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Kangaroo tendons could rebuild human knees better, stronger
Reconstructing knees with kangaroo tissue is one step, or hop, closer to being a reality, with human trials set to get under way in 2024.
“I’ve always said that kangaroos are nature’s greatest athletes,” says orthopedic surgeon Dr Nick Hartnell one of the authors of the study. “They really are the most impressive animals – they can jump lengths of up to 12 meters (39 ft), clear a three-meter (10-ft) fence and hop at 70 km/h (43 mph).
"Watching them in action, I started to wonder how much of this athletic ability was related to the way their tendons were formed, and whether they might be used to replace ruptured human ligaments,” he said.
Following years of research, Hartnell and his team are progressing towards a human xenograft trial to repair injuries such as a ruptured anterior cruciate ligament (ACL).
A xenograft, in which an organ or other tissue is transplanted from another species, is already a feature of surgeries such as replacing heart valves with those from donor pigs. However, biological compatibility is a huge barrier. The team believes it's also cracked the code on how to ensure the ‘foreign’ kangaroo tissue would not be rejected by the human recipient.
"Xenografts – using tendons from other species – have the potential to be a better option, but so far medicine has struggled both to find a suitable donor species that has strong, durable tendons that will not be rejected,” Dr Hartnell said.
While the Australian marsupial may not provide someone with superhuman jumping abilities, it does present a promising alternative to current treatment.
In the US, around 200,000 ACL ruptures occur each year, and up to a quarter of those require additional surgeries. The nature of the injury means additional tissue needs to be grafted at the injury site. Grafts taken from elsewhere on the patient’s body often increase pain and recovery time, and both those from deceased donors and synthetic sources present surgeons with other issues.
"There is a very limited supply of these cadaveric tendons available, and unfortunately the strength tends not to be as good as we would like, leaving the patient with a weaker knee,” Dr Hartnell said.
“In addition to this, up to a quarter of all ACL reconstructions fail,” he added. “If that happens, or the person has damaged two ligaments at once, or they are injured a second time, they are running out of options.”
The kangaroo tendon not only has the potential to be the best option, but could be sourced from elsewhere (culling, food production), where this part of the animal is used for pet food, if anything at all.
All of the research has been conducted on kangaroo tendons acquired from other industries, so has not involved any live animals.
"They are biologically superior as far as tendons are concerned, and currently all of that potential is just being wasted because the tendons aren't being used for anything,” Dr Hartnell added.
The team hopes a successful human trial will pave the way for the kangaroo tendons to be used in procedures worldwide.
注释：
tendon: n
表示" 腱"，means "a cord or band of inelastic tissue connecting a muscle with its bony attachment"，如：A tendon consists of parallel fibres. 腱由平行的纤维组成。
orthopedic: adj
表示" 整形外科的"，means "of or relating to orthopedics"，如：Patients recovering from broken limbs are housed in the hospital's orthopedic ward. 病人们住在医院整形外科的病房以恢复他们残损的肢体。
rupture: v
表示"（使）破裂"，means " burst or break open so that sth comes out of its closed container"，如：He'll rupture a muscle if he goes on dancing like that! 他要是继续那样跳舞，会跳得皮开肉裂！
ligament: n
表示" 韧带；连接物"，means "a sheet or band of tough fibrous tissue connecting bones or cartilages or supporting muscles or organs"，如：I had a deep bone bruise and damaged ligaments. 我的骨头重重地挫伤，导致韧带受伤。
xenograft：n
表示" [医]异种移植物"，means "tissue from an animal of one species used as a temporary graft (as in cases of severe burns) on an individual of another species"，如：Thus xenograft， or xenotra lantation is a sort of holy grail for tra lantation， since animals would provide an endle su ly of orga for tra lantation. 既然动物可以为移植提供无尽的来源，异种移植一直是人们梦寐以求的事。
anterior cruciate ligament: n
表示"前十字韧带"，如：The anterior cruciate ligament (ACL) is a strong band of tissue that is located within the knee and connects the thighbone (femur) to the shinbone (tibia). 前交叉韧带（ACL）是一结实的组织，它位于膝关节内，连接大腿骨（股骨）和小腿骨（胫骨）。
marsupial: n
表示" 有袋动物"，means "mammals of which the females have a pouch (the marsupium) containing the teats where the young are fed and carried"，如：The koala, which is a marsupial, is like a kangaroo. 树熊，就像袋鼠一样是有袋科动物。
graft: v
表示" 嫁接；移植"，means " attach sth as a graft"，如：New skin had to be grafted on. 需要移植新皮肤。
cadaveric: adj
表示" 尸体的"，means "of or relating to a cadaver or corpse"，如：Study Design. An in vitro human cadaveric biomechanical study. 研究设计:一个体外人尸体生物学机制研究。
中文简要说明：
人类不断追求医学突破，过程中经常仰赖动物作为重要的智库，美国在2022年完成首例猪心移植人体的手术，虽然该名患者在2个月后死亡，却为异种移植（xenotransplantation）写下新的里程碑；澳洲医学界最近则研究以袋鼠的肌腱作为人类韧带的替代品，初步成果已发表在《美国运动医学》期刊（The American Journal of Sports Medicine），预计2024年就会进行人体试验。
根据外媒「New Atlas」报导，前十字韧带是稳定膝关节的主要构造，根据统计，美国每年有多达20万人发生前十字韧带断裂，其中1/4患者情况严重，需要接受移植手术。目前医学上多利用病患自身的组织进行重建，但这么做不仅增加病患痛苦，术后复原的时间也长，而使用往生者的组织或合成纤维，又会面临取得不易或强度不足等等问题，澳洲医学界于是将目光瞄准当地指标性动物——袋鼠。
参与这项研究的整形外科医师哈特奈尔（Nick Hartnell）说：「我总说袋鼠是自然界最出色的运动员，它们可以跳到12公尺远，轻松跨过近3公尺高的栅栏，时速可达70公里。」袋鼠优越的运动能力，使它们成为修复人类韧带的首选。
利用袋鼠的组织作为移植来源，虽然无法为人类带来超人般的跳跃能力，却是目前极为看好的替代治疗方式。根据澳洲袋鼠产业协会（Kangaroo Industries Association of Australia）2023年估计，澳洲袋鼠的数量可能已经达到6千万只，政府虽然保护袋鼠，但也允许少量商业猎捕，医学实验所需的袋鼠肌腱便是从这里取得。
哈特奈尔说：「从生物学来看，袋鼠的肌腱构造非常优秀，但目前它们都被浪费掉，没有发挥任何用途。」研究小组深信，他们已经解决移植袋鼠肌腱可能造成的免疫排斥问题，希望能在明年进入临床试验阶段，以便未来造福更多需要的病人。
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