A Feasibility Study on 3D Bioprinting of Microfat Constructs Towards Wound Healing Applications

Abstract

Chronic wounds affect over 400,000 people in the United States alone, with up to 60,000 deaths each year from non-healing ulcerations. Tissue grafting (e.g., autografts, allografts, and xenografts) and synthetic skin substitutes are common treatment methods, but most solutions are limited to symptomatic treatment and do not address the underlying causes of the chronic wound. Use of fat grafts for wound healing applications has demonstrated promise but these grafts suffer from low cell viability and poor retention at the wound site resulting in suboptimal healing of chronic wounds. Herein, we report on an innovative closed-loop fat processing system (MiniTCTM) that can efficiently process lipoaspirates into microfat clusters comprising of highly viable regenerative cell population (i.e., adipose stromal cells, endothelial progenitors) preserved in their native niche. Cryopreservation of MiniTCTM isolated microfat retained cell count and viability. To improve microfat retention and engraftment at the wound site, microfat was mixed with methacrylated collagen (CMA) bioink and 3D printed to generate microfat-laden collagen constructs. Modulating the concentration of microfat in CMA constructs had no effect on print fidelity or stability of the printed constructs. Results from the Alamar blue assay showed that the cells remain viable and metabolically active in microfat-laden collagen constructs for up to 10 days in vitro. Further, quantitative assessment of cell culture medium over time using ELISA revealed a temporal expression of proinflammatory and anti-inflammatory cytokines indicative of wound healing microenvironment progression. Together, these results demonstrate that 3D bioprinting of microfat-laden collagen constructs is a promising approach to generate viable microfat grafts for potential use in treatment of non-healing chronic wounds.

3D-Bioprinted Biomimetic Multilayer Implants Comprising Microfragmented Adipose Extracellular Matrix and Cells Improve Wound Healing in a Murine Model of Full-Thickness Skin Defects

“…A recent study used a closed-loop fat processing system to prepare microfat clusters and mix them with methacrylate collagen (CMA) for bioprinting. 43 The microfat clusters contained a large number of adipocytes, oil, and stromal cells, which are very different from the focus of this study. To evaluate the effect of 3D-bioprinted biomimetic multilayer implants consisting of mFAECM and cells for wound healing in vivo, we prepared a full-thickness skin defect model in nude mice (Figure 6A).…”

“…There has been no prior study on the direct application of adipose-derived, nonpepsin-digested ECM to the construction of skin substitutes by 3D bioprinting. A recent study used a closed-loop fat processing system to prepare microfat clusters and mix them with methacrylate collagen (CMA) for bioprinting . The microfat clusters contained a large number of adipocytes, oil, and stromal cells, which are very different from the focus of this study.…”

Biofabrication's Contribution to the Evolution of Cultured Meat

“…Schmitt et al mixed cryopreserved microfat tissue and methacrylated collagen to obtain a bioink. [83] The bioink was processed into a bath of gelatin microspheres [84] and was stabilized afterward by UV crosslinking for 1 min. The authors reported that also high densities of the microfat could be introduced to the collagen without deteriorating the printing quality.…”

3D bioprinting: opportunities for wound dressing development

“…When trauma occurs, the structural integrity of blood vessels is damaged, and a significant volume of blood leaks out of them, resulting in blood loss and harm to other organs that, in severe situations, can be fatal [41]. Normally, vasoconstriction occurs first after injury to slow blood flow [40,42,43]. Platelets are then activated to form a primary thrombus via an endogenous and exogenous coagulation cascade reaction.…”