Antioxidant additives reduce reactive oxygen species production in articular cartilage during exposure to cryoprotective agents

Chondrocyte Viability of Particulated Porcine Articular Cartilage Is Maintained in Tissue Storage After Cryoprotectant Exposure, Vitrification, and Tissue Warming

OBJECTIVE

Vitrification of articular cartilage (AC) is a promising technique which may enable long-term tissue banking of AC allografts. We previously developed a 2-step, dual-temperature, multi-cryoprotectant agent (CPA) loading protocol to cryopreserve particulated AC (1 mm3 cubes). Furthermore, we also determined that the inclusion of ascorbic acid (AA) effectively mitigates CPA toxicity in cryopreserved AC. Prior to clinical translation, chondrocytes must remain viable after tissue re-warming and before transplantation. However, the effects of short-term hypothermic storage of particulated AC after vitrification and re-warming are not documented. This study evaluated the chondrocyte viability of post-vitrified particulated AC during a 7-day tissue storage period at 4 °C. We hypothesized that porcine particulated AC could be stored for up to 7 days after successful vitrification without significant loss of cell viability, and these results would be enhanced when cartilage is incubated in storage medium supplemented with clinical grade AA.

DESIGN

Three experimental groups were examined at 5 time points: a fresh control (only incubated in medium), a vitrified - AA group, and a vitrified + AA group (N = 7).

RESULTS

There was a mild decline in cell viability but both treatment groups maintained a viability of greater than 80% viable cells which is acceptable for clinical translation.

CONCLUSION

We determined that particulated AC can be stored for up to 7 days after successful vitrification without a clinically significant decline in chondrocyte viability. This information can be used to guide tissue banks regarding the implementation of AC vitrification to increase cartilage allograft availability.

CPA toxicity screening of cryoprotective solutions in rat hearts

In clinical practice, donor hearts are transported on ice prior to transplant and discarded if cold ischemia time exceeds ∼5 h. Methods to extend these preservation times are critically needed, and ideally, this storage time would extend indefinitely, enabling improved donor-to-patient matching, organ utilization, and immune tolerance induction protocols. Previously, we demonstrated successful vitrification and rewarming of whole rat hearts without ice formation by perfusion-loading a cryoprotective agent (CPA) solution prior to vitrification. However, these hearts did not recover any beating even in controls with CPA loading/unloading alone, which points to the chemical toxicity of the cryoprotective solution (VS55 in Euro-Collins carrier solution) as the likely culprit. To address this, we compared the toxicity of another established CPA cocktail (VEG) to VS55 using ex situ rat heart perfusion. The CPA exposure time was 150 min, and the normothermic assessment time was 60 min. Using Celsior as the carrier, we observed partial recovery of function (atria-only beating) for both VS55 and VEG. Upon further analysis, we found that the VEG CPA cocktail resulted in 50 % lower LDH release than VS55 (N = 4, p = 0.017), suggesting VEG has lower toxicity than VS55. Celsior was a better carrier solution than alternatives such as UW, as CPA + Celsior-treated hearts spent less time in cardiac arrest (N = 4, p = 0.029). While we showed substantial improvement in cardiac function after exposure to vitrifiable concentrations of CPA by improving both the CPA and carrier solution formulation, further improvements will be required before we achieve healthy cryopreserved organs for transplant.

The effect of sucrose supplementation on chondrocyte viability in porcine articular cartilage following vitrification

