Replantation of Cryopreserved Fingers: An “Organ Banking” Breakthrough

Long-Term Survival and Functional Recovery of Cryopreserved Vascularized Groin Flap and Below-the-Knee Rat Limb Transplants

Effective cryopreservation of large tissues, limbs, and organs has the potential to revolutionize medical post-trauma reconstruction options and organ preservation and transplantation procedures. To date, vitrification and directional freezing are the only viable methods for long-term organ or tissue preservation, but are of limited clinical relevance. This work aimed to develop a vitrification-based approach that will enable the long-term survival and functional recovery of large tissues and limbs following transplantation. The presented novel two-stage cooling process involves rapid specimen cooling to subzero temperatures, followed by gradual cooling to the vitrification solution (VS) and tissue glass transition temperature. Flap cooling and storage were only feasible at temperatures equal to or slightly lower than the VS Tg (i.e., -135°C). Vascularized rat groin flaps and below-the-knee (BTK) hind limb transplants cryopreserved using this approach exhibited long-term survival (>30 days) following transplantation to rats. BTK-limb recovery included hair regrowth, normal peripheral blood flow, and normal skin, fat, and muscle histology. Above all, BTK limbs were reinnervated, enabling rats to sense pain in the cryopreserved limb. These findings provide a strong foundation for the development of a long-term large-tissue, limb and organ preservation protocol for clinical use.

Cryopreservation of tissues and organs: present, bottlenecks, and future

Tissue and organ transplantation continues to be an effective measure for saving the lives of certain critically ill patients. The organ preservation methods that are commonly utilized in clinical practice are presently only capable of achieving short-term storage, which is insufficient for meeting the demand for organ transplantation. Ultra-low temperature storage techniques have garnered significant attention due to their capacity for achieving long-term, high-quality preservation of tissues and organs. However, the experience of cryopreserving cells cannot be readily extrapolated to the cryopreservation of complex tissues and organs, and the latter still confronts numerous challenges in its clinical application. This article summarizes the current research progress in the cryogenic preservation of tissues and organs, discusses the limitations of existing studies and the main obstacles facing the cryopreservation of complex tissues and organs, and finally introduces potential directions for future research efforts.

Improving the ischemia-reperfusion injury in vascularized composite allotransplantation: Clinical experience and experimental implications

Long-time ischemia worsening transplant outcomes in vascularized composite allotransplantation (VCA) is often neglected. Ischemia-reperfusion injury (IRI) is an inevitable event that follows reperfusion after a period of cold static storage. The pathophysiological mechanism activates local inflammation, which is a barrier to allograft long-term immune tolerance. The previous publications have not clearly described the relationship between the tissue damage and ischemia time, nor the rejection grade. In this review, we found that the rejection episodes and rejection grade are usually related to the ischemia time, both in clinical and experimental aspects. Moreover, we summarized the potential therapeutic measures to mitigate the ischemia-reperfusion injury. Compare to static preservation, machine perfusion is a promising method that can keep VCA tissue viability and extend preservation time, which is especially beneficial for the expansion of the donor pool and better MHC-matching.

A cryopreservation method for bioengineered 3D cell culture models

Technologies to cryogenically preserve (a.k.a. cryopreserve) living tissue, cell lines and primary cells have matured greatly for both clinicians and researchers since their first demonstration in the 1950s and are widely used in storage and transport applications. Currently, however, there remains an absence of viable cryopreservation and thawing methods for bioengineered, three-dimensional (3D) cell models, including patients' samples. As a first step towards addressing this gap, we demonstrate a viable protocol for spheroid cryopreservation and survival based on a 3D carboxymethyl cellulose scaffold and precise conditions for freezing and thawing. The protocol is tested using hepatocytes, for which the scaffold provides both the 3D structure for cells to self-arrange into spheroids and to support cells during freezing for optimal post-thaw viability. Cell viability after thawing is improved compared to conventional pellet models where cells settle under gravity to form a pseudo-tissue before freezing. The technique may advance cryobiology and other applications that demand high-integrity transport of pre-assembled 3D models (from cell lines and in future cells from patients) between facilities, for example between medical practice, research and testing facilities.

Application of Cryopreservation Technique in the Preservation of Rat Limbs

OBJECTIVE

The aim of this study was to observe the physiologic and pathologic changes of severed fingers (limbs) under different storage conditions through animal experiments, and to screen out the best preservation conditions.

METHODS

Sixty healthy adult male Sprague-Dawley rats were selected and evenly divided into 4 preservation groups, including conventional low-temperature dry (CLTD), the University of Wisconsin (UW) solution, cryopreservation, and cryopreservation + UW solution preservation group. After harvesting the limbs, were preservated for 72 hours and 7 days, respectively. Then the limbs were thawed and replanted in situ. Sciatic nerves were collected for hematoxylin & eosin (H&E) staining and observed the changes in tissue morphology.

