The extracellular matrix (ECM) not only provides structural support in tissues but also regulates cellular processes and tissue homeostasis. The lysyl oxidase (LOX) family of enzymes, consisting of LOX and lysyl oxidase-like enzymes (LOXL1-4), is involved in ECM remodeling by catalyzing the crosslinking of collagen and elastin. Dysregulation of these enzymes is implicated in the pathogenesis of various diseases, including organ fibrosis and tumor development. Furthermore, LOX family members have been shown to affect radiotherapy responses, with specific involvement in radioresistance and radiation-induced fibrosis. This review summarizes the structural and functional characteristics of the LOX family, highlighting their roles in fibrotic diseases such as pulmonary fibrosis, liver fibrosis, and cardiac diseases, their roles in tumor progression, relevance in radiotherapy, and treatment targeting LOX and LOXLs. Understanding the underlying mechanisms and potential therapies is critical for developing novel strategies in both disease identification and management.

Background and Aims: In hereditary hemorrhagic telangiectasia (HHT), severe liver vascular malformations are associated with mutations in the Activin A Receptor‐Like Type 1 ( ACVRL1 ) gene encoding ALK1, the receptor for bone morphogenetic protein (BMP) 9/BMP10, which regulates blood vessel development. Here, we established an HHT mouse model with exclusive liver involvement and adequate life expectancy to investigate ALK1 signaling in liver vessel formation and metabolic function. Approach and Results: Liver sinusoidal endothelial cell (LSEC)‐selective Cre deleter line, Stab2‐iCreF3 , was crossed with Acvrl1 ‐floxed mice to generate LSEC‐specific Acvrl1 ‐deficient mice ( Alk1 HEC‐KO ). Alk1 HEC‐KO mice revealed hepatic vascular malformations and increased posthepatic flow, causing right ventricular volume overload. Transcriptomic analyses demonstrated induction of proangiogenic/tip cell gene sets and arterialization of hepatic vessels at the expense of LSEC and central venous identities. Loss of LSEC angiokines Wnt2 , Wnt9b , and R‐spondin‐3 ( Rspo3 ) led to disruption of metabolic liver zonation in Alk1 HEC‐KO mice and in liver specimens of patients with HHT. Furthermore, prion‐like protein doppel ( Prnd ) and placental growth factor ( Pgf ) were upregulated in Alk1 HEC‐KO hepatic endothelial cells, representing candidates driving the organ‐specific pathogenesis of HHT. In LSEC in vitro , stimulation or inhibition of ALK1 signaling counter‐regulated Inhibitors of DNA binding (ID)1–3, known Alk1 transcriptional targets. Stimulation of ALK1 signaling and inhibition of ID1–3 function confirmed regulation of Wnt2 and Rspo3 by the BMP9/ALK1/ID axis. Conclusions: Hepatic endothelial ALK1 signaling protects from development of vascular malformations preserving organ‐specific endothelial differentiation and angiocrine signaling. The long‐term surviving Alk1 HEC‐KO HHT model offers opportunities to develop targeted therapies for this severe disease.

BACKGROUND:Filament perforation is a widely-used method to induce subarachnoid hemorrhage (SAH) in mice. Whereas the perforation site has been assumed to be in the branching of middle cerebral artery (MCA) and anterior cerebral artery (ACA), we recently observed more proximal perforations.METHODS:Filament perforation was performed in CD1- (n = 10) and C57Bl/6N-mice (n = 9) ex vivo. The filament was left in place and the perforation site was microscopically assessed. Digital subtraction angiography (DSA) was performed in CD1- (n = 9) and C57Bl/6J-mice (n = 29) and anatomical differences of the internal carotid artery (ICA) were determined.RESULTS:Whereas in C57Bl/6N-mice perforation occurred in the proximal intracranial ICA in 89% (n = 8), in CD1-mice the perforation site was in the proximal ICA in 50% (n = 5), in the branching between MCA and ACA in 40% (n = 4), and in the proximal ACA in 10% (n = 1). DSA revealed a stronger angulation (p<0.001) of the ICA in CD1-mice (163.5±2.81°) compared to C57Bl/6J-mice (124.5±5.49°). Body weight and ICA-angle showed no significant correlation in C57Bl/6J- (r = -0.06, pweight/angle = 0.757) and CD1-mice (r = -0.468, pweight/angle = 0.242).CONCLUSION:Filament perforation in mice occurs not only at the hitherto presumed branching between MCA and ACA, but seems to depend on mouse strain and anatomy as the proximal intracranial ICA may also be perforated frequently.

