Diverse aging rates in ectothermic tetrapods provide insights for the evolution of aging and longevity

Comparative studies of mortality in the wild are necessary to understand the evolution of aging; yet, ectothermic tetrapods are underrepresented in this comparative landscape, despite their suitability for testing evolutionary hypotheses. We present a study of aging rates and longevity across wild tetrapod ectotherms, using data from 107 populations (77 species) of nonavian reptiles and amphibians. We test hypotheses of how thermoregulatory mode, environmental temperature, protective phenotypes, and pace of life history contribute to demographic aging. Controlling for phylogeny and body size, ectotherms display a higher diversity of aging rates compared with endotherms and include phylogenetically widespread evidence of negligible aging. Protective phenotypes and life-history strategies further explain macroevolutionary patterns of aging. Analyzing ectothermic tetrapods in a comparative context enhances our understanding of the evolution of aging.Animal science

In vitro bonding of pre-seeded chondrocytes

This study investigated the capacity of seeded chondrocytes to join separate cartilage disc matrices in an in vitro model. Articular cartilage discs were harvested from pigs and devitalized by multiple freeze/thaw cycles. The devitalized cartilage discs were incubated in the presence (experimental group) or absence (control group) of chondrocytes for 10 days in order to allow chondrocytes to adhere to the matrix. After culturing, pairs of cartilage discs were held in apposition in a 48-multiwell plate and cultured for two and eight weeks. Twelve experimental composites (with cells) and twelve controls (without cells) were prepared per each time point. Samples were retrieved from culture and grossly inspected for adherence and processed for histological evaluation. Histological sections demonstrated the presence of new cartilage matrix formed by seeded chondrocytes bonding the two matrix discs together and producing glycosaminoglycans (GAG) able to diffuse within the devitalized tissue. Generally, gross adherence between the discs was demonstrated in the experimental samples, while the controls did not show any bonding. We conclude that isolated and seeded chondrocytes produce a new cartilaginous matrix, capable to join devitalized cartilage discs in vitro

Cell-based bonding of articular cartilage : an extended study

This study evaluated the biomechanical characteristics of newly formed cartilaginous tissue synthesized from isolated chondrocytes and seeded onto devitalized cartilage in an extended study in vivo. Cartilage from porcine articular joints was cut into regular discs and devitalized by multiple freeze-thaw cycles. Articular chondrocytes were enzymatically isolated and incubated in suspension culture in the presence of devitalized cartilage discs for 21 days. This procedure allowed the isolated chondrocytes to adhere to the devitalized matrix surfaces. Chondrocyte-matrix constructs were assembled with fibrin glue and implanted in dorsal subcutaneous pockets in nude mice for up to 8 months. Histological evaluation and biomechanical testing were performed to quantify the integration of cartilage pieces and the mechanical properties of the constructs over time. Histological analysis indicated that chondrocytes grown on devitalized cartilage discs produced new matrix that bonded and integrated individual cartilage elements with mechanically functional tissue. Biomechanical testing demonstrated a time dependent increase in tensile strength, failure strain, failure energy, and tensile modulus to values 5-30% of normal articular cartilage by 8 months in vivo. The values recorded at 4 months were not statistically different from those collected at the latest time point, indicating that the limits of the biomechanical property values were reached after four months from implantation