Current evidence on potential of adipose derived stem cells to enhance bone regeneration and future projection

Table 2 Summary of the preclinical studies involving bone regeneration induced by transplantation of adipose-derived stem cells

Animal model	Scaffold used	ADSCs per implant	Time frame	Defect healing outcomes	Ref.
-Beagle Dogs; -Unilateral radial segmental defect-10 mm	β-TCP/poly l-lactide-co-glycolide-co-ε-caprolactone composite scaffold	1 × 106 canine ADSCs	20 wk	33.90 ± 4.31	Kang et al[56]
-Wistar albino rats; -Middle zygomatic arch defect; -3 mm wide	No scaffold	Rat inguinal fat pad derived SVF	20 wk	The average new bone growth in the experimental group was 1.1 mm, significantly higher than control	Toplu et al[57]
Group 1: Pre-differentiated ADSCs
-New Zealand white rabbits; -Mid-diaphysis of left ulna; -20 mm long	Porous polylactic glycolic acid scaffold	1 × 106 rabbit SVF cells	8 wk	Approximately 55%	Kim et al[58]
-Beagle dogs; -Parietal bone; -20 mm × 20 mm full-thickness defect	Coral scaffold	60 × 106 of canine ADSCs	24 wk	84.19 ± 6.45	Cui et al[59]
-Lewis rats; -Calvarial defect -8 mm wide	Polylactic scaffold	0.1 × 106 rat ADSCs	8 wk	Coculture of endothelial- and osteoblast-induced ADSC showed no significant improvement over undifferentiated cells	Shah et al[60]
-Lewis rats; -Calvarial defect; -8 mm wide	Poly (D,L-Lactide) scaffold	0.1 × 106 rat ADSCs	8 wk	Osteogenic-induced ADSC generated 0.91 ± 0.65 mm3 new bone, significantly higher than endothelial-induced ADSC	Sahar et al[61]
Group 2: FGF, VEGF, PDGF, and ADSCs
-Osterix‐mCherry reporter mice; -Closed transverse diaphysis fractures of the right femur	No scaffold	0.3 × 106 wild-type mice ADSCs	35 d	The experimental group induced significantly larger mineralized surface and bone callus compared to cell-free and non-transduced controls.	Zhang et al[62]
-Balb/c nude mice; -Parietal bone defect; -4 mm wide	Whitlockite‐reinforced gelatin/heparin cryogels	1 × 106 human ADSCs	8 wk	> 16%	Kim et al[63]
-CD1 nude mice; -Parietal bone defect; -4 mm wide	Coral scaffold	1.5 × 106 human ADSCs	8 wk	95.40%	Behr et al[64]
-Sprague Dawley rats; -Distal femoral cancellous bone -3.5 mm wide and 5 mm deep defect	Trimodal mesoporous bioactive glass scaffold	20 × 106 cell/mL until saturation; rat ADSCs	8 wk	14.25 ± 3.57	Du et al[65]
-Nu/Nu J mice; -Parietal bone; -4 mm wide	Polycaprolactone - fibrin scaffold containing heparin-conjugated decellularized bone	0.2 × 106 human ADSCs	12 wk	The experimental group induced a significantly larger new bone volume compared to the control without PDGF	Rindone et al[66]
Group 3: BMP and ADSCs
-Sprague Dawley rats; -Full-thickness parietal bone defect -5 mm wide	Polylactic glycolic acid scaffold	0.0025 × 106 human ADSCs	8 wk	33.3 ± 29.0	Park et al[67]
-Chinese white rabbits; -Full-thickness calvarial defects; -8 mm	Fibrin gel matrix	3 × 106 rabbit ADSCs	12 wk	Approximately 48	Lin et al[68]
-Japanese white rabbits; -Segmental radial defect; -15 mm	Nano-hydroxyapatite/recombinant human-like collagen/poly (lactic acid) scaffold	2 × 106 cells/ml; rabbit ADSCs	12 wk	97.25 ± 2.06	Hao et al[69]
-Taiwan Lee-Sung minipigs; -Mid-shaft left femur defect; -30 mm long	Apatite coated poly (L-lactide-co-glycolide) scaffolds	100 × 106 cells/animal; minipig ADSCs	12 wk	Experimental group’s new bone formation showed equivalent density and volume compared to native bone and is significantly better than non-transduced control	Lin et al[70]
-CD-1 nude mice; -Full-thickness parietal bone defect -3 mm wide	Porous poly(lactic-co- glycolic acid) scaffold	3 × 106 cells/mL; ADSC from C57BL/6 mouse	6 wk	77%	Fan et al[71]
-Nude mice; -Parietal bone defect; -4 mm wide	Polylactic glycolic acid scaffold	5 × 105 human ADSCs	12 wk	83%	Li et al[72]
