Increased yield of endothelial cells from peripheral blood for cell therapies and tissue engineering

Development of in vitro endothelialized drug-eluting stent using human peripheral blood-derived endothelial progenitor cells

We propose in vitro endothelialization of drug-eluting stents (DES) to overcome late stent thrombosis by directly introducing late-outgrowth human endothelial progenitor cells (EPCs) at the target site utilizing abluminal DES. Isolated EPCs were confirmed as late-outgrowth EPCs by flow cytometric analysis. Abluminally paclitaxel-loaded stents were seeded with different cell concentrations and durations to determine optimal seeding conditions, in both uncrimped and crimped configurations. The seeding yield was determined by evaluating the percent coverage of the stent struts' area. The EPC-seeded DES were exposed to arterial shear stress to evaluate the effect of high shear stress on EPCs. To investigate how much paclitaxel elutes during the seeding procedure, a pharmacokinetic analysis was performed. Finally, to validate the proof of concept, EPC-seeded DES were placed on a fibrin matrix with and without smooth muscle cells (SMCs) and cultured for 3 days under perfusion. The seeding procedure resulted in 47% and 26% coverage of the stent surface in uncrimped and crimped conditions, respectively. After the optimal seeding, almost 99% of drug was still available. When EPC-seeded DES were placed on a fibrin matrix and cultured for 3 days, the EPCs confluently covered the stent surface and spread to the surrounding fibrin gel. When EPC-seeded DES were placed on SMC-containing fibrin layers, cells in contact with the struts died. EPCs can be successfully seeded onto DES without losing drug-eluting capability, and EPCs exhibit sufficient proliferative ability. EPC-seeded DES may combine early re-endothelialization ability with the antirestenotic effectiveness of DES.

Promotion of skin wound healing using prevascularized oral mucosal cell sheet

BACKGROUND

This study examined the potential use of our newly developed prevascularized oral mucosal cell sheet for the treatment of skin wounds.

METHODS

Mucosal cell sheets containing cultured keratinocytes and plasma fibrin without (K sheet) or with a mixture of fibroblasts and endothelial progenitor cells (PV sheet) were transplanted into full-thickness skin excisional wounds of nude mice.

RESULTS

This technique was successful for in vitro culture; expanding keratinocytes, fibroblasts, and endothelial progenitor cells; and generating prevascularized mucosal cell sheets. Cell sheets promoted in vivo wound healing with rapid wound closure and less scarring compared to controls. This result was more apparent in the PV than the K sheet (P < .05). Wounds covered with cell sheets showed less expression of TGFB1, ACTA2, and FN1 mRNAs than the controls (P < .05).

CONCLUSION

The prevascularized mucosal cell sheet showed in vivo efficacy and tissue plasticity in cutaneous wounds by promoting accelerated healing.

Use of a pre-vascularised oral mucosal cell sheet for promoting cutaneous burn wound healing

Pre-vascularised cell sheets have been used to promote early angiogenesis and graft survival. However, the use of pre-vascularised mucosal cell sheets for burn wounds has been rarely evaluated. Therefore, we examined the applicability of an oral pre-vascularised mucosal cell sheet that we had previously developed for the treatment of cutaneous burn wounds.

Methods: Mucosal keratinocytes, fibroblasts, and endothelial progenitor cells were isolated from the oral mucosa and peripheral blood and were expanded in vitro. Mucosal cell sheets were generated by seeding cultured keratinocytes onto a mixture of fibroblasts, endothelial cells, and fibrin. Third-degree burn wounds were created on the backs of rats and were covered with the cell sheets, skin grafts, or silastic sheets as a control. Gross and microscopic findings and gene expression profiles of wounds were compared among the groups.

Results: CD31-positive microvessels were observed in the fibrin-matrix layer of the cell sheet. In the cutaneous burn wound model, the cell sheets promoted wound healing, with accelerated wound closure and less scarring than with silastic sheets and skin grafts. The cell sheets had more microvessels and proliferating cells and less neutrophil infiltration and fibrotic features than the controls or skin grafts. The cell sheet induced higher mRNA expression of KRT14, VEGFA, IL10, and AQP3 and lower mRNA expression of TGFB1, IL6, ICAM1, ACTA2, and FN1 than did the controls or skin grafts.

Conclusions: The pre-vascularised mucosal cell sheet promotes cutaneous burn wound healing.