Objectives: New CBCT devices have been developed which can provide "low- dose CBCTs (LD- CBCT)". Aim of this study is to investigate the suitability of LD- CBCT for measurement of alveolar buccal/oral bone. Methods and materials: Vestibular and oral bone loss of the teeth of seven porcine mandibles free of soft tissues were investigated by Micro- CT and three CBCT- modes: high- dose (HD), standard- dose (SD) and low- dose (LD). Radiographic measurements of bone loss (bl) and vestibular and oral bone thickness (bt) were made by two raters at 69 sites. Measurement means and differences, Intraclass correlation (ICC) and Bland-Altman plots were calculated. Results: ICCs between raters(r) concerning bl were 0.954 for HD, 0.949 for SD and 0.945 for LD; concerning bt they were 0.872 for HD, 0.845 for SD and 0.783 for LD. Means of differences of bt measurements were -0.01 mm(r1)/0.00 mm(r2) for HD, 0.04 mm(r1)/0.02 mm(r2) for SD and 0.02 mm(r1)/0.04 mm(r2) for LD; for bl measurements they were 0.06 mm(r1)/0.05 mm(r2) for HD, -0.01 mm(r1)/0.13 mm(r2) for SD and 0.07 mm(r1)/0.16 mm(r2) for LD. Linear regression indicates no noticeable differences between methods and the raters with respect to bl and bt. Conclusions Relating to the CBCT- device used in this study, LD- CBCT is a promising method to detect and describe buccal and oral periodontal bl and bt. Further studies with human anatomic structures must confirm these results.

Within the bone marrow microenvironment, endothelial cells (EC) exert important functions. Arterial EC support hematopoiesis while H-type capillaries induce bone formation. Here, we show that BM sinusoidal EC (BM-SEC) actively control erythropoiesis. Mice with stabilized β-catenin in BM-SEC (Ctnnb1OE-SEC) generated by using a BM-SEC-restricted Cre mouse line (Stab2-iCreF3) develop fatal anemia. While activation of Wnt-signaling in BM-SEC causes an increase in erythroblast subsets (PII-PIV), mature erythroid cells (PV) are reduced indicating impairment of terminal erythroid differentiation/reticulocyte maturation. Transplantation of Ctnnb1OE-SEC hematopoietic stem cells into wildtype recipients confirms lethal anemia to be caused by cell-extrinsic, endothelial-mediated effects. Ctnnb1OE-SEC BM-SEC reveal aberrant sinusoidal differentiation with altered EC gene expression and perisinusoidal ECM deposition and angiocrine dysregulation with de novo endothelial expression of FGF23 and DKK2, elevated in anemia and involved in vascular stabilization, respectively. Our study demonstrates that BM-SEC play an important role in the bone marrow microenvironment in health and disease.

Patient-derived xenograft (PDX) models have emerged as versatile preclinical platforms for investigation of functional pathomechanisms in myelodysplastic syndromes (MDS) and other myeloid neoplasms. However, despite increasingly improved methodology, engraftment efficiencies frequently remain low. Humanized three-dimensional scaffold models (ossicle xenotransplantation models) in immunocompromised mice have recently been found to enable improved engraftment rates of healthy and malignant human hematopoiesis. We therefore interrogated the feasibility of using four different three-dimensional ossicle-based PDX models for application with primary MDS samples. In a fully standardized comparison, we evaluated scaffold materials such as Gelfoam, extracellular matrix (ECM), and human or xenogenous bone substance in comparison to intrafemoral (IF) co-injection of bone marrow (BM)-derived mesenchymal stromal cells (MSCs) and CD34+ hematopoietic stem and progenitor cells (HSPCs). Our study included13 primary MDS patient samples transplanted in parallel according to these five different conditions. Engraftment of MDS samples was assessed by flow cytometry, immunohistological staining, and molecular validation. We determined that three-dimensional ossicle-based methods achieved higher relative rates of engraftment and enabled long-term retrievability of patient-derived MSCs from implanted ossicles. In summary, HSPCs and MSCs derived from MDS BM, which did not significantly engraft in NSG mice after intrafemoral injection, were able to colonize humanized scaffold models. Therefore, these models are promising new xenotransplantation techniques for addressing preclinical and functional questions of the interaction between hematopoiesis and the BM niche in MDS.