Vitrification can extend the banking life of articular cartilage (AC) and improve osteochondral transplantation success. Current vitrification protocols require optimization to enable them to be implemented in clinical practice. Sucrose as a non-permeating cryoprotective agent (CPA) and clinical grade chondroitin sulfate (CS) and ascorbic acid (AA) as antioxidants were investigated for their ability to improve a current vitrification protocol for AC. The aim of this study was to assess the impact of sucrose and CS/AA supplementation on post-warming chondrocyte viability in vitrified AC. Porcine osteochondral dowels were randomly vitrified and warmed with one established protocol (Protocol 1) and seven modified protocols (Protocols 2-8) followed by chondrocyte viability assessment. Sucrose supplementation in both vitrification and warming media (Protocol 4) resulted in significantly higher (p = 0.018) post-warming chondrocyte viability compared to the protocol without sucrose (Protocol 1). There was no significant difference (p = 0.298) in terms of post-warming chondrocyte viability between sucrose-supplemented DMEM + CS solution (Protocol 4) and Unisol-CV (UCV) + CS (Protocol 6) solution. Clinical grade CS and AA contributed to similar post-warming chondrocyte viability to previous studies using research grade CS and AA, indicating their suitability for clinical use. The addition of an initial step (step 0) to reduce the initial concentration of CPAs to minimize osmotic effects did not enhance chondrocyte viability in the superficial layer of AC. In conclusion, sucrose-supplemented DMEM + clinical grade CS (Protocol 4) could be an ideal protocol to be investigated for future use in clinical applications involving vitrified AC.

Catalytic anti-oxidative stress for osteoarthritis treatment by few-layered phosphorene

As one of the most common representations of articular cartilage damage, osteoarthritis (OA) is characterized by the apoptosis and dysfunction of chondrocytes as well as the progressive degradation of extracellular matrix, of which the main components are glycosaminoglycan and type Ⅱ collagen. Few-layered phosphorene (FLP) has been attracting great attentions in biomedical fields owing to the excellent capability of in-situ catalysis for scavenging oxidate-associated molecules, especially the reactive oxygen species (ROS) and reactive nitrogen species (RNS). Herein, FLP has been fabricated and employed for articular cartilage protection by means of deleting oxidate-associated molecules. The in vitro results show that as low as 200 ​μg/mL FLP is capable of diminishing oxidative damages on the osteoarthritic chondrocytes through the efficient elimination of ROS, H₂O₂ and NO. Meanwhile, the cartilage matrix protection has also been achieved at 200 ​μg/mL FLP by the uniform restoration of glycosaminoglycan and type Ⅱ collagen. FLP enables the nanocatalytic treatment for the overloaded oxidative stress in the injured articular cartilage and represents a promising alternative for osteoarthritis therapy.

Effectiveness of Clinical-Grade Chondroitin Sulfate and Ascorbic Acid in Mitigating Cryoprotectant Toxicity in Porcine Articular Cartilage

High concentrations of cryoprotective agents (CPAs) are required to achieve successful vitrification of articular cartilage; however, CPA cytotoxicity causes chondrocyte death. To reduce CPA toxicity, supplementation with research-grade additives, in particular chondroitin sulfate (CS) and ascorbic acid (AA), have previously been shown to improve chondrocyte recovery and metabolic function after exposure to CPAs at hypothermic conditions. However, it is necessary to evaluate the pharmaceutical equivalent clinical grade of these additives to facilitate the supplementation of additives into future vitrification protocols, which will be designed for vitrifying human articular cartilage in tissue banks. We sought to investigate the effectiveness of clinical-grade CS, AA, and N-acetylcysteine (NAC) in mitigating toxicity to chondrocytes during CPA exposure and removal, and determine whether a combination of two additives would further improve chondrocyte viability. We hypothesized that clinical-grade additives would exert chondroprotective effects comparable to those of research-grade additives, and that this protective effect would be enhanced if two additives were combined when compared with a single additive. The results indicated that both clinical-grade and research-grade additives significantly improved cell viability (p < 0.10) compared with the negative control (CPA with no additives). CS, AA, and NAC+AA increased cell viability significantly (p < 0.10) compared with the negative control. However, NAC, NAC+CS, and CS+AA did not improve cell viability when compared with the negative control (p > 0.10). We demonstrated that supplementation with clinical-grade CS or AA significantly improved chondrocyte viability in porcine cartilage subjected to high CPA concentrations, whereas supplementation with clinical-grade NAC did not benefit chondrocyte viability. Supplementation with clinical-grade additives in CPA solutions can mitigate CPA toxicity, which will be important in translating previously developed effective protocols for the vitrification of articular cartilage to human tissue banks.

