Systematic Reviews
Copyright ©The Author(s) 2020.
World J Orthop. Jul 18, 2020; 11(7): 328-344
Published online Jul 18, 2020. doi: 10.5312/wjo.v11.i7.328
Table 1 Descriptive summaries of the identified studies investigating the effect of oxysterols on bone formation in spinal fusion models (n = 5)
Ref. (level of evidence)Species (n)Surgical model and scaffold(s) usedExperimental groups (n)Assessment method and time pointFusion rate (no. fused/total)
Johnson et al[21], 2011 (V)Rat (n = 59)L4–L5 PLF using a collagen sponge supplemented with Oxy341, Oxy49, or rhBMP-2A. DMSO only (control) (n = 9)No motion bilaterally via manual palpation at 9 wk post-operativelyA. 0% (0/9)
B. 5-μg rhBMP-2 (n = 10)B. 100% (10/10)
C. 0.2-mg Oxy34 (n = 10)C. 0% (0/10)
D. 2-mg Oxy34 (n = 10)D. 50% (5/10)
E. 20-mg Oxy34 (n = 10)E. 100% (10/10)
F. 20-mg Oxy49 (n = 10)F. 100% (10/10)
Stappenbeck et al[20], 2012 (V)Rat (n = 30)L4-L5 PLF using a collagen sponge supplemented with Oxy41, Oxy18, or Oxy212A. 2-mg Oxy4 (n = 10)Fusion rate was not reported; however, via μ-computed tomographic analysis, treatment with Oxy21 led to significantly larger de novo bone volumes compared to treatment with Oxy4, which was comparable to treatment with Oxy18
B. 2-mg Oxy18 (n = 10)
C. 2-mg Oxy21 (n = 10)
Montgomery et al[19], 2014 (V)Rat (n = 38)L4-L5 PLF using a collagen sponge supplemented with Oxy1332 or rhBMP-2A. DMSO only (control) (n = 7)No motion bilaterally via manual palpation at 8 wk post-operativelyA. 0% (0/7)
B. 5-μg rhBMP-2 (n = 8)B. 100% (8/8)
C. 0.2-mg Oxy133 (n = 8)C. 0% (0/8)
D. 2-mg Oxy133 (n = 8)D. 50% (4/8)
E. 20-mg Oxy133 (n = 7)E. 86% (6/7)
Scott et al[31], 2015 (V)Rabbit (n = 22)L4-L5 PLF using iliac crest autograft supplemented with Oxy133 or rhBMP-2A. Saline only (control) (n = 5)No motion bilaterally via manual palpation at 8 wk post-operativelyA. 0% (0/5)
B. 30-μg rhBMP-2 (n = 6)B. 83.3% (5/6)
C. 20-mg Oxy133 (n = 6)C. 83.3% (5/6)
D. 60-mg Oxy133 (n = 5)D. 80% (4/5)
Buser et al[33], 2017 (V)Rat (n = 64)L3-L5 posterolateral fusion (PLF) using a collagen sponge supplemented with Oxy133 and/or rhBMP-2A. DMSO only (control) (n = 32, 8 rats/4 segments each)No motion at the operated segment via manual palpation at 8 wk post-operativelyA. 0% (0/32)
B. 0.5-µg rhBMP-2 (n = 32, 8 rats/4 segments each)B. 69% (22/32)
C. 5-µg rhBMP-2 (n = 32, 8 rats/4 segments each)C. 100% (32/32)
D. 5-mg Oxy133 (n = 32, 8 rats/4 segments each)D. 100% (32/32)
E. 20-mg Oxy133 (n = 32, 8 rats/4 segments each)E. 100% (32/32)
F. 0.5-µg rhBMP2 + 5-mg Oxy133 (n = 32, 8 rats/4 segments each)F. 100% (32/32)
G. 0.5-µg rhBMP2 + 20-mg Oxy133 (n = 32, 8 rats/4 segments each)G. 100% (32/32)
H. 5-µg rhBMP2 + 20-mg Oxy133 (n = 32, 8 rats/4 segments each)H: 100% (32/32)
1Oxy4 and Oxy34 are identical.
2Oxy21 and Oxy133 are identical. PLF: Posterolateral inter-transverse process spinal fusion; rhBMP-2: Recombinant human bone morphogenetic protein-2; DMSO: Dimethyl sulfoxide.
