Table 3.

Published in vivo studies in large animal models on mesenchymal stem cells for spinal arthrodesis procedures.

Animal model	MSCs source	Other biological adjuvant	Scaffold material	Experimental time (weeks)	Spinal fusion level	Experimental design	Main outcome	Reference
Pig	ADSCs from inguinal subcutaneous tissue	None	DBM	8 and 12 weeks	L2–L6	Group 1: one cage was left and three filled with freeze dried irradiated cancellous pig bone graft Group 2: freeze dried irradiated cancellous pig bone graft Group 3: cancellous bone autograft Group 4: bone graft with 3D osteogenic differentiated ADSCs	µ-CT scan, microradiography, and histology/histomorphometry demonstrated a significant increase in bone content in group 4	[50]
Sheep	Expanded and osteogenic induced BMSCs from iliac crest (5-6 × 107)	Fibrin	TCP/HA	12 weeks	L1–L6	Group 1: HA with MSCs Group 2: TCP/HA with MSCs Group 3: autograft	(i) Radiography, manual palpation, histological analysis, and SEM analyses revealed demonstrated better bone formation in group 2 compared to group 1 (ii) Histomorphometry detected 55.8% of new bone in group 3, followed by group 2 (42.7%) and group 1 (10.7%)	[51]
Sheep	Allogenic sheep mesenchymal precursor cells (MPCs) from BM from iliac crest	None	HA/TCP	16–36 weeks	L2–L5	Group 1: autograft Group 2: HA/TCP Group 3: HA/TCP with MPCs (25 × 106) Group 4: HA/TCP with MPCs (75 × 106) Group 5: HA/TCP with MPCs (225 × 106)	Computed tomography, high-resolution radiography, biomechanical testing, organ pathology, bone histopathology, and bone histomorphometry showed that allogeneic mesenchymal precursor cells produced fusion efficacy similar to that achieved using iliac crest autograft	[52]
Sheep	Allogenic MPCs from BM from sheep iliac crest	None	HA/TCP	16 weeks	L4-L5	Group 1: autograft Group 2: HA/TCP with MPCs (2.5 × 106) Group 3: HA/TCP with MPCs (6.5 × 106) Group 4: HA/TCP with MPCs (12.5 × 106)	(i) Manual palpation of the fusion site indicated solid fusion in more than 75% of MPC-treated group and 65% of group 1 (ii) Computed tomography and histomorphometry analyses showed all animals in the MPCs groups and group 1 fusion masses were present at 16 weeks	[53]
Sheep	Expanded and osteoinduced BM from iliac crest	None	HA	6 months	L4-L5	Group 1: autograft Group 2: allograft Group 3: HA Group 4: HA with MSCs.	(i) By CT scan and histology lumbar fusion were higher for groups 1 and 2 (70%) than for group 3 (22%) and group 4 (35%) (ii) New bone formation was higher for groups 1 and 2 (iii) Group 4 had a better fusion rate than group 3, but the histology showed no significant differences between them in terms of quantity of bone formation	[54]
Sheep	BM concentrate (1.5 × 106 in 0.2 mL)	None	Natural bone collagen scaffold (NBCS) from human organic bone particles	6 and 10 weeks	L3-L4 and L4-L5	Group 1: autograft Group 2: NBCS Group 3: BMCs Group 4: NBCS with BMCs	(i) Solid spinal fusion was achieved in all six segments (6/6) in group 4 at 10 weeks, compared with 4/8 segments in group 1, 2/8 segments in group 2, and 3/6 segments in group 3 (ii) The biomechanical stiffness of fusion masses and bone volume at the fusion site were higher in group 4 (p < 0.05) (iii) At 10 weeks, the radiographic score reached was significantly higher in group 4 than in groups 1, 2 and 3 (iv) Histological findings revealed that group 4 induced new bone formation integrated well with host bone tissue	[55]
Ewes	Allogenic MPCs (5 × 106) or allogenic amnion epithelial stem cells (5 × 106 AECs)	None	Fidji interbody cage made from polyetheretherketone and HA/TCP	3 months	C3-C4	Group 1: cage packed with autograft Group 2: cage packed with HA/TCP Group 3: cage packed with HA/TCP and MPCs Group 4: cage packed with HA/TCP and AECs Group 5: controls	(i) Significant fusion mass was detected in group 3 compared to that in groups 1, 2, or 4 (ii) CT scan at 3 months revealed that 5/6 animals in group 3 (83%) had continuous bony bridging compared with 0/ 5 of group 4 and 1/6 of group 1 and 2/6 of group 2 (p < 0.01)	[56]
Ewes	Allogeneic MPCs (5 × 106 or 10 × 106)	None	Fidji interbody cage made from polyetheretherketone and HA/TCP	3 months	C3-C4 anterior cervical discectomy and fusion with a interbody cage	Group 1: cage packed with autograft Group 2: cage packed with HA/TCP Group 3: cage packed with HA/TCP and 5 × 106 MPCs Group 4: cage packed with HA/TCP and 10 × 106 MPCs Group 5: controls	(i) No significant differences were found between groups 3 and 4 (ii) CT scan showed that 9/12 (75%) MPC-treated animals had continuous bony bridging compared with 1/6 of group 1 and 2/6 of group 2 (p < 0.019 and p < 0.044, resp.) (iii) By quantitative CT, density of new bone in MPC-treated animals was 121% higher than in group 2 (p < 0.017) and 128% higher than in group 1 (p < 0.0001)	[57]
Pig	BMSCs (10 × 106)	rhBMP-2 (0.6 mg)	Bioresorbable scaffolds made from medical grade poly (Σ-caprolactone)-20% tricalcium phosphate (mPCL/TCP)	9 months	L2-L3 and L4-L5	Group 1: mPCL/TCP with rhBMP-2 Group 2: mPCL/TCP with BMSCs Group 3: mPCL/TCP Group 4: autograft	(i) The mean radiographic scores were 3.0, 1.7, 1.0, and 1.8 for groups 1 to 4, respectively (ii) The bone volume fraction of group 1 was twofold higher than group 2 (iii) Histology, µ-CT, and biomechanical evaluation showed solid and comparable fusion between groups 1 and 4 (iv) Group 2 showed inferior quality of fusion when compared with groups 1 and 4 while group 3 showed no fusion even at 9 months	[58]
Ovine	Autogenous whole BM or BM concentrate	None	TCP	6 months	L4-L5	Group 1: autograft Group 2: TCP with BM concentrate Group 3: TCP with whole bone marrow/ Group 4: TCP .	(i) At 6 months, 33% of group 2 and 25% of the group 1 sites were fused, compared with 8% of group 3 and 0% of group 4 (ii) Histology of fused samples showed denser bone formation in group 2 than in group 1 sites	[59]