Hairong Peng

Dominant negative Bmp5 mutation reveals key role of BMPs in skeletal response to mechanical stimulation

BackgroundOver a hundred years ago, Wolff originally observed that bone growth and remodeling are exquisitely sensitive to mechanical forces acting on the skeleton. Clinical studies have noted that the size and the strength of bone increase with weight bearing and muscular activity and decrease with bed rest and disuse. Although the processes of mechanotransduction and functional response of bone to mechanical strain have been extensively studied, the molecular signaling mechanisms that mediate the response of bone cells to mechanical stimulation remain unclear.ResultsHere, we identify a novel germline mutation at the mouse Bone morphogenetic protein 5 (Bmp5) locus. Genetic analysis shows that the mutation occurs at a site encoding the proteolytic processing sequence of the BMP5 protein and blocks proper processing of BMP5. Anatomic studies reveal that this mutation affects the formation of multiple skeletal features including several muscle-induced skeletal sites in vivo. Biomechanical studies of osteoblasts from these anatomic sites show that the mutation inhibits the proper response of bone cells to mechanical stimulation.ConclusionThe results from these genetic, biochemical, and biomechanical studies suggest that BMPs are required not only for skeletal patterning during embryonic development, but also for bone response and remodeling to mechanical stimulation at specific anatomic sites in the skeleton.

[Ex-vivo gene therapy with BMP-4 for critically sized defects and enhancement of fracture healing in an osteoporotic animal model].

Fractures in osteoporotic bones or segment defects are problematic bone lesions with a reduced biological capability of regeneration. We tested the hypothesis that cell-mediated ex vivo gene therapy to deliver BMP4 can heal critically sized defects and improve bone healing in osteoporotic rats. Primary muscle-derived cells were isolated from the hindlimb muscle of rats and retrovirally transduced to express bone morphogenic protein 4 (BMP4). The bone formation was evaluated following local application of these cells in critically sized defects and in fractures of osteoporotic bones. Radiographic analysis revealed bridging callus formation in a critically sized defect in all specimens using muscle-derived cells expressing BMP4 at 12 weeks. These findings were confirmed by histological evaluation, which revealed callus bone formation with good integration to the distal and proximal bone. Following treatment with muscle-derived cells expressing BMP4, the bone healing process in the osteoporotic bone was improved to the level similar to that of normal bone. The ex vivo gene therapy could be a promising tool for the treatment of osteoporotic fractures and critically sized defects. The reduced number of complications (nonunions, loss of reduction, and fragment dislocation), shortening of hospitalization period, and improvement of bone strength are decisive advocates for this treatment option.ZusammenfassungProblematische Knochenläsionen wie Frakturen bei Osteoporose und Segmentdefekte besitzen eine verminderte biologische Regenerationspotenz. Die zusätzliche Applikation von Wachstumsfaktoren in Verbindung mit der Ex-vivo-Gentherapie könnte hierfür eine mögliche Therapiemethode darstellen.Aus der Muskulatur von Ratten wurden Myofibroblasten isoliert und retroviral transduziert, um eine Expression von „Bone-morphogenic-Proteinxa04“ (BMP4) zu erreichen. Der Einfluss dieser Zellen auf die Knochenneubildung wurde nach der lokalen Anwendung in knöchernen Segmentdefekten sowie in Frakturen osteoporotischer Knochen der Ratte untersucht.Die Ex-vivo-Gentherapie isolierter Myofibroblasten konnte durch die zellvermittelte Applikation von BMP4 kritische Substanzdefekte im Femur der Ratte nach 12xa0Wochen überbrücken und knöchern überbauen. Die Frakturheilung im osteoporotischen Knochen zeigte 4xa0Wochen nach Ex-vivo-Gentherapie eine vermehrte Kallusbildung gegenüber Frakturen im osteoporotischen Knochen ohne Therapie.Die Ex-vivo-Gentherapie stellt eine vielversprechende Therapiemethode bei osteoporotischen Frakturen und Segmentdefekten dar. Geringere Komplikationen (Pseudarthrosen, Repositionsverlust, Fragmentdislokation), kürzere Hospitalisationszeiten sowie Verbesserung der Knochenqualität stellen dabei wichtige klinische Aspekte dar.AbstractFractures in osteoporotic bones or segment defects are problematic bone lesions with a reduced biological capability of regeneration. We tested the hypothesis that cell-mediated ex vivo gene therapy to deliver BMP4 can heal critically sized defects and improve bone healing in osteoporotic rats.Primary muscle-derived cells were isolated from the hindlimb muscle of rats and retrovirally transduced to express bone morphogenic protein 4 (BMP4). The bone formation was evaluated following local application of these cells in critically sized defects and in fractures of osteoporotic bones.Radiographic analysis revealed bridging callus formation in a critically sized defect in all specimens using muscle-derived cells expressing BMP4 at 12xa0weeks. These findings were confirmed by histological evaluation, which revealed callus bone formation with good integration to the distal and proximal bone. Following treatment with muscle-derived cells expressing BMP4, the bone healing process in the osteoporotic bone was improved to the level similar to that of normal bone.The ex vivo gene therapy could be a promising tool for the treatment of osteoporotic fractures and critically sized defects. The reduced number of complications (nonunions, loss of reduction, and fragment dislocation), shortening of hospitalization period, and improvement of bone strength are decisive advocates for this treatment option.

