Inhibition of osteoclast differentiation and bone resorption by N-methylpyrrolidone

Regulation of RANKL (receptor activator of nuclear factor κB ligand)-induced osteoclast differentiation is of current interest in the development of antiresorptive agents. Osteoclasts are multinucleated cells that play a crucial role in bone resorption. In this study, we investigated the effects of N-methylpyrrolidone (NMP) on the regulation of RANKL-induced osteoclastogenesis. NMP inhibited RANKL-induced tartrate-resistant acid phosphatase activity and the formation of tartrate-resistant acid phosphatase-positive multinucleated cells. The RANKL-induced expression of NFATc1 (nuclear factor of activated T cells, cytoplasmic 1) and c-Fos, which are key transcription factors for osteoclastogenesis, was also reduced by treatment with NMP. Furthermore, NMP induced disruption of the actin rings and decreased the mRNAs of cathepsin K and MMP-9 (matrix metalloproteinase-9), both involved in bone resorption. Taken together, these results suggest that NMP inhibits osteoclast differentiation and attenuates bone resorption. Therefore, NMP could prove useful for the treatment of osteoporosis or other bone diseases associated with excessive bone resorption

BMP-2 and BMP-2/7 heterodimers conjugated to a fibrin/hyaluronic acid hydrogel in a large animal model of mild intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is etiologically associated with low back pain and is currently only treated in severe cases with spinal fusion. Regenerative medicine attempts to restore degenerated tissue by means of cells, hydrogels, and/or growth factors and can therefore be used to slow, halt, or reverse the degeneration of the IVD in a minimally invasive manner. Previously, the growth factors bone morphogenetic proteins 2 and 7 (BMP-2, -7) were shown to enhance disc regeneration, in vitro and in vivo. Since BMPs have only a short in vivo half-life, and to prevent heterotopic ossification, we evaluated the use of a slow release system for BMP-2 homodimers and BMP-2/7 heterodimers for IVD regeneration. BMP growth factors were conjugated to a fibrin/hyaluronic acid (FB/HA) hydrogel and intradiscally injected in a goat model of mild IVD degeneration to study safety and efficacy. Mild degeneration was induced in five lumbar discs of seven adult Dutch milk goats, by injections with the enzyme chondroitinase ABC. After 12 weeks, discs were treated with either FB/HA-hydrogel only or supplemented with 1 or 5 μg/mL of BMP-2 or BMP-2/7. BMPs were linked to the FB/HA hydrogels using a transglutaminase moiety, to be released through an incorporated plasmin cleavage site. After another 12 weeks, goats were sacrificed and discs were assessed using radiography, MRI T2* mapping, and biochemical and histological analyses. All animals maintained weight throughout the study and no heterotopic bone formation or other adverse effects were noted during follow-up. Radiographs showed significant disc height loss upon induction of mild degeneration. MRI T2* mapping showed strong and significant correlations with biochemistry and histology as shown before. Surprisingly, no differences could be demonstrated in any parameter between intervention groups. To our knowledge, this is the first large animal study evaluating BMPs conjugated to an FB/HA-hydrogel for the treatment of mild IVD degeneration. The conjugated BMP-2 and BMP-2/7 appeared safe, but no disc regeneration was observed. Possible explanations include too low dosages, short follow-up time, and/or insufficient release of the conjugated BMPs. These aspects should be addressed in future studies