Vocal fold restoration after scarring: biocompatibility and efficacy of an MSC-based bioequivalent.

BACKGROUND: There is growing interest to application of regenerative medicine approaches in otorhinolaryngological practice, especially in the framework of the therapy of vocal fold (VF) scar lesions. The used conservative and surgical methods, despite the achieved positive outcomes, are frequently unpredictable and do not result in the restoration of the VF's lamina propria's structure, which provides the mechanical properties necessary for vibration. In this connection, the aim of this study was to ascertain the safety and efficacy of a bioequivalent in the treatment of VF scars using a rabbit model of chronic damage. METHODS: The bioequivalent consisted of a hydrogel system based on a PEG-fibrin conjugate and human bone marrow-derived MSC. It was characterized and implanted heterotopically into rats and orthotopically into rabbits after VF scar excision. RESULTS: We showed that the fabricated bioequivalent consisted of viable cells retaining their metabolic and proliferative activity. While being implanted heterotopically, it had induced the low inflammatory reaction in 7 days and was well tolerated. The orthotopic implantation showed that the gel application was characterized by a lower hemorrhage intensity (p = 0.03945). The intensity of stridor and respiratory rate between the groups in total and between separate groups had no statistically significant difference (p = 0.96 and p = 1; p = 0.9593 and p = 0.97…1, respectively). In 3 days post-implantation, MSC were detected only in the tissues closely surrounding the VF defect. The bioequivalent injection caused that the scar collagen fibers were packed looser and more frequently mutually parallel that is inherent in the native tissue (p = 0.018). In all experimental groups, the fibrous tissue's ingrowth in the adjacent exterior muscle tissue was observed; however, in Group 4 (PEG-Fibrin + MSC), it was much less pronounced than it was in Group 1 (normal saline) (p = 0.008). The difference between the thicknesses of the lamina propria in the control group and in Group 4 was not revealed to be statistically significant (p = 0.995). The Young's modulus of the VF after the bioequivalent implantation (1.15 ± 0.25 kPa) did not statistically significantly differ from the intact VF modulus (1.17 ± 0.45 kPa); therefore, the tissue properties in this group more closely resembled the intact VF. CONCLUSIONS: The developed bioequivalent showed to be biocompatible and highly efficient in the restoration of VF's tissue.

Mechanical properties of anterior lens capsule assessed with AFM and nanoindenter in relation to human aging, pseudoexfoliation syndrome, and trypan blue staining.

The purpose of this study is the mechanical characterization of the mid-to- old-age human anterior lens capsules (ALCs) obtained by capsulorhexis using Atomic Force Microscopy (AFM) and a nanoindenter at different spatial scales. The dependencies on the human age, presence or absence of pseudoexfoliation syndrome (PEX), and application of trypan blue staining during the surgery were analyzed. The measurements on both the anterior (AS) and epithelial (ES) sides of the ALC were conducted and the effect of cells present on the epithelial side was carefully accounted for. The ES of the ALC had a homogenous distribution of the Young's modulus over the surface as shown by the macroscale mapping with the nanoindenter and local AFM indentations, while the AS was more heterogeneous. Age-related changes were assessed in groups ranging from the mid-age (from 48 years) to old-age (up to 93 years). We found that the ES was always stiffer than the AS, and this difference decreased with age due to a gradual decrease in the Young's modulus of the ES and an increase in the modulus of the AS. No significant changes were found in the mechanical properties of ALCs of PEX patients versus the PEX-free group, as well as in the properties of the ALC with and without trypan blue staining.

Cell spheroid fusion: beyond liquid drops model.

Biological self-assembly is crucial in the processes of development, tissue regeneration, and maturation of bioprinted tissue-engineered constructions. The cell aggregates-spheroids-have become widely used model objects in the study of this phenomenon. Existing approaches describe the fusion of cell aggregates by analogy with the coalescence of liquid droplets and ignore the complex structural properties of spheroids. Here, we analyzed the fusion process in connection with structure and mechanical properties of the spheroids from human somatic cells of different phenotypes: mesenchymal stem cells from the limbal eye stroma and epithelial cells from retinal pigment epithelium. A nanoindentation protocol was applied for the mechanical measurements. We found a discrepancy with the liquid drop fusion model: the fusion was faster for spheroids from epithelial cells with lower apparent surface tension than for mesenchymal spheroids with higher surface tension. This discrepancy might be caused by biophysical processes such as extracellular matrix remodeling in the case of mesenchymal spheroids and different modes of cell migration. The obtained results will contribute to the development of more realistic models for spheroid fusion that would further provide a helpful tool for constructing cell aggregates with required properties both for fundamental studies and tissue reparation.

Chemical cross-linking of xenopericardial biomeshes: A bottom-up study of structural and functional correlations.

Decellularized bovine pericardium (DBP)-based biomeshes are the gold standard in reconstructive surgery. In order to prolong their stability after the transplantation, various chemical cross-linking strategies are employed. However, structural and functional properties of the biomeshes differ in dependence on the cross-linker used. Here, we performed a bottom-up study of structural and functional alterations of DBP-based biomeshes following cross-linking with hexamethylene diisocyanate (HMDC), ethylene glycol diglycidyl ether (EGDE), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and genipin. The in vitro cytotoxicity tests supported their clinical applicability. Their structural differences (eg roughness, fibre thickness, pore morphology) were evaluated using the two-photon confocal laser scanning, atomic force, scanning electron and polarized light microscopies. HMDC and EDC samples appeared to be the roughest. Complex mechanical trials indicated the tendency to reduced Young's Modulus and mechanical anisotropy values of DBP upon cross-linking. The lowest mechanical anisotropy was found in EDC and genipin sample groups. In vitro collagenase susceptibility was the highest for EDC samples and the lowest for EGDE samples. The comparative analysis of the results allowed us to recognize the strengths and weaknesses of each cross-linker in relation to a particular clinical application.