Single Application of Low-Dose, Hydroxyapatite-Bound BMP-2 or GDF-5 Induces Long-Term Bone Formation and Biomechanical Stabilization of a Bone Defect in a Senile Sheep Lumbar Osteopenia Model

Abstract

Effects of hydroxyapatite (HA) particles with bone morphogenetic BMP-2 or GDF-5 were compared in sheep lumbar osteopenia; in vitro release in phosphate-buffered saline (PBS) or sheep serum was assessed by ELISA. Lumbar (L) vertebral bone defects (Ø 3.5 mm) were generated in aged, osteopenic female sheep (n = 72; 9.00 ± 0.11 years; mean ± SEM). Treatment was: (a) HA particles (2.5 mg; L5); or (b) particles coated with BMP-2 (1 µg; 10 µg) or GDF-5 (5 µg; 50 µg; L4; all groups n = 6). Untouched vertebrae (L3) served as controls. Three and nine months post-therapy, bone formation was assessed by osteodensitometry, histomorphometry, and biomechanical testing. Cumulative 14-day BMP release was high in serum (76–100%), but max. 1.4% in PBS. In vivo induction of bone formation by HA particles with either growth factor was shown by: (i) significantly increased bone volume, trabecular and cortical thickness (overall increase HA + BMP vs. control close to the injection channel 71%, 110%, and 37%, respectively); (ii) partial significant effects for bone mineral density, bone formation, and compressive strength (increase 17%; 9 months; GDF‑5). Treatment effects were not dose-dependent. Combined HA and BMPs (single low-dose) highly augment long-term bone formation and biomechanical stabilization in sheep lumbar osteopenia. Thus, carrier-bound BMP doses 20,000-fold to 1000-fold lower than previously applied appear suitable for spinal fusion/bone regeneration and improved treatment safety.

Topical Application of Butyl Flufenamate Ointment Promotes Cranial Defect Healing in Mice by Inducing BMP2 Secretion in Skin Mesenchymal Stem Cells

“…We found that butyl flufenamate ointment and FFA promoted BMP2 secretion in mSMSCs both in vivo and in vitro. Butyl flufenamate ointment and FFA are generally believed to play an anti-inflammatory role [ 26 , 27 , 28 ]; we are the first to show that they can induce mSMSCs to secrete the key osteogenic factor BMP2 [ 29 , 30 , 31 ]. Although the mechanism of action by which the topical application of butyl flufenamate ointment accelerates healing of cranial defects in mice has not been completely elucidated, it is mediated by promoting BMP2 secretion in mSMSCs.…”

BMP-2 (and partially GDF-5) coating significantly accelerates and augments bone formation close to hydroxyapatite/tricalcium-phosphate/brushite implant cylinders for tibial bone defects in senile, osteopenic sheep

“…Finally, the cylinders were coated with recombinant human BMP-2 (rhBMP-2; 25 and 250 µg) or rhGDF-5 (125 and 1250 µg) by application of the BMP-containing solutions on the cylinders and subsequent sterile drying in circulating air at room temperature (Table 1 ; [ 49 ]). In brief, non-glycosylated BMP-2 was produced in E. coli using patented procedures (patent DE 199 44 626 A1; [ 49 ] and references therein) also commonly used for clinical trials in humans, GDF-5 by analogous procedures. The present dosages were chosen on the basis of BMP doses successfully applied in previous experiments with BMP-coated hydroxyapatite-titanium tibia implants [ 45 ].…”

“…Calculating the surface area required for single layer binding of BMP-2 or GDF-5, the loading protein should have been completely immobilized on the surface of the CP cylinders. Although the release kinetics of the loaded protein were not formally analyzed, an almost complete cumulative release of the surface-coated BMPs from the CP cylinders in serum within 14 days can be assumed on the basis of previous results from HA-particles ([ 49 ] and references therein).…”

“…Short-term groups received their 3rd injection 10 days before sacrifice, while the long-term group animals received a total of 5 injections (including one at 10 days before sacrifice). Oxytetracycline is incorporated into newly formed osteoid and thus “dynamically” marks bone formation within ~10 days after application (compare with images in [ 49 , 52 ]). Dynamic histomorphometrical analyses were performed in plastic-embedded sections using a fluorescence microscope (Axiovert 200 M ™ , Carl Zeiss, Microimaging GmbH, Oberkochen, Germany), 20-fold magnification, a Zeiss PlanNeoFluar-objective (excitation wavelength of 390 nm; emission wavelength of 512 nm) with an AxioCam color camera (12 V DC, 0.7 A) and the respective software (AxioVision 3.8, Carl Zeiss).…”

LIPUS-S/B@NPs regulates the release of SDF-1 and BMP-2 to promote stem cell recruitment-osteogenesis for periodontal bone regeneration

“…BMP-2 is one of the most important osteogenic growth factors in the BMP family. It has been applied for clinical fracture therapy and its ability to promote osteogenic differentiation of MSC has been demonstrated in many studies ( Lo et al, 2012 ; Hasenbein et al, 2022 ).…”