RESULTS

Replantation was successful in 11 of 15 rats (73%) in the cryopreservation + UW group, and the walking function of the 9 (82%) rats in cryopreservation + UW group were significantly better than that of the cryopreservation preservation group. Additionally, the H&E staining results shown that the CLTD group nerve bundles were morphologically damaged, and there were more acellular structures and tissue fragments; the UW group nerve bundles were less injured and the perineurium was more complete and more orderly. The nerve bundles in the cryopreservation group and the cryopreservation + UW group are tightly arranged, and the tissue morphology is regular. Compared with the cryopreservation + UW group, the completeness of the cryopreservation group was not sufficient.

CONCLUSIONS

The cryopreservation technology combined with the UW solution is a new and effective method for preservation of severed limbs.

Clinical guideline for vascularized composite tissue cryopreservation

At the Summit on Organ Banking through Converging Technologies held recently in Boston, tissue and organ cryopreservation technology was a topic of considerable interest. Although cryopreservation has been widely used in clinical practice, it currently remains limited to bloodless tissues with simple structures and functions that are small or thin, for example, ultra-thin skin, ovarian tissue slices, and other similar tissues. For whole organs, except for successful cryopreservation of rat ovaries (2002) and hind limbs (August 2002), successful cryopreservation of vascularized animal tissues or organs and their replantation have not yet been reported. We conducted histological and electron microscopic examinations on muscle after blood supply restoration to explain this problem and describe our experience with the goal of informing our colleagues to further develop the technology. To achieve broad application of vascularized tissue and organ cryopreservation, we have summarized our experience and established a clinical application scope for vascularized composite tissue cryopreservation.

Unique Techniques or Approaches in Microvascular and Microlymphatic Surgery

Several methods can be used for identifying tissues for transfer in donor-site-depleted patients. A fillet flap can be temporarily stored in other parts of the body and transferred back to the site of tissue defect, including covering the amputated stump of the lower extremity. Human arm transplant is rare and has some unique concerns for the surgery and postsurgical treatment. Cosmetics of the narrow neck of transferred second toes can be improved with insertion of a flap. Lymphedema of the breast after cancer treatment can be diagnosed with several currently available imaging techniques and treated surgically with lymphaticovenous anastomosis.

A Global View of Digital Replantation and Revascularization

Survival rates of digital replantation vary in different regions and countries, and Asian surgeons see more challenging cases and have developed some unique methods. Replantation of multiple digits in one or both hands can follow a structure-by-structure method or a digit-by-digit method. For replanting all 10 digits, 3 or 4 teams should be organized. Flow-through flaps, often venous flaps, can be taken from the distal forearm or lower extremity to repair defects of soft tissues and arteries. A pedicled digital artery flap from the adjacent digit can also repair tissue defects and supply blood to the replanted digit.

Microsurgical Tissue Transfer in Complex Upper Extremity Trauma

Microsurgical tissue transfer may provide reconstructive option for extensive loss of tissues due to upper extremity trauma or tumor resection. This article reviews the authors' experience in using microsurgical tissue transfers for reconstruction of upper extremity trauma.

Major Changes in Lymphatic Microsurgery and Microvascular Surgery in Past 20 Years

This article summarizes the major changes seen in lymphatic microsurgery and microvascular surgery in first 20 years of the 21st century. Lymphatic microsurgery is discussed first, as more advances have been seen in imaging of the lymphatic system, lymphatico-venous anastomosis, and vascularized lymph node transfers. During the past 2 decades, there have been more patient population changes than major technical evolutions in microvascular surgery, although new techniques and modifications emerged and became clinical routines, with the landscape of microvascular surgery evolving in this time period.

Emergency Hand and Reconstructive Microsurgery in the COVID-19-Positive Patient

The case spectrum in hand surgery is one of extremes-purely elective day surgery cases under local anesthesia to mangling limb injuries that require immediate, and frequently, lengthy, surgery. Despite the cancellation of most elective orthopedic and plastic surgical procedures, hand surgeons around the world continue to see a steady stream of limb-threatening cases such as severe trauma and infections that require emergent surgical care. With the increase in community-spread, an increasing number of COVID-19-infected patients may be asymptomatic or have mild, nonspecific or atypical symptoms. Some of them may already have an ongoing, severe infection. The time-sensitive nature of some of these cases means that hand surgeons may need to operate urgently on patients who may be suspected of COVID-19 infections, often before confirmatory test results are available. General guidelines for perioperative care of the COVID-19-positive patient have been published. However, our practices differ from those of general orthopedic and plastic surgery, primarily because of the focus on trauma. This article discusses the perioperative and technical considerations that are essential to manage the COVID-19 patient requiring emergency care, without compromising clinical outcomes and while ensuring the safety of the attending staff.

Composite Tissue Preservation

Composite tissue (CT) preservation is important to outcomes after replant or transplant. Since the first limb replant, the mainstay of preservation has been static cold storage with the amputated part being placed in moistened gauze over ice. Historically, the gold-standard in solid organ preservation has been static cold storage with specialized solution, but this has recently evolved in the last few decades to develop technologies such as machine perfusion and even persufflation. This review explores the impact of cooling and oxygenation on CT, summarizes the work done in the area of CT preservation, discusses lessons learned from our experience in solid organ preservation, and proposes future directions.