There is significant variability in the materials commonly used for interbody cages in spine surgery. It is theorized that three-dimensional (3D)-printed interbody cages using porous titanium material can provide more consistent bone ingrowth and biological fixation. The purpose of this study was to provide an evidence-based approach to decision-making regarding interbody materials for spinal fusion. A comparative animal study was performed. A skeletally mature ovine lumbar fusion model was used for this study. Interbody fusions were performed at L2-L3 and L4-L5 in 27 mature sheep using three different interbody cages (ie, polyetheretherketone [PEEK], plasma sprayed porous titanium-coated PEEK [PSP], and 3D-printed porous titanium alloy cage [PTA]). Non-destructive kinematic testing was performed in the three primary directions of motion. The specimens were then analyzed using micro-computed tomography (µ-CT); quantitative measures of the bony fusion were performed. Histomorphometric analyses were also performed in the sagittal plane through the interbody device. Outcome parameters were compared between cage designs and time points. Flexion-extension range of motion (ROM) was statistically reduced for the PTA group compared with the PEEK cages at 16 weeks (p-value=.02). Only the PTA cages demonstrated a statistically significant decrease in ROM and increase in stiffness across all three loading directions between the 8-week and 16-week sacrifice time points (p-value≤.01). Micro-CT data demonstrated significantly greater total bone volume within the graft window for the PTA cages at both 8 weeks and 16 weeks compared with the PEEK cages (p-value<.01). A direct comparison of interbody implants demonstrates significant and measurable differences in biomechanical, µ-CT, and histologic performance in an ovine model. The 3D-printed porous titanium interbody cage resulted in statistically significant reductions in ROM, increases in the bone ingrowth profile, as well as average construct stiffness compared with PEEK and PSP.

Chronic bacterial infections associated with biofilm formation are often difficult to resolve without extended courses of antibiotic therapy. Mesenchymal stem cells (MSC) exert antibacterial activity in vitro and in acute bacterial infection models, but their activity in chronic infection with biofilm models has not been previously investigated. Therefore, we studied the effects of MSC administration in mouse and dog models of chronic infections associated with biofilms. Mice with chronic Staphylococcus aureus implant infections were treated by i.v. administration of activated or non-activated MSC, with or without antibiotic therapy. The most effective treatment protocol was identified as activated MSC co-administered with antibiotic therapy. Activated MSC were found to accumulate in the wound margins several days after i.v. administration. Macrophages in infected tissues assumed an M2 phenotype, compared to untreated infections which contained predominately M1 macrophages. Bacterial killing by MSC was found to be mediated in part by secretion of cathelicidin and was significantly increased by antibiotics. Studies in pet dogs with spontaneous chronic multi drug-resistant wound infections demonstrated clearance of bacteria and wound healing following repeated i.v. administration of activated allogeneic canine MSC. Thus, systemic therapy with activated MSC may be an effective new, non-antimicrobial approach to treatment of chronic, drug-resistant infections.

The autophagy pathway has been recognized as a mechanism of survival and therapy resistance in cancer, yet the extent of autophagy’s function in metastatic progression is still unclear. Therefore, we used murine models of metastatic cancer to investigate the effect of autophagy modulation on metastasis development. Pharmacologic and genetic autophagy inhibition were able to impede cell proliferation in culture, but did not impact the development of experimentally induced 4T1 and B16-F10 metastases. Similarly, autophagy inhibition by adjuvant chloroquine (CQ) treatment did not delay metastasis in an orthotopic 4T1, tumor-resection model. However, neoadjuvant CQ treatment or genetic autophagy inhibition resulted in delayed metastasis development, whereas stimulation of autophagy by trehalose hastened development. Cisplatin was also administered either as a single agent or in combination with CQ. The combination of cisplatin and CQ was antagonistic. The effects of autophagy modulation on metastasis did not appear to be due to alterations in the intrinsic metastatic capability of the cells, as modulating autophagy had no impact on migration, invasion, or anchorage-independent growth in vitro. To explore the possibility of autophagy’s influence on the metastatic microenvironment, bone marrow–derived cells (BMDCs), which mediate the establishment of the premetastatic niche, were measured in the lung and in circulation. Trehalose-treated mice had significantly more BMDCs than either vehicle- or CQ-treated mice. Autophagy inhibition may be most useful as a treatment to impede early metastatic development. However, modulating autophagy may also alter the efficacy of platinum-based therapies, requiring caution when considering combination therapies.

Purpose: There is increasing recognition that progress in immuno-oncology could be accelerated by evaluating immune-based therapies in dogs with spontaneous cancers. Osteosarcoma (OS) is one tumor for which limited clinical benefit has been observed with the use of immune checkpoint inhibitors. We previously reported the angiotensin receptor blocker losartan suppressed metastasis in preclinical mouse models through blockade of CCL2–CCR2 monocyte recruitment. Here we leverage dogs with spontaneous OS to determine losartan's safety and pharmacokinetics associated with monocyte pharmacodynamic endpoints, and assess its antitumor activity, in combination with the kinase inhibitor toceranib. Patients and Methods: CCL2 expression, monocyte infiltration, and monocyte recruitment by human and canine OS tumors and cell lines were assessed by gene expression, ELISA, and transwell migration assays. Safety and efficacy of losartan-toceranib therapy were evaluated in 28 dogs with lung metastatic OS. Losartan PK and monocyte PD responses were assessed in three dose cohorts of dogs by chemotaxis, plasma CCL2, and multiplex cytokine assays, and RNA-seq of losartan-treated human peripheral blood mononuclear cells. Results: Human and canine OS cells secrete CCL2 and elicit monocyte migration, which is inhibited by losartan. Losartan PK/PD studies in dogs revealed that a 10-fold-higher dose than typical antihypertensive dosing was required for blockade of monocyte migration. Treatment with high-dose losartan and toceranib was well-tolerated and induced a clinical benefit rate of 50% in dogs with lung metastases. Conclusions: Losartan inhibits the CCL2–CCR2 axis, and in combination with toceranib, exerts significant biological activity in dogs with metastatic osteosarcoma, supporting evaluation of this drug combination in patients with pediatric osteosarcoma. See related commentary by Weiss et al., p. 571