La cryopréservation de tissus composites: principe, revue de la littérature et expérience de l'équipe bordelaise

Good Manufacturing Practice-Compliant Cryopreserved and Thawed Native Adipose Tissue Ready for Fat Grafting

Background: As adipose tissue-derived mesenchymal stem cells are becoming the tool of choice for many clinical applications; standardized cryopreservation protocols are necessary to deliver high-quality samples. For this purpose, the cryopreservation and thawing of native adipose tissue under GMP conditions could represent an extremely useful and powerful tool for the direct reinfusion of the tissue, and consequently, of its stromal vascular fraction. Methods: In this study, 19 samples of adipose tissue were cryopreserved and characterized before and after storage in liquid nitrogen vapors. Of these 19 samples, 14 were processed in research and 5 in a GMP-compliant environment. Storage with and without cryopreservation medium was also evaluated. After one week to three months of storage, samples were thawed, washed, enzymatically digested, and characterized with flow cytometry. Results: The results show that there is a loss of nearly 50% of total nucleated cells during the cryopreservation/thawing process. Non-GMP and GMP samples are comparable for all parameters analyzed. This study also allowed us to exclude the cryopreservation of adipose tissue without any cryopreservation medium. Conclusions: The data shown in this work are consistent with the idea that native adipose tissue, if properly processed and controlled, could be a useful source of cells for regenerative medicine, keeping in mind that there is a clear difference in the quality between fresh and thawed samples.

Application of cryopreserved autologous skin replantation in the treatment of degloving injury of limbs

Degloving injury is a common and intractable injury with the bone and tendon exposed and contamination, the stripped skin cannot be replanted immediately and will be discarded, although auto-graft is needed for subsequent wound repair. In this study, autologous skin cryopreservation technique was applied to the treatment of severe limb degloving injuries. The clinical data of 9 patients from January 2016 to December 2018 were analyzed retrospectively. Among the 9 cases, 1 case developed necrosis due to wound infection, and the rest survived 60-100%. The replanted cryopreserved skin were soft and resilient, with poor sensory recovery, varying degrees of discoloration and no hair growth. Cryopreservation provides more time for improving the wound and whole-body condition. The frozen skin had good quality and high survival rate. Our study can effectively use the degloving skin, reduce the damage of the donor area.

The addition of albumin improves Schwann cells viability in nerve cryopreservation

The purpose of the current study was to establish a valid protocol for nerve cryopreservation, and to evaluate if the addition of albumin supposed any advantage in the procedure. We compared a traditional cryopreservation method that uses dimethyl sulfoxide (DMSO) as cryoprotectant, to an alternative method that uses DMSO and albumin. Six Wistar Lewis rats were used to obtain twelve 20 mm fragments of sciatic nerve. In the first group, six fragments were cryopreserved in 199 media with 10% DMSO, with a temperature decreasing rate of 1 °C per minute. In the second group, six fragments were cryopreserved adding 4% human albumin. The unfreezing process consisted of sequential washings with saline in the first group, and saline and 20% albumin in the second group at 37 °C until the crioprotectant was removed. Structural evaluation was performed through histological analysis and electronic microscopy. The viability was assessed with the calcein-AM (CAM) and 4',6-diamino-2-fenilindol (DAPI) staining. Histological results showed a correct preservation of peripheral nerve architecture and no significant differences were found between the two groups. However, Schwann cells viability showed in the CAM-DAPI staining was significantly superior in the albumin group. The viability of Schwann cells was significantly increased when albumin was added to the nerve cryopreservation protocol. However, no significant structural differences were found between groups. Further studies need to be performed to assess the cryopreserved nerve functionality using this new method.

Irradiation at 11 kGy conserves the biomechanical properties of fascia lata better than irradiation at 25 kGy

The objective of this study was to determine the biomechanical properties of the fascia lata and the effects of three preservation methods: freezing, cryopreservation with dimethylsulfoxide solution and lyophilization; and to compare the effects of low-dose (11 kGy) and normal-dose (25 kGy) gamma-ray sterilization versus no irradiation. 248 samples from 14 fasciae latae were collected. Freezing samples were frozen at -80 °C. Cryopreservation with dimethylsulfoxide solution samples were frozen with 10 cl dimethylsulfoxide solution at -80 °C. Lyophilization samples were frozen at -22 °C and lyophilized. Each preservation group were then randomly divided into 3 irradiation groups. The cryopreservation with dimethylsulfoxide solution samples had significantly worse results in all 3 irradiation conditions. Young's modulus was lower for the freezing samples (p < 0.001) and lyophilization samples groups (p < 0.001). Tear deformation was lower for the freezing samples (p = 0.001) and lyophilization samples groups (p = 0.003), as was stress at break (p < 0.001 and p < 0.001). Taking all preservation methods together, samples irradiated at 25 kGy had worse results than the 0 kGy and 11 kGy groups in terms of Young's modulus (p = 0.007 and p = 0.13) and of stress at break (p = 0.006 and p = 0.06). The biomechanical properties of fascia lata allografts were significantly worse under dimethylsulfoxide cryopreservation. The deleterious effects of irradiation were dose-dependent.

