丁香園 - 醫(yī)學交流社區(qū)，分享臨床經驗、病例討論、考試科研、求職晉升經驗
Xenogeneic bone grafting materials
異種骨移植材料
Author: Dr Mike Barbeck, Dr Ronald Unger, Prof. Dr Frank Witte, Prof. Dr Sabine Wenisch & Prof. Dr Dr Reiner Schnettler, Germany
翻譯者：西瓜柚子?
Nowadays, a variety of bone substitutes are available for the clinical user. Interestingly, these materials significantly differ regarding their raw materials or manufacturing processes. As an alternative to autologous bone tissue (autograft), which is still applied as “gold standard” due to its extensive regenerative properties, bone substitutes from other natural sources become more and more relevant in regenerative dentistry. These bone substitute materials are either derived from human (allograft) or animal origin (xenograft).
如今，臨床用戶可以選擇多種骨替代材料。有趣的是，這些材料在原料或制造過程方面有很大的不同。作為自體骨組織（自體移植）的替代品，自體骨組織由于其廣泛的再生特性仍然被應用為“金標準”，來自其他天然來源的骨替代材料在再生牙科中變得越來越重要。這些骨替代材料要么來自人類（同種異體移植），要么來自動物（異種移植）。
圖1 cerabone?顆粒保留有松質骨結構
圖2,3?cerabone?顆粒的表面微結構，顯示了天然微結構的保留和基于無細胞成骨細胞小室的純化狀態(tài)。cerabone?顆粒的橫截面(微CT)，顯示了異種骨移植材料完成純化后保留有層狀天然結構。?
In case of these materials, the obtained bony extracellular matrix based on calcium phosphates should finally serve as bone substitute (Figs. 1–3). Based on the physicochemical similarity of this class of bone substitutes to the autologous bone tissue, it can be assumed that these materials are the ideal choice for osseous regeneration. Preferentially, bovine bone is used as source tissue in the daily dental practice, as in case of the two primarily applied bone substitute materials Bio-Oss? and cerabone?.
在這些材料的情況下，所得到的基于磷酸鈣的骨質細胞外基質最終應該作為骨替代材料（圖1-3）?；谶@類骨替代材料與自體骨組織在物理化學上的相似性，可以假設這些材料是骨再生的理想選擇。在日常牙科實踐中，牛骨是作為源組織的首選，就像兩種主要應用的骨替代材料Bio-Oss?和cerabone?一樣。
Safety aspects and purification processes
安全性方面和純化過程
?For the clinical application of bone substitutes from natural sources it is inalienable to purify the donor tissue from immunogens to guarantee a regeneration process without complications such as rejections or disease transmissions. To ensure the safe application of such bone substitute materials, different purification steps of the donor tissue are applied.
對于來自天然來源的骨替代材料的臨床應用，必須將供體組織從免疫原中純化，以保證一個沒有并發(fā)癥（如排斥或疾病傳播）的再生過程。為了確保這類骨替代材料的安全應用，對供體組織進行了不同的純化步驟。
The first step is the suitable selection of donor animals before the initiation of the purification process. Hence, for the production of Bio-Oss? and cerabone? bovine femoral heads from registered suppliers located in Australia and New Zealand are processed as both countries are recognised to have a negligible BSE risk according to the World Organisation for Animal Health (OIE). Afterwards, complex purification steps including both chemical and physical methods are applied for a complete purification. However, those methods are occasionally discussed because of possible rejection reactions or a transfer of pathogens while applying bone grafting materials. In this context, the temperature treatment for the purification plays a major role. Bio-Oss? is processed at temperatures of approximately 300 °C, while the bone substitute material cerabone? is purified by notably higher temperatures of up to 1,250 °C.This difference in temperature seems to be of significant importance for the safe application of xenogeneic bone substitutes.
在純化過程的啟動之前，第一步是合適的選擇供體動物。因此，為了生產Bio-Oss?和cerabone?，來自澳大利亞和新西蘭的注冊供應商提供的牛股骨頭被用于加工，因為這兩個國家被世界動物衛(wèi)生組織(OIE)認定為具有可忽略的BSE風險。之后，應用復雜的純化步驟，包括化學和物理方法，以實現完全純化。然而，這些方法有時會引起爭議，因為在應用骨移植材料時可能會發(fā)生排斥反應或病原體的轉移。在這方面，純化過程中的溫度處理起著重要作用。Bio-Oss?是在約300°C的溫度下加工的，而骨替代材料cerabone?則是在高達1,250°C的溫度下純化的。這種溫度差似乎對異種骨替代物的安全應用非常重要。?
