, Fagerholm P, Dravida S, Heyne B, Scaiano JC, Watsky MA, Shinozaki N, Lagali N, Munger R, Li F. Recombinant human collagen for tissue engineered corneal substitutes. Biomaterials 2008; 29:1147-58. [DOI: 10.1016/j.biomaterials.2007.11.011] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Accepted: 11/07/2007] [Indexed: 11/25/2022]
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Liu Y, Griffith M, Watsky MA, Forrester JV, Kuffova L, Grant D, Merrett K, Carlsson DJ. Properties of porcine and recombinant human collagen matrices for optically clear tissue engineering applications. Biomacromolecules 2006; 7:1819-28. [PMID: 16768403 DOI: 10.1021/bm060160o] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Porcine and recombinant human atelocollagen I solutions were cross-linked with a water soluble carbodiimide at various stoichiometries and collagen concentrations (5-20 w/w %). The resulting hydrogels were clear and, when used as cell growth matrices, allowed cell and nerve visualization in vitro and in vivo. We have previously reported that, after six months of implantation in pigs' and rabbits' corneas, these robust hydrogels allowed regeneration of host cells and nerves to give optically clear corneas with no detected loss in thickness, indicating stable engraftment. Here, the biocompatible hydrogel formulations leading to this novel in vivo performance were characterized for amine consumption, gel hydration, thermal properties, optical clarity, refractive index, nutrient diffusion, biodegradation, tensile measurements, and average pore diameters. Gels with excellent in vitro (epithelial overgrowth, neurite penetration) and in vivo performance (clarity, touch sensitivity regeneration) had 4-11 nm pores, yet had glucose and albumin diffusive coefficients similar to mammalian corneas and allowed neurite extension through the gels.
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Affiliation(s)
- Y Liu
- National Research Council Canada, 1200 Montreal Road, Ottawa, Canada ON K1A 0R6
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Merrett K, Cornelius RM, McClung WG, Unsworth LD, Sheardown H. Surface analysis methods for characterizing polymeric biomaterials. J Biomater Sci Polym Ed 2003; 13:593-621. [PMID: 12182547 DOI: 10.1163/156856202320269111] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Surface properties have an enormous effect on the success or failure of a biomaterial device, thus signifying the considerable importance of and the need for adequate characterization of the biomaterial surface. Microscopy techniques used in the analysis of biomaterial surfaces include scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and confocal microscopy. Spectroscopic techniques include X-ray photoelectron spectroscopy, Fourier Transform infrared attenuated total reflection and secondary ion mass spectrometry. The measurement of contact angles, although one of the earlier techniques developed remains a very useful tool in the evaluation of surface hydrophobicity/hydrophilicity. This paper provides a brief, easy to understand synopsis of these and other techniques including emerging techniques, which are proving useful in the analysis of the surface properties of polymeric biomaterials. Cautionary statements have been made, numerous authors referenced and examples used to show the specific type of information that can be acquired from the different techniques used in the characterization of polymeric biomaterials surfaces.
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Affiliation(s)
- K Merrett
- Department of Chemical Engineering, University of Ottawa, ON, Canada
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Merrett K, Griffith CM, Deslandes Y, Pleizier G, Dubé MA, Sheardown H. Interactions of corneal cells with transforming growth factor β2-modified poly dimethyl siloxane surfaces. ACTA ACUST UNITED AC 2003; 67:981-93. [PMID: 14613248 DOI: 10.1002/jbm.a.10165] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The downgrowth of corneal epithelial cells at the interface of an artificial cornea and the host eye tissue poses a significant problem to be overcome in developing a successful implant. As a means of inhibiting the proliferation of corneal epithelial cells on the stromal surface of the implant, we examined the immobilization of transforming growth factor beta-2 (TGF-beta2) via a bifunctional poly ethylene glycol (PEG) spacer to poly dimethyl siloxane (PDMS) surfaces. Growth factor immobilization was confirmed by modification with (125)I-labeled TGF-beta 2. The modified surfaces were also characterized by advancing water contact angles, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Although the amount of growth factor covalently bound to the surface was difficult to quantify apparently due to strong interactions between the growth factor and the PEG layer and high levels of adsorption, differences in the modified surfaces, suggestive of the presence of a significant amount of TGF-beta 2, were found. In vitro interactions of the modified surfaces with human corneal epithelial and stromal cells were examined. Growth factor surface concentrations as well as culture in the absence and presence of serum and other adhesive proteins were examined. Corneal stromal and epithelial cells cultured on the TGF-beta 2-modified surfaces consistently gave results opposite to those expected. Likely, the most notable and surprising result was the almost complete lack of adhesion of the stromal cells, with coverage averaging between 3 and 5%. In comparison, corneal epithelial cell growth appeared to be promoted by the presence of the immobilized growth factor, with cell coverage averaging 50-60% at 7 days of culture. A TGF-beta 2 concentration effect was noted with both cell types in the absence of serum, with increases in the coverage at higher TGF-beta 2 concentrations. The observed cell growth appeared to be the result of interactions between the cells and active growth factor, because the addition of anti-TGF-beta 2 to the culture medium reduced cell coverage to levels similar to those noted on control surfaces. Therefore, although TGF-beta 2-modified surfaces may not be suitable as corneal epithelial cell inhibiting surfaces, interactions of surface immobilized growth factor and corneal cells are complex and should be further examined.
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Affiliation(s)
- K Merrett
- Department of Chemical Engineering, University of Ottawa, 161 Louis Pasteur St., Ottawa ON, K1N 6N5, Canada
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Merrett K, Griffith CM, Deslandes Y, Pleizier G, Sheardown H. Adhesion of corneal epithelial cells to cell adhesion peptide modified pHEMA surfaces. J Biomater Sci Polym Ed 2002; 12:647-71. [PMID: 11556742 DOI: 10.1163/156856201316883467] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Epithelialization of a corneal implant is a desirable property. In this study we compared surface modification of poly (2-hydroxyethyl methacrylate) (pHEMA) with the cell adhesion peptides RGDS and YIGSR. Various parameters in the tresyl chloride activation and modification reactions were considered in order to maximize surface coverage with the peptide including tresyl chloride reaction solvent. tresyl chloride reaction time, tresyl chloride concentration, peptide concentration, and peptide reaction pH. Surface chemistry and corneal epithelial cell adhesion to the modified surfaces were examined. X-ray photoelectron spectroscopy data suggested that while peptide modification had occurred, surface coverage with the peptide was incomplete. Acetone was found to result in a higher fraction of nitrogen and surface bound carboxyl groups compared to dioxane and ether. Furthermore, corneal epithelial cell adhesion to the surfaces for which acetone was used for the activation reaction was significantly greater. Statistical analysis of the various samples suggests that lower peptide concentrations and higher tresyl chloride reaction times result in better cell adhesion. Furthermore, modification with YIGSR resulted in higher surface concentrations and better cell adhesion than modification with RGDS. Little or no cell adhesion was noted on the unmodified pHEMA controls. Protein adsorption results suggest that the differences in cell adhesion cannot be attributed to differences in serum protein adsorption from the culture medium. We conclude that YIGSR modified surfaces have significant potential for further development in corneal applications.
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Affiliation(s)
- K Merrett
- Department of Chemical Engineering, University of Ottawa, ON, Canada
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Rosengarten PL, Tuxen DV, Dziukas L, Scheinkestel C, Merrett K, Bowes G. Circulatory arrest induced by intermittent positive pressure ventilation in a patient with severe asthma. Anaesth Intensive Care 1991; 19:118-21. [PMID: 2012271 DOI: 10.1177/0310057x9101900126] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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