-Nude mice; -Subcutaneous implantation	Porous poly(lactic-co- glycolic acid) scaffold	0.01 × 106 rat ADSCs	4 wk	Transduced ADSC construct induced more bone and vessel formation compared to cell-free and non-transduced control	Weimin et al[73]
-CD‐1 nude mice; -Right parietal bone defect; -4 mm wide	Polylactic glycolic acid scaffold	0.15 × 106 human ADSCs	6 wk	Up to 100%	Levi et al[74]
-Athymic nude rat; -Mandible defect; -5 × 5 mm	Chitosan/chondroitin sulfate scaffold	0.25 × 106 ADSCs from C57BL/6 mouse	8 wk	Approximately 43%	Fan et al[75]
Group 4: Genetically manipulated ADSCs
-BALB/c nude mice; -Subcutaneous implantation	β-tricalcium phosphate scaffold	2 × 106 human ADSCs	8 wk	Approximately 30%	Wang et al[76]
-Sprague Dawley rats; -Calvarial defect; -8 mm wide and 1 mm thick	Poly (sebacoyl diglyceride) scaffold	Rat ADSCs	8 wk	50.53 ± 4.45	Xie et al[77]
Group 5: Engineered scaffolds and ADSCs
-C57BL6/J mice; -Mid femur defect; -2 mm	Strontium-substituted hydroxyapatite poly (γ-benzyl-l-glutamate) scaffold	5 × 106 C57BL6/J mice ADSCs	8 wk	Approximately 38%	Gao et al[78]
-Sprague Dawley rats; -Full-thickness femur defect; -4 mm wide	NaB/polylactic glycolic acid scaffold	1 × 106 rat ADSCs	4 wk	ADSC-seeded poly lactic glycolic acid scaffold with 0.05% NaB induced the highest bone density, compared to cell-free control and other concentration of NaB	Doğan et al[79]
-Balb/c nude mice; -Cranium defect; -4 mm wide	SiRNA lipidoid nanoparticle immobilized on polydopamine coated PLGA scaffold	1.0 × 106 human ADSCs	8 wk	Approximately 75%	Shin et al[80]
-Sprague Dawley rats; -Calvarial defect; -5 mm wide	Collagen-resveratrol scaffold	0.05 × 106 human ADSCs	2 wk	Undifferentiated ADSC-seeded construct exhibited better osteogenesis compared to controls and osteoinduced ADSC seeded scaffold	Wang et al[81]
-Athymic nu/nu mice; -Subcutaneous implantation	Alginate microspheres	0.5 × 106 rabbit ADSC	12 wk	Approximately 41%	Man et al[82]
Group 6: Manipulation of recipient host and ADSCs
-Sprague-Dawley rats; -Calvarial defect; -7 mm wide	Polylactic glycolic acid scaffold	1 × 106 human ADSCs	12 wk	Approximately 60%	Wang et al[83]
-C57 black/DBA mice; -Supracondylar right femur defect -0.9 mm wide	Hydrogel	0.3 × 106 mice ADSC	8 wk	Approximately 50%	Deng et al[84]
-Osteoporotic Sprague-Dawley female rats; -Distal epiphysis left femur defect; -3 mm wide	Gelatin	2 × 106 rat ADSCs	5 wk	Approximately 23%	Li et al[85]
Group 7: Allogeneic ADSCs
-New Zealand white rabbits; -Ulna defect; -15 mm	Demineralized bone matrix	60 × 106 rabbit ADSCs	12 wk	Both allogeneic and autologous ADSC seeded construct induced almost complete defect repair while cell-free control remained unrepaired	Gu et al[86]
-Sprague Dawley rats; -Ulna defect; -8 mm long	Demineralized bone matrix	60 × 106 rat ADSCs	24 wk	Radiographs and histology confirmed superior bone healing in the experimental group compared to cell-free control	Wen et al[87]
-Beagle Dogs; -Parietal bone defect; -20 × 20 mm	Coral scaffold	60 × 106 of canine ADSC	24 wk	Approximately 70%	Liu et al[88]
-Wistar rats; -Left radius defect; -4 mm long	Heterogeneous deproteinized bone	0.1 × 106 rat ADSCs	8 wk	Radiographs and histology confirmed improved healing in osteoinduced ADSC/scaffold group compared to undifferentiated ADSC, cell-free, and blank controls	Liu et al[89]
Group 8: Non-manipulated or unaltered ADSCs
Decellularized matrices
-CD1 nude mice; -Distal femur defect -3 mm	Human cancellous bone scaffold	0.5 × 106 human ADSCs	8 wk	hADSCs-seeded scaffold induced significantly superior defect healing compared to cell-free scaffold	Wagner et al[90]
-C57BL/6 mice; -Calvarial defect; -4 mm wide	Extracellular matrix deposited on porcine small intestinal submucosa	0.0025 × 106 of human ADSCs	4 wk	21.77 ± 6.99	Zhang et al[91]
-Institute of Cancer Research mice; -Full-thickness parietal defect; -4 mm wide	Decellularized tendon	1.0 × 106 human ADSCs	8 wk	86%	Ko et al[92]
