Mesenchymal stromal cells modulate tissue repair responses within the injured vocal fold

Abstract

Objectives/Hypothesis: This study aimed to determine whether local injection of human mesenchymal stromal cells (MSC) could modulate the early inflammatory response within injured vocal folds (VFs) to promote wound-healing processes.Study Design: Experimental xenograft model. Methods: VF injury was surgically induced by bilateral resection of the lamina propria of rabbits, and MSC were immediately injected into the injured area of both VFs. Animals were sacrificed on days 2, 4, and 24. Histological analyses were performed by hematoxylin and eosin, Masson's Trichrome, and elastin staining. Cell death was visualized by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and the M2 macrophage marker, CD163, detected by immunohistochemistry. Persistence of injected MSC was evaluated by fluorescent in situ hybridization (FISH). Quantitative polymerase chain reaction was performed on the contralateral VF.Results: Histological examination at days 2 and 4 indicated that MSC were able to reduce tissue inflammation, with gene expression analysis confirming a significant reduction of proinflammatory markers, interleukin (IL)-1β, and IL-8. FISH demonstrated low-level persistence of injected MSC at both time points, and TUNEL confirmed localized cell death at the injury site. Increased levels of CD163+ anti-inflammatory macrophages indicated a change in the immune milieu, supporting wound resolution. Evidence of a more organized collagen matrix suggests that MSC may enhance the production of a functional repair tissue after injury, despite their low-level persistence within the tissue.Conclusions: This study demonstrates that MSC are able to positively modulate the early wound-healing response through resolution of the inflammatory phase and promotion of tissue repair.

Treatment of vocal fold scarring with autologous bone marrow-derived human mesenchymal stromal cells—first phase I/II human clinical study

“…Our preclinical testing demonstrated the safety of MSC injection into the VF, with no side effects evidenced [18][19][20][21][22]. We have furthermore confirmed the safety and effectiveness of delivering MSCs within HA hydrogel in vivo.…”

“…Numerous pre-clinical in vivo models to evaluate the effects of local administration of MSCs into scarred VFs have been reported, each suggesting positive effects on wound healing and regeneration of inherent VF characteristics and functionality [16][17][18]. Our own in vivo model in rabbits demonstrated both short-and long-term effects of MSC injection on VF tissue inflammation, architecture, and function [19][20][21][22]. Despite lowlevel persistence of the MSCs within the injury site, long-term effects were seen on matrix composition and tissue architecture, with lowered type I collagen content, reduced lamina propria (LP) thickening, and normalized histology compared to untreated injured controls [19][20][21][22].…”

“…Our own in vivo model in rabbits demonstrated both short-and long-term effects of MSC injection on VF tissue inflammation, architecture, and function [19][20][21][22]. Despite lowlevel persistence of the MSCs within the injury site, long-term effects were seen on matrix composition and tissue architecture, with lowered type I collagen content, reduced lamina propria (LP) thickening, and normalized histology compared to untreated injured controls [19][20][21][22]. Viscoelastic parameters, from rheometry, demonstrated a significant improvement in tissue functionality after MSC treatment [19,20].…”

“…No patient was excluded because of leakage. Cell dosage was based on previous animal safety data and adjusted for difference in membranous VF volume between humans and rabbits [19][20][21][22][23]. The ethical permissions also included a second treatment arm where MSC was mixed with a HA gel scaffold.…”

“…Investigation into MSC mode of action within these studies showed that MSCs significantly expedite resolution of acute phase inflammation within the injured tissue (equivalent to scar tissue resection within the clinical context). Acute phase pro-inflammatory cyto/chemokines including interleukin (IL)-1b and IL-8 were reduced within MSC-treated VFs and increased levels of CD163+ anti-inflammatory macrophages within 2-4 days after damage [22].…”