Acute effects of direct cell implantation into the heart: a pressure–volume study to analyze cardiac function

Microencapsulation to reduce mechanical loss of microspheres: implications in myocardial cell therapy

OBJECTIVE

Previous regenerative studies have demonstrated massive cell losses after intramyocardial cellular delivery. Therefore, efforts at reducing mechanical losses may prove more successful in optimising cellular therapy. In this study, we hypothesized that escalating mesenchymal stem cells (MSCs) dose will not produce corresponding improvement in cardiac function due to washout of the small cells in microcirculation. Using microspheres similar in size to MSCs, that are encapsulated in alginate-poly-l-lysine-alginate (APA), we tested the hypothesis that size is an important factor in early losses.

METHODS

In experiment I, five groups of rats (n=9 each) underwent coronary ligation; group I had no treatment; the other groups received escalating 0.5 × 10(6), 1.5 × 10(6), 3 × 10(6) and 5 × 10(6) of MSCs each. Echocardiogram was performed at baseline, 2 days and 7 weeks after surgery. In experiment II, cell-sized microspheres (10 μm) were encapsulated in APA microcapsules. In group I (n=16), rats received bare microspheres, group II (n=16) microspheres within 200 μm microcapsules and in group III (n=16), microspheres within 400 μm microcapsules. After 20 min, hearts were quantified for the amount retained.

RESULTS

Myocardial function did not improve further with escalating cell doses beyond an initial response at 1.5 × 10(6) cells. Encapsulated microspheres in 200 μm and 400 μm microcapsules demonstrated a fourfold increase in retention rate compared with 10 μm microspheres.

CONCLUSION

We concluded that suboptimal functional improvement in this animal model starts at 1.5 × 10(6) cells and does not respond to escalating cell doses. Improving mechanical retention is possible by increasing the size of the injectate. Microencapsulation could be used to encapsulate donor cells and facilitate functional improvement in cellular heart failure therapy.

Microencapsulated stem cells for tissue repairing: implications in cell-based myocardial therapy

Stem cells have the unique properties of self-renewal, pluripotency and a high proliferative capability, which contributes to a large biomass potential. Hence, these cells act as a useful source for acquiring renewable adult cell lines. This, in turn, acts as a potent therapeutic tool to treat various diseases related to the heart, liver and kidney, as well as neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease. However, a major problem that must be overcome before it can be effectively implemented into the clinical setting is a suitable delivery system that can retain an optimal quantity of the cells at the targeted site for a maximal clinical benefit; a system that will give a mechanical as well as an immune protection to the foreign cells, while at the same time enhancing the yields of differentiated cells, maintaining cell microenvironments and sustaining the differentiated cell functions. To address this issue we opted for a novel delivery system, termed the ‘artificial cells’, which are semipermeable microcapsules with strong and thin multilayer membrane components with specific mass transport properties. Here, we briefly introduce the concept of artificial cells for encapsulation of stem cells and investigate the application of microencapsulation technology as an ideal tool for all stem transplantations and relate their role to the emerging field of cellular cardiomyoplasty.

Myoblast-based cardiac repair: xenomyoblast versus allomyoblast transplantation

OBJECTIVE

We sought to investigate immune cell kinetics in relation to skeletal myoblast survival and heart function improvement after nonautologous skeletal myoblast transplantation in a rat model of myocardial infarction.

METHODS

One week after myocardial infarction, 208 Wistar rats were grouped into group 1 (n = 24, receiving 150 muL of medium only), group 2 (n = 24, receiving 150 muL of medium and cyclosporine [INN: ciclosporin]), group 3 (n = 40, human skeletal myoblast transplantation), group 4 (n = 40, human skeletal myoblast transplantation with cyclosporine treatment), group 5 (n = 40, rat skeletal myoblast transplantation), and group 6 (n = 40, rat skeletal myoblast transplantation with cyclosporine treatment). The hearts were harvested at 10 minutes and 1, 4, 7, and 28 days after cell transplantation. Skeletal myoblast survival was confirmed by means of immunohistochemical studies and quantified by using real-time polymerase chain reaction. Host immune responses were assessed by immunostaining for macrophages and CD4+ and CD8+ lymphocytes. Heart function was evaluated by means of echocardiographic analysis.

