Saalbach A, Stein M, Lee S, Krügel U, Haffner-Luntzer M, Krohn K, Franz S, Simon J C, Tuckermann J, Anderegg U
Dept. of Dermatology, Venereology and Allergology, Medical Faculty, Leipzig University, Germany.
Institute of Comparative Molecular Endocrinology (CME), Ulm University, Germany.
Matrix Biol Plus. 2024 Oct 9;24:100163. doi: 10.1016/j.mbplus.2024.100163. eCollection 2024 Dec.
Bone consists of a complex mineralised matrix that is maintained by a controlled equilibrium of synthesis and resorption by different cell types. Hyaluronan (HA) is an important glycosaminoglycan in many tissues including bone. Previously, the importance of HA synthesis for bone development during embryogenesis has been shown. We therefore investigated whether HA synthesis is involved in adult bone turnover and whether abrogation of HA synthesis in adult mice would alter bone quality. To achieve complete abrogation of HA synthesis in adult mice, we generated a novel Has-total knockout (Has-tKO) mouse model in which a constitutive knockout of Has1 and Has3 was combined with an inducible, Ubc-Cre-driven Has2 knockout. By comparing bone tissue from wild-type, Has1,3 double knockout and Has-tKO mice, we demonstrate that Has2-derived HA mainly contributes to the HA content in bone. Furthermore, Has-tKO mice show a significant decrease of bone integrity in trabecular and cortical bone, as shown by µ-CT analysis. These effects are detectable as early as five weeks after induced Has2 deletion, irrespective of sex and progress with age. Mesenchymal stem cells (MSC) during osteogenic differentiation showed that Has2 expression is increased while Has3 expression is decreased during differentiation. Furthermore, the complete abrogation of HA synthesis results in significantly reduced osteogenic differentiation as indicated by reduced marker gene expression (Runx-2, Tnalp, Osterix) as well as alizarin red staining. RNAseq analysis revealed that MSC from Has-tKO are characterised by decreased expression of genes annotated for bone and organ development, whereas expression of genes associated with chemokine related interactions and cytokine signalling is increased. Taken together, we present a novel mouse model with complete deletion of HA synthases in adult mice which has the potential to study HA function in different organs and during age-related HA reduction. With respect to bone, HA synthesis is important for maintaining bone integrity, presumably based on the strong effect of HA on osteogenic differentiation.
骨骼由复杂的矿化基质组成，该基质通过不同细胞类型合成与吸收的受控平衡得以维持。透明质酸（HA）是包括骨骼在内的许多组织中的一种重要糖胺聚糖。此前，已证明HA合成在胚胎发育期间对骨骼发育的重要性。因此，我们研究了HA合成是否参与成年骨骼的更新，以及成年小鼠中HA合成的消除是否会改变骨骼质量。为了在成年小鼠中实现HA合成的完全消除，我们构建了一种新型的Has全敲除（Has-tKO）小鼠模型，其中Has1和Has3的组成型敲除与诱导型、Ubc-Cre驱动的Has2敲除相结合。通过比较野生型、Has1,3双敲除和Has-tKO小鼠的骨组织，我们证明Has2衍生的HA主要促成骨骼中的HA含量。此外，如µ-CT分析所示，Has-tKO小鼠的小梁骨和皮质骨的骨完整性显著降低。这些影响在诱导Has2缺失后最早五周即可检测到，与性别无关，并随年龄增长而加重。间充质干细胞（MSC）在成骨分化过程中显示，Has2表达增加而Has3表达减少。此外，如标记基因表达（Runx-2、Tnalp、Osterix）降低以及茜素红染色所示，HA合成的完全消除导致成骨分化显著降低。RNAseq分析显示，来自Has-tKO的MSC的特征是与骨骼和器官发育相关的基因表达降低，而与趋化因子相关相互作用和细胞因子信号传导相关的基因表达增加。综上所述，我们提出了一种成年小鼠HA合酶完全缺失的新型小鼠模型，该模型有潜力研究HA在不同器官以及与年龄相关的HA减少过程中的功能。就骨骼而言，HA合成对于维持骨完整性很重要，这可能是基于HA对成骨分化的强大作用。