Table 2 Descriptive summaries of the identified studies investigating the effect of oxysterols on bone formation in critical-sized alveolar defect models (n = 2)
Ref. (level of evidence)Species (n)Surgical model and scaffold(s) usedExperimental groups (n)Assessment method and time pointBone regeneration (%):1
Lee et al[35], 2017 (V)Rat (n = 9)Regeneration of critical-size alveolar defects (left and right maxillary first molars) using equimolar amounts of 20(S)-OHC and 22(S)-OHC (dissolved in 1% DMSO in PBS) or rhBMP-2 in solutionA. DMSO only (control) (n = 3)Bone regeneration as assessed via µ-CT at 15 days of healing.A. Approximately 45%
B. 15-µg rhBMP-2 (n = 3)B. Approximately 53%
C. 0.40-µg of 20(S)-OHC and 22(S)-OHC (n = 3)C. Approximately 65%
Bakshi et al[37], 2019 (V)Rat (n = not reported)Regeneration of a critical-size alveolar defect (7 mm × 4 mm × 3 mm) using a collagen sponge supplemented with rhBMP-2 or a mixture of 20(S)-OHC and 22(R)-OHC oxysterolsA. No treatmentBone regeneration as assessed via µ-CT at 8 weeks of healing.A. Approximately 65%
Collagen spongeB. No additiveB. Approximately 72%
C. 12.5-µg of rhBMP-2C. Approximately 92%a
D. 20-mg of 20(S)-OHC and 22(R)-OHCD. Approximately 90%a
1Percent bone regeneration of critical-sized defect.
aP < 0.05, compared to collagen sponge only and to no treatment. rhBMP-2: Recombinant human bone morphogenetic protein-2; OHC: Hydroxycholesterol; DMSO: Dimethyl sulfoxide; PBS: Phosphate buffer solution; µ-CT: Micro-computed tomography.
Table 3 Descriptive summaries of the identified studies investigating the effect of oxysterols on bone formation in critical-sized calvarial defect models (n = 6)
Ref. (level of evidence)Species (n)Surgical model and scaffold(s) usedExperimental groups (n)Assessment method and time pointBone regeneration (%):1
Aghaloo et al[17], 2007 (V)Rat (n = 15)Regeneration of critical-sized, bilateral parietal defects (5-mm) using PLGA (porosity: 92%) scaffolds supplemented with 20(S)-OHC and 22(S)-OHC.A. PBS only (control) (n = 12 defects)Bone regeneration as assessed via µ-CT at 6 weeks of healing.A. approximately 12%
B. 70-ng 20(S)-OHC + 70-ng 22(S)-OHC (n = 9 defects)B. approximately 21%a
C. 700-ng 20(S)-OHC + 700-ng 22(S)-OHC (n = 9 defects)C. approximately 22%a
Hokugo et al[30], 2014 (V)Rat (n = not reported)Regeneration of critical-sized, right parietal defects (5-mm) using a gelatin hydrogel soaked with 20(S)-OHC or incorporating 20(S)-OHC-containing micelles.A. No implantation (empty defect) (n = 4 defects)Percent bone regeneration was not reported; however, via μ-CT observation at 6 wk, “no” bone regeneration was observed in untreated defects, “some” bone formation was noted in the periphery of defects implanted with gelatin hydrogel and gelatin hydrogel + 20(S)-OHC, and “robust” bone formation was observed in defects treated with gelatin hydrogel + 20(S)-OHC-micelle.
B. Gelatin hydrogel alone (n = 4 defects) (mass not reported)
C. 20(S)-OHC-gelatin hydrogel (without micelle) (n = 4 defects) (mass not reported)
D. 20(S)-OHC-micelle-gelatin hydrogel (n = 4 defects) (mass not reported)
Hokugo et al[32], 2016 (V)Rabbit (n = 25)Regeneration of critical-sized cranial defect (6-mm; 4 defects/cranium) using a collagen sponge supplemented with rhBMP-2 and/or Oxy49.A. No treatment (empty defect) (n = 5)Bone regeneration as assessed via µ-CT at 6 weeks of healing.A. approximately 10%a
B. Collagen sponge only (n = 5)B. approximately 35%
C. 75-μg rhBMP-2 (n = 5)C. approximately 65%a
D. 1-mg Oxy49 (n = 5)D. approximately 55%a
E. 10-mg Oxy49 (n = 5)E. approximately 65%a
Li et al[36], 2017 (V)Rabbit (n = not reported)Regeneration of critical-sized cranial defect (8-mm; 4 defects/cranium) using a collagen sponge supplemented with Oxy1332 and/or rhBMP-2.A. No treatment (n ≥ 6 defects)Percent bone regeneration was not reported; however, via micro-CT analysis at 6 wk, significantly greater bone formation was observed following treatment with either 10-mg Oxy133 or 7-μg rhBMP-2 relative to treatment with collagen alone.