Point-of-Care Rapid-Seeding Ventricular Assist Device with Blood-Derived Endothelial Cells to Create a Living Antithrombotic Coating

The most promising alternatives to heart transplantation are left ventricular assist devices and artificial hearts; however, their use has been limited by thrombotic complications. To reduce these, sintered titanium (Ti) surfaces were developed, but thrombosis still occurs in approximately 7.5% of patients. We have invented a rapid-seeding technology to minimize the risk of thrombosis by rapid endothelialization of sintered Ti with human cord blood-derived endothelial cells (hCB-ECs). Human cord blood-derived endothelial cells were seeded within minutes onto sintered Ti and exposed to thrombosis-prone low fluid flow shear stresses. The hCB-ECs adhered and formed a confluent endothelial monolayer on sintered Ti. The exposure of sintered Ti to 4.4 dynes/cm for 20 hr immediately after rapid seeding resulted in approximately 70% cell adherence. The cell adherence was not significantly increased by additional ex vivo static culture of rapid-seeded sintered Ti before flow exposure. In addition, adherent hCB-ECs remained functional on sintered Ti, as indicated by flow-induced increase in nitric oxide secretion and reduction in platelet adhesion. After 15 day ex vivo static culture, the adherent hCB-ECs remained metabolically active, expressed endothelial cell functional marker thrombomodulin, and reduced platelet adhesion. In conclusion, our results demonstrate the feasibility of rapid-seeding sintered Ti with blood-derived hCB-ECs to generate a living antithrombotic surface.

Accelerated oral wound healing using a pre-vascularized mucosal cell sheet

Cell sheets with pre-vascularization have recently been developed but remain relatively untested in oral wound healing. Therefore, we examined the potential utility of our newly developed pre-vascularized mucosal cell sheets in oral wound healing. Mucosal keratinocytes, fibroblasts, and endothelial progenitor cells were primarily cultured for in vitro cell expansion from mucosa and blood of Sprague-Dawley rats. Mucosal cell sheets were generated using cultured keratinocytes and plasma fibrin (K sheet) or keratinocytes and a mixture of fibrin, fibroblasts, and endothelial cells (PV sheet). Autologous sheets were transplanted on deep wounds in the buccal region of rats. The gross and histological characteristics of wound healing were compared among control wound, K sheet, and PV sheet groups. We successfully cultured and expanded keratinocytes, fibroblasts, and endothelial progenitor cells in vitro for generating mucosal cell sheets with or without pre-vascularization. In the in vivo oral wound model, compared with the control wound, the PV sheet group exhibited rapid wound closure more prominently than the K sheet group. The histological healing in the PV sheet group was similar to that in rat normal buccal mucosa without fibrosis. The pre-vascularized mucosal cell sheet exhibited in vivo efficacy in oral wound healing by promoting accelerated healing.

Safety profile and long-term engraftment of human CD31+ blood progenitors in bone tissue engineering

BACKGROUND

Endothelial progenitor cells (EPCs) participate in angiogenesis and induce favorable micro-environments for tissue regeneration. The efficacy of EPCs in regenerative medicine is extensively studied; however, their safety profile remains unknown. Therefore, our aims were to evaluate the safety profile of human peripheral blood-derived EPCs (hEPCs) and to assess the long-term efficacy of hEPCs in bone tissue engineering.

METHODS

hEPCs were isolated from peripheral blood, cultured and characterized. β tricalcium phosphate scaffold (βTCP, control) or 10⁶ hEPCs loaded onto βTCP were transplanted in a nude rat calvaria model. New bone formation and blood vessel density were analyzed using histomorphometry and micro-computed tomography (CT). Safety of hEPCs using karyotype analysis, tumorigenecity and biodistribution to target organs was evaluated.

RESULTS

On the cellular level, hEPCs retained their karyotype during cell expansion (seven passages). Five months following local hEPC transplantation, on the tissue and organ level, no inflammatory reaction or dysplastic change was evident at the transplanted site or in distant organs. Direct engraftment was evident as CD31 human antigens were detected lining vessel walls in the transplanted site. In distant organs human antigens were absent, negating biodistribution. Bone area fraction and bone height were doubled by hEPC transplantation without affecting mineral density and bone architecture. Additionally, local transplantation of hEPCs increased blood vessel density by nine-fold.

CONCLUSIONS

Local transplantation of hEPCs showed a positive safety profile. Furthermore, enhanced angiogenesis and osteogenesis without mineral density change was found. These results bring us one step closer to first-in-human trials using hEPCs for bone regeneration.

Production of endothelial progenitor cells from skin fibroblasts by direct reprogramming for clinical usages

Endothelial progenitor cells (EPCs) play an important role in angiogenesis. However, they exist in limited numbers in the human body. This study was aimed to produce EPCs, for autologous transplantation, using direct reprogramming of skin fibroblasts under GMP-compliant conditions. Fibroblasts were collected and cultured from the skin in DMEM/F12 medium supplemented with 5% activated platelet-rich plasma and 1% antibiotic-antimycotic solution. They were then transfected with mRNA ETV2 and incubated in culture medium under hypoxia (5% oxygen) for 14 d. Phenotype analysis of transfected cells confirmed that single-factor ETV2 transfection successfully reprogrammed dermal fibroblasts into functional EPCs. Our results showed that ETV2 mRNA combined with hypoxia can give rise to functional EPCs. The cells exhibited functional phenotypes similar to endothelial cells derived from umbilical cord vein; they expressed CD31 and VEGFR2, and formed capillary-like structures in vitro. Moreover, these EPCs could significantly improve hindlimb ischemia in mouse models. Although the direct conversion efficacy was low (3.12 ± 0.98%), altogether our study demonstrates that functional EPCs can be produced from fibroblasts and can be used in clinical applications.