KIAA1199 deficiency enhances skeletal stem cell differentiation to osteoblasts and promotes bone regeneration.

Upon transplantation, skeletal stem cells (also known as bone marrow stromal or mesenchymal stem cells) can regulate bone regeneration by producing secreted factors. Here, we identify KIAA1199 as a bone marrow stromal cell-secreted factor in vitro and in vivo. KIAA1199 plasma levels of patients positively correlate with osteoporotic fracture risk and expression levels of KIAA1199 in patient bone marrow stromal cells negatively correlates with their osteogenic differentiation potential. KIAA1199-deficient bone marrow stromal cells exhibit enhanced osteoblast differentiation in vitro and ectopic bone formation in vivo. Consistently, KIAA1199 knockout mice display increased bone mass and biomechanical strength, as well as an increased bone formation rate. They also exhibit accelerated healing of surgically generated bone defects and are protected from ovariectomy-induced bone loss. Mechanistically, KIAA1199 regulates osteogenesis by inhibiting the production of osteopontin by osteoblasts, via integrin-mediated AKT and ERK-MAPK intracellular signaling. Thus, KIAA1199 is a regulator of osteoblast differentiation and bone regeneration and could be targeted for the treatment or management of low bone mass conditions.

Identification of a clinical signature predictive of differentiation fate of human bone marrow stromal cells.

BACKGROUND: Transplantation of human bone marrow stromal cells (hBMSCs) is a promising therapy for bone regeneration due to their ability to differentiate into bone forming osteoblastic cells. However, transplanted hBMSCs exhibit variable capacity for bone formation resulting in inconsistent clinical outcome. The aim of the study was to identify a set of donor- and cell-related characteristics that detect hBMSCs with optimal osteoblastic differentiation capacity. METHODS: We collected hBMSCs from 58 patients undergoing surgery for bone fracture. Clinical profile of the donors and in vitro characteristics of cultured hBMSCs were included in uni- and multivariable analysis to determine their predictive value for osteoblastic versus adipocytic differentiation capacity assessed by quantification of mineralized matrix and mature adipocyte formation, respectively. RESULTS: We identified a signature that explained > 50% of variation in osteoblastic differentiation outcome which included the following positive predictors: donor sex (male), absence of osteoporosis diagnosis, intake of vitamin D supplements, higher fraction of CD146+, and alkaline phosphate (ALP+) cells. With the exception of vitamin D and ALP+ cells, these variables were also negative predictors of adipocytic differentiation. CONCLUSIONS: Using a combination of clinical and cellular criteria, it is possible to predict differentiation outcome of hBMSCs. This signature may be helpful in selecting donor cells in clinical trials of bone regeneration.

Elevation of Pro-Inflammatory Cytokine Levels Following Intra-Articular Fractures-A Systematic Review.

Introduction: Intra-articular fractures are a major cause of post-traumatic osteoarthritis (PTOA). Despite adequate surgical treatment, the long-term risk for PTOA is high. Previous studies reported that joint injuries initiate an inflammatory cascade characterized by an elevation of synovial pro-inflammatory cytokines, which can lead to cartilage degradation and PTOA development. This review summarizes the literature on the post-injury regulation of pro-inflammatory cytokines and the markers of cartilage destruction in patients suffering from intra-articular fractures. Methods: We searched Medline, Embase, and Cochrane databases (1960-February 2020) and included studies that were performed on human participants, and we included control groups. Two investigators assessed the quality of the included studies using Covidence and the Newcastle-Ottawa Scale. Results: Based on the surveyed literature, several synovial pro-inflammatory cytokines, including interleukins (IL)-1ß, IL-2, IL-6, IL-8, IL-12p70, interferon-y, and tumor necrosis factor-α, were significantly elevated in patients suffering from intra-articular fractures compared to the control groups. A simultaneous elevation of anti-inflammatory cytokines such as IL-10 and IL-1RA was also observed. In contrast, IL-13, CTX-II, and aggrecan concentrations did not differ significantly between the compared cohorts. Conclusions: Overall, intra-articular fractures are associated with an increase in inflammation-related synovial cytokines. However, more standardized studies which focus on the ratio of pro- and anti-inflammatory cytokines at different time points are needed.