Microsurgical tunica albuginea transplantation in an animal model

Several andrological diseases require surgical repair or reconstruction of tunica albuginea, which envelops the corpora cavernosa penis. Despite intense research efforts involving a variety of biological materials, such as skin, muscle aponeurosis, human dura mater, tunica vaginalis, and pericardium, engineered tunica albuginea suitable for graft use is yet to be obtained. The study investigates microsurgical tunica albuginea allotransplantation in an animal model with the purpose of creation of an organ-specific tissue bank to store penile tissue, from cadaveric donors and male-to-female trans-sexual surgery, for allogeneic transplantation. Materials were tunica albuginea tissue explanted from 15 donor rats, cryopreserved at -80°C, gamma-irradiated, and implanted in 15 recipient rats, of which three rats were used as controls. Penile grafts were explanted at different time intervals; after macroscopic evaluation of the organ, the grafts were processed to morphological, histochemical, and immunohistochemical examinations by light microscopy. Detection of pro-inflammatory cytokines was also performed. Examination of the tunica albuginea allografts collected 1, 3, or 6 months after surgery and of control tunica albuginea fragments showed that tunica albuginea implants achieved biointegration with adjacent tissue at all-time points. The integration of cryopreserved rat tunica albuginea allografts, documented by our study, encourages the exploration of tunica albuginea allotransplantation in humans. In conclusion, the effectiveness and reliability of the tunica albuginea conditioning protocol described here suggest the feasibility of setting up a tunica albuginea bank as a further tissue bank.

Hand transplantation and vascularized composite tissue allografts in orthopaedics and traumatology

Composite tissue allograft (CTA) is defined as heterologous transplantation of a complex comprising skin and subcutaneous, neurovascular and mesenchymal tissue. Such techniques allow complex reconstruction using matched tissue, without donor site morbidity. The potential indications in orthopaedics-traumatology could in the future be more frequent than the present indications of heart, lung, liver, kidney and pancreas transplantation. International clinical experience clearly demonstrates the feasibility of CTA, both surgically and immunologically. However, immunosuppression remains indispensable, exposing the patient to risks that are not acceptable for purely functional surgery, except in very particular indications. The main hope for the future lies in induction of graft-specific tolerance.

Animal models of tracheal allotransplantation using vitrified cryopreservation

OBJECTIVE

Tracheal reconstruction continues to pose a significant challenge in thoracic surgery. The study objective was to develop a novel method to eliminate the antigenicity of tracheal allografts by using vitrified cryopreservation and present the experimental results after cervical tracheal replacement in rabbits.

METHODS

Fifteen New Zealand rabbits, irrespective of gender, weighing 2.5 to 3.0 kg, were randomly divided into 3 groups: (A), the experimental group (n = 5), tracheal allotransplantation after 4 weeks of vitrified cryopreservation; (B), the negative control group (n = 5), fresh tracheal autotransplantation; and (C), the positive control group (n = 5), fresh tracheal segments implanted as allografts. The patency of implanted grafts, lymphocytic infiltrate, cartilage scores, and ink perfusion to evaluate revascularization were used to investigate the impact of vitrified cryopreservation on the antigenicity of tracheal grafts and vascular regeneration.

RESULTS

Rabbits in groups A and B all had uneventful postoperative courses with patent lumens and structural integrity, with obvious vascular regeneration and less lymphocytic infiltrate. Although in excellent condition, animals were sacrificed after a short-term follow-up of 4 weeks for further examination as scheduled. In group C, massive lymphocytic infiltrate and inflammatory cells without noticeable revascularization were observed, and rabbits died within 2 weeks after surgery for airway stenosis or severe obstruction.

CONCLUSION

The antigenicity of tracheal allografts was significantly decreased by using the vitrified cryopreservation method, which would be a novel alternative method to store donor trachea to make tracheal banking possible.