Cell bricks-enriched platelet-rich plasma gel for injectable cartilage engineering - an in vivo experiment in nude mice

Abstract

Clinical application of platelet-rich plasma (PRP)-based injectable tissue engineering is limited by weak mechanical properties and a rapid fibrinolytic rate. We proposed a new strategy, a cell bricks-stabilized PRP injectable system, to engineer and regenerate cartilage with stable morphology and structure in vivo. Chondrocytes from the auricular cartilage of rabbits were isolated and cultured to form cell bricks (fragmented cell sheet) or cell expansions. Fifteen nude mice were divided evenly (n = 5) into cells-PRP (C-P), cell bricks-PRP (CB-P) and cell bricks-cells-PRP (CB-C-P) groups. Cells, cell bricks or a cell bricks/cells mixture were suspended in PRP and were injected subcutaneously in animals. After 8 weeks, all the constructs were replaced by white resilient tissue; however, specimens from the CB-P and CB-C-P groups were well maintained in shape, while the C-P group appeared distorted, with a compressed outline. Histologically, all groups presented lacuna-like structures, glycosaminoglycan-enriched matrices and positive immunostaining of collagen type II. Different from the uniform structure presented in CB-C-P samples, CB-P presented interrupted, island-like chondrogenesis and contracted structure; fibrous interruption was shown in the C-P group. The highest percentage of matrix was presented in CB-C-P samples. Collagen and sGAG quantification confirmed that the CB-C-P constructs had statistically higher amounts than the C-P and CB-P groups; statistical differences were also found among the groups in terms of biomechanical properties and gene expression. We concluded that cell bricks-enriched PRP gel sufficiently enhanced the morphological stability of the constructs, maintained chondrocyte phenotypes and favoured chondrogenesis in vivo, which suggests that such an injectable, completely biological system is a suitable cell carrier for cell-based cartilage repair.

Reconstruction of Alar Nasal Cartilage Defects Using a Tissue Engineering Technique Based on a Combined Use of Autologous Chondrocyte Micrografts and Platelet-rich Plasma: Preliminary Clinical and Instrumental Evaluation

“…30 Different from solid scaffold-based tissue engineering, injectable cartilage constructs require fluidity of components and instant establishment of a chondrogenic niche. Zhu et al 18 proved that fragmented chondrocyte macroaggregates (cell bricks) could stabilize the PRP gel efficiently in vivo and support chondrogenesis with stable morphology. 18 In this study, they found that such an injectable complex could support chondrogenesis of bone marrow mesenchymal stem cells (BMSCs) in vivo and demonstrated that such a complete biological graft could meet the requirement of nasal augmentation, thus holding future promise in craniofacial reconstruction.…”

“…18 In addition, BMSCs are capable of promoting angiogenesis through the secretion of GFs, in particular VEGF. 31 Angiogenesis is a crucial event for tissue regeneration 32 and tumor growth.…”

“…They found that chondrocyte bricks significantly inhibited vascular infiltration into PRP gels and slowed their degradation, thus maintaining the framework and shape of the PRP grafts. 18 They hypothesized that the cell brick–enriched PRP gel could be an ideal injectable niche for adults stem cells, which is expected to regenerate biological cartilage tissues with persistent cartilaginous phenotype, less deformation, and uniform histological structure. 18 …”

“…18 They hypothesized that the cell brick–enriched PRP gel could be an ideal injectable niche for adults stem cells, which is expected to regenerate biological cartilage tissues with persistent cartilaginous phenotype, less deformation, and uniform histological structure. 18 …”

Angiogenic Potential of Human Bone Marrow-Derived Mesenchymal Stem Cells in Chondrocyte Brick-Enriched Constructs Promoted Stable Regeneration of Craniofacial Cartilage

“…To provide injectable, mechanical supportive BMSC aggregate for cartilage regeneration, we developed a chondrocyte brick (CB; fragmented chondrocyte/ECM macroaggregates)‐enriched platelet‐rich plasma (PRP) gel. A previous study showed that mixing chondrocytes with cell bricks/PRP stabilized clots efficiently . In this study, we found that undifferentiated BMSCs could be well mixed with chondrocyte bricks in a PRP gel and self‐assembled into a macroaggregate of a size that can be used clinically.…”