Introduction: Next generation sequencing techniques have identified a large number of MDS associated acquired molecular lesions. However, translation of these possible molecular targets into new therapeutic strategies has been lagging behind. This is also due to a lack of functional experimental models of MDS, in which new hypotheses can be evaluated pre-clinically. Xenograft models in NSG mice have emerged as versatile preclinical platforms for investigation of functional pathomechanisms in MDS ([1] Medyouf et al., 2014, [2] Rouault-Pierre et al., 2017). The limiting factor of these models is the low engraftment of patient-derived CD34+ hematopoietic stem cells (HSCs). Efficient humanized 3D scaffolds in immune-compromised mouse models have been established, enabling to increase engraftment rates of normal and malignant hematopoiesis ([3] Reinisch et al., 2016, [4] Abarrategi et al., 2017). Therefore, we evaluated engraftment ability of IPSS low-risk, int-1 and high-risk-patient samples, in four different 3D scaffolds. Methods: Currently we transplanted samples from 10 MDS patients in parallel into NSG mice testing the following conditions: A) Intrafemoral co-injection of CD34+ HSCs and MSCs according to [1]. Subcutaneous implantation of 3D scaffolds. Gelfoam (B) and Bio-OSS (C) [4], Matrigel ossicles (D) [3] and primary human bone isolated after hip replacement, inserted with Gelfoam, preseeded in vitro with MSCs and mononuclear cells (MNCs) and injected in vivo with CD34+ HSCs 8 weeks after implantation (human bone ossicles) (E). Ossicles, bone marrow (BM), peripheral blood and spleens were analyzed 12 weeks after implantation of hematopoietic cells. Results: Gelfoam and human bone ossicles showed significantly higher hCD45+cell numbers compared to intrafemoral injection analyzed by flow cytometry. Engraftment in those two conditions was similarly robust. However, Gelfoam scaffolds showed higher percentual engraftment levels ranging up to 70% as compared to human bone ossicles ranging from 0.2% to 27%. Interestingly, we found systemic engraftment of hCD45+cells outside the injected bone fragment in the BM, peripheral blood and spleen solely in mice, which received human bone ossicles. In all other methods, hCD45+ cells could only be detected within the ossicles themselves. This result could possibly be explained due to transplantation of MNCs in this condition. That hypothesis was supported by another set of experiments using human bone ossicles (n=10), which showed that colonization of the scaffold was similar when transplanting either CD34+ cells + MSCs, MNCs+MSCs or MNCs only but systemic engraftment could only be seen in MNC transplanted mice. Conclusion: Our data show that hCD45+cells and MSCs from MDS BM were able to colonize humanized ossicle scaffolds. Gelfoam and human bone ossicles were the most promising novel methods to improve MDS xenograft models. For systemic engraftment, application of MNCs seems to be necessary. Disclosures Nolte: Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding.

Longitudinal in vivo imaging studies characterizing subarachnoid hemorrhage (SAH)-induced large artery vasospasm (LAV) in mice are lacking. We developed a SAH-scoring system to assess SAH severity in mice using micro CT and longitudinally analysed LAV by intravenous digital subtraction angiography (i.v. DSA). Thirty female C57Bl/6J-mice (7 sham, 23 SAH) were implanted with central venous ports for repetitive contrast agent administration. SAH was induced by filament perforation. LAV was assessed up to 14 days after induction of SAH by i.v. DSA. SAH-score and neuroscore showed a highly significant positive correlation (rsp = 0.803, p < 0.001). SAH-score and survival showed a negative significant correlation (rsp = −0.71, p < 0.001). LAV peaked between days 3–5 and normalized on days 7–15. Most severe LAV was observed in the internal carotid (Δmax = 30.5%, p < 0.001), anterior cerebral (Δmax = 21.2%, p = 0.014), middle cerebral (Δmax = 28.16%, p < 0.001) and basilar artery (Δmax = 23.49%, p < 0.001). Cerebral perfusion on day 5 correlated negatively with survival time (rPe = −0.54, p = 0.04). Arterial diameter of the left MCA correlated negatively with cerebral perfusion on day 3 (rPe = −0.72, p = 0.005). In addition, pseudoaneurysms arising from the filament perforation site were visualized in three mice using i.v. DSA. Thus, micro-CT and DSA are valuable tools to assess SAH severity and to longitudinally monitor LAV in living mice.

Optical coherence tomography (OCT) is a clinical standard in ophthalmology. Currently, its application in dentistry is gaining increasing interest. In this study, we tested the possibility to use a modified commercially available spectral domain OCT (SD-OCT) to assess the layer thickness of orthodontic surface sealants.