The Effect of Neonatal, Juvenile, and Adult Donors on Rejuvenated Neocartilage Functional Properties

Abstract

Cartilage does not naturally heal, and cartilage lesions from trauma and wear-and-tear can lead to eventual osteoarthritis. To address long-term repair, tissue engineering of functional biologic implants to treat cartilage lesions is desirable, but the development of such implants is hindered by several limitations including 1) donor tissue scarcity due to the presence of diseased tissues in joints, 2) dedifferentiation of chondrocytes during expansion, and 3) differences in functional output of cells dependent on donor age.Toward overcoming these challenges, 1) costal cartilage has been explored as a donor tissue, and 2) methods have been developed to rejuvenate the chondrogenic phenotype of passaged chondrocytes for generating self-assembled neocartilage. However, it remains unclear how the rejuvenation processes are influenced by donor age, and, thus, how to develop strategies that specifically target age-related differences. Using histological, biochemical, proteomic, and mechanical assays, this study sought to determine the differences among neocartilage generated from neonatal, juvenile, and adult donors using the Yucatan minipig, a clinically relevant large animal model. Based on the literature, a relatively young adult population of animals was chosen due to a reduction in functional output of human articular chondrocytes after 40 years of age. After isolation, costal chondrocytes were expanded, rejuvenated, and self-assembled, and the neocartilages were assessed. The aggregate modulus values of neonatal constructs were at least 1.65fold of those from the juvenile or adult constructs. Poisson's ratio also significantly differed among all groups, with neonatal constructs exhibiting values 49% higher than adult constructs. Surprisingly, other functional properties such as tensile modulus and glycosaminoglycan content did not significantly differ among groups. Total collagen content was slightly elevated in the adult constructs when compared to neonatal and juvenile constructs. A more nuanced view via bottom-up mass spectrometry showed that Col2a1 protein was not significantly different among groups, but content of several other collagen subtypes (i.e., Col1a1, Col9a1, Col11a2, and Col12a1) was modulated by donor age. For example, Col12a1 in adult constructs was found to be 102.9% higher than neonatal-derived constructs. Despite these differences, this study shows that different aged donors can be used to generate neocartilages of similar functional properties.

Impact of Inter- and Intra-Donor Variability by Age on the Gel-to-Tissue Transition in MMP-Sensitive PEG Hydrogels for Cartilage Regeneration

“…Several studies have reported reduced collagen synthesis in 3D cultures with donor age using agarose hydrogels and hydrolytically degradable poly­(ethylene glycol) hydrogels . On the contrary, a scaffold-free self-assembly process for 3D regeneration of cartilage reported similar biochemical contents regardless of donor age . These studies demonstrate that chondrocyte bioactivity differs with age of the donor but the extent may depend on the signaling factors (e.g., growth factors) and the culture environment.…”

“…13 On the contrary, a scaffold-free self-assembly process for 3D regeneration of cartilage reported similar biochemical contents regardless of donor age. 14 These studies demonstrate that chondrocyte bioactivity differs with age of the donor but the extent may depend on the signaling factors (e.g., growth factors) and the culture environment. Taken together, a successful cartilage tissue engineering strategy must consider the impact of donor variations.…”

A cell bank paradigm for preclinical evaluation of an analogous cellular product for an allogeneic cell therapy

“…Specifically, cells were isolated from six juvenile minipig donors (5-7 months old, three male, three female) and expanded to generate MCBs derived from each donor. We estimate that the juvenile cells used in this study correspond to approximately 10-12 years of age in the human [21]. It has been reported that in the human, chondrocytes isolated from donors under 13 years of age had greater proteoglycan production and collagen type II and type IX gene expression than adult donors [22].…”

Proteomic, mechanical, and biochemical development of tissue-engineered neocartilage

“…Recent in vitro studies have shown the similar mechanical and biochemical attributes of rib cartilage and articular cartilage, deeming costal cartilage a valuable cell source for articular cartilage tissue engineering [ 15 ]. Additionally, self-assembled neocartilages have recently been made from extensively passaged, rejuvenated costal chondrocytes [ 16 , 17 ], allowing for thousands of robust neocartilage implants to be made from one rib cartilage biopsy [ 18 ]. Self-assembled neocartilage implants made with costal chondrocytes have also been used to treat cartilage defects in Yucatan minipig models [ 19 ].…”