TABLE 5.
Studies regarding mesenchymal stromal cell-conditioned medium for treating hypertrophic scars in animal models.
| MSC source | Method of tissue extraction | MSC characterization | MSC treatment | Model | Groups of treatments and via of administration | Follow-up (days) | Assessment | Main outcome | Other outcomes | |
| Arjunan et al., 2020 | Human umbilical cords | Dissection | Flow cytometry and IF (Tra-1–60, Tra-1–81, SSEA-1, SSEA-4, Oct-4 and alkaline phosphatase, CD105, CD90, CD44) | MSCs at 70–89% confluence were used. CM was then collected | Murine. Keloid xenograft SCID mouse model, 3-6 mm, limbs | 50 μl intralesional injected - Placebo - HSF-CM - MSC- CM (n = 9/group) |
30 | Macroscopic appearance | MSC-CM group showed greater keloid reduction | A reduction in keloid tumor volumes (12.04 ± 3.69 vs. 54.65 ± 8.97 vs. 71.78 ± 20.67 mm) and weights (26.50 ± 6.38 vs. 76.70 ± 9.58 vs. 73.70 ± 12.12 mg) in the WJ-MSC-CM group compared with HSF-CM and untreated group were observed |
| Hu et al., 2020 | Murine bone marrow | Needle aspiration from tibia and femur | Flow cytometry (CD150+/CD74+). Osteogenic, adipogenic, chondrogenic differentiation | MSCs of passages 8–13 at 70% confluence. CM was then collected | Murine. Human HS-buried null mouse model, 6 mm, back | 200 μl subcutaneously injected every 7 days - DMEM - Botox - MSC-CM - MSC-CM+Botox (n = 4/group) |
28 | Macroscopic appearance, histology, IF, collagen deposition assay, fibroblast apoptosis assay (caspase-7 staining), qRT-PCR, WB | HS was the most reduced in MSC-CM+Botox group compared with the other groups. Scar weight was reduced up to 70% in MSC-CM+Botox, up to 80% in MSC-CM, up to 81% in botox, and up to 91% in control group | Collagen fiber deposition was eased and well-arranged after all treatments, except control group. α-SMA expression was lower in the combined regimen, MSC-CM, and botox than in DMEM group |
| Liu et al., 2018 | Human subcutaneous adipose tissue | Surgical excision of redundant tissue from surgical operations | Flow cytometry (CD105+/CD90+/ CD34−/CD45−/ CD19−). Adipogenic and osteogenic differentiation | MSCs of passages 3–4 at 80% confluence were used. CM was then collected | Murine. Keloid xenograft, 10 mm, back | 200 μl injected subcutaneously into each keloid xenograft every week - Untreated - DMEM - MSC-CM (n = 4/group) |
28 | Macroscopic appearance, histology, IHC, BrdU proliferation assay (bromodeoxyuridine/5-bromo-2′-deoxyuridine) (ELISA), qRT-PCR, contraction assay, phosphatidylserine apoptosis assay, antibody-based array | MSC-CM had a greater effect in scar reduction than control group. MSC-CM group decreased HS weight, by 34% compared with untreated group and by 23% compared with DMEM group | MSC-CM reduced the proportion of both cellularity/inflammatory cells and blood vessel density |
| Choi et al., 2017 | Human subcutaneous adipose tissue | Cesarean section | − | MSCs of passage 3 at 70–80% confluence were used. CM was then collected, and exosomes were created | Murine. Full-thickness wound scar, 20 mm × 15 mm, on dorsal surface | 200 μl intravenously injected - PBS - Exos-free CM - Exos-MSCs (n = 6/group) |
21 | Macroscopic appearance (photography), histology (HE, MT, picrosirius red), IHC, qRT-PCR | MSC-Exos treatment attenuated the thickness of the dermal layer and the length of the scar | The surface of the epidermis was more flattened, and collagen in the dermis was well distributed with less crosslinking in MSC-Exos group. MSC-Exos reduced collagen deposition, mitigated scar formation, and increased the ratio of collagen III |
