Bone Marrow Derived Mesenchymal Stem Cells Transduced with an Adenoviral Vector Carrying the Gene for Human BMP-2 Can Induce Anterior Spinal Fusion

Neill M. Wrigbt, MD
Jeuren Lou, MD
Su–Li Cbeng, PhD,
K Daniel Riew, MD
Louis Avioli, MD (St. Louis, MO)

Introduction:

Bone morphogenetic protein augments spinal fusion. However, applications in the intervertebral disc space have been unsuccessful. In this study, porcine bone marrow–derived stem cells (MSC) were transformed into an osteogenic phenotype by transduction with an adenoviral–BMP2 construct. These transduced MSC were injected into the intervertebral disc space to induce fusion.

Methods:

Rib MSC were harvested, expanded in vitro, and transduced with either Adv–BMP2 or Adv–bGal (control). BMP–2 expression was confirmed in vitro with immunostaining and Western blot. The osteoblastic potential of transduced MSC was confirmed with alkaline phosphatase activity and matrix mineralization. The expression of bone matrix proteins was determined by Western blot.

Adv–BMP2–MSC and control MSC (Adv–bGal and non–transduced) were autologously re–implanted into non–adjacent intervertebral discs of three pigs thoracoscopically. Animals were sacrificed at 6 weeks, and harvested spines were examined radiographically and histologically.

Results:

hBMP–2 was detected by Western blot only in the conditioned medium of Adv–BMP2–MSC. lmmunostaining confirmed expression of hBMP–2 in Adv–BMP2–MSC. The osteogenic potential of Adv–BMP2–MSC was evidenced by a five–fold increase in alkaline phosphatase activity and by matrix mineralization. Increased expression of type I collagen, osteopontin, and bone sialoprotein was demonstrated by Western blotting.

On radiographic analysis, only spaces implanted with Adv–BMP2– MSC demonstrated new bone formation. Histological analysis revealed new bone formation and disc space fusion only in levels treated with Adv–BMP2–MSC.

Conclusion:

Bone marrow–derived MSC were successfully transduced with Adv–BMP2 into an osteogenic phenotype. Furthermore, these transduced cells autonomously induced anterior intervertebral fusion.