Reconstitution and post-thaw storage of cryopreserved human mesenchymal stromal cells: Pitfalls and optimizations for clinically compatible formulants.

Introduction: The regenerative and immunomodulatory properties of multipotent mesenchymal stromal cells (MSCs) make them an intriguing asset for therapeutic applications. An off-the-shelf approach, using pre-expanded cryopreserved allogenic MSCs, bypasses many practical difficulties of cellular therapy. Reconstitution of a MSC product away from cytotoxic cryoprotectants towards a preferred administration solution might be favorable for several indications. Variations in MSC handling accompanied by a non-standardized use of reconstitution solutions complicate a general clinical standardization of MSC cellular therapies. In this study, we aimed to identify a simple and clinically compatible approach for thawing, reconstitution, and post-thaw storage of cryopreserved MSCs. Methods: Human adipose tissue-derived MSCs were expanded in human platelet lysate (hPL) supplemented culture medium and cryopreserved using a dimethyl sulfoxide (DMSO)-based cryoprotectant. Isotonic solutions (saline, Ringer's acetate and phosphate buffered saline (PBS)) with or without 2% human serum albumin (HSA) were used as thawing, reconstitution, and storage solutions. MSCs were reconstituted to 5 × 106 MSCs/mL for evaluating MSC stability. Total MSC numbers and viability were determined using 7-aminoactinomycin D (7-AAD) and flow cytometry. Results: For thawing cryopreserved MSCs the presence of protein was proven to be essential. Up to 50% of MSCs were lost when protein-free thawing solutions were used. Reconstitution and post-thaw storage of MSCs in culture medium and widely used PBS demonstrated poor MSC stability (>40% cell loss) and viability (<80%) after 1 h of storage at room temperature. Reconstitution in simple isotonic saline appeared to be a good alternative for post-thaw storage, ensuring >90% viability with no observed cell loss for at least 4 h. Reconstitution of MSCs to low concentrations was identified as critical. Diluting MSCs to <105/mL in protein-free vehicles resulted in instant cell loss (>40% cell loss) and lower viability (<80%). Addition of clinical grade HSA could prevent cell loss during thawing and dilution. Conclusion: This study identified a clinically compatible method for MSC thawing and reconstitution that ensures high MSC yield, viability, and stability. The strength of the method lies within the simplicity of implementation which offers an accessible way to streamline MSC therapies across different laboratories and clinical trials, improving standardization in this field.

Measured Levels of Human Adipose Tissue-Derived Stem Cells in Adipose Tissue Is Strongly Dependent on Harvesting Method and Stem Cell Isolation Technique.

BACKGROUND: Adipose tissue-derived stem cells are of great interest because of their properties of immune modulation, tissue regeneration, and multipotent differentiation. To advance development of stem cell-based treatments, determination of the physiologic concentration of adipose tissue-derived stem cells in human adipose tissue is relevant for proper guidance of stem cell treatment dosage, oncologic safety, and evaluation of efficacy. METHODS: A prospective comparative case-control study of 20 patients was conducted to determine the yield of adipose tissue-derived stem cells in periumbilical adipose tissue harvested by the widely used method of aspiration and in structurally intact adipose tissue harvested by excision. Stem cells were isolated using conventional enzymatic digestion and by a method combining enzymatic digestion with mechanical distortion. Stem cell yield was quantified by multicolor flow cytometry and colony-forming capacity. RESULTS: When only the conventional enzymatic digestion was used, no significant difference in adipose tissue-derived stem cell yield was observed. However, when enzymatic digestion was combined with mechanical distortion, twice as many stem cells were isolated from excised adipose tissue compared to aspirated adipose tissue. Inclusion of mechanical distortion significantly increased yield 5-fold in excised adipose tissue and 2-fold in aspirated adipose tissue. Combining enzymatic digestion and mechanical distortion, measured levels of excised adipose tissue reached 140 × 10 (95 percent CI, 62 to 220 × 10) adipose tissue-derived stem cells per gram of adipose tissue that corresponded to 26 × 10 (95 percent CI, 18 to 33 × 10) colony-forming units per gram. CONCLUSIONS: The study indicates that harvesting by aspiration halves the concentration of adipose tissue-derived stem cells in adipose tissue samples when compared to structural intact adipose tissue. Furthermore, the study presents stem cell yield higher than previously described in the current literature. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.

Isolation of Adipose Tissue-Derived Stem Cells: Enzymatic Digestion in Combination with Mechanical Distortion to Increase Adipose Tissue-Derived Stem Cell Yield from Human Aspirated Fat.

Mesenchymal stem cells (MSCs) are of great interest due to their properties of immune modulation, tissue regeneration, and multipotent differentiation. Future developments of clinical applications, however, require a higher yield of MSCs, lower number of passages of cells in culture, and shorter time from harvest to use. Optimization and standardization of techniques for mesenchymal adipose tissue-derived stem cell isolation offers solutions to current bottlenecks as a larger amount of MSCs can be isolated. These improvements result in shorter expansion time, fewer passages, less donor material needed, and higher MSC yield. This paper describes an MSC isolation method combining enzymatic digestion with mechanic disruption. This protocol is a standardized and easy-to-implement method for reaching significantly higher MSC yields compared to conventional enzymatic isolation protocols. Based on the results presented, we hypothesize that the combined enzymatic and mechanical method increases the surface area of the adipose tissue, facilitating digestion by enzymes. This approach reduces the amount of adipose tissue and in vitro expansion time needed to reach sufficient amounts of MSCs for clinical purposes. Importantly, the method does not require increased amounts of collagenase, nor does it impair the viability or differentiability of the MSCs. Using this protocol increases MSC yield by a factor of three. As a consequence, these results indicate that the physiological concentration of MSCs in adipose tissue is higher than previously assumed. © 2018 by John Wiley & Sons, Inc.

ICG angiography in immediate and delayed autologous breast reconstructions: peroperative evaluation and postoperative outcomes.

Postoperative complications in patients undergoing autologous breast reconstruction should be kept at the lowest possible level. Optimization of autologous breast reconstruction, especially techniques that can identify tissue perfusion and ischemia, will greatly benefit the patients and consequently society. Hence, the aim of this study was to evaluate the complication rates for autologous pedicle flap breast reconstructions, with and without the use of ICG-angiography. A single-institution retrospective review of mastectomy patients was performed. A total of 230 cases who underwent immediate or delayed, unilateral or bilateral pedicle autologous flap breast reconstruction between January 2013 and September 2016 was reviewed. Complication rates in the ICG-angiography and clinical assessment group were evaluated and compared. A total of 191 cases were identified of which 77 were evaluated with ICG-angiography, and 114 were evaluated clinically. There was no significant difference in overall complication rates between the two groups (ICG-angiography, 36.4%; Clinical assessment, 37.7%; p = .88). No significant difference was observed when stratifying for major or minor complications. However, when stratifying for the timing of the reconstruction, the rate of major complications was significantly lower in the ICG-angiography group (ICG-angiography, 0%; Clinical assessment 23.3%; p = .039). BMI was significantly associated with increased risk of minor complications (p = .018), whereas there was no correlation to age, prior smoking, chemotherapy, radiation, diabetes, or hypertension. Our study found that use of ICG-angiography was associated with a significant decrease in the rate of major complications for immediate autologous reconstructions.