Reply: The Efficacy of Perforator Flaps in the Treatment of Chronic Osteomyelitis

Exosomes Are Comparable to Source Adipose Stem Cells in Fat Graft Retention with Up-Regulating Early Inflammation and Angiogenesis

BACKGROUND

Exosomes derived from mesenchymal stem cells possess functional properties similar to those of their parent cells, suggesting that they could play a pivotal role in tissue repair and regeneration.

METHODS

Using lipotransfer as a surrogate, exosomes were isolated from mouse adipose-derived stem cell-conditioned medium and characterized. Minced fat tissue mixed with exosomes, source cells (cell-assisted lipotransfer), or saline was implanted subcutaneously in the lower back of C57/BL mice bilaterally (n = 16 each). Transferred fat tissues were harvested and analyzed at 3 and 10 weeks.

RESULTS

At 3 and 10 weeks after the transfer, fat grafts in groups of exosomes and cell-assisted lipotransfer showed better fat integrity, fewer oil cysts, and reduced fibrosis. At week 10, graft retention rates in cell-assisted lipotransfer (50.9 ± 2.4 percent; p = 0.03) and exosome groups (56.4 ± 1.6 percent; p < 0.001) were significantly higher than in the saline group (40.7 ± 4.7 percent). Further investigations of macrophage infiltration, inflammatory factors, angiogenic factors, adipogenic factors, and extracellular matrix revealed that those exosomes promoted angiogenesis and up-regulated early inflammation, whereas during mid to late stages of fat grafting, they exerted a proadipogenic effect and also increased collagen synthesis level similarly to their source cells.

CONCLUSIONS

The adipose-derived stem cell-derived exosomes demonstrated effects comparable to those of their source cells in achieving improved graft retention by up-regulating early inflammation and augmenting angiogenesis. These features may enable exosomes to be an attractive cell-free alternative in therapeutic regenerative medicine.

[Free flaps use in chronic wounds: Retrospective study about 91 cases]

INTRODUCTION

Chronic wounds represent a major health challenge with no current standardized surgical treatment. The use of free flaps is little discussed in the literature, with a supposed propensity to failure given unfavorable local conditions and land often debility. We present here the analysis of our monocentric experience of the use of free flaps in the curative treatment of chronic wounds.

PATIENTS ET METHODS

We performed a retrospective monocentric study over 18 years of all free flaps used for the treatment of a chronic wound between January 2001 and September 2016. Several criteria were evaluated on patients, wounds, free flaps used and immediate to late outcomes.

RESULTS

Ninety-one patients were included (sex ratio M/F: 3.55) with an average age of 41.6±16 years. Wounds were localized to the leg in 92.3% of cases and 58% of patients had initial osteomyelitis. The flaps used were predominantly muscle flaps (61.6%). The flaps survival rate was 92.3%. With a mean follow-up of 50 months, the reconstructive failure rate was 20.9%. The presence of a chronic osteomyelitis is the only statistically significant factor of reconstruction failure (P=0.0169) with a risk of failure multiplied by 5.

CONCLUSION

Our study demonstrates that the reliability of free flaps in the treatment of chronic wounds is comparable, regardless of the time since the initial cutaneous lesion, to that existing in the treatment of acute wounds or in the reconstruction after oncological excision. The presence of a chronic osteomyelitis, however, represents a major risk of reconstruction failure by increasing 5 times the risk of failure. Recent changes in the integumentary reconstruction paradigm of the lower limb will undoubtedly allow in the next few years to establish more rationally the place of muscle free flaps in the therapeutic armamentarium of chronic wounds.