Cell engraftment, vascularization, and inflammation after treatment of equine distal limb wounds with endothelial colony forming cells encapsulated within hydrogel microspheres

Randolph L Winter,Yuan Tian,Fred J Caldwell,Jey W Koehler,Shirley Fan,David A Pascoe,Wen J Seeto,Phillippe Gaillard,Elizabeth A Lipke,Anne A Wooldridge

doi:10.1186/s12917-020-2269-y

Randolph L Winter, Yuan Tian + Show 8 more

Open Access

https://doi.org/10.1186/s12917-020-2269-y

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Abstract

BackgroundEndothelial colony forming cells (ECFCs) may be useful therapeutically in conditions with poor blood supply, such as distal limb wounds in the horse. Encapsulation of ECFCs into injectable hydrogel microspheres may ensure cell survival and cell localization to improve neovascularization and healing. Autologous ECFCs were isolated from 6 horses, labeled with quantum nanodots (QD), and a subset were encapsulated in poly(ethylene) glycol fibrinogen microspheres (PEG-Fb MS). Full-thickness dermal wounds were created on each distal limb and injected with empty PEG-Fb MS, serum, ECFCs, or ECFCs encapsulated into PEG- Fb MS (ECFC/MS). Analysis included wound surface area (WSA), granulation tissue scoring (GS), thermography, collagen density staining, and immunohistochemical staining for endothelial and inflammatory cells. The purpose of this study was to track cell location and evaluate wound vascularization and inflammatory response after injection of ECFC/MS or naked ECFCs in equine distal limb wounds.ResultsECFCs were found near and within newly formed blood vessels up to 3 weeks after injection. ECFC and ECFC/MS groups had the greatest blood vessel quantity at week 1 in the wound periphery. Wounds treated with ECFCs and ECFC/MS had the lowest density of neutrophils and macrophages at week 4. There were no significant effects of ECFC or ECFC/MS treatment on other measured parameters.ConclusionsInjection of microsphere encapsulated ECFCs was practical for clinical use and well-tolerated. The positive ECFC treatment effects on blood vessel density and wound inflammation warrant further investigation.

Highlights

Endothelial colony forming cells (ECFCs) may be useful therapeutically in conditions with poor blood supply, such as distal limb wounds in the horse
Our group has demonstrated an effective method of cell delivery using injectable, cell-laden hydrogel microspheres, and we have shown increased vascularization and reduced inflammation in a research model of equine distal limb wounds treated with ECFCs
We showed that we can consistently create uniform, cell-laden microspheres for in vivo injection, the equine ECFCs survive encapsulation and injection, and Poly(ethylene) glycol (PEG)-Fb MS encapsulated labeled ECFCs were detected in tissues up to 3 weeks after injection

Summary

Introduction

Endothelial colony forming cells (ECFCs) may be useful therapeutically in conditions with poor blood supply, such as distal limb wounds in the horse. Distal limb wounds in the horse may have physical disruption of blood supply, excessive inflammation, and local ischemia and hypoxia, all of which contribute to the formation of exuberant granulation tissue (EGT) and slow wound healing times [1,2,3,4]. Wounds with EGT have an abundant vascular supply [2, 4]; these vessels may be dysfunctional and occluded, promoting fibroproliferation [3] Based on their ability to heal damaged blood vessels and form new vessels in vivo, endothelial colony forming cells (ECFCs) may be an attractive option for promoting wound healing in distal limb wounds of the horse. The low retention rate of injected cells of ~ 5–9% in animal models of disease may be caused by cell death associated with either the injection or the harsh environment into which they are injected [13, 14]

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