N-methyl pyrrolidone/bone morphogenetic protein-2 double delivery with in situ forming implants

Abstract

Bone morphogenetic proteins (BMPs) are growth and differentiation factors involved during development in morphogenesis, organogenesis and later mainly in regeneration processes, in particular in bone where they are responsible for osteoinduction. For more than a decade, recombinant human (rh)BMP-2 has been used in the clinic for lumbar spinal fusion at non-physiological high dosages that appear to be causative for side effects, like male sterility. A possible strategy to reduce the effective amount of rhBMP-2 in the clinic is the co-delivery with an enhancer of BMPs' activity. In an earlier study, we showed that N-methylpyrrolidone (NMP) enhances BMP activity in vitro and in vivo. Here we report on the development of a slow and sustained double delivery of rhBMP-2 and NMP via an in situ forming implant based on poly(lactide-co-glycolide). The results showed that the release of NMP can be adjusted by varying the lactide/glycolide ratio and the polymer's molecular weight. The same applied to rhBMP-2, with release rates that could be sustained from two to three weeks. In the in vivo model of a critical size defect in the calvarial bone of rabbits, the implant containing 50 mol% lactide performed better than the one having 75 mol% lactide in terms of defect bridging and extent of bony regenerated area. In situ forming implants for the double delivery of the BMP enhancer NMP and rhBMP-2 appear to be promising delivery systems in bone regeneration. ABSTRACTBone morphogenetic proteins (BMPs) are growth and differentiation factors involved during development in morphogenesis, organogenesis and later mainly in regeneration processes, in particular in bone where they are responsible for osteoinduction. For more than a decade, recombinant human (rh)BMP-2 has been used in the clinic for lumbar spinal fusion at non-physiological high dosages that appear to be causative for side effects, like male sterility. A possible strategy to reduce the effective amount of rhBMP-2 in the clinic is the co-delivery with an enhancer of BMPs' activity. In an earlier study, we showed that N-methylpyrrolidone (NMP) enhances BMP activity in vitro and in vivo. Here we report on the development of a slow and sustained double delivery of rhBMP-2 and NMP via an in situ forming implant based on poly(lactide-co-glycolide). The results showed that the release of NMP can be adjusted by varying the lactide/glycolide ratio and the polymer's molecular weight. The same applied to rhBMP-2, with release rates that could be sustained from two to three weeks. In the in vivo model of a critical size defect in the calvarial bone of rabbits, the implant containing 50 mol% lactide performed better than the one having 75 mol% lactide in terms of defect bridging and extent of bony regenerated area. In situ forming implants for the double delivery of the BMP enhancer NMP and rhBMP-2 appear to be promising delivery systems in bone regeneration.

The Use of Adipose Tissue-Derived Progenitors in Bone Tissue Engineering - a Review

“…Using an in situ forming implants (ISFI) system; we developed a slow and sustained double delivery mechanism for rh BMP-2 and its enhancer NMP. Using the dual delivery ISFI system, rh BMP-2 and NMP were shown to bridge the critical size defect in the calvarial bone and aid in bone regeneration [51]. Thus enhancer small molecules like NMP could replace the high dose of BMPs and activate the action of the growth factors for efficient osteogenesis.…”

Bone Regeneration Using N-Methyl-2-pyrrolidone as an Enhancer for Recombinant Human Bone Morphogenetic Protein-2 in a Rabbit Sinus Augmentation Model

“…In calvarial defects of critical size in rabbits, it was demonstrated that the addition of NMP enhanced an ineffective rhBMP-2 dose (12  μ g), leading to significant bone regeneration compared to a control scaffold [10]. In the present study, a smaller dose (3.75  μ g) was applied to each sinus.…”

“…To date, few in vivo studies have tested the use of NMP for localized bone regeneration [11, 19], especially when using low-dose rhBMP-2 [10]. In calvarial defects of critical size in rabbits, it was demonstrated that the addition of NMP enhanced an ineffective rhBMP-2 dose (12  μ g), leading to significant bone regeneration compared to a control scaffold [10].…”

“…NMP is a water- and solvent-soluble molecule of low weight, which makes it difficult to deliver in a controlled and slow manner [10]. NMP incorporated in the membrane starts to be released immediately after being placed at the surgical site, and the membrane becomes stiff again [19].…”

“…Even though NMP was originally used as a plasticizer, enhanced bone regeneration was observed in rabbit calvarial defects. In further experiments, NMP treatment increased alkaline phosphatase activity and calcium deposition in the presence of rhBMP-2 at a lower-than-usual dose [10]. At the molecular level, NMP enhanced the kinase activity of the bone morphogenetic protein (BMP) receptor type I homodimer, which led to increases in Smad and p38 phosphorylation.…”