Table 2

Characteristics of included studies.

Study	Study Design (Level of Evidence)	Sample Size and Demographic	Follow-Up, mo	Type and Site of Insertion	Dose, Cells (mean CFU-F)	Main Results	Radiological Results
Lewandrowski et al, 202315	Retrospective observational cohort (II)	N = 33, mean age = 47.6 y, and M:F = 18:15	24	Allogeneic polyclonal MSC, intradiscal	5 × 10⁶ allogeneic polyclonal MSC + 1% HA	ODI score Baseline 44.81; 1 mo 19.7; 3 mo 15.38; 6 mo 13.48; 12 mo 11.8; 24 mo 6.07 (P < 0.001) VAS score Baseline 82.2; 1 mo 33.1; 3 mo 25.7; 6 mo 20.3; 12 mo 18.1; 24 mo 17.4 (P < 0.001) 1 patient experienced severe LBP for 1 d, but otherwise, no adverse treatment effects were mentioned in the study	Baseline: Pfirrmann grade (mean ± SD): 4.06 ± 0.72 Result: 3.65 ± 0.81
Wolff et al, 202016	Retrospective pilot study (II)	N = 33, mean age = 45 y, and M:F = 19:14	12	BMC, Intradiscal	3 mL, cells NA	ODI improvement from baseline 2 wk 4.2%, 6–8 wk 26.7%; 3 mo 36.4%; 6 mo 55.6%; 12 mo 30.8% NRS improvement from baseline 2 wk 13.8%, 6–8 wk 45.8%; 3 mo 41.1%; 6 mo 23.5%; 12 mo 38.9% No remarkable adverse event reported	NA
Pettine et al, 201717	Prospective, nonrandomized (II)	N = 26, mean age = 40 y, and M:F = 11:15	36	Autologous BMC, Intradiscal	2–3 mL, 121 × 10⁶ per mL (2,713 per mL)	ODI score Baseline 56.7; 36 mo 17.5 (P < 0.001) VAS score Baseline 82.1; 36 mo 21.9 (P < 0.001) No adverse events related to the study	Baseline: Pfirrmann Grade IV = 4, Grade V = 11, Grade VI = 15, and Grade VII = 10. Result: 8 of 20 patients had improved Pfirrmann grade
Atluri et al, 202118	Open label, prospective controlled study (II)	N = (40 intervention/40 control), mean age = 60 y, and M:F = NA	12	Autologous bone marrow MSC; intradiscal, intraepidural, facet joint, and SI joint	2 mL (each level), 239.3 × 10⁶ per mL (4,987 per mL)	ODI score, intervention vs control Baseline 46.1 vs 44.3; 1 mo 33.4 vs 45.9; 3 mo 28.8 vs 47.3; 6 mo 29.9 vs 48.9; 12 mo 31.1 vs 49.5 (P < 0.001) NRS score, intervention vs control At baseline 71 vs 66; 1 mo 38 vs 68; 3 mo 31 vs 69; 6 mo 37 vs 66; 12 mo 42 vs 71 (P < 0.001)	NA
Orozco et al, 201119	Pilot study (II)	N = 10, mean age = 35 y, and M:F = 4:6	12	Autologous bone marrow cells, intradiscal	10⁷ cells per disc	ODI score Baseline 25; 3 mo 13; 6 mo 9.4; 12 mo 7.4 (P < 0.0001) VAS score Baseline 68.9; 3 mo 26.5; 6 mo 21.6; 12 mo 20 (P < 0.0001)	NA
Noriega et al, 201621	RCT (I)	N = 24, mean age = 38 y, and M:F = 17:7	12	Allogeneic mesenchymal bone marrow cells, Intradiscal	25 × 10⁶ in 2 mL saline per disc	ODI score, intervention vs control Baseline 34 vs 24; 1 wk 27 vs 20; 3 mo 16 vs 25; 6 mo 20 vs 30; 12 mo 22 vs 34 VAS score, intervention vs control Baseline 67 vs 62; 1 wk 63 vs 45; 3 mo 43 vs 46; 6 mo 40 vs 51; 12 mo 47 vs 47	Baseline (control vs intervention): Pfirrmann 3.15 ± 0.76 vs 3.68 ± 0.67 Results: 3.78 ± 0.82 vs 3.18 ± 0.87
Kumar et al, 201720	Phase 1 clinical trial, open label, single arm (II)	N = 10, mean age = 43.5 y, and M:F = 6:4	12	Adipose-derived MSC + HA, Intradiscal	Low dose 2 × 10⁷ cells/disc (n = 5); high dose 4 × 10⁷ cells/disc (n = 5)	ODI score Baseline 42.8; 1 mo 31.2; 3 mo 31.7; 6 mo 21.3; 12 mo 16.8 (P = 0.002) VAS score Baseline 65; 1 mo 46; 3 mo 43; 6 mo 32; 12 mo 29 (P = 0.002) No adverse event during 1 y follow-up	Baseline: Pfirrmann Grade IV = 10. Result: No increase in Pfirrmann grade
Amirdelfan et al, 202022	RCT (I)	N = 100 (6M 30/18M 30), age = 37.9–44.5 y, and M:F = 53:47	36	Allogeneic MPC +1% HA 1 mL (6 million and 18 million) control: saline and HA; Intradiscal	Low dose: 6 × 10⁶ MPC +1 mL 1% HA	ODI score Baseline 52.07; 1 mo 36.83; 3 mo 32.59; 6 mo 28.25; 12 mo 31.85; 24 mo 29.69; 36 mo 30.69 (P < 0.05) VAS score Baseline 69.67; 1 mo 40.93; 3 mo 30.28; 6 mo 25.93; 12 mo 31.48; 24 mo 33; 36 mo 35.69 (P < 0.05)	Baseline (control vs intervention): Grade II (0 vs 4), Grade III (12 vs 13), Grade IV (19 vs 32), Grade V (3 vs 4), Grade VI (2 vs 3), Grade VII (3 vs 3), and Grade VIII (1 vs 1). Results: No significant improvement in Pfirrmann score
Amirdelfan et al, 202022	RCT (I)	N = 100 (6M 30/18M 30), age = 37.9–44.5 y, and M:F = 53:47	36		High dose: 18 × 10⁶ MPC + 1 mL 1% HA	ODI score Baseline 50.67; 1 mo 37.33; 3 mo 32.89; 6 mo 31.7; 12 mo 29.59; 24 mo 28.75; 36 mo 24.95 (P < 0.05) VAS score Baseline 71.47; 1 mo 40.97; 3 mo 35.26; 6 mo 34.6; 12 mo 32.37; 24 mo 37.63; 36 mo 28.24 (P < 0.05)

Abbreviations: BMC, bone marrow concentrate; CFU-F, colony forming unit-fibroblast; HA, hyaluronic acid; LBP, low back pain; M:F, male:female; MPC, mesenchymal precursor cell; MSC, mesenchymal stem cell; NA, not applicable or not available; NRS, numeric rating scale; ODI, Oswestry Disability Index; RCT, randomized controlled trial; SI, sacroiliac; VAS, visual analog scale.