Cryopreservation (-20 °C) of canine corneoscleral tissue: histological, microbiological, and ultrastructural study

Fine mapping of CscpFtsY, a gene conferring the yellow leaf phenotype in cucumber (Cucumis sativus L.)

BACKGROUND

Leaf color mutants are ideal materials to study pigment metabolism and photosynthesis. Leaf color variations are mainly affected by chlorophylls (Chls) and carotenoid contents and chloroplast development in higher plants. However, the regulation of chlorophyll metabolism remains poorly understood in many plant species. The chloroplast signal-recognition particle system is responsible for the insertion of the light-harvesting chlorophyll a/b proteins (LHCPs) to thylakoid membranes, which controls the chloroplast development as well as the regulation of Chls biosynthesis post-translationally in higher plants.

RESULTS

In this study, the yellow leaf cucumber mutant, named yl, was found in an EMS-induced mutant library, which exhibited a significantly reduced chlorophyll content, abnormal chloroplast ultrastructure and decreased photosynthetic capacity. Genetic analysis demonstrated that the phenotype of yl was controlled by a recessive nuclear gene. Using BSA-seq technology combined with the map-based cloning method, we narrowed the locus to a 100 kb interval in chromosome 3. Linkage analysis and allelism test validated the candidate SNP residing in CsaV3_3G009150 encoding one homolog of chloroplast signal-recognition particle (cpSRP) receptor in Arabidopsis, cpFtsY, could be responsible for the yellow leaf phenotype of yl. The relative expression of CscpFtsY was significantly down-regulated in different organs except for the stem, of yl compared with that in the wild type (WT). Subcellular localization result showed that CscpFtsY located in the chloroplasts of mesophyll cells.

CONCLUSIONS

The yl mutant displayed Chls-deficient, impaired chloroplast ultrastructure with intermittent grana stacks and significantly decreased photosynthetic capacity. The isolation of CscpFtsY in cucumber could accelerate the progress on chloroplast development by cpSRP-dependant LHCP delivery system and regulation of Chls biosynthesis in a post-translational way.

Mechanical Stability of Cryopreserved Split-Thickness Tectonic Corneal Grafts

PURPOSE

To evaluate the influence of cryopreservation on the pressure-strain relationship of microkeratome dissected anterior stromal grafts (ASGs).

METHODS

Partial thickness ASGs were created from 7 pairs of human corneas and randomized to immediate grafting or grafting after 3 months of cryopreservation at -80°C into a whole globe ex vivo corneal perforation model. High frequency ultrasound speckle tracking was used to calculate the cross-sectional axial and lateral strains in each graft at increasing intraocular pressure (IOP) from 5 to 30 mm Hg. The mean axial and lateral strains were compared between the paired groups.

RESULTS

The mean axial and lateral strains were not significantly different between the cryopreserved and noncryopreserved ASGs. The mean lateral strains at 30 mm Hg in the noncryopreserved and cryopreserved grafts were 2.4% ± 2.1% and 1.4% ± 0.7% (P = 0.294), respectively. The mean axial strains at 30 mm Hg in the noncryopreserved and cryopreserved grafts were -7.8% ± 3.3% and -5.5% ± 3.0% (P = 0.198), respectively. A linear pressure-strain relationship was found for all grafts at physiologic IOP.

CONCLUSIONS

ASGs cryopreserved at -80°C maintain their IOP-strain relationship compared with noncryopreserved ASGs at physiologic pressures, supporting the potential use of cryopreserved human corneal stroma for patch grafting procedures.

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

OBJECTIVE

To evaluate microbiological, histological, and ultrastructural characteristics of short-term cryopreserved (STC) equine corneoscleral tissue (<1 year), and to compare it with long-term cryopreserved (LTC) tissue (>7 years).

ANIMALS STUDIED

Thirty-four healthy equine globes.

PROCEDURE

After a decontamination protocol, globes were enucleated and stored at -20°C in broad-spectrum antibiotics. Corneoscleral tissue was evaluated at different storage periods: 1 month-1 year (20 eyes) and 7-9 years (12 eyes). Two eyes were used as controls. Microbiologic study included direct (blood, McConkey, and Sabouraud agars) and enrichment (brain-heart infusion broth) cultures. Cryopreservation artifacts were evaluated by hematoxylin-eosin. Corneoscleral collagen organization and number of normal and dead keratocytes were established by transmission electron microscopy.

RESULTS

All microbiologic direct cultures were negative. Enrichment cultures were positive in 12.5% of corneal and 59.4% of scleral tissues (p_cornea  = 0.136; p_sclera  = 1.000). Cryopreservation artifacts were most commonly observed in LTC tissues (P = 0.002). Normal keratocytes were predominant in STC corneas (STC 60% and LTC 0%) and apoptotic ones in LTC (STC 40% and LTC 90%), whereas necrotic keratocytes were only seen in LTC (LTC 10%) (P = 0.001). No structural differences were detected in collagen organization between STC and LTC (p_cornea  = 1.000; p_sclera  = 0.703).

CONCLUSIONS

Cryopreservation of equine corneoscleral tissue did not yield direct bacterial contamination. Apoptosis is the main cause of death of cryopreserved equine 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 9 years without structural or microbiological impediment.