Romanowicz Genevieve E, Terhune Aidan H, Bielajew Benjamin J, Sexton Benjamin, Lynch Michelle, Mandair Gurjit S, McNerny Erin M B, Kohn David H
Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, MI, USA.
Department of Mechanical Engineering, College of Engineering, University of Michigan, MI, USA.
Bone Rep. 2022 Oct 19;17:101629. doi: 10.1016/j.bonr.2022.101629. eCollection 2022 Dec.
Compromises to collagen and mineral lead to a decrease in whole bone quantity and quality in a variety of systemic diseases, yet, clinically, disease manifestations differ between craniofacial and long bones. Collagen alterations can occur through post-translational modification via lysyl oxidase (LOX), which catalyzes enzymatic collagen cross-link formation, as well as through non-enzymatic advanced glycation end products (AGEs) such as pentosidine and carboxymethyl-lysine (CML). Characterization of the cross-links and AGEs, and comparison of the mineral and collagen modifications in craniofacial and long bones represent a critical gap in knowledge. However, alterations to either the mineral or collagen in bone may contribute to disease progression and, subsequently, the anatomical site dependence of a variety of diseases. Therefore, we hypothesized that collagen cross-links and AGEs differ between craniofacial and long bones and that altered collagen cross-linking reduces mineral quality in an anatomic location dependent. To study the effects of cross-link inhibition on mineralization between anatomical sites, beta-aminoproprionitrile (BAPN) was administered to rapidly growing, 5-8 week-old male mice. BAPN is a dose-dependent inhibitor of LOX that pharmacologically alters enzymatic cross-link formation. Long bones (femora) and craniofacial bones (mandibles) were compared for mineral quantity and quality, collagen cross-link and AGE profiles, and tissue level mechanics, as well as the response to altered cross-links via BAPN. A highly sensitive liquid chromatography/mass spectrometry (LC-MS) method was developed which allowed for quantification of site-dependent accumulation of the advanced glycation end-product, carboxymethyl-lysine (CML). CML was ∼8.3× higher in the mandible than the femur. The mandible had significantly higher collagen maturation, mineral crystallinity, and Young's modulus, but lower carbonation, than the femur. BAPN also had anatomic specific effects, leading to significant decreases in mature cross-links in the mandible, and an increase in mineral carbonation in the femur. This differential response of both the mineral and collagen composition to BAPN between the mandible and femur highlights the need to further understand how inherent compositional differences in collagen and mineral contribute to anatomic-site specific manifestations of disease in both craniofacial and long bones.
在多种全身性疾病中，胶原蛋白和矿物质受损会导致全骨数量和质量下降，然而在临床上，颅面骨和长骨的疾病表现有所不同。胶原蛋白的改变可通过赖氨酰氧化酶（LOX）的翻译后修饰发生，LOX催化酶促胶原蛋白交联的形成，也可通过非酶促晚期糖基化终产物（AGEs）如戊糖苷和羧甲基赖氨酸（CML）发生。对交联和AGEs的表征，以及颅面骨和长骨中矿物质和胶原蛋白修饰的比较，代表了知识上的关键空白。然而，骨中矿物质或胶原蛋白的改变可能会导致疾病进展，进而导致多种疾病对解剖部位的依赖性。因此，我们假设颅面骨和长骨之间的胶原蛋白交联和AGEs存在差异，并且改变的胶原蛋白交联会在解剖部位依赖性地降低矿物质质量。为了研究交联抑制对不同解剖部位矿化的影响，对快速生长的5至8周龄雄性小鼠施用β-氨基丙腈（BAPN）。BAPN是LOX的剂量依赖性抑制剂，可在药理学上改变酶促交联的形成。比较长骨（股骨）和颅面骨（下颌骨）的矿物质数量和质量、胶原蛋白交联和AGEs谱以及组织水平力学，以及通过BAPN改变交联后的反应。开发了一种高度灵敏的液相色谱/质谱（LC-MS）方法，该方法可对晚期糖基化终产物羧甲基赖氨酸（CML）的部位依赖性积累进行定量。下颌骨中的CML比股骨中的高约8.3倍。下颌骨的胶原蛋白成熟度、矿物质结晶度和杨氏模量显著高于股骨，但碳酸化程度低于股骨。BAPN也有解剖学特异性作用，导致下颌骨中成熟交联显著减少，股骨中矿物质碳酸化增加。下颌骨和股骨之间矿物质和胶原蛋白组成对BAPN的这种差异反应凸显了进一步了解胶原蛋白和矿物质固有的组成差异如何导致颅面骨和长骨中疾病的解剖部位特异性表现的必要性。
