Wikström J, Syväjärvi H, Urtti A, Yliperttula M
Drug Discovery and Development Technology Center, University of Helsinki, Helsinki, Finland.
J Gene Med. 2008 May;10(5):575-82. doi: 10.1002/jgm.1173.
In cell therapy, microencapsulated cells secrete therapeutic protein, which is further released from the microcapsules. In principle, some secreted, but unreleased, protein may accumulate in the microcapsules. The kinetic simulation model was built to simulate the potential accumulation of the protein in the microcapsules.
The alginate microcapsules were cross-linked with divalent cations to encapsulate either flourescein isothiocyanate (FITC)-dextrans (molecular weights = 4.3, 10.5, 43 kDa) or retinal pigment epithelial cells (ARPE-19). The cells were genetically engineered to produce secreted alkaline phosphatase (SEAP). SEAP production from the cells was quantified with and without microcapsulation and, finally, the cells were killed with toxin to quantify the secreted but yet unreleased SEAP from the microcapsules. The empirical three-compartment kinetic model was constructed based on the release of FITC-dextrans of different molecular weights from the alginate microcapsules with different pore sizes. Protein secretion from the cells into the microcapsules was added to the model. The impact of the microcapsule wall permeability on the steady-state amounts of secreted protein in the microcapsules and in the hypothetical target compartment in the body was simulated. The simulations were compared to the experimental data from the microencapsulated SEAP secreting ARPE-19 cells.
The model and the data show that substantial amounts (10-15 daily doses) of protein may accumulate in the microcapsules with poor wall permeability. At high permeability, the accumulation was insignificant. The pharmacokinetic simulations show that even a 1.5-fold increase in the wall permeability may result in a substantial peak in the drug amount in the target compartment, especially if the elimination rate of the protein is high.
The kinetic simulation model for protein secretion from microcapsulated cells is a useful tool for the early kinetic prediction and risk assessment of cell therapy.
在细胞治疗中，微囊化细胞分泌治疗性蛋白质，该蛋白质会进一步从微囊中释放出来。原则上，一些已分泌但未释放的蛋白质可能会在微囊中积累。构建动力学模拟模型以模拟蛋白质在微囊中的潜在积累情况。
将藻酸盐微囊与二价阳离子交联，以包裹异硫氰酸荧光素（FITC）-葡聚糖（分子量分别为4.3、10.5、43 kDa）或视网膜色素上皮细胞（ARPE-19）。对细胞进行基因工程改造以产生分泌性碱性磷酸酶（SEAP）。在有和没有微囊化的情况下对细胞产生的SEAP进行定量，最后，用毒素杀死细胞以定量微囊中已分泌但尚未释放的SEAP。基于不同分子量的FITC-葡聚糖从不同孔径的藻酸盐微囊中释放的情况构建了经验性三室动力学模型。将细胞向微囊内的蛋白质分泌情况添加到该模型中。模拟了微囊壁通透性对微囊中以及体内假设的靶区室中分泌蛋白稳态量的影响。将模拟结果与来自微囊化分泌SEAP的ARPE-19细胞的实验数据进行比较。
模型和数据表明，壁通透性较差的微囊中可能会积累大量（10 - 15个每日剂量）的蛋白质。在高通透性时，积累不明显。药代动力学模拟表明，即使壁通透性增加1.5倍，也可能导致靶区室中药物量出现大幅峰值，尤其是当蛋白质消除率较高时。
微囊化细胞蛋白质分泌的动力学模拟模型是细胞治疗早期动力学预测和风险评估的有用工具。
