title: Anterior Cruciate Ligament-Derived Stem Cells Transduced With BMP2 Accelerate Graft-Bone Integration After ACL Reconstruction.
abstract: BACKGROUND
  Strong graft-bone integration is a prerequisite for successful graft remodeling after reconstruction of the anterior cruciate ligament (ACL) using soft tissue grafts. Novel strategies to accelerate soft tissue graft-bone integration are needed to reduce the need for bone-tendon-bone graft harvest, reduce patient convalescence, facilitate rehabilitation, and reduce total recovery time after ACL reconstruction.
  
  
  OBJECTIVE
  The application of ACL-derived stem cells with enhanced expression of bone morphogenetic protein 2 (BMP2) onto soft tissue grafts in the form of cell sheets will both accelerate and improve the quality of graft-bone integration after ACL reconstruction in a rat model.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  ACL-derived CD34+ cells were isolated from remnant human ACL tissues, virally transduced to express BMP2, and embedded within cell sheets. In a rat model of ACL injury, bilateral single-bundle ACL reconstructions were performed, in which cell sheets were wrapped around tendon autografts before reconstruction. Four groups containing a total of 48 rats (96 knees) were established (n = 12 rats; 24 knees per group): CD34+BMP2 (100%), CD34+BMP2 (25%), CD34+ (untransduced), and a control group containing no cells. Six rats from each group were euthanized 2 and 4 weeks after surgery, and each graft was harvested for immunohistochemical and histological analyses. The remaining 6 rats in each group were euthanized at 4 and 8 weeks to evaluate in situ tensile load to failure in each femur-graft-tibia complex.
  
  
  RESULTS
  In vitro, BMP2 transduction promoted the osteogenic differentiation of ACL-derived CD34+ cells while retaining their intrinsic multipotent capabilities. Osteoblast densities were greatest in the BMP2 (100%) and BMP2 (25%) groups. Bone tunnels in the CD34+BMP2 (100%) and CD34+BMP2 (25%) groups had the smallest cross-sectional areas according to micro-computed tomography analyses. Graft-bone integration occurred most rapidly in the CD34+BMP2 (25%) group. Tensile load to failure was significantly greater in the groups containing stem cells at 4 and 8 weeks after surgery. Tensile strength was greatest in the CD34+BMP2 (100%) group at 4 weeks, and in the CD34+BMP2 (25%) group at 8 weeks.
  
  
  CONCLUSIONS
  ACL-derived CD34+ cells transduced with BMP2 accelerated graft-bone integration after ACL reconstruction using soft tissue autografts in a rat model, as evidenced by improved histological appearance and graft-bone interface biology along with tensile load to failure at each time point up to 8 weeks after surgery.
  
  
  CONCLUSIONS
  A primary disadvantage of using soft tissue grafts for ACL reconstruction is the prolonged time required for bony ingrowth, which delays the initiation of midsubstance graft remodeling. The lack of consistent correlation between the appearance of a "healed" ACL on postoperative magnetic resonance imaging and readiness to return to sport results in athletes being released to sport before the graft is ready to handle high-intensity loading. Therefore, it is desirable to identify strategies that accelerate graft-bone integration, which would reduce the time to biologic fixation, improve the reliability of biologic fixation, allow for accelerated rehabilitation, and potentially reduce the incidence of early graft pullout and late midsubstance failure.
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Stem Cell Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kawakami
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Stem Cell Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Takayama
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Stem Cell Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Stem Cell Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Mifune
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Stem Cell Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Center for Regenerative Sports Medicine, Steadman Philippon Research Institute, Vail, Colorado, USA.|Department of Orthopaedic Surgery, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
authors.forename: James H
authors.initials: JH
authors.lastname: Cummins
authors.affiliation: Center for Regenerative Sports Medicine, Steadman Philippon Research Institute, Vail, Colorado, USA.|Department of Orthopaedic Surgery, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Warth
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Freddie H
authors.initials: FH
authors.lastname: Fu
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Stem Cell Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Center for Regenerative Sports Medicine, Steadman Philippon Research Institute, Vail, Colorado, USA.|Department of Orthopaedic Surgery, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA.
authors.forename: Johnny
authors.initials: J
authors.lastname: Huard
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000166:cytology*; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D010012:Osteogenesis; D051381:Rats; D011923:Rats, Nude; D015203:Reproducibility of Results; D033581:Stem Cell Transplantation; D055815:Young Adult
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2
keywords: angiogenesis; anterior cruciate ligament reconstruction; bone morphogenetic protein 2 (BMP2); gene therapy; osteogenesis; stem cells