Natural Cryoprotective and Cytoprotective Agents in Cryopreservation: A Focus on Melatonin

Cryoprotective and cytoprotective agents (Cytoprotective Agents) are fundamental components of the cryopreservation process. This review presents the essentials of the cryopreservation process by examining its drawbacks and the role of cytoprotective agents in protecting cell physiology. Natural cryoprotective and cytoprotective agents, such as antifreeze proteins, sugars and natural deep eutectic systems, have been compared with synthetic ones, addressing their mechanisms of action and efficacy of protection. The final part of this article focuses melatonin, a hormonal substance with antioxidant properties, and its emerging role as a cytoprotective agent for somatic cells and gametes, including ovarian tissue, spermatozoa and spermatogonial stem cells.

The effect of cryoprotectant vehicle solution on cartilage cell viability following vitrification

Osteochondral allografts are often used to repair large articular cartilage defects to prevent or delay the onset of osteoarthritis. This approach is limited by the timely acquisition and use of allograft tissue since standard hypothermic protocols allow for a maximum storage of 4 weeks. Vitrification is a proven technique for the long-term preservation of cells and tissues, but requires careful determination of parameters to be successful, particularly for articular cartilage. One parameter that is infrequently considered is the choice of cryoprotectant vehicle solution. The aim of this study was to evaluate the impact of a subset of vehicle solutions on an established vitrification protocol for articular cartilage. These solutions were phosphate-buffered saline (PBS), Dulbecco's Modified Eagle's Medium: Nutrient Mixture F-12 (DMEM), X-VIVO, and Unisol-CV (UCV). Both the solution pH at various points throughout vitrification and the cell viability of porcine articular cartilage slices following vitrification were measured. Using randomized block ANOVA, it was found that the normalized cell viability of articular cartilage vitrified in UCV was significantly greater than that of PBS (p < 0.05) and may be greater than those of DMEM and X-VIVO (p < 0.1). There was no correlation between pH parameters and cell viability, although significant differences between calculated pH parameters were identified. These results provide information to guide the design of effective vitrification protocols for articular cartilage.

Vitrification of Intact Porcine Femoral Condyle Allografts Using an Optimized Approach

OBJECTIVE

Successful preservation of articular cartilage will increase the availability of osteochondral allografts to treat articular cartilage defects. We compared the effects of 2 methods for storing cartilage tissues using 10-mm diameter osteochondral dowels or femoral condyles at -196°C: (a) storage with a surrounding vitrification solution versus (b) storage without a surrounding vitrification solution. We investigated the effects of 2 additives (chondroitin sulfate and ascorbic acid) for vitrification of articular cartilage.

DESIGN

Healthy porcine stifle joints (n = 11) from sexually mature pigs were collected from a slaughterhouse within 6 hours after slaughtering. Dimethyl sulfoxide, ethylene glycol, and propylene glycol were permeated into porcine articular cartilage using an optimized 7-hour 3-step cryoprotectant permeation protocol. Chondrocyte viability was assessed by a cell membrane integrity stain and chondrocyte metabolic function was assessed by alamarBlue assay. Femoral condyles after vitrification were assessed by gross morphology for cartilage fractures.

RESULTS

There were no differences in the chondrocyte viability (~70%) of 10-mm osteochondral dowels after vitrification with or without the surrounding vitrification solution. Chondrocyte viability in porcine femoral condyles was significantly higher after vitrification without the surrounding vitrification solution (~70%) compared to those with the surrounding vitrification solution (8% to 36%). Moreover, articular cartilage fractures were not seen in femoral condyles vitrified without surrounding vitrification solution compared to fractures seen in condyles with surrounding vitrification solution.

CONCLUSIONS

Vitrification of femoral condyle allografts can be achieved by our optimized approach. Removing the surrounding vitrification solution is advantageous for vitrification outcomes of large size osteochondral allografts.