Ex-vivo-gentherapie mit BMP4 bei kritischen substanzdefekten und frakturen im osteoporotischen tiermodell

Fractures in osteoporotic bones or segment defects are problematic bone lesions with a reduced biological capability of regeneration. We tested the hypothesis that cell-mediated ex vivo gene therapy to deliver BMP4 can heal critically sized defects and improve bone healing in osteoporotic rats. Primary muscle-derived cells were isolated from the hindlimb muscle of rats and retrovirally transduced to express bone morphogenic protein 4 (BMP4). The bone formation was evaluated following local application of these cells in critically sized defects and in fractures of osteoporotic bones. Radiographic analysis revealed bridging callus formation in a critically sized defect in all specimens using muscle-derived cells expressing BMP4 at 12 weeks. These findings were confirmed by histological evaluation, which revealed callus bone formation with good integration to the distal and proximal bone. Following treatment with muscle-derived cells expressing BMP4, the bone healing process in the osteoporotic bone was improved to the level similar to that of normal bone. The ex vivo gene therapy could be a promising tool for the treatment of osteoporotic fractures and critically sized defects. The reduced number of complications (nonunions, loss of reduction, and fragment dislocation), shortening of hospitalization period, and improvement of bone strength are decisive advocates for this treatment option.ZusammenfassungProblematische Knochenläsionen wie Frakturen bei Osteoporose und Segmentdefekte besitzen eine verminderte biologische Regenerationspotenz. Die zusätzliche Applikation von Wachstumsfaktoren in Verbindung mit der Ex-vivo-Gentherapie könnte hierfür eine mögliche Therapiemethode darstellen.Aus der Muskulatur von Ratten wurden Myofibroblasten isoliert und retroviral transduziert, um eine Expression von „Bone-morphogenic-Proteinxa04“ (BMP4) zu erreichen. Der Einfluss dieser Zellen auf die Knochenneubildung wurde nach der lokalen Anwendung in knöchernen Segmentdefekten sowie in Frakturen osteoporotischer Knochen der Ratte untersucht.Die Ex-vivo-Gentherapie isolierter Myofibroblasten konnte durch die zellvermittelte Applikation von BMP4 kritische Substanzdefekte im Femur der Ratte nach 12xa0Wochen überbrücken und knöchern überbauen. Die Frakturheilung im osteoporotischen Knochen zeigte 4xa0Wochen nach Ex-vivo-Gentherapie eine vermehrte Kallusbildung gegenüber Frakturen im osteoporotischen Knochen ohne Therapie.Die Ex-vivo-Gentherapie stellt eine vielversprechende Therapiemethode bei osteoporotischen Frakturen und Segmentdefekten dar. Geringere Komplikationen (Pseudarthrosen, Repositionsverlust, Fragmentdislokation), kürzere Hospitalisationszeiten sowie Verbesserung der Knochenqualität stellen dabei wichtige klinische Aspekte dar.AbstractFractures in osteoporotic bones or segment defects are problematic bone lesions with a reduced biological capability of regeneration. We tested the hypothesis that cell-mediated ex vivo gene therapy to deliver BMP4 can heal critically sized defects and improve bone healing in osteoporotic rats.Primary muscle-derived cells were isolated from the hindlimb muscle of rats and retrovirally transduced to express bone morphogenic protein 4 (BMP4). The bone formation was evaluated following local application of these cells in critically sized defects and in fractures of osteoporotic bones.Radiographic analysis revealed bridging callus formation in a critically sized defect in all specimens using muscle-derived cells expressing BMP4 at 12xa0weeks. These findings were confirmed by histological evaluation, which revealed callus bone formation with good integration to the distal and proximal bone. Following treatment with muscle-derived cells expressing BMP4, the bone healing process in the osteoporotic bone was improved to the level similar to that of normal bone.The ex vivo gene therapy could be a promising tool for the treatment of osteoporotic fractures and critically sized defects. The reduced number of complications (nonunions, loss of reduction, and fragment dislocation), shortening of hospitalization period, and improvement of bone strength are decisive advocates for this treatment option.