RESULTS

The majority of macrophages and lymphocytes infiltrated in the acute phase (from day 1 to day 7) and then subsided by day 28. The donor skeletal myoblasts survived and differentiated well in all skeletal myoblast transplantation groups. Allogeneic skeletal myoblasts showed a superior survival rate than xenogeneic skeletal myoblasts (P < .01). Cyclosporine inhibited the infiltration of the immunocytes, enhanced skeletal myoblast survival, and improved heart performance compared with that seen in the groups not receiving cyclosporine treatment (P < .05).

CONCLUSIONS

Allomyoblasts survive better than do xenomyoblasts after transplantation into infarcted myocardium. After inhibition of immunocyte infiltration by means of immunosuppressive treatment, skeletal myoblast survival is enhanced, with improved heart performance. These findings suggest the feasibility of nonautologous myoblast transplantation with immunosuppressive treatment.

Massive mechanical loss of microspheres with direct intramyocardial injection in the beating heart: Implications for cellular cardiomyoplasty

OBJECTIVE

Direct intramyocardial injection is a common route of donor cell administration for myocardial cell therapy. Studies have demonstrated a significant and rapid loss of implanted cells, which is thought to be biologically caused. We hypothesized that mechanical loss of cells from the contracting myocardium might actually be the main culprit.

METHODS

Intramyocardial injections of fluorescent microspheres (10 microm) were carried out in both small and large animal models. The hearts of Lewis rats (250-350 g) received 3 x 10(6) microspheres injected into the left ventricular myocardium. Rats were divided evenly between two experienced operators. The nonbeating (n = 2) and beating (n = 5) hearts of piglets (7.5-7.8 kg) received 3 x 10(6) microspheres. The hearts were excised within 10 minutes, and the microspheres retained in the myocardium were quantified with fluorescent flow cytometry.

RESULTS

In the beating-heart rat model, the microsphere retention rates after a single injection were similar with and without purse-string occlusion of needle puncture sites and slightly lower than after multiple site injections (6.19% +/- 4.05% vs 5.44% +/- 5.66% vs 8.83% +/- 3.29%). There were no significant operator-dependent differences. The retention rates in beating porcine hearts were higher than those in the rats (P < .05) but markedly lower than those in nonbeating porcine hearts (11.1% vs 67.4%).

CONCLUSION

Mechanical leakage and washout may account for a major portion of cell loss after cell implantation, and efforts aimed at reducing mechanical loss in the beating heart may yield a greater benefit than those targeting biologic loss alone.

Bone marrow cell-seeded biodegradable polymeric scaffold enhances angiogenesis and improves function of the infarcted heart

BACKGROUND

The present study examined whether a bioengineered polyglycolic acid cloth (PGAC) impregnated with bone marrow cells (BMC) improved the function and angiogenesis of the infarcted heart.

METHODS AND RESULTS

The coronary artery was ligated in Lewis rats and the infarcted area was covered with a PGAC in group 1 (n=8), with a PGAC containing basic-fibroblast growth factor (b-FGF) in group 2 (n=11) and a PGAC containing b-FGF and freshly isolated BMC in group 3 (n=10). In addition, BMC derived from transgenic mice expressing green fluorescent protein (GFP)-BMC were seeded into a PGAC, which was sutured over the infarcted area of C57BL/6 mice (n=5). In the rat study, developed and systolic pressures, dp/dt max and dp/dt min) were the highest in group 3, as were the capillary density in the PGAC and infarcted area. In the mouse study, there were few GFP-BMC in the PGAC, but none in the infarcted area.

CONCLUSIONS

A PGAC with BMC improved cardiac function by inducing angiogenesis without migration of BMC. Freshly isolated BMC work as angiogenic inducers and a PGAC is useful as a "drug delivery system".