| Li et al., 2016 | Human adipose tissue | Liposuction | Flow cytometry (CD73+/CD90+/ CD34−/CD14−), adipogenic and osteogenic differentiation | MSCs of passages 3–5 at 80–90% confluence were used. CM was then collected | Murine. Full-thickness excisional wound, 10 mm, back | 1,000 μl subcutaneously injected into each scar at four points - DMEM - MSC-CM (n = 6/group) |
14 | Macroscopic appearance (photography), histology (HE and Masson trichrome staining), immunohistochemistry, qRT-PCR, WB | Reduced scar formation and fibrosis were observed in MSC-CM group | MSC-CM decreased the expression of Col1, Col3, and α-SMA |
| Du et al., 2016a | Murine placenta | Placenta collected | Flow cytometry (CD29+, CD31−, CD34−, CD44+, CD45− and HLA-DR−) | MSCs of passage 3 were used. Normoxic CM, hypoxic CM, and hypoxic plus inhibitor CM (HIF-1α) were collected | Murine. Hypertrophic scald mouse model, 20 mm, back | 100 μl injected subcutaneously - Control - Normoxic MSC-CM - Hypoxic MSC-CM - HIF-1a inhibitor+hypoxic MSC-CM (n = 10/group) |
15 | Macroscopic appearance, histology (HE), WB | MSC-CM reduced scar formation | MSC-CM attenuated inflammatory responses and decreased the deposition of collagens |
| Du et al., 2016b | Human placenta | Placenta collected | Flow cytometry and immunofluorescence positive for CD73+, CD90+, CD105+, CD34−, CD45−, HLA-DR− | MSCs of passages 3–6 at 80–90% confluence were used. Normoxic CM and hypoxic CM were collected | Murine. Hypertrophic scald mouse model, 20 mm, back | 100 μl injected subcutaneously - Normal medium - Normoxic MSC-CM - Hypoxic MSC-CM (n = 10/group) |
15 | Macroscopic appearance (photography), contracture rate histology (HE), Trypan blue staining, qRT-PCR, WB, ELISA, wound healing assay | Hypoxic MSC-CM reduced scar formation and decreased wound size compared with normal medium and normoxic MSC-CM | Decreased levels of TGF-β1 and collagen I were observed using hypoxic MSC-CM. Hypoxic MSC-CM also inhibited the proliferation and migration of skin fibroblasts |
| Wu et al., 2015 | Human bone marrow | − | Flow cytometry (CD14, CD34, CD45, CD44, and CD73) | MSCs of passages 5–10 at 80% confluence were used. CM was then collected | Murine. Skin fibrosis model. Hypertrophic skin, almost 2-fold greater thickness than normal skin, back. | 100 μl injected subcutaneously into the lesion every - Placebo - MSC-CM - BM-MSC-CM with TGF-β3 blocked (n = 5/group) |
21 | Macroscopic appearance, histology (HE), IHC, cellular proliferation (Ki-67) | MSC-CM decreased skin fibrosis | MSC-CM decreased the fibroblast viability, reduced skin dermal thickness, and inhibited cells proliferation. Moreover, MSC-CM-treated group exhibited significantly fewer proliferating cells compared with MSC-CM with TGF-β3-blocked |
| Zhang et al., 2015 | Rabbit adipose tissue | Surgical excision of inguinal fat pad | Flow cytometry (CD73+/CD90+/ CD34−/CD14−). Adipogenic and osteogenic differentiation | MSCs of passage 3 at 80–90% confluence were used. CM was then collected | Rabbit. Full-thickness wound scar, 10 mm, ear | 200 μl intralesionally injected into center of each scar - Untreated (n = 4) - MSCs (n = 4) - MSC-CM (n = 4) - DMEM (n = 12) |
35 | Macroscopic appearance, histology (HE, MT), IHC, qRT-PCR, gene expression, ultrasonography | MSCs and MSC-CMs decreased scar hypertrophy and led to scar with a more normal appearance | MSCs and MSC-CM decreased α-smooth muscle actin and collagen type I. MSC-CM was less effective than MSCs |
BM, bone marrow; CM, conditioned medium; DMEM, Dulbecco’s modified Eagle medium; ELISA, enzyme-linked immunosorbent assay; Exos, exosomes; HE, hematoxylin and eosin; HS, hypertrophic scar; HSF, human skin fibroblast; IF, immunofluorescence; IHC, immunohistochemistry; MSCs, mesenchymal stromal cells; MT, Masson’s trichrome; qRT-PCR, real-time quantitative polymerase chain reaction; WB, Western blotting; WJ, Wharton’s jelly.