Ex-vivo-Gentherapie mit BMP4 bei kritischen Substanzdefekten und Frakturen im osteoporotischen Tiermodell@@@Treatment of critically sized defects and enhancement of fracture healing in an osteoporotic animal model based on ex vivo gene therapy using BMP4

Fractures in osteoporotic bones or segment defects are problematic bone lesions with a reduced biological capability of regeneration. We tested the hypothesis that cell-mediated ex vivo gene therapy to deliver BMP4 can heal critically sized defects and improve bone healing in osteoporotic rats. Primary muscle-derived cells were isolated from the hindlimb muscle of rats and retrovirally transduced to express bone morphogenic protein 4 (BMP4). The bone formation was evaluated following local application of these cells in critically sized defects and in fractures of osteoporotic bones. Radiographic analysis revealed bridging callus formation in a critically sized defect in all specimens using muscle-derived cells expressing BMP4 at 12 weeks. These findings were confirmed by histological evaluation, which revealed callus bone formation with good integration to the distal and proximal bone. Following treatment with muscle-derived cells expressing BMP4, the bone healing process in the osteoporotic bone was improved to the level similar to that of normal bone. The ex vivo gene therapy could be a promising tool for the treatment of osteoporotic fractures and critically sized defects. The reduced number of complications (nonunions, loss of reduction, and fragment dislocation), shortening of hospitalization period, and improvement of bone strength are decisive advocates for this treatment option.ZusammenfassungProblematische Knochenläsionen wie Frakturen bei Osteoporose und Segmentdefekte besitzen eine verminderte biologische Regenerationspotenz. Die zusätzliche Applikation von Wachstumsfaktoren in Verbindung mit der Ex-vivo-Gentherapie könnte hierfür eine mögliche Therapiemethode darstellen.Aus der Muskulatur von Ratten wurden Myofibroblasten isoliert und retroviral transduziert, um eine Expression von „Bone-morphogenic-Proteinxa04“ (BMP4) zu erreichen. Der Einfluss dieser Zellen auf die Knochenneubildung wurde nach der lokalen Anwendung in knöchernen Segmentdefekten sowie in Frakturen osteoporotischer Knochen der Ratte untersucht.Die Ex-vivo-Gentherapie isolierter Myofibroblasten konnte durch die zellvermittelte Applikation von BMP4 kritische Substanzdefekte im Femur der Ratte nach 12xa0Wochen überbrücken und knöchern überbauen. Die Frakturheilung im osteoporotischen Knochen zeigte 4xa0Wochen nach Ex-vivo-Gentherapie eine vermehrte Kallusbildung gegenüber Frakturen im osteoporotischen Knochen ohne Therapie.Die Ex-vivo-Gentherapie stellt eine vielversprechende Therapiemethode bei osteoporotischen Frakturen und Segmentdefekten dar. Geringere Komplikationen (Pseudarthrosen, Repositionsverlust, Fragmentdislokation), kürzere Hospitalisationszeiten sowie Verbesserung der Knochenqualität stellen dabei wichtige klinische Aspekte dar.AbstractFractures in osteoporotic bones or segment defects are problematic bone lesions with a reduced biological capability of regeneration. We tested the hypothesis that cell-mediated ex vivo gene therapy to deliver BMP4 can heal critically sized defects and improve bone healing in osteoporotic rats.Primary muscle-derived cells were isolated from the hindlimb muscle of rats and retrovirally transduced to express bone morphogenic protein 4 (BMP4). The bone formation was evaluated following local application of these cells in critically sized defects and in fractures of osteoporotic bones.Radiographic analysis revealed bridging callus formation in a critically sized defect in all specimens using muscle-derived cells expressing BMP4 at 12xa0weeks. These findings were confirmed by histological evaluation, which revealed callus bone formation with good integration to the distal and proximal bone. Following treatment with muscle-derived cells expressing BMP4, the bone healing process in the osteoporotic bone was improved to the level similar to that of normal bone.The ex vivo gene therapy could be a promising tool for the treatment of osteoporotic fractures and critically sized defects. The reduced number of complications (nonunions, loss of reduction, and fragment dislocation), shortening of hospitalization period, and improvement of bone strength are decisive advocates for this treatment option.

923. Muscle Stem Cells Genetically Modified to Express a VEGF Antagonist Display an Impaired Ability for Cardiac Repair

Background: The exact mechanism by which cardiac cell transplantation exerts therapeutic improvements in cardiac function is unclear. One possible mechanism is that the transplanted cells act by promoting neoangiogenesis within the infarct through their release of angiogenic factors. Our previous research has demonstrated that skeletal muscle-derived stem cells (MDSCs) expressed vascular endothelial growth factor (VEGF), a potent angiogenic factor, after transplantation in infarcted hearts. These results led us to hypothesize that VEGF expression by the transplanted MDSCs mediates functional improvements. To test this hypothesis, we performed a set of experiments in which we genetically modified MDSCs to overexpress VEGF (gain-of-function) or overexpress soluble FLT-1, which is a soluble VEGF receptor and antagonist of VEGF (loss-of-function).