A functional three-dimensional microphysiological human model of myeloma bone disease.

Human myeloma bone disease (MBD) occurs when malignant plasma cells migrate to the bone marrow and commence inimical interactions with stromal cells, disrupting the skeletal remodeling process. The myeloma cells simultaneously suppress osteoblastic bone formation while promoting excessive osteoclastic resorption. This bone metabolism imbalance produces osteolytic lesions that cause chronic bone pain and reduce trabecular and cortical bone structural integrity, and often culminate in pathological fractures. Few bone models exist that enable scientists to study MBD and the effect therapies have on restoring the bone metabolism imbalance. The purpose of this research was to develop a well characterized three-dimensional (3D) bone organoid that could be used to study MBD and current or potential treatment options. First, bone marrow stromal cell-derived osteoblasts (OBs) mineralized an endosteal-like extracellular matrix (ECM) over 21 days. Multiple analyses confirmed the generation of hydroxyapatite (HA)-rich bone-like tissue fragments that were abundant in alkaline phosphatase, calcium, and markers of osteoblastic gene expression. On day 22, bone marrow macrophage (BMM)-derived osteoclasts (OCs) were introduced to enhance the resorptive capability of the model and recapitulate the balanced homeostatic nature of skeletal remodeling. Tartrate-resistant acid phosphatase 5b (TRAcP-5b), type I collagen C-telopeptide (CTX-1), and gene expression analysis confirmed OC activity in the normal 3D organoid (3D in vitro model of normal bonelike fragments [3D-NBF]). On day 30, a human multiple myeloma (MM)-derived plasmacytoma cell line was introduced to the 3D-NBF to generate the 3D-myeloma bone disease organoid (3D-MBD). After 12 days, the 3D-MBD had significantly reduced total HA, increased TRAcP-5b levels, increases levels of CTX-1, and decreased expression of osteoblastic genes. Therapeutic intervention with pharmaceutical agents including an immunomodulatory drug, a bisphosphonate, and monoclonal restored HA content and reduced free CTX-1 in a dose-dependent manner. This osteogenically functional model of MBD provides a novel tool to study biological mechanisms guiding the disease and to screen potential therapeutics. © 2021 American Society for Bone and Mineral Research (ASBMR).

Human ileal organoid model recapitulates clinical incidence of diarrhea associated with small molecule drugs.

Drug-induced gastrointestinal toxicity (GIT) is a common treatment-emergent adverse event that can negatively impact dosing, thereby limiting efficacy and treatment options for patients. An in vitro assay of GIT is needed to address patient variability, mimic the microphysiology of the gut, and accurately predict drug-induced GIT. Primary human ileal organoids (termed 'enteroids') have proven useful for stimulating intestinal stem cell proliferation and differentiation to multiple cell types present in the gut epithelium. Enteroids have enabled characterization of gut biology and the signaling involved in the pathogenesis of disease. Here, enteroids were differentiated from four healthy human donors and assessed for culture duration-dependent differentiation status by immunostaining for gut epithelial markers lysozyme, chromogranin A, mucin, and sucrase isomaltase. Differentiated enteroids were evaluated with a reference set of 31 drugs exhibiting varying degrees of clinical incidence of diarrhea, a common manifestation of GIT that can be caused by drug-induced thinning of the gut epithelium. An assay examining enteroid viability in response to drug treatment demonstrated 90% accuracy for recapitulating the incidence of drug-induced diarrhea. The human enteroid viability assay developed here presents a promising in vitro model for evaluating drug-induced diarrhea.