Short peptide analogs as alternatives to collagen in pro-regenerative corneal implants

Jaganmohan R Jangamreddy,Michel K.C Haagdorens,M Mirazul Islam,Philip Lewis,Ayan Samanta,Per Fagerholm,Aneta Liszka,Monika K Ljunggren,Oleksiy Buznyk,Emilio I Alarcon,Nadia Zakaria,Keith M Meek,May Griffith

doi:10.1016/j.actbio.2018.01.011

Abstract

Short collagen-like peptides (CLPs) are being proposed as alternatives to full-length collagen for use in tissue engineering, on their own as soft hydrogels, or conjugated to synthetic polymer for mechanical strength. However, despite intended clinical use, little is known about their safety and efficacy, mechanism of action or degree of similarity to the full-length counterparts they mimic. Here, we show the functional equivalence of a CLP conjugated to polyethylene glycol (CLP-PEG) to full-length recombinant human collagen in vitro and in promoting stable regeneration of corneal tissue and nerves in a pre-clinical mini-pig model. We also show that these peptide analogs exerted their pro-regeneration effects through stimulating extracellular vesicle production by host cells. Our results support future use of CLP-PEG implants for corneal regeneration, suggesting the feasibility of these or similar peptide analogs in clinical application in the eye and other tissues. Statement of significanceAlthough biomaterials comprising full-length recombinant human collagen and extracted animal collagen have been evaluated and used clinically, these macromolecules provide only a limited number of functional groups amenable to chemical modification or crosslinking and are demanding to process. Synthetic, customizable analogs that are functionally equivalent, and can be readily scaled-up are therefore very desirable for pre-clinical to clinical translation. Here, we demonstrate, using cornea regeneration as our test bed, that collagen-like-peptides conjugated to multifunctional polyethylene glycol (CLP-PEG) when grafted into mini-pigs as corneal implants were functionally equivalent to recombinant human collagen-based implants that were successfully tested in patients. We also show for the first time that these materials affected regeneration through stimulation of extracellular vesicle production by endogenous host cells that have migrated into the CLP-PEG scaffolds.

Highlights

The current global need for replacement organs and tissues requires numbers that far exceed the donor supply
Successful testing in a simple organ system like the cornea will allow for the extension to more complex applications such as skin and heart, as we have shown with collagen after minimal modification [12,13,14]
Both control recombinant human collagen type III (RHCIII)-methacryloyloxyethyl phosphorylcholine (MPC) implants (Fig. 1a) and collagen-like peptide (CLP)-polyethylene glycol (PEG) implants (Fig. 1b) were optically clear, with over 90% light transmission, exceeding that of the human cornea [21] and a refractive index that approximates that of the human cornea [22] (Table S2A)

Summary

Introduction

The current global need for replacement organs and tissues requires numbers that far exceed the donor supply. While the use of recombinantly produced human collagen eliminates heterogeneity, these are still large macromolecules that require significant processing This makes short peptide analogs that are readily prepared, customized and scaled-up, very attractive ECM alternatives for regenerative medicine. Several in vitro and in vivo studies have reported that such short ECM-mimicking peptides can stimulate regeneration in a range of organ systems including bone and spinal cord [2,3]. Despite their great potential, little is known about their safety and efficacy, mechanism of action, or functional equivalence to their clinically evaluated full-length counterparts

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Discussion

Conclusion