The purification process of bovine bone tissue was evaluated in a recent review by Kim et al. 3 Interestingly, the authors concluded that the inactivation of prions in Bio-Oss? is rather based on the applied temperature than a result of the treatment with highly concentrated sodium hydroxide (NaOH). While this chemical process was described as efficient by Wenz et al., the reliability and sensitivity of the used tests were questioned by Kim et al. In this review, the authors describe that prions will only be effectively destroyed by heating up to 1,000 °C for five minutes. Furthermore, the according EU-guidelines for medical devices utilising animal tissues and their derivatives (Part 1: Application of risk management, EN ISO 22442-1), point out that a treatment at temperatures above 800 °C is reducing the risk of the transmission of Transmissible Spongiform Encephalopathies (TSEs) to an acceptable minimum.
Kim等人對牛骨組織的純化過程進行了評價。有趣的是，作者得出結論，Bio-Oss?中朊病毒的滅活更多地是基于應用的溫度，而不是高濃度氫氧化鈉(NaOH)的處理結果。雖然Wenz等人描述了這種化學過程是有效的，但Kim等人質疑了所使用的測試的可靠性和敏感性。在這篇綜述中，作者描述了朊病毒只有在加熱到1,000°C五分鐘后才能有效地被破壞。此外，關于利用動物組織及其衍生物(第1部分：風險管理的應用，EN ISO 22442-1)的醫(yī)療器械的歐盟指南指出，在800°C以上的溫度下處理可以將傳播可傳染性海綿狀腦病(TSEs)的風險降低到可接受的最低水平。
To assure a maximum level of safety, cerabone? is heated to temperatures above 1,200 °C during processing. Thus, organic parts like cells and proteins are removed and even potentially contained prions and other pathogens are destroyed. Despite the treatment at high temperatures, the natural bone structure is preserved (Figs. 1–3) making cerabone? a safe and reliable product for bone regeneration applications.
為了確保最高水平的安全性，在加工過程中，cerabone?被加熱到超過1,200°C的溫度。因此，有機部分如細胞和蛋白質被去除，甚至可能含有的朊病毒和其他病原體也被破壞。盡管經過高溫處理，天然骨結構仍然保持不變(圖1-3)，使cerabone?成為骨再生應用中安全可靠的產品。
Figure 4一個示意圖，說明了大多數應用的骨移植材料引起的細胞和炎癥過程，植入床血管化過程和骨組織再生過程之間的相關性
Inflammation and bone regeneration
炎癥和骨再生
Data from preclinical and clinical studies show comparable values for new bone formation, remaining bone grafting material and connective tissue for both xenogeneic bone substitutes mentioned above (Tab. 1). These results refer to similar biological activities of Bio-Oss? and cerabone?. However, in case of cerabone? higher numbers of multinucleated giant cells (MNGCs) were found within the first days after its implantation. Furthermore, the comparison to different other studies shows that the initial number of MNGCs in case of cerabone? is significantly lower as found in the implant bed of fast degradable synthetic materials based on tricalcium phosphates. These results confirm several other studies claiming the long-term stability of xenogeneic bone substitutes as it was shown that MNGCs are involved in the biodegradation of bone-grafting materials by phagocytosis.6, 7
來自臨床前和臨床研究的數據顯示，對于上述兩種異種骨替代物，新骨形成、殘留骨移植材料和結締組織的值相當(表1)。這些結果表明Bio-Oss?和cerabone?具有類似的生物活性。然而，在cerabone?植入后的最初幾天內，發(fā)現多核巨細胞(MNGCs)的數量較高。此外，與不同其他研究的比較顯示，在cerabone?植入床中發(fā)現MNGCs初始數量明顯低于磷酸三鈣這種快速可降解的合成材料。這些結果證實了其他幾項研究的說法，即異種骨替代物的長期穩(wěn)定性，因為已經證明MNGCs通過吞噬作用參與骨移植材料的生物降解。
