Cartilage repair across germ layer origins

In Vivo Stable Allogenic Cartilage Regeneration in a Goat Model Based on Immunoisolation Strategy Using Electrospun Semipermeable Membranes

Tissue engineering is a promising strategy for cartilage defect repair. However, autologous cartilage regeneration is limited by additional trauma to the donor site and a long in vitro culture period. Alternatively, allogenic cartilage regeneration has attracted attention because of the unique advantages of an abundant donor source and immediate supply, but it will cause immune rejection responses (IRRs), especially in immunocompetent large animals. Therefore, a universal technique needs to be established to overcome IRRs for allogenic cartilage regeneration in large animals. In the current study, a hybrid synthetic-natural electrospun thermoplastic polyurethane/gelatin (TPU/GT) semipermeable membrane to explore the feasibility of stable allogenic cartilage regeneration by an immunoisolation strategy is developed. In vitro results demonstrated that the rationally designed electrospun TPU/GT membranes has ideal biocompatibility, semipermeability, and an immunoisolation function. In vivo results further showed that the semipermeable membrane (SPM) efficiently blocked immune cell attack, decreased immune factor production, and cell apoptosis of the regenerated allogenic cartilage. Importantly, TPU/GT-encapsulated cartilage-sheet constructs achieved stable allogeneic cartilage regeneration in a goat model. The current study provides a novel strategy for allogenic cartilage regeneration and supplies a new cartilage donor source to repair various cartilage defects.

Research progress in seed cells for cartilage tissue engineering

Cartilage defects trouble millions of patients worldwide and their repair via conventional treatment is difficult. Excitingly, tissue engineering technology provides a promising strategy for efficient cartilage regeneration with structural regeneration and functional reconstruction. Seed cells, as biological prerequisites for cartilage regeneration, determine the quality of regenerated cartilage. The proliferation, differentiation and chondrogenesis of seed cells are greatly affected by their type, origin and generation. Thus, a systematic description of the characteristics of seed cells is necessary. This article reviews in detail the cellular characteristics, research progress, clinical translation challenges and future research directions of seed cells while providing guidelines for selecting appropriate seed cells for cartilage regeneration.

New Insights into Xenotransplantation for Cartilage Repair: Porcine Multi-Genetically Modified Chondrocytes as a Promising Cell Source

Transplantation of xenogenic porcine chondrocytes could represent a future strategy for the treatment of human articular cartilage defects. Major obstacles are humoral and cellular rejection processes triggered by xenogenic epitopes like α-1,3-Gal and Neu5Gc. Besides knockout (KO) of genes responsible for the biosynthesis of respective epitopes (GGTA1 and CMAH), transgenic expression of human complement inhibitors and anti-apoptotic as well as anti-inflammatory factors (CD46, CD55, CD59, TNFAIP3 and HMOX1) could synergistically prevent hyperacute xenograft rejection. Therefore, chondrocytes from different strains of single- or multi-genetically modified pigs were characterized concerning their protection from xenogeneic complement activation. Articular chondrocytes were isolated from the knee joints of WT, GalTKO, GalT/CMAH-KO, human CD59/CD55//CD46/TNFAIP3/HMOX1-transgenic (TG), GalTKO/TG and GalT/CMAHKO/TG pigs. The tissue-specific effectiveness of the genetic modifications was tested on gene, protein and epitope expression level or by functional assays. After exposure to 20% and 40% normal human serum (NHS), deposition of C3b/iC3b/C3c and formation of the terminal complement complex (TCC, C5b-9) was quantified by specific cell ELISAs, and generation of the anaphylatoxin C5a by ELISA. Chondrocyte lysis was analyzed by Trypan Blue Exclusion Assay. In all respective KO variants, the absence of α -1,3-Gal and Neu5Gc epitope was verified by FACS analysis. In chondrocytes derived from TG animals, expression of CD55 and CD59 could be confirmed on gene and protein level, TNFAIP3 on gene expression level as well as by functional assays and CD46 only on gene expression level whereas transgenic HMOX1 expression was not evident. Complement activation in the presence of NHS indicated mainly effective although incomplete protection against C3b/iC3b/C3c deposition, C5a-generation and C5b-9 formation being lowest in single GalTKO. Chondrocyte viability under exposure to NHS was significantly improved even by single GalTKO and completely preserved by all other variants including TG chondrocytes without KO of xenoepitopes.

Human nasoseptal chondrocytes maintain their differentiated phenotype on PLLA scaffolds produced by thermally induced phase separation and supplemented with bioactive glass 1393

Damage of hyaline cartilage such as nasoseptal cartilage requires proper reconstruction, which remains challenging due to its low intrinsic repair capacity. Implantation of autologous chondrocytes in combination with a biomimetic biomaterial represents a promising strategy to support cartilage repair. Despite so far mostly tested for bone tissue engineering, bioactive glass (BG) could exert stimulatory effects on chondrogenesis. The aim of this work was to produce and characterize composite porous poly(L-lactide) (PLLA)/1393BG scaffolds via thermally induced phase separation (TIPS) technique and assess their effects on chondrogenesis of nasoseptal chondrocytes. The PLLA scaffolds without or with 1, 2.5, 5% BG1393 were prepared via TIPS technique starting from a ternary solution (polymer/solvent/non-solvent) in a single step. Scaffolds were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetric analysis (DSC). Human nasoseptal chondrocytes were seeded on the scaffolds with 1 and 2.5% BG for 7 and 14 days and cell survival, attachment, morphology and expression of SOX9 and cartilage-specific extracellular cartilage matrix (ECM) components were monitored. The majority of chondrocytes survived on all PLLA scaffolds functionalized with BG for the whole culture period. Also inner parts of the scaffold were colonized by chondrocytes synthesizing an ECM which contained glycosaminoglycans. Type II collagen and aggrecan gene expression increased significantly in 1% BG scaffolds during the culture. Chondrocyte protein expression for cartilage ECM proteins indicated that the chondrocytes maintained their differentiated phenotype in the scaffolds. BG could serve as a cytocompatible basis for future scaffold composites for osteochondral cartilage defect repair. Abbreviations: AB: alcian blue ACAN: gene coding for aggrecan; BG: Bioactive glass; 2D: two-dimensional; 3D: three-dimensional; COL2A1: gene coding for type II collagen; DAPI: 4',6-diamidino-2-phenylindole; DMEM: Dulbecco's Modified Eagle's Medium; DMMB: dimethylmethylene blue; DSC: Differential scanning calorimetric analysis; ECM: extracellular matrix; EDTA: ethylenediaminetetraacetic acid; EtBr: ethidium bromide; FCS: fetal calf serum; FDA: fluorescein diacetate; GAG: glycosaminoglycans; HDPE: high density polyethylene; HE: hematoxylin and eosin staining; HCA: hydoxylapatite; PBE: phosphate buffered EDTA100 mM Na₂HPO₄ and 5 mM EDTA, pH8; PBS: phosphate buffered saline; PFA: paraformaldehyde; PG: proteoglycans; PI: propidium iodide; PLLA: Poly-L-Lactic Acid Scaffold; RT: room temperature; SD: standard deviation; SEM: scanning electron microscopy; sGAG: sulfated glycosaminoglycans; SOX9/Sox9: SRY (sex-determining region Y)-box 9 protein; TBS: TRIS buffered saline; TIPS: Thermally Induced Phase Separation; XRD: X-ray diffraction analysis.