B. Collagen sponge only (n ≥ 6 defects)
C. 7-μg rhBMP-2 (n ≥ 6 defects)
D. 1-mg Oxy133 (n ≥ 6 defects)
E. 10-mg Oxy133 (n ≥ 6 defects)
Cui et al[34], 2017 (V)Mouse (n = 12)Regeneration of critical-sized, right side cranial defects (3-mm) using MeGC hydrogels supplemented with BMSCs and either SA/Cholesterol or SA/20(S)-OHC sterosomes.A. No treatment (empty defect) (n = 4)Bone regeneration as assessed via µ-CT at 6 wk of healing.A. 7%
B. SA/Cholesterol sterosome (n = 4) (mass not reported)B. 31%
C. SA/20(S)-OHC sterosome (n = 4) (mass not reported)C. 61%a
Huang et al[38], 2019 (V)Rabbit (n = 6)Regeneration of critical-sized cranial defect (6-mm; 4 defects/cranium) using an inorganic bovine bone graft (Bio-Oss) supplemented with SVA and/or 20(S)-OHC.A. No supplementation (Bio-Oss only; control) (n = 6 defects)Percent bone regeneration was not reported; however, via histological analysis at 4 wk, bone regeneration was increased following treatment with SVA, 20(S)-OHC, and, especially, SVA + 20(S)-OHC, relative to no supplementation (Bio-Oss only control). A synergistic effect was observed with combinatorial treatment of SVA and 20(S)-OHC.
B. 0.5-mg of SVA (n = 6 defects)
C. 1.0-μg of 20(S)-OHC (n = 6 defects)
D. 0.5-mg of SVA + 1.0-μg of 20(S)-OHC (n = 6 defects)
1Percent bone regeneration of critical-sized defect.
2Oxy133 and Oxy21 are identical.
aP < 0.05 compared to PBS only (Aghaloo et al[17]), collagen sponge only (Hokugo et al[32]), or no treatment (empty defect) (Cui et al[34]). rhBMP-2: Recombinant human bone morphogenetic protein-2; PLGA: Poly(lactic-co-glycolic acid); SVA: Simvastatin; OHC: Hydroxycholesterol; µ-CT: Micro-computed tomography; MeGC: Methacrylated chitosan; SA: Stearylamine; BMSCs: Bone marrow-derived mesenchymal stem/stromal cells.
Table 4 Summary of unique oxysterols investigated for in vivo bone tissue engineering in animal models
Oxysterol nameChange from cholesterol1Effect on in vivo bone formation (defect model)Ref.
20(S)-OHCOH group at C20(S)Increase2 (alveolar and calvarial)Aghaloo et al[17], 2007; Hokugo et al[30], 2014; Lee et al[35], 2017; Cui et al[34], 2017; Bakshi et al[37], 2019; Huang et al[38], 2019
22(R)-OHCOH group at C22(R)Increase2,3 (alveolar)Bakshi et al[37], 2019
22(S)-OHCOH group at C22(S)Increase2,3 (calvarial)Aghaloo et al[17], 2007
Oxy4/Oxy34OH group at C20(S), single bond between C5 and C6, OH group at C6(S)Increase2 (spinal fusion)Johnson et al[21], 2011; Stappenbeck et al[20], 2012
Oxy18OH group at C20(S), single bond between C5 and C6, OH group at C6(S), deuterated carbons at C22 and C23Increase4 (spinal fusion)Stappenbeck et al[20], 2012
Oxy21/Oxy133OH group at C20(S), single bond between C5 and C6, OH group at C6(S), n-hexane at C20(S)Increase2 (spinal fusion, calvarial)Stappenbeck et al[20], 2012; Montgomery et al[19], 2014; Scott et al[31], 2015; Li et al[36], 2015; Buser et al[33], 2017
Oxy49OH group at C20(S), single bond between C5 and C6, OH group at C6(S), double bond between C25 and C27Increase2 (spinal fusion, calvarial)Johnson et al[21], 2011; Hokugo et al[32], 2016
1(S) and (R) denote stereoisomerism. Refer to Figure 3 for molecular structures.
2Statistically significant relative to control.
3Used in combination with 20(S)-OHC.
4Significantly greater bone formation relative to Oxy4/Oxy34 (internal positive control). OHC: Hydroxycholesterol.