Interestingly, the MNGCs were identified as foreign body giant cells (FBGCs) based on their molecule expression. 8 However, more information is still needed to get further conclusion regarding their differentiation. 8, 9 Interestingly, the degradation process of bone substitutes and the process of bone tissue regeneration are closely connected via the relevant cell types such as macrophages and MNGCs (Fig. 4). In this context, it was shown that both macrophages and MNGCs on the one side express pro-inflammatory molecules that are relevant for the degradation process, but also secrete antiinflammatory substances needed for tissue regeneration. 9 One of the most important signaling molecules is the vascular endothelial growth factor (VEGF), which has direct and indirect impact onto different processes important for successful tissue regeneration. 8, 9 Thus, VEGF induces angiogenesis at the implant site, which has indirectly a positive influence on bone tissue growth, and also direct influence on the development and activity of osteoblasts.8,10
有趣的是，根據它們的分子表達，MNGCs被鑒定為異物巨細胞(FBGCs)。然而，還需要更多的信息才能得出更進一步的結論，關于它們的分化。有趣的是，骨替代材料的降解過程和骨組織再生過程通過相關細胞類型如巨噬細胞和MNGCs緊密聯系在一起(圖4)。在這方面，已經證明，巨噬細胞和MNGCs一方面表達對降解過程有關的促炎分子，但另一方面也分泌對組織再生有必要的抗炎物質。最重要的信號分子之一是血管內皮生長因子(VEGF)，它對成功組織再生的不同過程有直接和間接的影響。因此，VEGF在植入部位誘導血管生成，這對骨組織生長有間接的積極影響，也對成骨細胞的發(fā)育和活性有直接影響。
Figure 5 Cerabone ??產品家族
Tab .1 Bio-Oss?和cerabone?在組織形態(tài)學方面的結果，顯示了新形成的骨、殘留的骨移植材料和結締組織的相當值
In case of the xenogeneic bone substitute material cerabone?, it can be assumed that the observed higher numbers of MNGCs might have a positive effect on bone regeneration. Interestingly, an initially improved bioactivity for cerabone? combined with a higher vascularisation at the implant site was demonstrated, which might be based on the increased number of MNGCs compared to Bio-Oss?. 2 Thus, an improving effect on bone regeneration could be concluded after the application of cerabone?. In combination with the hydrophilic nature of this material, 1 which has been shown to significantly support the regeneration process by promoting the growth of osteoblasts, cerabone? can be considered as a reliable bone grafting material with an assured safety for both clinical user and patient.
就cerabone?這種異種骨替代材料而言，可以推測觀察到的MNGCs數量較高可能對骨再生有積極作用。有趣的是，cerabone?與Bio-Oss?相比，顯示出初始改善的生物活性和植入部位更高的血管化，這可能是基于MNGCs數量增加的原因。因此，在應用cerabone?后可以得出對骨再生有改善作用的結論。結合這種材料的親水性質，1?它已經被證明能夠通過促進成骨細胞的生長顯著地支持再生過程，cerabone?可以被認為是一種可靠的骨移植材料，為臨床用戶和患者確保最高可能的安全性。
Summary
總結
Altogether, it can be concluded that the xenogeneic bone substitute material cerabone? is able to ensure the highest possible safety from disease transmission due to the high temperature treatment. Furthermore, it is assumable that the relatively high numbers of multinucleated giant cells express high amounts of antiinflammatory molecules and support a fast and high implant bed vascularisation and therefore, might favour the bone regeneration process.
總之，可以得出結論，異種骨替代材料cerabone?由于高溫處理能夠確保高安全性，降低疾病傳播。此外，MNGCs相對較高的數量表達大量抗炎分子，并支持快速和高效植入部位血管化，因此可能有利于骨再生過程。
附錄：?對比異種骨移植物與天然骨成分和結構對比
Note:
1.兩種骨移植材料，均不是完全的化學配比的羥基磷灰石材料，鈣磷比( Ca/P ratio )在1.75 和1.33之間，鈣占主要成分
2.比較低溫燒結的Bio-Oss，具有纖維質紋理（Fibrillar texture）[是指細胞或組織中纖維狀結構，如細胞骨架或細胞外基質的排列和取向];而兩次高溫燒結的Cerabone,是致密光滑的表面，并且伴有小顆粒，這個和羥基磷灰石陶瓷一樣。
3.晶體尺寸也隨著溫度的增加，而增加，溶解度降低。很多物理特征隨著溫度的增加而改變：比表面積，結晶度，晶體粒度，物相組成成分等。
?參考文獻：
Barbeck M, Unger R, Witte F, et al. Xenogeneic bone grafting materials[J]. Int Mag Oral Implant, 2017, 3: 34-36.
Peri? Ka?arevi? Z, Kavehei F, Houshmand A, et al. Purification processes of xenogeneic bone substitutes and their impact on tissue reactions and regeneration[J]. The International journal of artificial organs, 2018, 41(11): 789-800.
