“Vitrification and Nanowarming Enable Long-Term Organ Cryopreservation and Life-Sustaining Kidney Transplantation in a Rat Model”, Zonghu Han, Joseph Sushil Rao, Lakshya Gangwar, Bat-Erdene Namsrai, Jacqueline L. Pasek-Allen, Michael L. Etheridge, Susan M. Wolf, Timothy L. Pruett, John C. Bischof, Erik B. Finger2023-06-09 ()⁠:

[previous rabbit kidney 1984] Banking cryopreserved organs could transform transplantation into a planned procedure that more equitably reaches patients regardless of geographical and time constraints. Previous organ cryopreservation attempts have failed primarily due to ice formation, but a promising alternative is vitrification, or the rapid cooling of organs to a stable, ice-free, glass-like state. However, rewarming of vitrified organs can similarly fail due to ice crystallization if rewarming is too slow or cracking from thermal stress if rewarming is not uniform.

Here we use nanowarming, which employs alternating magnetic fields to heat nanoparticles within the organ vasculature, to achieve both rapid and uniform warming, after which the nanoparticles are removed by perfusion.

We show that vitrified kidneys can be cryogenically stored (up to 100 days) and successfully recovered by nanowarming to allow transplantation and restore life-sustaining full renal function in nephrectomized recipients in a male Rattus norvegicus model.

Scaling this technology may one day enable organ banking for improved transplantation.

Figure 6: Representative appearance of fresh control kidney before cannulation and recovery (<em>n</em> = 5), 60-h cold-stored kidney at the time of intraoperative transplant organ failure (<em>n</em> = 1), fresh control kidney transplants at day 30 post transplant (<em>n</em> = 5), nanowarmed kidney transplants at day 30 post transplant (<em>n</em> = 5). (a) Gross images in situ. (b) Bisected kidneys following explant. (c) Histology of renal cortex (H&E). (d) Histology of renal medulla (H&E). Scale bars are 100µm. H&E hematoxylin and eosin.
Figure 6: Representative appearance of fresh control kidney before cannulation and recovery (n = 5), 60-h cold-stored kidney at the time of intraoperative transplant organ failure (n = 1), fresh control kidney transplants at day 30 post transplant (n = 5), nanowarmed kidney transplants at day 30 post transplant (n = 5). (a) Gross images in situ. (b) Bisected kidneys following explant. (c) Histology of renal cortex (H&E). (d) Histology of renal medulla (H&E). Scale bars are 100µm. H&E hematoxylin and eosin.

…Postoperatively, all fresh control and nanowarmed kidney transplants continued to produce urine, and all animals survived for the full 30-day study period. In syngeneic (Lewis to Lewis) nanowarmed kidney recipients, serum creatinine levels (a principal measure of renal function) were higher on postop day 1 than in the control transplants (Figure 7b). Creatinine in the nanowarmed kidney recipients continued to rise, peaking between days 2–3, and then gradually declined to reach control levels over 2–3 weeks. From day 14 onward, the creatinine in nanowarmed recipients was not statistically-significantly different from that in control kidney recipients. The creatinine fell below 2.0mg/dL by day 19 and into the normal range for healthy rats on day 23, remaining 0.4–0.8mg/dL until the end of follow-up.

During the first two postoperative weeks, nanowarmed kidney recipients also experienced more metabolic dysfunction than control transplants. Hyperkalemia peaked on days 2–3 and slowly declined after that (Figure 7c). Partially compensated metabolic acidosis (low pH, low HCO3-, and low pCO2) was also resolved by day 15 (Figure 7d–f). Serum lactate levels were slightly above the normal range but normalized by days 7–10 (Figure 7g).

Following transplant, both control and nanowarmed kidney recipients increased body weight. Initially, nanowarmed organ recipients experienced greater weight gain, presumably due to hypervolemia. This ~10% excess weight gain resolved by days 10–12, after which body mass increased in parallel to control transplants (Figure 7i). After an initial drop in hemoglobin in both groups due to surgical blood loss, hemoglobin rose steadily in the postop period, suggesting intact renal erythropoietin production and/or potentially hemoconcentration (Figure 7h).

At the end of the planned post-transplant follow-up (postop day 30), animals were sacrificed for serum and urine analyses and histology. Both serum and urine laboratory parameters demonstrated statistically similar, and essentially normal, kidney function in both groups (Tables 1 & 2)…As such, we can speculate that nanowarmed kidneys will have long-term outcomes similar to those seen in standard deceased donor transplantation.

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