-Sprague Dawley rats; -Two-wall periodontal intrabony defect; -2.6 × 2.0 × 2.0 mm	Amniotic membrane	0.3 × 106 human ADSCs	3 wk	ADSC-seeded scaffold resulted in a significantly smaller defect size than the control	Wu et al[93]
Ceramics
-Sheep; -Tibia; -3.2 cm long defect	Hydroxyapatite-based particle in a semi-solid milieu	56 × 106 human ADSCs	12 wk	The experimental group showed bridging and significantly better healing compared to control	Ben-David et al[94]
-New Zealand White rabbits; -Full-thickness proximal medial tibia defect; -8 mm wide	Hydroxyapatite	0.2 × 106 rabbit ADSCs	8 wk	The new bone area was equivalent between seeded and unseeded scaffold; however, ADSC seeded construct represented preferable histological characteristics	Arrigoni et al[95]
-New Zealand White rabbits; -Full-thickness proximal medial tibia; -8 mm in diameter	Hydroxyapatite	1.5 × 106 rabbit ADSCs	8 wk	ADSC-seeded scaffold exhibited better scaffold resorption than cell-free scaffold and superior histological characteristics compared to all controls	De Girolamo et al[96]
-Fisher 344 rats; -Calvarial defect; -5 mm wide	Hydroxyapatite	0.4 × 105 rat ADSCs	8 wk	16.88 ± 1.52	Xia et al[97]
-T and B cell-deficient NOD SCID mice; -Subcutaneous implantation	Type I collagen (30%) and magnesium-enriched hydroxyapatite	1 × 106 human ADSCs	8 wk	hADSC-seeded presented improved osteogenesis and angiogenesis compared to cell-free scaffold control	Calabrese et al[98]
-Miniature Pigs; -Mandibular defect -3 cm × 1 cm × 2 cm	Tri-calcium phosphate- poly (D,L-lactide-co-glycolide) scaffolds	5 × 106 porcine ADSCs	12 wk	34.8 ± 4.80	Probst et al[99]
Bioactive glass
-Wistar rats; -Full-thickness calvarial defect; -8 mm wide	Bioactive glass	0.5 × 106 rat ADSCs	12 wk	ADSC-seeded scaffold group exhibited significantly more bone repair and higher bone density compared to blank control. ADSC construct’s result was equivalent to that of autologous bone graft	Saçak et al[100]
-Sprague Dawley rats; -Parietal bone defect; -8 mm wide	Icariin doped bioactive glass	0.5 × 106 rat ADSCs	12 wk	The experimental group saw the complete repair of the defect while all controls showed various degrees of incomplete healing; repair in the experimental group is characterized by mature bone and complete scaffold resorption	Jing et al[101]
Polymers
-Wistar rats; -Calvarial defect; -5 mm wide	Polycaprolactone scaffold	0.05 × 106 human ADSCs	8 wk	Both undifferentiated and osteo-induced ADSC-seeded scaffold resulted in preferable histological features and higher expression of osteogenesis and angiogenesis markers	Caetano et al[102]
Platelet-rich plasma as carrier material
-Beagle dogs; -Tibial defects; -10 mm wide	Activated platelet-rich plasma	1.0 × 106 human ADSCs	6 wk	68.97 ± 0.91	Cruz et al[103]
-F344 rat; -Calvarial defect; -5 mm wide	Activated platelet-rich plasma	0.2 × 106 rat ADSCs	8 wk	95.60	Tajima et al[104]
Hybrid materials
-New Zealand white rabbits; -Calvarial defect; -10 mm wide	Hyaluronic acid-g-chitosan-g-poly (N-isopropylacrylamide) embedded with biphasic calcium phosphate microparticles and PRP	0.1 × 106 rabbit ADSCs	16 wk	The experimental group induced obvious significant bone formation and defect bridging. Cell-free scaffold control showed negligible defect repair	Liao et al[105]
-Sprague Dawley rats; -Parietal defect; -5 mm wide	Multi-layered stacking of electrospun polycaprolactone/gelatin membranes	0.006 × 106 rat ADSCs	12 wk	Up to 90%	Wan et al[106]
-Balb/c nude mice; -Calvarial defect; -4 mm wide	1H,1H,2H,2H-per- fluorodecyl acrylate (97%) and glycidyl methacrylate coated paper scaffold	1.0 × 106 cells/paper human ADSCs	8 wk	92%	Park et al[107]

ADSCs: Adipose-derived stem cells; SVF: Stromal Vascular Fraction; PRP: Platelet-rich plasma.