Pericapsular fibrotic overgrowth mitigated in immunocompetent mice through microbead formulations based on sulfated or intermediate G alginates

Abba E Coron; Joachim S Kjesbu; Fredrikke Kjærnsmo; José Oberholzer; Anne Mari A Rokstad; Berit L Strand

doi:10.1016/j.actbio.2021.10.004

Pericapsular fibrotic overgrowth mitigated in immunocompetent mice through microbead formulations based on sulfated or intermediate G alginates

Acta Biomater. 2022 Jan 1:137:172-185. doi: 10.1016/j.actbio.2021.10.004. Epub 2021 Oct 8.

Authors

Abba E Coron¹, Joachim S Kjesbu², Fredrikke Kjærnsmo¹, José Oberholzer³, Anne Mari A Rokstad⁴, Berit L Strand⁵

Affiliations

¹ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.; Centre of Molecular Inflammation Research, Department of Clinical and Molecular Research, Norwegian University of Science and Technology, Trondheim, Norway.
² NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
³ Charles O. Strickler Transplant Center. Division of Transplantation, Department of Surgery, University of Virginia, VA 22903, USA.
⁴ Centre of Molecular Inflammation Research, Department of Clinical and Molecular Research, Norwegian University of Science and Technology, Trondheim, Norway.; Centre for Obesity, Clinic of Surgery, St. Olav's University Hospital, NO-7006 Trondheim, Norway.
⁵ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.. Electronic address: berit.l.strand@ntnu.no.

PMID: 34634509
DOI: 10.1016/j.actbio.2021.10.004

Abstract

Cell encapsulation in alginate microbeads is a promising approach to provide immune isolation in cell therapy without immunosuppression. However, the efficacy is hampered by pericapsular fibrotic overgrowth (PFO), causing encapsulated cells to lose function. Stability of the microbeads is important to maintain immune isolation in the long-term. Here, we report alginate microbeads with minimal PFO in immunocompetent C57BL/6JRj mice. Microbead formulations included either alginate with an intermediate (47 %) guluronate (G) content (IntG) or sulfated alginate (SA), gelled in Ca²⁺/Ba²⁺ or Sr²⁺. A screening panel of eleven microbead formulations were evaluated for PFO, yielding multiple promising microbeads. Two candidate formulations were evaluated for 112 days in vivo, exhibiting maintained stability and minimal PFO. Microbeads investigated in a human whole blood assay revealed low cytokine and complement responses, while SA microbeads activated coagulation. Protein deposition on microbeads explanted from mice investigated by confocal laser scanning microscopy (CLSM) showed minimal deposition of complement C3. Fibrinogen was positively associated with PFO, with a high deposition on microbeads of high G (68 %) alginate compared to IntG and SA microbeads. Overall, stable microbeads containing IntG or SA may serve in long-term therapeutic applications of cell encapsulation. STATEMENT OF SIGNIFICANCE: Alginate-based hydrogels in the format of micrometer size beads is a promising approach for the immunoisolation of cells in cell therapy. Clinical trials in type 1 diabetes have so far had limited success due to fibrotic responses that hinder the diffusion of nutrients and oxygen to the encapsulated cells, resulting in graft failure. In this study, minimal fibrotic response towards micrometer size alginate beads was achieved by chemical modification of alginate with sulfate groups. Also, the use of alginate with intermediate guluronic acid content resulted in minimally fibrotic microbeads. Fibrinogen deposition was revealed to be a good indicator of fibrosis. This study points to both new microsphere developments and novel insight in the mechanisms behind the fibrotic responses.

Keywords: Alginate; Biocompatibility; Fibrinogen; Fibrosis; Microbeads.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Alginates* / pharmacology
Animals
Fibrosis
Glucuronic Acid
Hexuronic Acids
Mice
Mice, Inbred C57BL
Microspheres
Sulfates*

Substances

Alginates
Hexuronic Acids
Sulfates
Glucuronic Acid