Preclinical Animal Models in Facial Transplantation

Computed tomographic characteristics of anatomical variations of external and internal jugular veins in dogs

The external jugular vein (EJV) has been commonly used for clinical procedures in veterinary medicine, while the internal jugular vein (IJV) has been used mainly for research. Limited literature regarding anatomical variants in both EJV and IJV is available. The objectives of this descriptive retrospective study were to identify the number of dogs with variations of the jugular veins in canine patients undergoing CT of the head and neck and characterize these variations. Of 1000 dogs, 193 dogs (19.3%) had anatomical variations. Six types of anatomical variations were identified. The most common Type I was the absence of the linguofacial vein (72.0%, n = 139), with the lingual, facial, and maxillary veins entering the EJV at a common branching point. Type II described a variable course of the EJV and IJV, which in some dogs resulted in the absence of the EJV (14.0%, n = 27). Type III was a variable anastomotic loop formed by the linguofacial or maxillary vein cranial or at the junction of the EJV (4.2%, n = 8). In Type IV, the EJV was either suspected to be aplastic or markedly reduced in diameter compared with the contralateral side just distal to its formation (3.6%, n = 7). Type V was found in only six dogs (3.1%) with unilateral differences in the diameter of the IJV. Six of 193 dogs had a combination of more than one variation (Type VI, 3.1%). Type I was significantly observed more frequently in meso- and dolichocephalic breeds. Type II was significantly observed more frequently in brachycephalic breeds.

A systematic review of immunomodulatory strategies used in skin-containing preclinical vascularized composite allotransplant models

BACKGROUND

Acute rejection remains a vexing problem in vascularized composite allotransplantation (VCA). Available immunosuppressive regimens are successful at minimizing alloimmune response and allowing VCA in humans. However, repeated rejection episodes are common, and systemic side effects of the current standard regimen (Tacrolimus, MMF, Prednisone) are dose limiting. Novel immunomodulatory approaches to improve allograft acceptance and minimize systemic toxicity are continuously explored in preclinical models. We aimed to systematically summarize past and current approaches to help guide future research in this complex field.

METHODS

We conducted a systematic review of manuscripts listed in the MEDLINE and PubMed databases. For inclusion, articles had to primarily investigate the effect of a therapeutic approach on prolonging the survival of a skin-containing preclinical VCA model. Non-VCA studies, human trials, anatomical and feasibility studies, and articles written in a language other than English were excluded. We followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.

RESULTS

The search retrieved 980 articles of which 112 articles were ultimately included. The majority of investigations used a rat model. An orthotopic hind limb VCA model was used in 53% of the studies. Cell and drug-based approaches were investigated 58 and 52 times, respectively. We provide a comprehensive review of immunomodulatory strategies used in VCA preclinical research over a timeframe of 44 years.

CONCLUSION

We identify a transition from anatomically non-specific to anatomical models mimicking clinical needs. As limb transplants have been most frequently performed, preclinical research focused on using the hind limb model. We also identify a transition from drug-based suppression therapies to cell-based immunomodulation strategies.

Preservation solutions for attenuation of ischemia-reperfusion injury in vascularized composite allotransplantation

Vascularized composite allotransplantation represents the final level of the reconstructive ladder, offering treatment options for severe tissue loss and functional deficiencies. Vascularized composite allotransplantation is particularly susceptible to ischemia–reperfusion injury and requires preservation techniques when subjected to extended storage times prior to transplantation. While static cold storage functions to reduce ischemic damage and is widely employed in clinical settings, there exists no consensus on the ideal preservation solution for vascularized composite allotransplantation. This review aims to highlight current clinical and experimental advances in preservation solution development and their critical role in attenuating ischemia–reperfusion injury in the context of vascularized composite allotransplantation.