Cryopreservation (−20 °C) of feline corneoscleral tissue: histologic, microbiologic, and ultrastructural study

Abstract

Cryopreservation of feline corneoscleral tissue seems to reduce bacterial contamination over time. Apoptosis is the main cause of death of cryopreserved feline keratocytes. Based on the lack of significant structural differences between STC and LTC samples, these cryopreserved tissues could potentially be used for tectonic support for at least 10 years without structural or microbiological impediment.

Cryopreservation (−20°C) of equine corneoscleral tissue: Microbiological, histological, and ultrastructural study

“…The presence of stromal bubbles between the collagen fibrils was the only sign detected by histology. These artifacts have been described previously as freeze‐thaw artifacts and differ in morphology from those due to sample processing . Bubbles were more evident in LTC tissues where they were distributed along stromal full‐thickness.…”

“…Apoptosis was the main mechanism of keratocyte death in the present study, as previously described in pigs, rabbits, cats, dogs, and humans . When compared with cellular necrosis, this active process of cell destruction characterized by chromatin aggregation and lack of inflammation or damage to the neighboring tissue could reduce the collagen fibril disruption and induce less damage to the donor tissue .…”

“…These artifacts have been described previously as freeze-thaw artifacts and differ in morphology from those due to sample processing. [35][36][37][38] Bubbles were more evident in LTC tissues where they were distributed along stromal full-thickness. Conversely in STC tissues, bubbles were seen only in partial stroma thickness.…”

“…These results do not greatly differ from the ones obtained in other animal species, such as the dog and the cat, in which highly satisfactory results have also been reported . Although these studies suggested 6‐18 months as the maximum storage time for cryopreserved corneal tissue at −20°C, the statement was not objectively demonstrated until recently when research studies in dogs and cats found that corneoscleral tissue could potentially be used for tectonic transplantation for at least 8 and 10 years, respectively, without structural or microbiological impediment . To the best of the authors’ knowledge, there are no reports on the recommended storage time for equine corneoscleral tissue; hence, this is the first study that objectively establishes that equine corneoscleral tissue, used for tectonic support, can be successfully cryopreserved at −20°C for up to 9 years.…”

“…Apoptosis was the main mechanism of keratocyte death in the present study, as previously described in pigs, rabbits, cats, dogs, and humans. 28,29,38,39 When compared with cellular necrosis, this active process of cell destruction characterized by chromatin aggregation and lack of inflammation or damage to the neighboring tissue could reduce the collagen fibril disruption and induce less damage to the donor tissue. 40 The cryopreservation process induces the death of epithelial cells, keratocytes, and endothelial cells, reducing corneal transparency after keratoplasty, especially in perforated corneas.…”