Research into homeopathic potentization with in vitro models uses cultured cells (cell lines or isolated cells ex vivo) to assess the effects of homeopathic preparations. More specifically, basophils, lymphocytes, granulocytes, fibroblasts, osteoblasts, and others have been used. Some authors define in vitro more broadly as “cellular or subcellular entities in isolation from a living organism”, which means that test systems using molecules of biological origin (e.g. enzymes) were also classified as in vitro systems.
This research field has been examined in a qualitative review by Bellavite et al . and in a systematic, more quantitative review by Witt et al.. The latter came to the following conclusion: “From 75 publications, 67 experiments (1/3 of them replications) were evaluated. Nearly 3/4 of them found a high potency effect […] Nearly 3/4 of all replications were positive.” Witt et al. also used a score to assess methodology, experimental standardization and reporting quality, checking for 10 criteria. 44 experiments (66%) scored 6 points or higher indicating a reasonable control of bias, and out of these, 34 (77%) yielded evidence for effects of homeopathic preparations. Out of these 44 experiments, 18 used succussed controls, and in 12 out of these 18 experiments (67%) effects of potentized preparations were observed against placebo.
Analyzing the results in more detail, basophile granulocytes were used most frequently (42%), followed by non-cellular systems (27%), and cultured cells (19%). Lymphocytes (6%), erythrocytes (3%), or neutrophiles (3%) were seldomly used. Comparing the three major research fields, the average quality score was comparable (basophils 6.6, non-cellular systems 5.7, cultured cells 6.3). Interestingly, cultured cells seemed to be less responsive to homeopathic preparations (5 out of 13 experiments, 38%), compared to basophil granulocytes (23 out of 28 experiments, 82%) or non-cellular systems (15 out of 18 experiments, 83%). Restricting this analysis to experiments with a quality score ≥6, a similar pattern emerged: cultured cells seemed to be less responsive (5 out of 9 experiments, 56%), compared to basophil granulocytes (17 out of 21 experiments, 81%) or non-cellular systems (10 out of 12 experiments, 83%).
Summarizing, according to the reviews analyzed, there is good empirical evidence for specific effects of homeopathic preparations over placebo in in-vitro models. Basophilic granulocytes seem to be the most promising experimental approach, followed by enzymatic assays. Cell cultures seem to be less responsive to homeopathic remedies. The last systematic review of this research field was published in 2007, so an update seems to be warranted. Investigations into the mode of action seem to be justified based on the available empirical evidence. DNA microarray or real-time PCR studies yielded first hints at modulation of gene expression, which need to be elaborated on in more detail.
